TunnelTalk Annual Review 2020-2021

2020

Annual Review

Direct by Design

2020

Into

2021

project progress and developments within the industry, the TunnelTalk Annual Review for 2020-2021 charts also the impact of the global coronavirus pandemic. While there have been delays and cost increases as a result, the projects have adapted effectively with workers and management staff taking readily to the necessary health and safety initiatives introduced – initiatives that are perhaps here to stay.

As part of its 2020-2021 coverage, TunnelTalk published a series of industry Focuses on concrete linings, TBM selection, NATM/SCL/SEM projects, the hydro industry and the dilemma of underground nuclear waste management. Inclusion of these reports in the Annual Review yearbook are a précis of the full articles and their author references on the main web magazine. The Focuses and several other 2020-2021 articles attracted important Feedback from industry professionals and these too are included in the Annual Review articles.

As conferences and events in-person remained cancelled during 2020-early 2021, being replaced with virtual online alternatives, the Annual Review is published again this year as a digital edition with plans to print a hard copy version at a later date.

Annual Review

2020

From the Editor’s Desk: In its annual compilation of worldwide

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CONTENTS

FOCUS: NUCLEAR WASTE MANAGEMENT 21 Global dilemma of nuclear waste management 22 Public debate to progress nuclear waste options 24 Russia to improve nuclear waste management 25 Disposal programme for UK radioactive waste 26 USA nuclear waste options undermined by politics 27 Excavation and operation of Hungary repository FOCUS: HYDROPOWER DEVELOPMENTS 28 Global review of hydropower developments 30 Hydroelectric waterway inspections and failures 33 Alternative design for Snowy 2.0 34 Nepal prepares for second TBM waterway drive 35 Lesotho Phase II procurement 36 Melamchi watering-up gate failure 36 Fatal flood hits Himalayan hydro works FOCUS: NATM/SCL/SEM 37 Intricate excavation upgrades London metro station 38 Car parking excavations in Jerusalem 40 Rohtang pushed NATM to the limits FOCUS: CONCRETE LININGS 42 Spraying ultra-high performance FRC 42 Videos: Steel fibre concrete; Face to Face with Marc Vandewalle 43 Shotcrete best practice recommendations 44 Single-shell lining design and advantages 45 Integrated engineering for quality segmental linings 46 Choosing the right fibre for SFRC precast segments FOCUS: TBM SELECTION 49 Who should choose the TBM? 50 TBM risk assessment and selection 52 TBM procurement, risk, and technology advancement 54 Crossover XRE for navigating fault zones AUSTRALIA AND NEW ZEALAND 55 Sydney’s underground highway network continues to expand 58 West Gate TBMs remain idle in Melbourne 59 Sydney Metro buildout 61 Melbourne Metro rail excavations 62 Brisbane advances Cross River Rail link 62 Graphite iron joins concrete segments on Perth link 63 Auckland centre of underground activity

Copyright© TunnelTalk 2020. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic or otherwise, without the prior permission of the copyright owner.

All views expressed in this journal are those of the respective contributors and are not necessarily the opinions of the publisher, neither do the publishers endorse any of the claims made in the articles or the advertisements.

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Weekly Alert

Previous Editions

While international travel for many of us remains restricted, we miss our annual opportunities to meet, greet, network and socialise at the diary of events and exhibitions. Hopefully later in 2021early in 2022 we will all meet again. n

GLOBAL PERSPECTIVE 6 A grim 2020 leads to a new world in 2021 9 News, Careers Moves, Tributes, Conferences, Honours & Awards

Direct by Design

Article Archive

THE AMERICAS 64 Underground developments for Seattle LRT 65 Rehabilitation option for Hudson rail links in New York 66 BART to San Jose options and shortlisted bidders 67 Acciona-Ghella selected for Broadway Subway project 68 Toronto advances phased metro expansion 69 Mobilizing for the Los Angeles outfall drive 70 USA CSO projects continue in a challenging year 75 Argentina begins Agua Sur drives EUROPE 76 Driving MTS progress at Woodsmith Mine 77 Scope of Oslo raw water project 78 Political interference on the Helsinki-Tallinn plan 78 Construction phase initiated for Fehmarnbelt Link 79 Lötschberg inflow through lining system failure 81 High speed rail excavations begin for UK HS2 83 Yet more money agreed to complete Crossrail 84 Lyon-Turin rail link advance 85 Records being set on Brenner Base line 86 Plans for increasing Trans-Siberian rail capacity 86 Kiev Metro prepares plans for expansion 87 Moscow Metro ready for further expansion 88 Settlement after 2009 Cologne Metro disaster 88 Breakthrough on Istanbul Metro 89 Bidders shortlisted for large-diameter Thames crossing 89 Santa Lucia mega TBM breakthrough 90 Stonehenge progress despite legal challenge 90 TBM selected for Swinoujscie road link 91 Tideway continues and counts cost of Covid 92 London Main Ring inspection and maintenance 93 Power cables to move underground across Snowdonia 93 Cooling system progress at Hinkley Point 93 Replacement required to repair UK aqueduct ASIA 94 TBMs engaged in Asia 95 Mumbai Metro structures, methods and progress 96 Crossover TBM for Mumbai hard rock drives 97 Mumbai Metro NATM station 98 Chinese TBM for Mumbai coastal highway drives 98 Metro excavation to roll on in Kuala Lumpur 99 Giant karst cave encounter in China 100 Breakthrough after tough drive in China 100 Mega slurry TBM ready for Shanghai river crossing 101 Shanghai completes complex highway drive

PUBLISHER - EXECUTIVE EDITOR

DESIGN and PRODUCTION MANAGER

Shani Wallis

Claire Hunt

BUSINESS DEVELOPMENT EXECUTIVE

Adela Buglass PRODUCTION ASSISTANTS

Laura Skorczeski

TunnelTalk ANNUAL REVIEW VOLUME 11 Order extra copies2020 of the 2010-2020 issues online

Julie Burchell

CONTRIBUTORS

Jonathan Rowland Karen Martin Eugene Gerden Roland Herr Jaroslaw Adamowski

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A grim 2020 leads to a new world in 2021 Shani Wallis, TunnelTalk

their jobs. The reality is shared by public transport agencies in other major capital cities hit hard by the pandemic.

A consensus of opinion is that, even if it were possible, a return to normal will be different. The need for 9am-5pm commuting to a central office five days a week has proven to be unnecessary and the need for international travel for business meetings and conferences is equally considered expendable by the managers of many companies. The shutdown and much reduced level of air travel and highway traffic is a welcome reprieve for air quality and the natural environment.

Exactly how the world will be shaped in the future, and as a direct result of the 2020 pandemic, is now the focus for visionary civil and social engineers.

In the shorter term, the task is to shape a social and economic recovery. While billions, even trillions, have been spent on supporting businesses and workers through loans and furlough payments and the growing numbers of unemployed, what many agree is needed is an infrastructure construction led recovery similar to the New Deal programme of public works projects spearheaded by President

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TunnelTalk ANNUAL REVIEW 2020

A city without a metro system is likened to a skyscraper without an elevator

Credit: The Economist

GLOBAL PERSPECTIVE

T

here was only one story in 2020 Covid-19. There is no country, no inhabited island, no continent, no community, spared the spread of the infection.

For the underground construction industry, all projects have had to cope with the imposed pandemiccontrol lockdowns and regulations.

Social distancing, occupational health restrictions and supply chain disruptions have caused inevitable production and progress slow downs and cost increases.

Nonetheless, projects have continued and that is a credit to the managers and teams of workers who have carried on.

Some construction companies have taken matters into their own hands to manage testing and isolation strategies.

In Malaysia, as an example, the MCCGamuda JV working on the Putrajaya Line 2 of the Klang Valley MRT in Kuala Lumpur, established its own Covid-19 testing laboratory for its workers. It is a laboratory established within weeks to conduct its own polymerase chain reaction (PCR) test for the infection and in response to two constructions sites being closed down by the government after hundreds of workers contracted the virus. The JV has a workforce of some 20,000 personnel at all levels, including 7,000 labourers working across the 50km Line 2 alignment.

The other global reality has been the work from home where possible. While these have been understood and managed through a surge in the development and improvement of online video and group meeting systems, the impact on empty city centre offices has been devastating for all the support services including the commuter trains and metro services.

A report in The Economist magazine reported that ridership of the Subway in New York City had fallen by 75% compared with typical daily ridership, with the agency losing $200 million/week due to lost fare, toll and subsidy revenues.

Subway services were reduced by 40%, long promised capital projects have been delayed or suspended and up to 8,400 agency workers were predicted to lose

Franklin Roosevelt in the USA in the 1930s to recover from the Great Depression that started in 1928. Such a programme provides wages rather than handouts and leaves something worthy and tangible as a legacy.

An interesting point in The Economist report is that where Covid-19 caused a reduction in New York Subway ridership of 75%, during the Great Depression the fall was 12% in the years 1929 to 1933.

There are differences with the current crisis and the unemployment it is generating, but a common denominator is the lack of national resilience preparedness. Chief among them is a lack of investment in education and vocational training. Training and retraining of those who have lost jobs across the globe will not be a short redress.

There is the question of money to lead a construction investment recovery. So many nations have expended huge financial capacity to address the consequences of the pandemic, compounding already high national borrowings, and taking advantage of historically low interest rates. As an example, Chancellor of the Exchequer for the UK, as one of the global G7 nations, announced in November 2020 that the UK will borrow £394 billion in the year 2020, 19% or one fifth of the nation’s GDP (gross domestic product) and the highest ever in peace time. Borrowings will continue to be high through the coming recovery years with underlying debt for the nation equalling 97.57% of GDP by 2025/2026. This is in addition to the future financial uncertainty of the UK fully outside the European Union, as of 1 January 2021, and standing alone on the international stage.

There are also the political decisions needed to approve major infrastructure projects as part of a Covid New Deal recovery. As so often happens, start of so-called shovel-ready projects are delayed, postponed or cancelled at the last minute for political or financial reasons.

Only rarely has the end of one project rolled seamlessly onto a subsequent capital investment. There are examples where this can happen, including in Singapore and Hong Kong where building out of metro systems is an ongoing government-

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Global market survey

A

s the long-established organization representing the industry globally, the ITA, International Tunnelling and Underground Space Association, released its 2019 survey of industry activity. While it admits that acquiring global data is difficult, it has harnessed the input from its 78 Member Nations and a total of 96 countries collecting more than 80%90% of what has been logged in term of tunnelling works during 2019. The data represents more than 4,200 underground construction projects of all types and values from mega construction projects to the smallest in scale. Of these 1,615 were in construction in 2019 and another 2,615 were in study or planning.

As a headline, the survey reports that the global output for tunnels and underground space construction in 2019

“As we in the industry have always known, there is light in the tunnel as well as at its end.” staff. Approval of Line 3 could see the same thing happen again from the end of Line 2 without the disruptive demobilisation of equipment and teams that so often takes place at the end of projects.

In the UK, existing projects including the Tideway CSO project in London and the Highspeed 2 connection between London and Birmingham, will continue and there is Government commitment to progress new projects into construction, including the Lower Thames and Silvertown highway crossing under the Thames in

London and the Stonehenge highway tunnel project in southern England. Design and procurement preparations for other industry projects, including Crossrail 2 in London and the underground rail link between Reading and Heathrow Airport, are suspended.

Other countries have brought forward major projects to support a Covid-19 recovery. In Australia, the Suburban Rail Loop project in Melbourne and major new road and rail projects in Sydney are being promoted as vital aspects of planned economic recoveries in the aftermath of the grim consequences of 2020.

A final consideration for the industry and capital investment strategies is the type of infrastructure in which to invest. It is the mega transportation projects that

was €125 billion, up from €86 billion in 2016 and representing a growth of between 7% and 9% per annum with an average output of 5,200km per annum.

While global growth did slow in 2020, due to lower productivity and the delayed start of projects as a consequence of the coronavirus pandemic, with overall global construction expectations for 2021 at $10.1 trillion, the ITA survey predicts an investment in underground projects over the next 11 years of €1,385 billion.

China, as by far the most active in the underground construction industry, dominates and influences the survey data.

Altogether it represents more than 2,000 projects in the 2019 survey with 750 in construction and 1,280 in planning. Of the estimated €1,385 billion of tunnelling works over the coming 11 years, €472 billion is in China. For the projects in construction in 2019, the output to be

invested to complete these projects during the coming three years is estimated at €360 billion, including €200 billion for projects in China.

A review of the data indicates that of the €125 billion underground construction output and 5,200km excavated in 2019, rail accounted for 29% of the length and 34% of the output, road for 29% in kilometres and 40% in output, metro for 9% in kilometres but 16% in output, and those representing hydro and utility projects 33% in length and 10% in cost. In terms of usage, Japan provided the most detailed breakdown of its investment in underground construction over time both in capital expenditure and usage.

In terms of percentage of GDP (gross domestic product) underground construction worldwide represents an estimated 1.7‰, varying from 0.1‰ in North America to 3.9‰ in Asia and 3.5‰ in China. n

GLOBAL PERSPECTIVE

supported strategy, with Singapore making the added commitment that its metro extensions will all be underground, including under brownfield sites, to preserve its surface space that has a value that it values. There are examples in China where investment in high speed railways, highways, urban traffic links and metro systems never end, with established teams moving from one project to the next.

One of the best examples of seamless rollover has been in Malaysia where the MMC-Gamuda JV began construction of the Klang Valley MRT Line 2 in Kuala Lumpur soon after completing Line 1, ensuring redeployment of eight of the Line 1 TBMs and other equipment inventories onto Line 2 along with the all the trained and experienced workers, engineers and

Source: ITA market survey

Top left: Of projects in construction in 2019, an estimated €360 billion is required to complete them over the coming three years; Top right: 2019 global investment in underground construction by purpose and length excavated Bottom left: Investment in underground infrastructure as a percentage of GDP is predicted to continue to increase Bottom right: Japan investment in underground infrastructure from 1998 to 2016

Global tunnelling output per GDP

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TunnelTalk ANNUAL REVIEW 2020

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GLOBAL PERSPECTIVE

Hyperloop is advancing as a land transportation option of the near future are the highest percentage engagement of underground design and construction expertise, but will such transport infrastructure projects be needed to the same degree in a post Covid-19 world.

Many who view the immediate future as a glass half full, rather than half empty, predict that city centres will recover and ridership of public transport and highway networks will bounce back with perhaps a 20% overall reduction as a result of altered working, travelling and trading environments.

Under that prediction, will there be the same pressure as pre-Covid-19 times to invest in urban, national and international fixed transportation links is the question.

If the answer is yes, then happy days will be here again. If the answer is no, replacement activity and new business streams will need to be found. Perhaps the other major crisis facing the globe – that is climate change – will provide the answer with much increased investment in flood alleviation projects, hydro and nuclear power stations for cleaner, greener energy production, urgent advance of underground projects to manage the urgent issue of nuclear waste disposal, further projects to replace electricity cables underground rather than on pylons, and a greater, much greater, emphasis on the building of water supply and waste water management systems so desperately needed in the mega conurbations and cities of the developed as well as developing and under-developed nations of the world.

To end an otherwise gloomy annual review with a ray of positivity, it is without doubt the underground dimension that will remain a necessary aspect of human society development and as we in the industry have always known, there is light in the tunnel as well as at its end.

Looking to the future, the rising urgency to address the consequences of global climate change provides a new business focus for the three main public investment industries of transportation, water management and power generation.

Transportation

An unfortunate consequence of the pandemic has been travellers shying away from crowded mass transit metro and train services. However, for the future, more metro systems and high speed intercity and national connections as an alternative to air travel will become a focus.

Hyperloop for high speed land connections for both passengers and

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TunnelTalk ANNUAL REVIEW 2020

freight transportation presents an exciting vision as does the development of floating tunnels across deep water barriers. Of the different hyperloop projects being developed, Virgin Hyperloop is making most headway, conducting its first human passenger tests of the system at its fullscale test facility in Nevada, USA. Four passengers travelled at 173km/hr along the 500m above-ground test tube with the pod propelled by electric magnetic levitation in a tube pressurised to nearvacuum environment. Many metro and high-speed rail expansion projects are progressing and others are in advanced planning and feasibility stages.

Energy generation

The shift to carbon emission limiting electric power generation is an ongoing process around the world with extensive underground infrastructure needed for both. Long water conveyance networks and immense underground caverns are created for the operation of hydropower stations. There is still substantial hydro power potential in the world yet to be exploited. The 2020 TunnelTalk Focus explored developments within the hydro industry (see p28).

Cooling water systems are a central element of nuclear power plants and similar sized caverns as those created for hydro schemes could be excavated for the safer location of nuclear power plants underground. In tandem with nuclear power plants is the continuing urgent need for underground repositories for the safe long term and secure storage of the radioactive waste generated by the operation, maintenance and decommissioning of nuclear power stations. The vision of underground nuclear power plants could include creation of an underground facility of secure storage of the associated waste in the same location and as part of the same construction project. The TunnelTalk Focus articles present the current state of nuclear waste management in different nuclear power generating countries of the world (see p21).

Water supply and drainage

Many have long predicted that management of the fresh water resources on the planet will be a global political and humanitarian urgency for the future, not only for the under privileged of the world but for those who use a disproportionate amount of the resource. As well as supply

and distribution of potable water, the need is to manage fresh wastewater and stormwater. All nations of the world are progressing both supply and wastewater management projects all with a focus on underground infrastructure.

Technological advance

For the industry as a whole, the future must also include technological advance of the underground excavation processes to reduce the costs involved, increase the speed of advance and reduce the industry’s carbon footprint. The work has already begun and there are leading examples of how robotics and artificial intelligence is providing significant developments and improvements in excavation performance, safety and by association the costs of underground construction.

Others are concentrating on more efficient and environmentally conscious methods of recycling and disposing of excavated materials.

A significant development is the conversion of diesel operated equipment in the industry to battery powered alternatives. Unlike the introduction of battery powered cars and road vehicles, the scale of providing battery alternatives for construction equipment has been a barrier. To address this issue, a company in Ireland, Xerotech, has developed an off-the-shelf platform approach to battery systems with the batteries needed for different types of construction equipment being built by adding standard lithium nickel manganese cobalt oxide (NMC) or lithium nickel cobalt aluminium oxide (NCA) technology components or cells.

Together with technological advance, the industry is concentrating also on new forms of contract that are modelled specifically for the underground construction, and the risks associated, to improve the procurement and delivery of underground infrastructure. A recent development is the introduction of the joint FIDIC-ITA Emerald Book form of contract developed specifically for underground construction projects.

While we all planned for a bettermanaged year in 2021, subject to the ongoing impact of the pandemic, the future will be mapped by how we develop the fabric of society with the underground at the forefront of the construction possibilities and requirements. n

References •

Underground excavation wish list – TunnelTalk, January 2020

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Robbins embarking on a new chapter

U

nder a seamless transition, Robbins is to go forward in business under a changed ownership strategy with 100% of the governance coming back to Robbins and eliminating any other jointownership entity. “Where we had financial and ownership arrangements with other entities over the past few years, these are now dissolved and we continue business as we did in earlier times, under our own management and business strategy,” said Lok Home, President and CEO of the company in an interview with TunnelTalk. To execute the change, Home has established a new holding company, Global TBM Company, and has purchased substantially all the assets of the existing company from the receiver. The previous shareholders at the time the receiver took control were Lok Home as company CEO, numerous Robbins employees and NHI of China, which became insolvent in 2018.

It was several years ago when Robbins decided to extensively enter the EPBM market that it required a financial partner to support the expansion, explained Home.

Having had a long-standing association with NFM of France, which was 100% owned at the time by NHI of China, Robbins concluded that a three-way partnership between NHI, NFM and Robbins was the solution. Robbins retained 40% of the shares in the consortium. However, it became apparent that this strategy was no longer viable when state-owned NHI became insolvent and Lok Home leads future NFM was put up for for Robbins sale. Home then began the complex process of taking back the 60% share owned by NHI. It is the conclusion of that process that creates a new future for the company within the Global TBM Company and with a name change from The Robbins Company to Robbins.

Home joined Robbins as a young mining engineer in the late 1960s. After a 15-year period with the company, he accepted a post to manage the Jarva

TBM business that had recently been acquired by Atlas Copco. When Atlas Copco management decided to move the Jarva TBM division back to Sweden, Home established Boretec with partners, including Tony Peach of Australia. Atlas Copco then bought Robbins in the mid1990s but the association did not last and Home took the opportunity to buy Robbins in 1998. As a result Boretec was consolidated into Robbins and operated at The Robbins Company. Closure of the recent transaction with the receivers of the foreclosed NHI USA TBM interests brings all Robbins assets back under the sole ownership of Home.

Under the terms of the asset buy back, Robbins owns seven subsidiaries, with workshop operations in China, India, Mexico, Brazil, Chile and elsewhere; the conveyor head office and workshop in West Virginia; the cutter operations in Kent, Washington; and the smallbore manufacturing facility in Solon. The company also has active agents in 20 additional countries. Together with the principle management and engineering team, including Doug Harding, Dennis Ofiara, Dean Workman, Brad Grothen, and field service leader Steve Chorley, the Robbins team includes engineers from China, Italy, France, Spain, Japan and many other countries. “We are a united nations of employees,” said Home, “and have some very talented young engineers that are showing effective leadership.”

“We start 2021 with no significant bank or institutional debt and have many projects to look forward to, as well as managing current operation and delivery of Crossover and main beam rock TBMs equipped for challenging geological conditions. For the future, our clients can depend on Robbins to deliver high-quality and technically welldesigned machines for very difficult projects.

That is where Robbins really stands out.

We have always been focused on building the best and strongest machines and will continue to do so.”

In looking to the future of the TBM marketplace globally, Home said there will be no shortage of projects in the coming decades, particularly as developing countries begin to focus on their urgent underground infrastructure needs in

water management, metros, and intercity connectivity. “Every great city of the world has an underground metro system, and current developments prove that more of these underground projects will be managed by TBMs, rather than drill+blast or other alternatives. The TBM manufacturing industry has shown that modern machines can go through any ground – if well designed, set up and equipped. There may well be additional manufacturers in the international marketplace, as work in China winds down, but the scale of the work into the future will keep us busy.”

Robbins continues its many industry involvements, including with the ITA (International Tunneling and Underground Space Association) and its associate member organizations, and with the global industry community. “The ITA has the ability and the resources to lead the industry in addressing some of the international developments needed to advance the underground infrastructure industry.

For example,” he said, “we need more standardization and ITA could help with that. There are so many different diameters for metro running tunnels and more standardization would lead to economies of scale and a reduction in costs. ITA could help with the development of different lining systems. At present we have shotcrete and cast concrete on one side and precast bolted and gasketed segmental linings on the other. There should be different options between those extremes. We need better contracting environments, better consulting standards, better dispute resolution practices. Leaders of the industry, functioning through the ITA and its committees, including ITAtech that I am part of, can spearhead and bring about these changes.” n

I N D U S T RY N E W S

Shani Wallis, TunnelTalk

References • • • • • •

Learning from difficult rock TBM drive experiences – TunnelTalk, January 2021 Crossover XRE navigates fault zones in Turkey – TunnelTalk, June 2020 Robbins celebrates 60 years of achievement – TunnelTalk, October 2012 China deal for Robbins – TunnelTalk, June 2016 NFM for sale from insolvent Chinese owner – TunnelTalk, September 2018 Video: Face to Face with Dick Robbins, former President of The Robbins Company

Epiroc to phase out Meyco shotcreting line

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pecific reasons for the decision by Epiroc to discontinue its Meyco concrete spraying business were not forthcoming nor were answers to queries as to why the product line was phased out rather than sold. Epiroc manufactured six products in the concrete spraying line at its product companies in Örebro (Sweden), Nashik (India) and Nanjing (China).

In a press release statement Sarah Hoffman, Vice President Marketing for the Underground division at Epiroc, said: “We are constantly reviewing our customer solutions offering to ensure we keep Epiroc

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strong and agile for the future. Epiroc will ensure a minimum impact on customers and will fulfil orders on hand, warranty undertakings and the service support thereafter.”

The Meyco product line was acquired in 2013 by Atlas Copco, from which Epiroc was created in a restructure of the Swedish mining and tunnelling equipment manufacturer in 2017. BASF itself sold its construction chemicals division to Texas Lone Star, a global private equity firm, in January 2020.

The core product lines of Epiroc are drilling jumbos, rock excavation

TunnelTalk reporting equipment and construction tools. Based in Stockholm, Sweden, the shareholder listed company had revenues of SEK 41 billion in 2019 and has more than 14,000 employees for operations in more than 150 countries. The Meyco business was part of the Underground and Parts & Services divisions of Epiroc. n

References •

BASF sells Meyco division to Atlas Copco – TunnelTalk, December 2012

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CAREER MOVES

Career Moves

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32 tunnel projects throughout North America. Previously, he was Project & Quality Manager at CSI Tunnel Systems, and before that was Quality Manager at Modern Continental Construction. “With Louis in our team, we have a portfolio built on more than 75 segmental liner projects in North America and internationally,” said Walter Siryk, President and Principal at United Underground Precast. Through its affiliation with United Concrete Products, founded in 1954, United Precast benefits from its fully-owned NPCA and PCI Certified plant assets, quality testing, and concreting expertise.

Dec 2020: Strata Worldwide appointed Mike Rispin to lead the launch of its new global division, Strata Tunneling. Rispin joins as Vice President – Tunneling and brings more than 36 years of international expertise to the position, having worked previously for companies including BASF, Normet and Dyno Nobel. He is a professional engineer with membership in the American Society of Civil Engineers Mike Rispin (ASCE) and is currently the July 2020: McMillen Jacobs Associates Vice Chair of the Underground Construction elected Victor Romero, PE, CPEng, to Association (UCA) of SME to become Underground Division President in June 2021. Established in President to lead the 1992, Strata worldwide supplies products executive management, including emergency refuge chambers, strategy, and operational proximity detection devices, collision functions of the Division. avoidance systems, IoT (internet of things) As a graduate of the networking, automated environmental University of California, monitoring, and specialty chemicals to Berkeley, and of the the mining and underground construction Colorado School of industry. From its central headquarters Mines, Romero has been in Atlanta, Georgia, USA, Mike Berube, Victor Romero with McMillen Jacobs for President and CEO of Strata Worldwide almost 30 years, serving in a number of roles said: “We will continue to invest in the including leading expansion of the practice in underground industry resources to support Australia and New Zealand. As an employeeMike and allocate R&D funds to grow our owned firm, McMillen Jacobs Associates product line.” provides comprehensive technical services Nov 2020: After moving from his post in the to the heavy civil, underground, and water Singapore office, Andreas Raedle is now the resources industries.

Arup Underground-Infrastructure Leader for May 2020: The international Ramboll the Americas. In the USA, and consultancy firm in Denmark welcomed based in San Francisco, Raedle Andrew Shaw to its immersed tunnelling has the brief to grow the Arup team.

Working in tunneling and underground the head office in engineering practice and to Copenhagen, Shaw be responsible for technical joins the Major Crossings leadership and excellence. division of the Ramboll Through his career Raedle has Tunnel Department, as gained extensive experience an immersed tunnel in securing and implementing expert with 30 years large, multidisciplinary Andreas Raedle of experience.

He projects. Prior to joining Arup joins Ramboll from Andrew Shaw and being posted to Singapore, he was for Capita Property and four years in the UK working for the Hochtief/ Infrastructure where he was Technical Murphy construction JV on its Crossrail Director. His recent experience includes the tunnels under the Thames River. Prior to that detailed design of the Shatin to Central metro he was design manager for Hochtief in his immersed tunnel in Hong Kong, and as the home country Germany. During his five years client’s technical advisor on the Second in Singapore, Raedle was involved on the Midtown immersed tunnel in Virginia, USA. Deep Tunnel Sewerage System-Phase II; the Shaw is a Chartered Engineer (CEng) and Thomson and Cross Island Metro Lines; the a Fellow of the Institution of Civil Engineers Central Interceptor and City Rail Link projects (FICE) and has a proven track record of in Auckland; the Brisbane Cross River Rail leading delivery of complex designs for and Sydney Metro West projects; the Kuala design-build contractor clients.

Lumpur Phase 2 and Phase 3 Metro projects; Feb 2020: The Normet Group Board of and the Orange Line for Metro Bangkok.

Directors welcomed a new member in Lars Sep 2020: United Underground Precast, Engström who is also currently chairman formed to meet the demands of delivering and a board member of several companies. durable precast concrete segmental liners, In the past he has served as President at micro-tunneling pipe, and other precast Sandvik Mining & Rock Technology, Chief elements for underground Executive Officer at BE projects, welcomed Luigi Lars Engström Louis Falco Group, Chief Executive ‘Louis’ Falco as Vice Officer at Munters President of Engineering & Group, and Divisional Quality. Falco is recognized President at Atlas in the industry for his Copco. Engström brings expertise and experience international industry in segment manufacturing experience to Normet as gained across more than it continues to grow.

TunnelTalk ANNUAL REVIEW 2020

Feb 2020: Bringing more than 25 years of experience at two national consulting firms, Celal Kirandag joined the HNTB national tunnel and underground team as senior project engineer based in Santa Ana, Southern California. As an expert in 3D analysis of segmental tunnel Celal Kirandag linings subject to seismic forces and ground-structure interaction, Kirandag’s experience includes underground projects for the Westside Extension and the Regional Connector projects for the Los Angeles Metro, the Bosphorus TBM road tunnel crossing in Turkey, and the SR99 Alaskan Way Viaduct Replacement TBM highway project in Seattle.

Jan 2020: Joining C.W. Felice as Chief Engineer, Jack Mulvoy brings project delivery experience and an expertise for being clientoriented when preparing efficient and cost-effective solutions to complex projects.

Mulvoy previously served as Chief Engineer for DSI Tunneling with responsibility for design, technology transfer and construction support in North America.

Jack Mulvoy C.W. Felice specialises in geostructural engineering services in all types of ground conditions and the integration of design and construction with traditional and alternative project delivery systems.

Jan 2020: AECOM added three renowned experts to its practice in the Americas.

Bob Frew transferred from the London office as an expert for large diameter TBM tunnels. When in the UK Frew worked on the Channel Tunnel Rail Link, the Copenhagen Metro, the Chong Ming Tunnel in Shanghai and the Tuen Mun-Chek Lap Kok subsea highway link in Hong Kong which holds the world record for the largest diameter TBM to date at 57.75ft (17.6m).

Giuseppe Gaspari will lead the engineering practice in Canada. His experience includes design and program management for major projects including the Istanbul Kadikoy-Kartal Metro Line in Turkey and the Brenner Base rail project between Italy and Austria. He also provided technical leadership for the Ontario Line in Toronto.

Dr Ana Ruiz is a ventilation and life safety expert with experience in numerical modeling using subway environmental simulation and computational fluid dynamic modeling for fire scenarios. Ruiz has led tunnel ventilation design projects for Chennai metro stations in India and the 86th Street subway station in New York City. Ruiz has been a member of the USA NFPA 502 technical committee since 2012 and has served as the Spanish representative of Ministry and Industry in the CERN Council. n Bob Frew, Giuseppe Gaspari and Ana Ruiz

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NFM becomes part of BMS France he future of NFM TBM design, manufacturing and service is secured with a takeover of the business by French foundations and underground works company BMS, Béton Matériel Service, based in Lyon and with offices in Paris and Toulouse. Philippe Adrien, former CEO of NFM tunnelling operations, is providing advice and continuity for the company into integration under new ownership by BMS. BMS President Jean de Saint Julien and his financial partner Peninsular Capital Management secured the takeover deal and creation of its new NFM Engineering division. NFM Engineering will specialize

in the engineering for TBM and related services in France and internationally and will operate in three areas of expertise: engineering studies, technical assistance on site with service, spare parts and cutting tools supply; and bringing their experience to clients via: • TBM specifications and feasibility studies • Refurbishment and technical adaptations of used TBMs • Compliance of equipment with codes and standards • Commercial interfacing in France and abroad • Site training, and

Management buyout of Datwyler gaskets business TunnelTalk reporting

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or all business operations, there is no change, was the message from managers of Datwyler Sealing Technologies who bought out the civil engineering division from the Datwyler Group. The significant change is a name change to SEALABLE Solutions GmbH, which, the new owners say, expresses the philosophy and focus of the international business.

“We have concluded a management buyout that takes us back to the situation as it was before we were bought in 2012 by Datwyler,” said existing manager Matthias Orth.

“Our heritage goes back to the original company Phoenix GmbH which took over the production facilities after the reunification of Germany in 1991 and developed it into the centre of profile production, including the tunnelling industry for segment gaskets and shield seals for TBM launch and breakthroughs. Then came a period of some change of ownership from Continental via a manager buy-in and most recently in 2012 by Datwyler of Switzerland. In all these eras, the production facility in Waltershausen, in the middle of Germany, was completely independent and a driving force behind the development of seals for tunnel construction.”

The buyout by existing managers Orth and Matthias

Klug includes the manufacturing facility and a team of more than 180 employees, and sales of gaskets and products in more than 50 countries. In recent annual accounts, the civil engineering division for Datwyler has generated annual sales of about CHF40 million or €38 million.

From his office in New Jersey, regional sales representative for North America, Peter Tiedemann told TunnelTalk, “the manufacturing facility in Waltershausen is a modern, streamlined production with a large capacity.

Production operations are ongoing during this coronavirus situation and some of our notable projects include the Thimble Shoals highway tunnel under Chesapeake Bay; Delaware aqueduct bypass; and Los Angeles Metro Westside extension contracts in the USA; Hiroshima Expressway, Japan; West Gate highway, Melbourne, Australia; Tuen Moon Chek Lap Kok undersea highway, Hong Kong; the three new tunnels under the Suez Canal, Egypt; Follo Line railway project, Norway; and the Woodsmith potash mine mineral transport system in the UK.” n

References • •

Webuild News Release

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ebuild has completed its 65% acquisition of Astaldi, creating the new group, Progetto Italia. Webuild financed its participation with cash raised from a capital increase in November 2019 that was entirely subscribed and paid-in

by Salini Costruttori, CDP Equity, Banco BPM, Intesa Sanpaolo, UniCredit and other institutional investors.

The Group will have the capacity to act quickly on investment programmes

www.TunnelTalk.com

EPBM for Thimble Shoals parallel tunnel – TunnelTalk, August 2017 Delaware bypass designed for high pressure water control – TunnelTalk, August 2017

• Project management NFM was previously owned by Mühlhäuser of Germany before it became insolvent in late 2019 and before that by NHI, a State owned company of China, from 2008 until it encountered financial trouble in 2018 and lost the financial support of the Chinese State. n

References • • •

Mühlhäuser asset buyouts – TunnelTalk, February 2020 NFM for sale from insolvent Chinese owner – TunnelTalk, September 2018 China adds CIFA and NFM to European acquisitions – TunnelTalk, September 2008

WSP acquires Golder TunnelTalk reporting

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mployee-owned Golder Associates, headquartered in Canada, is acquired by consulting firm WSP. Together the two companies will employ about 54,000 professionals with 14,000 of those dedicated to accelerating the green transition.

Under the terms of the agreement WSP will acquire all of the issued and outstanding shares of Enterra Holdings Ltd, the holding company of Golder, for an aggregate cash consideration of US$1.14 billion, about CAD$1.5 billion. WSP part funded acquisition capital from a new US$960 million underwritten bank financing agreement.

WSP began in 1969 as the Williams Sale Partnership in the UK. In 2012 Genivar of Canada acquired WSP and in 2014 adopted WSP as the corporate brand. In 2014 WSP began its global expansion strategy with acquisition of the USA-based Parsons Brinckerhoff consultancy firm. Recent global acquisitions include Mouchel Consulting of the UK in 2016; Louis Berger of the USA in 2018; Ecology and Environment Inc of the USA, and Orbicon of Denmark in 2019.

Golder was founded in 1960 in Canada by soil mechanics engineer Dr Hugh Golder, highways engineer Larry Soderman of Canada, and engineer Victor Milligan, originally of Ireland. Through the early 1970s, the firm established operations in Canada, the USA, the UK and Australia while working on projects around the world. Headquartered in Mississauga, Ontario, the firm today has more than 7,000 employees in 155 offices in 30 countries across six continents. In 2017 it acquired the Alan Auld consultancy practice of the UK. n

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TunnelTalk reporting

References • •

Alan Auld acquisition by Golder Associates – TunnelTalk, October 2017 Rebranding of WSP | Parsons Brinckerhoff – TunnelTalk, May 2017

Webuild completes acquisition of Astaldi promoted by national governments for large, strategic infrastructure projects and will be able to contribute to the advancement of the Sustainable Development Goals (SDGs) set by the United Nations in the fight against climate change.

The acquisition will guarantee that work involving Astaldi, including Line 4 of Milan Metro, the Naples-Bari high-speed railway and the Hurontario light rail transit near Toronto, Canada, will continue.

“We will make the most of Italian knowhow and help to modernise the country by unblocking current and launching new projects that support sustainable growth over the long term and help to relaunch the economy after the Covid-19 pandemic,” said Pietro Salini, Chief Executive of Webuild.

“We will be bigger, better organised and more efficient to compete in international markets and relaunch the Italian market for infrastructure,” he added. n

TunnelTalk ANNUAL REVIEW 2020

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Tributes Dr Harvey Parker 1936 - 2020

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ew in the industry will be unaware of Harvey Parker. Through more than 55 years in civil engineering he guided many a project through its planning, feasibility, design and construction phases, was known as an honest broker of advice and information for complex decision making by clients and owners of high-profile potentially high-risk projects, and was a friend, colleague, co-worker and mentor to so many in the industry.

Through his association Harvey Parker with the ITA, International Tunnelling and Underground Space Association, and as its President from 2004 to 2007, he took on the role as father to the international industry, encouraging more countries to join the Association and for them to explore the role of the underground in their development of vital national infrastructure.

Through the ITA, he worked with the United Nations to promote the recognition of underground space for environmental and social sustainability, an effort that resulted in a

change of the ITA name during his Presidency to include Underground Space. In 2019, and for his career and contributions to the industry, he was awarded the ITA Lifetime Achievement Award, which followed a Lifetime Achievement recognition from the USA Underground Construction Association in 2018.

After earning an MS in Civil Engineering from Harvard, and a PhD in Civil Engineering with a Minor in Geology from the University of Illinois Urbana-Champaign, Parker’s contributions to the industry are many and varied. Through all a constant thread was his interest in working at the forefront of innovations and state of the art. His PhD thesis in the mid-1970s was on the development of steel fiber shotcrete. His interests also had a focus on geotechnical investigations and risk management.

His pioneering work included the planning and design of the Mount Baker Ridge highway and transit tunnel in Seattle of the 1980s, still the largest diameter soil tunnel in the world, and the SR99 Alaskan Way highway in Seattle that used, at the time, the largest TBM in world at 17.4m diameter.

Parker’s first transit project in the early

Friedrich Blindow 1933 - 2021

TRIBUTES

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hen introduced, there were few who understood, and knew how to design, apply and control the excavation method called at the time NATM. One of them was Freidrich Blindow. As a design engineer and a contractor, he knew that the concept would not work without both in direct and seamless collaboration.

The international adoption of NATM (the new as opposed to the old Austrian tunnelling method), that went on to morph into the SCL, sprayed concrete lining, method in the UK and the SEM, sequential excavation method, in the USA, was thanks to those with the ability to convey the advantages of the concept around the world to engineers in different countries.

In a conference presentation, Blindow listed the main advantages of NATM: • Rock pressure, so feared before, is supported in close contact to the ground.

• The rock is handled gently to preserve stability and security of the excavation.

• The flexible excavation method can minimise deformations and settlements.

• The excavation area remains free of bracings.

• Excavation can be readily changed for transitions, junctions and enlargements.

• Cover can be less than the previous one tunnel diameter practical limit.

• Cost reductions by 50% in comparison with other methods.

There is only one significant disadvantage of the method, he admitted, and that is its dependence on experienced engineers who are willing to accept responsibility, and of a skilled crew.

Blindow began his career with Beton- und Monierbau in 1965.

Having worked with the company on the first NATM project in Germany, the Schwaikheimer rail project in the 1960s, he compiled a portfolio of design and construction contracts, and expert panel services in support of NATM and its proper application around the world. Highlights include the Karawanken railway and Tauern highway in Austria; Pallaresa highway in Barcelona; Hanging Lake highway in Colorado; and the Munich, Bonn, Nurnberg, Dortmund, Frankfurt, Bochum and Vienna Metros.

With Beton- und Monierbau Innsbruck, Blindow took the Friedrich Blindow company into international joint ventures, notably in the UK on the Heathrow baggage tunnel project in the early 1990s and as a JV partner on the Channel Tunnel North Downs rail link to London in 1998. Blindow also gave evidence to the ICE inquiry of the Heathrow rail link collapse of NATM station caverns in the UK in 1994. It was as a consequence of the collapse that NATM in the UK was renamed as SCL and redefined as a pre-designed prescriptive method with high design factors of safety and permitting no changes once into construction. While the means of excavation of NATM and SCL are the same, the processes of application are significantly different. Towards the end of his career Blindow established his own management company for promoting NATM and assisting with claims development.

Blindow will be remembered as a well respected colleague, business partner, fellow engineer, and international collaborator. n

References • • •

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Bonn Metro: NATM chosen to pass under Federal rail tracks – TunnelTalk, May 1990 Heathrow baggage tunnel – TunnelTalk, October 1994 Heathrow failures highlight NATM misunderstandings – TunnelTalk, March 1999

TunnelTalk ANNUAL REVIEW 2020

1980s, was with the Los Angeles Metro, guiding the client through early successes and troubles and navigating successfully with fellow advisors, the lifting of a ban on heavy rail tunnelling under Los Angeles. He also worked on the WMATA Metro system in Washington DC, the New York Subway, and the Boston and Chicago transit systems, as well as on enlarging rail tunnels in the USA to carry stacked container freight trains, and on underground management of nuclear waste projects.

Parker gave back to the industry as chairman of several organizations in the USA including the US National Committee on Tunneling Technology, The Underground Technology Research Council, and the Underground Shotcrete Subcommittee for the American Concrete Institute Committee.

Wherever he went and in whichever forum he was engaged, Harvey’s energy, enthusiasm and sense of purpose was infectious, creative, productive. This will be missed as part of his legacy. n

References •

ITA Lifetime Achievement Award 2019 – TunnelTalk, November 2019

Niko Kleuters 1954 – 2021

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echanical engineering was the life enthusiasm of Niko Kleuters - a life cut short by a fatal two car collision while travelling in Zimbabwe.

Best known as the head of the Wirth TBM manufacturing company in Germany, which he joined in 1978 as a design engineer, Kleuters was the driver for all the TBM projects and for developing and introducing several new inventions. Significant among these was the TBM undercutting concept that was used in prototype on Niko Kleuters the Uetliberg highway in Switzerland in the late 1990s.

Other notable projects managed by Kleuters include: • The Storebaelt undersea rail link in Denmark in the 1990s as part of the Howden Wirth era; • The Pingling highway in Taiwan with the two largest diameter Wirth TBMs at the time; • The two gripper TBMs and their full backup systems on the Quinling railway project in China; • Design, production and launch of a mobile mining machine based on the undercutting technology; • The Veriena railway link in Switzerland; • The Lesoto Highlands Water Project Delivery Tunnel North double shield machine; and • The two machines that worked alongside two Herrenknecht machines on the Guardarrama twin tube high speed rail project in Spain.

While the management buyout of Wirth in the 1990s was his greatest achievement, it was not to last. ln the late 2000s, the business was bought out by Aker of Norway with the intellectual property of Wirth subsequently sold to become the European operation of Chinese manufacturer CREG, based in Erkelenz. Kleuters assisted CREG negotiate the buyout and became an independent consultant thereafter.

Kleuters was a team leader who never gave up on a mission. An untimely loss of an engineer who helped shape the TBM industry during its turbulent and cutting edge project era of the 1980s, 1990s, and 2000s. n

References • • • • •

Wirth acquired by Norwegians – TunnelTalk, June 2009 CREG takes over Wirth – TunnelTalk, November 2013 Storebaelt - the final chapters – TunnelTalk, May 1995 Early TBM experience at Qinling – TunnelTalk, January 2000 Marathon at Guadarrama – TunnelTalk, November 2005

www.TunnelTalk.com

BASF Construction Chemicals now MBCC Group s of October 2020, and after one of the largest carve-out corporate divestments, the BASF Construction Chemicals business, with sales of about €2.6 billion in 2019, is now the newly formed, fully standalone MBCC Group. A purchase agreement in December 2019 with an affiliate of the private equity firm Lone Star of Texas, USA, began the ownership transfer of the Construction Chemicals business for a cash and debt-free purchase price of €3.17 billion.

From its headquarters in Mannheim, Germany, and with about 7,500 employees in production and sales offices in more than 60 countries, the Construction Chemicals business has a new name, a new chief executive officer and with most of the team at the customer level still in place and operating as usual.

With the well-established brands Master Builders Solutions®, PCI®, Thermotek®, Wolman®, Colorbiotics® and Watson Bowman Acme®, the MBCC group is among the leading global suppliers of admixtures and supplies in the construction systems market.

Through the Master Builders Solutions brands, MBCC Group will continue to provide products, engineering expertise and training workshops to meet the needs in the underground construction (UGC) industry worldwide. The UGC ranges comprises: • Shotcrete admixtures • Injection materials

Dramix® production in USA Bekaert News Release

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o meet ‘made and melted’ requirements in the USA, Bekaert has established a larger fibre production facility in WilkesBarre, Pennsylvania.

The company will produce its range of Dramix® steel fibers at the new facility to supply steel fibres manufactured in the USA for all underground concrete applications. For steel products to comply with the made in America requirements, the steel must also be forged or melted in the USA. The move of its fibre manufacturing to Wilkes-Barre in Pennsylvania will bring product supply closer to Bekaert’s main customers. Meanwhile support will continue from the Shelbyville facility in Texas. n

References •

•

Video: Marc Vandewalle speaks of steel fibre introduction to the tunnelling industry – TunnelCast, May 2020 TunnelTECH: Fibre-reinforced concrete for precast segments – TunnelTalk, May 2014

www.TunnelTalk.com

• A range of TBM technologies including soil conditioners, anti-abrasion and dust control agents, tail sealants, main bearing greases, pre-injection materials and annulus grouts • Waterproofing systems including spray applied materials and double bonded waterproofing membranes • Resin and cementitious grouting systems for rock bolting and cable bolting The Master Builders Solutions Underground Construction operations in Europe, Russia, Middle East and Africa are headed by Arvid Dokken, with James Lindsay managing North America, Luciano Lopez heading South America and Ed Pilkington managing the Asia Pacific region.

Thomas Breiner is Global Business Director Admixture Systems, Dr Jochen Fabritius, a civil engineer by training, is the new Chief Executive Officer, and Dr Sven Asmus is MBCC Group Chief Technology Officer. Nick Chittenden, Regional Manager of the Middle East, Russia and Africa zones, is well known in the international tunnelling industry through his work as Chair of the ITAtech Committee of the International Tunnelling and Underground Space Association (ITA).

From its founding as Master Builders in 1909, the business had many owners until BASF acquired it from Degussa in 2006. In 2013, BASF bundled 30 brands under the Master Builders Solutions brand. Under the new ownership the

TunnelTalk reporting company re-establishes its independent and focused perspective.

In early 2021, MBCC signed purchase agreements to acquire Germany based TPH Bausysteme and Australia based Bluey Technologies, adding to its portfolio in acrylates and polyurethanes for ground consolidation, water control solutions and construction chemicals and services for the infrastructure market.

With headquarters in Norderstedt, Germany, and warehouses and sales offices in Europe and Asia, TPH supplies products and systems for injection technology, joint sealing and bonding, concrete renovation and surface protection.

Based in Sydney, Australia, Bluey Technologies provides design and engineering services and related products to the civil construction industry across Australia, New Zealand, South East Asia and Europe. Its extensive range of products includes engineered, high-performance cements, waterproofing products and ground improvement solutions used in critical applications for transport and civil infrastructure projects. n

References • •

Rebrand for new solutions division at BASF – TunnelTalk, October 2013 Demonstrating spray-on waterproofing – TunnelTalk, June 2013

DSI Underground becomes part of Sandvik and adds Edvirt to its portfolio

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fter initiating a sales process in early 2020, Triton sold its ownership of DSI Underground to Sandvik of Sweden. The acquisition will add the DSI Underground ground support and reinforcement products, from bolting systems to injection chemicals and resin capsules to the Sandvik Mining and Rock Solutions business area. The acquisition will combine the DSI Underground resources, expertise, sales footprint and 22 local production facilities worldwide with the Sandvik range of rock drilling, loading and hauling equipment, tools and support services, to create a wide range of products and services to the international mining and tunnelling industries.

The negotiated purchase price with Sandvik is €943 million on a cash and debt free basis. In 2020, DSI Underground had 2,000 engineers and technical specialists operating in 70 countries and expected revenues of about €518 million, excluding four DSI Underground joint ventures that are also part of the acquisition. These include agreements concluded in 2016 with Jennmar for joint operations in different market areas of the world.

Triton, a European private equity house, acquired DYWIDAG-Systems International (DSI) from previous owners BAML (Bank of America Merrill Lynch) and Barclays Capital, which had taken over DSI in 2010 from CVC Capital Partners.

In 2019 the publicly listed Sandvik Group had about 40,000 employees operating in more than 160 countries, and recorded revenues for 2019 of about SEK 100 billion (€100 billion).

“This acquisition is an important step in our growth ambition,” said Stefan Widing, President

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TunnelTalk reporting and CEO of Sandvik. “The DSI Underground global reach will further strengthen our global market position.” Henrik Ager, President of Sandvik Mining and Rock Solutions, said, “the acquisition also gives DSI Underground access to the Sandvik R&D resources.”

Michael Reich, CEO of DSI Underground, said, “After 16 years of private equity ownership, DSI Underground once again has an industrial owner that shares similar values, thinking and behaviour.”

In early 2021, DSI Underground SMART, a wholly owned subsidiary of DSI Underground, increased its investment in vehicle safety and innovation underground by acquiring 100% of Swedish training and virtual reality company Edvirt. Edvirt will continue to operate as a standalone company and with DSI Underground SMART will become part of Sandvik Mining and Rock Solutions.

“Tunneling requires efficient and intelligent digital solutions and Edvirt, with DSI Underground SMART will offer virtual training to support safety and productivity underground,” said DSI Underground CEO Reich. n

References • • •

DSI restructures and confirms Jennmar deals – TunnelTalk, November 2016 New private equity owners for DSI – TunnelTalk, June 2011 Sweden leads training for shotcrete operators – TunnelTalk, June 2017

TunnelTalk ANNUAL REVIEW 2020

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GRAND PARIS EXPRESS, FRANCE

TOGETHER WE MORE THAN CO By 2024 at the end of project phase 1, Société du Grand Paris, 13 construction companies and 21 Herrenknecht state-of-the-art TBMs will connect the Parisian underground metro network with the suburbs. Grand Paris Express provides an exceptional opportunity to train the next generation of engineers and pushes innovation forward. herrenknecht.com/grandparis

BUILD ONNECTIONS

Client: Société du Grand Paris Contractors: BAM Bessac Bouygues TP Demathieu Bard Eiffage GC Implenia NGE / NGE GC Pizzarotti Razel-Bec Soletanche Bachy France / Soletanche Bachy Tunnels Spie Batignolles Vinci Construction Webuild

Virtual alternative for 2020 WTC and ITA business

CONFERENCES

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aving been caught in the maelstrom of the rapidly spreading global pandemic, the WTC 2020 organisers in Malaysia held the virtual alternative as a first for the World Tunnel Congress series. In three months, a virtual alternative to a programme that had been in the making for a physical gathering in Kuala Lumpur for three years was prepared and staged. This was no small feat under such unprecedented circumstances.

Like all new systems, it took time for those interested in participating to learn their way around the congress and its accompanying virtual exhibition hall. The virtual alternative also took extra effort by presenters to record their presentations for online access and for exhibitors to populate and attend their virtual booths. It is a credit to the 263 authors who prepared their recorded paper presentations, all of which were available for online viewing on their schedule programme slot. After a slow start to become familiar with the processes, attendees appreciated the presentations and connected with authors and exhibitors and in different ways than the usual five day in-person schedule.

There was news also from the IEM organising committee that a 70% refund would be offered to those who claim it due to the cancellation of the physical conference

in May, and conversion to the virtual alternative in September, when at the start, no refunds of any kind were being offered.

Many however were still not entirely satisfied, suggesting that a 100% refund should have been offered. The ITA stated that it waived its substantial revenues that would normally flow to the ITA from a WTC event to secure at least the 70% refund. The refund issue brought into sharp focus the need to review the contracts ITA enters with the hosts of its World Tunnel Congress brand and series of events, an issue discussed during the 2020 virtual ITA General Assembly.

The content of most of the virtual presentations was of the standard of normal WTCs ranging from the very good to excellent in content and presentation, to the very good in content but difficult to understand in presentation, to the poor on both counts.

Some of this is due to the reviewing process of the abstracts and papers and much is due to the experience of presenters to present in English as the official language of the WTCs. There was facility on the viewing platform to leave a public question for the presenter but no facility to download the presentation or the paper. E-Proceedings were available for download after the virtual congress and hard copies of the proceedings in three volumes are available to purchase.

Virtual Congress for Kuala Lumpur and for the ITA General Assembly in 2020

TunnelTalk ANNUAL REVIEW 2020

Shani Wallis, TunnelTalk For screen viewing of the presentations, the viewing window was very small with no full screen viewing facility and information on the slides was too small to read or appreciate.

This is where a copy of the paper is essential as part of the full conference experience, either in person or virtually.

One of the more engaging sessions was the hour-long live streamed Q&A panel discussion with those representing clients, contractors and suppliers discussing the development of AI and robotics, where developments might progress in the future, procurement strategies for mega projects and the disconnect between the civil works and the M&E works on major metro and transportation projects.

In the virtual exhibition area, the facilities on the booths was limited, depending on the size of the booth purchased, and interaction with those attending the booths sporadic.

TunnelTalk visited most of the virtual booths, dropping a business card and leaving a chat message. The chat window worked well once engaged, if a bit slow.

For download of materials on the booths, they all have a generic tag line, requiring that they be renamed into a save folder. Not sure why the original titles of the company pdfs could not have been used or why, like other virtual events including the NAT in June in the USA, the exhibitors themselves could not have uploaded their own materials. All had to be sent to the organisers for upload with the generic file tags.

A personal disappointment is that there are no desks or booths for the media at the congress. This is an agreement between the industry media and the ITA in its annual WTC series but was overlooked for the virtual alternative.

All in all, the virtual event was the best possible perhaps under the circumstance and credit is owed to the technicians who made it happen. We all felt the loss however of not being able to attend the event as planned and in person in Kuala Lumpur and missed the regular annual opportunity to meet friends and colleagues and manage business connections and network with like-minded professionals from around the world.

This too is missed in 2021 with the Copenhagen, Denmark, May event cancelled and moved to April 2022. The decision, tabled at the virtual ITA General Assembly of 2020 and agreed by the 74 Member Nations of the Association, considered the uncertainty about the control of the coronavirus pandemic a risk that required a decision to take cancellation action earlier rather than further into the physical staging processes. The ITA will instead stage virtual events of its own during 2021 and anticipate that a gathering at the WTC 2022 in Copenhagen will be possible.

At its virtual General Assembly for 2020, the representatives of the 78 Member Nations of the International Tunnelling and Underground Space Association (ITA) took vital decisions on behalf of the membership.

www.TunnelTalk.com

As well as the a vote to cancel the WTC of 2021 in Copenhagen and move it to April 2022, the financial and social consequences of having to cancel the physical WTC in 2020 in Kuala Lumpur at the last minute was clearly explained in a presentation by ITA Executive Council Vice President Arnold Dix, Australia, who represented ITA in cancellation negotiations with IEM, Institution of Engineers Malaysia.

Dix explained how the ITA agreed to forego the financial revenues that the annual WTC events accrue for the ITA and its operations in efforts to secure for delegates, exhibitors and sponsors a 70% refund from IEM for the cancellation of the physical events in May and in September and for transfer to the virtual alternative. For ITA the WTC2020 loss is a lump sum of €50,000 plus a percentage of the event revenues. WTCs are the greatest contributor of operating revenues to the Association with WTC2019 in Naples, Italy, reported as contributing the most, in financial terms, of any previous WTC. After paying the 70% refunds, the losses in unrecoverable expenses for the event will be 1.2 million MYR, about €250,000.

Dix explained that the ITA is not a party to any of the commercial or financial arrangements of a WTC, that these are entirely under the auspices of the event organisers and the jurisdictions of the host countries. Several Member Nations asked if the financial report by IEM had been audited and why it was not a 100% for the refunds.

ITA President Jenny Yan, China, said that everyone had suffered under the necessary cancellation circumstances, that lessons had to be learned from the crisis, and asked the IEM to share the financial numbers with the Member Nations.

ITA First Vice President Lars Babendererde, Germany, explained the impact of the cancellation of the WTC 2021 event in Denmark on the sequence of future WTCs. Rearrangement of the Copenhagen WTC in Denmark to April 2022 was made possible by the agreement of Member Nation Mexico which had been selected at the WTC2019 General Assembly in Naples, Italy, to host the Congress in Cancun in 2022. Mexico explained that it did not forego its selection to host a WTC but that it would need to see the new rules to be applied before making a full commitment.

Having voted to cancel a WTC in 2021, savings in expenditure centres for the Association would be required to adjust for reduced revenues. The budget forecasts, with expenditure reductions, illustrated that the Association could maintain a positive balance, albeit with a reduced revenue of by as much as 40-50%, from approximately €800,000 to about €500,000.

Other items of business at the virtual General Assembly included two changes to the bylaws. The first change is that all Member Nations must prepare and submit an annual report on the activity of the Member Nation representative society or organisation and a report on the tunnelling and underground infrastructure planning and construction activity in the country; and The second change is that only Member Nations who have paid the Member Nation subscription to the Association

by January of each year will have the right to vote at the year’s General Assembly.

There were reports also from the Governance task force convened in 2019 to review the operation of the Association as a one-off investment, and a report setting out the strategy for the development of the Association for the coming three years.

At its extraordinary February 2021 General Assembly, a report by the Executive Council task force reviewed the rules for presenting proposals to host WTCs and the criteria for managing the events.

ITA Vice President Randy Essex, USA, as leader of the task force, presented a report for the proposed changes for bidding for and hosting WTCs and explained that the coronavirus pandemic, and the WTC2020 in Kuala Lumpur, brought to light further considerations for the review.

Greece was selected to host the WTC2023 after winning by 33 votes to 14 in a head to head with Turkey. The 49th annual gathering of the WTC is to be hosted by The Greek Tunnelling Society and held in Athens at the Megaron Athens International Conference Centre from 12 to 18 May 2023 with the theme Expanding Underground. n

References • • •

A new era begins for ITA at WTC2019 Naples, Italy – TunnelTalk, May 2019 Steep curve ahead to keep ITA relevant – TunnelTalk, May 2016 See article and video reports of all previous WTC events from Agra, India in 2008 in the TunnelTalk Archive

www.TunnelTalk.com

Organized by the

Greek Tunnelling Society (GTS)

WTC 2023 Expanding Underground knowledge & passion to make a positive impact on the world

12-18 May

WTC 2023 - Athens

@AthensWTC2023

WTC 2023 - Athens

@2023Wtc

Professional Congress Organizer: +30210 6833600 +30210 6847700

info@athenswtc2023.gr www.convin.gr

2020 Canadian TAC Awards

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HONOURS & AWARDS

n its 2020 annual awards, TAC, the Tunnelling Association of Canada, recognized outstanding achievements by individuals and projects in different parts of the country.

The Lifetime Achievement Award honours the long career of Rick Staples in recognition of his involvement with numerous projects over the course of four decades in the industry and his support of TAC, including being President of the Association during the highly successful World Tunnel Congress of 2010 in Vancouver, and representing TAC and Member Nation Canada in the ITA International Tunnelling and Underground Space Association.

Two young engineers, Connor Langford and Andre Solecki, are recipients of the 2020 Young Tunneller of the Year Award. Having selected careers in the underground engineering field, Langford and Solecki have been involved in leading projects in Canada, filling roles of responsibility and showing leadership for the successful management and execution of underground works.

Three mined stations of the Eglinton Crosstown LRT project in Toronto won Project of the Year of more than CAD$100 million. Design, excavation and construction of the Laird, Avenue and Oakwood Stations is an outstanding success for the Crosslinx Transit Solutions Joint Venture of Dragados, AECON, Ellis Award video for Eglinton Crosstown LRT, Toronto Don and SNC Lavalin, its design engineers Dr Sauer and Partners and gGravity, and for the project client Metrolinx.

The Project of the Year Award of up to $100 million went to the Riverside Stormwater Interceptor in Saint Lambert, Quebec where contractors and consulting engineers Ward & Burke Microtunnelling, Les Watch the video  Entreprises Michaudville,

TunnelTalk reporting CIMA+, Golder, Hatch, ABS and the client la Ville de Saint-Lambert used microtunnelling pipejacking to complete a section of the interceptor under the foundations of a road and a railway bridge.

The Canadian Innovation Initiative Award went to the teams that completed the McLoughlin Point Wastewater Treatment Plant Cross Harbour Force Main and Outfall in Victoria, British Columbia. The Harbour Resource Partners of the Aecom, Graham Construction Joint Venture, Michels and the CRD, completed the project successfully using horizontal directional drilling for the cross-harbour force main and microtunnelling for the effluent outfall.

TAC The 2021 Awards will be presented at the 2020 Vision Underground conference in October 2021. n

References •

Videos: Canada honours global input to its national fabric – TunnelTalk, October 2019

Richard Staples; Connor Langford; Andre Solecki

UCA honours in USA

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utstanding contributions and achievements are recognised by the UCA Underground Construction Association of the USA. John Reilly, Henry Russell and George Williamson receive 2020 Lifetime Achievement Awards, Dr James Mahar is recipient of the outstanding Educator of the Year Award, Gary Almeriras receives the Outstanding Individual and the Regional Connector for the Los Angeles Metro is recognised as the Project of the Year.

John Reilly developed the Cost Estimate Validation Process that bases real out-turn cost of a project within a range of lower, when everything progresses according to plan with no, or few, unexpected changes, to higher when the worst case scenarios on a risk register are encountered. The concept has been applied to several projects including the SR99 TBM highway tunnel project in Seattle and the new runway and terminal at the Lima airport in Peru. John, a native of Australia, remains committed to the international tunnelling industry through his work for the UCA and the ITA.

Henry Russell is known through his current employment with Mott MacDonald and before that with Parsons Brinckerhoff.

His specialist field is in the maintenance and rehabilitation of underground infrastructure in which he has designed and managed many projects in the USA and abroad. Henry also maintains an active role in the UCA and the ITA where he is Animateur of its Working Group 6 on Maintenance and Repair.

Through his expertise in the underground construction industry, George Williamson has promoted the introduction of innovative technologies from Japan and Europe. Through his long career with Traylor Bros, he was instrumental in particular in the introduction and development of pressurised facecontrol TBMs and high specification bolted and gasketed one-pass segmental linings to many projects in the USA. The north-east seaboard is the career home-base for construction engineer Gary Almeraris. As the Vice President of Operations for construction contractor Skanska USA in the north east and its leading underground expert, Gary

John Reilly; Henry Russell; George Williamson; Gary Almeraris; James Mahar

TunnelTalk reporting has overseen major infrastructure in the regions for rail, road, metro, water supply and wastewater management.

As a senior lecturer in the departments of civil engineering and geosciences at the Idaho State University, Dr James Mahar is awarded Educator of the Year. He is also a visiting Assistant Professor in the Department of Civil Engineering at the University of Illinois at Urbana-Champaign.

Dr Mahar is known for his teaching of students in the fields of engineering geology and underground construction and how these subjects apply to real underground infrastructure.

Safe excavation of TBM drives, deep open cut excavations, an SEM (sequential excavation method) crossover cavern as an alternative to open cut, the first SEM operation in Los Angeles, and complex underpinning of historic buildings wins for the teams of the Regional Connector metro project in Los Angeles the UCA 2020 Project of the Year Award. The project has been recognised with several awards including the Project of the Year of the ITA 2019 Awards with a budget between €50 million and €500 million. The project introduces new excavation methods and underground excavation technologies to the Los Angeles region where many new transit and underground projects are in development. n

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Video: Achievements celebrated in 2019 ITA Awards – TunnelTalk, November 2019

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Major project of 2020: Sydney Metro City & Southwest Line

ITA Awards hail international achievements

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he most ground-breaking innovation, achievements and outstanding projects in the international tunnelling and underground space industry are celebrated each year by the ITA Awards of the International Tunnelling and Underground Space Association. After a challenging year, especially on safety issues, the 2020 ITA Awards conference event and announcement of the winners of the eight categories took place online.

Congratulations to the winners and finalists for each of the eight categories and to all who took part.

Major Project of the Year + €500 million John Holland/CPB/Ghella JV took the top award for the TBM tunnelling and station excavation works for the Sydney Metro City & Southwest Line Project in Australia.

The new line from Chatswood through to the Sydney CBD to Sydenham and Bankstown included TBM drives under Sydney Harbour, roadheader excavation for large station caverns and 57 cross passages. Five TBMs completed 15.5km of twin segmentally lined running tunnels using a slurry Mixshield for the twin drives under the Harbour.

TunnelTalk reporting Fellow finalists: • Ryfast, construction of the longest sub-sea road tunnel in the world, Norway • Yanqing to Chongli expressway Jinjiazhuang spiral tunnel project, China Project of the Year up to €500 million The Chinatown Station of the San Francisco Central Subway Program was recognised for its excavation beneath the narrow streets, historic buildings,

numerous utilities and through poor ground conditions. The main station cavern at 192m long x 16.7m wide x 13m high with an excavated cross section of 202m2, is one of the largest excavations in poor ground and soil-like materials in the USA. Off street access enabled SEM excavation of the station cavern in two directions, running as many as four operations.

on the Nyingchi-Lhasa section of the Sichuan-Tibet railway, China • High performance EPB excavation in mixed face and variable ground with up to 7 bar groundwater pressure, Mexico

HONOURS & AWARDS

Fellow finalists: • Uma Oya multipurpose hydro development project, Sri Lanka • Large scale underpass using multiple construction methods at Banxuegang hightech-city, China • Micangshan Expressway Tunnel, China Renovation and projects up to €50 million Presented to two finalists. For the FEDRO renovation method in Switzerland, a new non-reinforced primary lining was cast in an operating road tunnel using night shifts and keeping all traffic lanes open during the day.On the Lower Otta hydropower project in Norway, works included excavation and construction of an intake structure with a 200m2 trash rack area and two intake gates; 10km of 90m2 unlined headrace and tailrace, surge shafts upstream and downstream, and a 65,000m3 powerhouse with 15,000m3 of concrete works. The project was based on a virtual design and construction (VDC) process where a digital twin was established and construction was performed directly based on BIM and without production of 2D drawings.

Fellow finalists: • Nord Stream 2 trenchless microtunnelling shore crossing by Züblin, Germany • Subway station construction in a complex environment, China Technical Innovation of the Year Presented to the developers of an automated geological forward-prospecting technique mounted on hard rock TBMs and applied in China. The active-source seismic prospecting system is coupled with a realtime forward- prospecting technique using TBM drilling noise to realize accurate 3D

Battered drilled shafts as permanent ground support in San Francisco imaging of faults and fractured zones within a 120m range. Through remote control, automatic data is available within 10 minutes and TBM construction activities will not be influenced. The technique has been applied on 21 engineering projects of a total 67.42km without missing any major disaster sources.

Fellow finalists: • Digital condition assessment of Brunel brick tunnels, UK • GB-InSAR system for real-time face safety monitoring, Italy • A laser-guided profiling system for conventional tunnelling, Spain Overcoming the challenge The Chengdu-Guiyang high-speed railway project in China encountered a giant karst cave and an underground river in the Yujingshan mountain crossing (see p99). The 50m-120m high x 95m long x 230m wide karst feature at 60m below the ground surface was 1.08 million m3 with the 18km long underground river flowing through it. An integrated tunnel + bridge structure was the selected solution with a groundwater system constructed to manage the underground river, seepage through fissures and rainy-season floods.

Fellow finalists: • Working under 89.3°C ground temperature in the Sangzhuling tunnel

Project of the year: Chinatown Subway Station, San Francisco, USA

Oddities of the underground Hidden beneath historical Jerusalem are archaeological sites of more than 3,000 years old. Tunnel design and building expertise in soft ground and archaeological fill was required to proceed with the excavations and make the site accessible to the public. Excavation is carried out using custom-made drill machines adapted to small spaces and steel ribs and steel plates as temporary and permanent support. Unexpected finds can lead to sudden changes in the direction of excavation, often accompanied by low overburden and difficult ground conditions.

Unlike conventional excavation in which the muck is removed, the nature of this project is to keep the muck for further research by scientists.

Fellow finalist: • The Drammen spiral tunnel – Norway Innovations for use of Underground Spaces The open-cut Union Square/Market Street Station in San Francisco, USA, applied battered drilled shafts as permanent ground and excavation support of the station that include a 400ft long concourse and platform box at about 100ft below the street. With the battered piles at about 140ft deep, the ingenuity was installing the battered shafts in the limited space between the segmentally lined TBM tunnel, that was pre-excavated through the station zone, and the property line either side of the Market Street.

Fellow finalists: • Oil reserves caverns, Padur, India • Shenzhen integrated traffic hub, China Young Tunneller of the Year Awarded to Josh Barry of Australia from among his fellow candidates who are all congratulated for the careers they are establishing in their particular specialities and home countries: Laurence Delplace, Belgium; Dimitrios Litsas, Greece; Sandeep Singh Nirmal, India; Qingfang Liu, China.

Josh started his career at Aurecon as a student engineer in Melbourne in 2007 after returning from an exchange programme in geotechnical engineering in Canada at the University of Waterloo. This interest was furthered through a move to Hong Kong in 2011 where Josh Barry he took on challenges on the South Island Line. In 2016, he moved to Bangkok where he created and led the first Aurecon tunnel team in Thailand. n

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See reports on all past ITA Award recipients on www.TunnelTalk.com

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Global dilemma of nuclear waste management which generates its own volumes of nuclear and contaminated waste. For the purposes of storing or disposing of waste, the thermal heat generated by nuclear waste is as much of an issue as its radioactive level.

Nuclear material can emit temperatures of 200-250ºC and controlling the build-up of heat in the management of waste is a significant design consideration.

The greatest volume of civil-use nuclear waste is generated by the nuclear power industry. According to the WNA, there are 440 operating nuclear power reactors today in 31 countries. These operating reactors have a total installed electricity producing capacity of 2.653 trillion kWh and represent about 10.5% of the world electricity generation.

“The consensus... is that the safest place for the storage of nuclear waste of all levels is underground” Others are being planned, are in construction, or ready to come online. These include the first floating nuclear power plant, the Akademik Lomonosov in Russia. “It is one of the first of the new type of smaller reactors that will bring nuclear energy to smaller grids and for different applications,” said John Lindberg of the WNA. Countries building their first nuclear power plants to add to the 31 countries with nuclear power generation include the United Arab Emirates, Belarus, Turkey and Bangladesh. There are plans also for the first schemes in Egypt and Uzbekistan.

“Of all the used fuel discharged from reactors, about one third has been recycled, with the remainder kept in storage pending either reprocessing or final disposal,” said Lindberg. “The reprocessing of nuclear materials is a well-established practice in France, Russia and the UK and there are innovative reactor designs being developed that can use up to 97% of the fuel, compared with about 3% in current reactors,” he added.

Shani Wallis, TunnelTalk The consensus among scientists, engineers, users of nuclear materials and the general public, is that the safest place for the storage of nuclear waste of all levels is underground. The potential for design, excavation and construction of underground waste repositories is tremendous.

The UK, which commissioned the world’s first fully operational nuclear power plant at Calder Hall at Windscale in England in 1956 and currently has 15 operating nuclear power reactors, had a radioactive waste inventory of 133,000m3 in early 2019.

Underground facilities to hold these existing and projected volumes of nuclear waste require labyrinths of expansive scale.

The question as to why these underground facilities for the long-term storage of nuclear waste are not in construction or already constructed is a question of politics. While the IAEA and the WNA coordinate expertise from across the world to inform global policymaking for the management of nuclear waste, their member nations all make their own decisions and policies.

In the case of the UK and other democratic government countries, the hosting of an underground storage facility has to be on a voluntary basis. This is a notoriously difficult process to promote and market from a national government perspective, leading to a state of inertia.

It is the thankfully rare occasion of accidents and disasters in the nuclear industry that concentrates political attention and moves the debate. The disaster of the Chernobyl power station in 1986, and the disaster of the Fukushima power plant after the catastrophic tsunami of March 2011 in Japan, raised public awareness and had the direct effect of leading the people and Government of Germany to close eight of its 17 nuclear reactors immediately and to begin decommissioning of them all by the end of 2022.

That the industry can design, excavate

FOCUS: NUCLEAR WASTE MANAGEMENT

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he world has been living with a nuclear environment for more than 75 years, for defence, for power generation and in the fields of science, research and medicine. As the amount of nuclear material and the waste it generates has grown exponentially, the long-term management of the spent and decommissioned nuclear fuel and contaminated materials remains an issue that lies interminably stalled in many nuclear countries.

It is difficult to investigate the scale of use, waste generation and management in the nuclear defence industries, which the consensus for all around the world assumes, despite international limitation agreements, is still significant. The same data for peacetime industries can be researched and reported with the assistance of international associations including the IAEA, International Atomic Energy Association of the United Nations and the World Nuclear Agency (WNA).

The WNA, an agency headquartered in the UK and with a membership of international companies and organisations, promotes a wider understanding of nuclear energy by producing authoritative information, developing common industry positions, sharing best practices, and contributing to the energy debate.

For the management of civil and military use waste, there are four main categories; low level, intermediate level, high level waste and spent nuclear fuel. Examples of low level waste include radioactively contaminated clothing, equipment and tools and medical tubes, swabs and hypodermic syringes. Intermediate waste comprises resins, chemical sludge and metal nuclear fuel cladding, as well as contaminated materials from reactor decommissioning.

High level waste is the highly radioactive materials produced as a by-product of the reactions that occur inside nuclear reactors and takes one of two forms with spent reactor fuel considered to be waste when accepted for disposal.

Spent fuel can also be reprocessed,

Generation of nuclear power worldwide in 2017 as recorded by the World Nuclear Agency

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Public debate to progress nuclear waste options

FOCUS: NUCLEAR WASTE MANAGEMENT

and construct underground spaces specifically for the storage of nuclear waste, there is no doubt. The references are the long road and rail tunnels excavated around the world and the impressive underground caverns excavated for the machine halls of hydropower plants and for the CERN particle physics research laboratory in Switzerland. It is often wondered why nuclear reactors are not also built into underground caverns.

Feedback from Nick Barton, Independent Consultant The article presents the suggestion of building nuclear power plants and their reactors underground. Selecting the geological locations would be difficult, significantly less than the geological study and investigation for siting a nuclear waste repository, but technically it is possible. The underground location of reactors would have huge safety bonuses and we know that caverns of 50m span in moderate to good rock are of limited problem.

For operation of nuclear power plants underground, an artificial lake with sufficient area for cooling lagoons, and entry into rocky hillsides to no more than 100m-200m vertical depth are not insurmountable siting targets. Q-values of the host rock would need to be reasonable.

As an example of what is possible underground, we can refer to the Baihetan hydropower project in China where they have such huge machine halls beneath either side of the fast flowing Jinsha River to generate electricity via 16 x 1,000 MW capacity turbines. The machine halls measure an outstanding 453m long x 35m span x 89m high. The caverns are currently the largest in the world.

Feedback from Markus Klein, Berkshire Hathaway Specialty Insurance, Australia Liabilities for the safe and secure disposal of nuclear waste are sitting not only with parties involved in operation of nuclear (fission) power plants and spent nuclear fuel recycling plants but also, to a certain degree, with the insurance/reinsurance industry and the states, representing nuclear re/insurance pools. It is complicated.

The question here is, these stockpiles of nuclear waste are not popping out of the blue, right? Has the whole supply and responsibility chain been thought through thoroughly in the first place?

Tunnel industry professionals know much better and in far more granular detail than I, what an interpretative geotechnical report entails, and exactly as the name says, there is interpretation of certain facts and figures and there is likely to be more than one interpretation on hand.

At this stage I would not bet on an international treaty, agreed and signed, to tackle nuclear waste underground deposit solutions in the next 10-20 years, unless political pressure piles up to deliver on reducing greenhouse gases in the absence of nuclear fusion technology, and the renaissance of nuclear fission. n

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Waste management at Yucca Mountain – TunnelTalk, May 2002 Spectacular excavations for physics research – TunnelTalk, August 2001

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Example of policy factors for long-term management of nuclear waste

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arious countries are at various stages of progress in implementing nuclear waste management strategies, including development of geologic repositories, interim storage facility, and/or fuel recycling.

Until recently, the construction of long-term deep geologic repositories has been the subject of much public debate.

More recent advances demonstrate that long-term radioactive waste disposal practices are sustainable. Developments in Finland, Sweden and Canada show it is possible to make the technological and political decisions to move forward with geologic repository siting through constructive levels of public engagement with a potential host community.

Finland, Sweden and Canada are considered prime examples of engaging the public successfully on discussions about radioactive waste and final used fuel disposal. These public engagements are based on eight objectives of adaptability; community well-being; economic viability; environmental integrity; fairness; public health and safety; security; and worker health and safety.

In Finland, the effort surrounding disposal of high-level waste has been ongoing for decades, with the examination of four different sites taking place between 19932000. In 2001 a location had been selected, and excavation work for a deep underground rock characterisation and research facility began in 2004. In 2015, the Government of Finland issued the construction license for the final waste repository, with start of operations expected in the mid-2020s.

The Onkalo site follows the Swedish disposal concept of isolating the used fuel in copper placement canisters, covering the canisters with bentonite clay, and sealing the repository without the possibility of retrieving them once all waste placement activities are complete.

The expected combined length of tunnels and shafts at Onkalo in Finland will total approximately 9.8km.

Sweden has not only managed to successfully engage the public on site selection for a final deep geologic repository, but also currently operates facilities for low and intermediate-level waste, deposited in rock vaults at the Forsmark facility, which was commissioned in 1988.

The total length of the tunnels at Sweden’s proposed final geologic

John C H Lindberg FRSA, World Nuclear Association, UK repository, developed by the Swedish Nuclear Fuel and Waste Management Company would be some 66km in which the repository occupies 3-4km2 underground. Following emplacement of the used nuclear fuel canisters, the tunnels and rock caverns would be sealed permanently. Construction is expected to start in the mid-2020s with placement operations to begin about 10 years later.

The technological approach for the proposed geological repository in Canada is to first store the used fuel bundles in wet storage at the reactor site for five to 10 years. The fuel is then placed into concrete and steel containers for interim storage by the power station operator under its operating license, until a permanent disposal facility is sited, constructed, licensed and in operation.

Since the early 2000s, the Nuclear Waste Management Organization of Canada has studied proposals for a deep geologic repository at between 500m to 1,000m deep in the stable Canadian Shield rock formation with waste containers stored below the water table and surrounded by bentonite clay. Unlike the Finnish and Swedish concepts, Canada proposes to design its storage capability with the potential for retrieving the waste. The capacity for retrieval is planned to be exercised until future generations have confidence in the waste storage system or determine other routes of waste management to explore based on future technologies. By 2023, Canada expects to narrow the list of interested possible host communities to determine a final site and to begin operation in the mid-2030s.

Public debate for progress

For nuclear power to maintain its social license to operate, the technical and political decisions surrounding radioactive waste management must be resolved.

Public debates leading to an increase of public acceptance for proposed radioactive waste management solutions is demonstrated in the successful public involvement for repository siting in Canada, Finland and Sweden, with their positive projected path towards completion.

Several other nations are also engaged in developing a deep geological

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Starting in the early 1990s, the National Agency for Radioactive Waste Management (ANDRA) in France began to study the suitability of two rock types - argillite and granite. The stiff clay rock argillite is approximately 155 million years old and sits in the Callovo-Oxfordian area at a depth of 400m to 600m. Experiments at the Meuse Haute-Marne laboratory have generated scientific information to ensure that the clay layer of the Callovo-Oxfordian provides the desired properties for a disposal facility, with numerous deep bore-holes having been drilled since 1994. Commissioning of the proposed Cigéo geologic disposal facility is programmed to occur before 2035.

Japan

The disposal facility in Japan is envisioned to be constructed in a stable rock formation more than 300m underground, with proposed host rock types to include crystalline and sedimentary rocks. While geologically and structurally comparable to similar terrains elsewhere in the world, the siting of a GDF in Japan is complicated by the seismic activity in the country. In 2017, Japan published a map of possible locations for the siting of a national nuclear geologic storage Underground geological laboratory, Japan

facility, based on a number of scientific characteristics and parameters. Tests have been conducted at a depth of 500m at the Horonobe Underground Research Centre, as well as at a depth of 1,000m in igneous rock at the Tona Geoscience Centre. Japan expects to initiate the site selection process in the later 2020s with start of operation projected at 2040.

Germany

The proposed disposal facility in Germany was to be sited at Gorleben. Exploratory activities performed at Gorleben were analyzed and their results published, confirming the potential suitability of the favorable properties of the rock salt formation at this location. Initial exploratory work at Gorleben began in 1979 with exploration drilling activities conducted over an area of about 300km2 based upon results from seismic investigations in the 1930s and 1950s conducted by the oil and gas industry.

Exploratory work continued at the site during a twenty-year period, concluding in 2000 when 11km of exploration boreholes and geotechnical wells were drilled to investigate the material and structural condition of the salt dome.

With the adoption of the StandAG Repository Site Selection Act in 2014, the Gorleben site is to be treated like any other possible site in Germany during a new site selection process, which is expected be concluded in the early 2030s.

United States of America

Source: Horonobe Underground Research Centre

The proposed Yucca Mountain site for disposal of high-level, long-lived nuclear waste in the USA is often referred to as the most studied piece of real estate on the planet. In 2002, then Secretary of State for Energy Spencer Abraham provided the USA Congress a comprehensive report providing extensive detail on the work conducted at Yucca Mountain, and a voluminous Environmental Impact Statement. This report demonstrated that the proposed repository would have little to no adverse effect on future populations or the environment. Collected and analyzed data from some 8 miles (13km) of test tunnels and 450 boreholes drilled

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deep into the mountain were obtained to study the rock, water movement, and susceptibility to earthquakes of the proposed repository.

The Yucca Mountain program ceased in 2009, by then President Obama. Under his direction, a Blue Ribbon Commission on America’s Nuclear Future was established and in 2012 it submitted its final report on recommendations for the USA nuclear waste management program. The next phase of the process is for the current administration and Congress to determine a path forward.

Scope of the projects

Exploratory activities at proposed GDF sites are providing a wealth of valuable scientific information and learning experiences. However, ensuring that proposed GDFs around the world are able to be constructed will require that this knowledge is retained and that related GDF projects have access to educated, creative and skilful practitioners over many decades. These construction projects will use modern technology and highly sophisticated equipment methodologies based on previous exploratory studies.

Individuals with sought after skills will include, but are not limited to, those with knowhow to excavate into a host geology, prepare short and long-range plans and production sequences, select and schedule needed equipment, monitor the safety of personnel and equipment, and optimize all site processes.

The scope of excavation work needed to establish the underground facilities required for the safe long-term disposal of the volume of high-level nuclear waste that already exists is on an expansive scale. With one repository currently nearing completion, and alternative disposal methods, such as deep horizontal boreholes, being developed, the future in nuclear waste management looks promising. n

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France

Used fuel held in a pool at a Canadian nuclear power plant

Source: Canadian Nuclear Safety Commission

disposal facility to isolate radioactive waste and used nuclear fuel in stable formations over extended time periods.

An operating disposal facility satisfies both societal and industrial needs in terms of having a management strategy in place. The availability and suitability of igneous crystalline and volcanic rocks, argillaceous clay rocks and salts is being explored. Though complex, the designing and construction of a geologic disposal facility (GDF) is founded on the knowledge and practical experience gained in the underground civil engineering and mining industries over hundreds of years.

The siting of a GDF is dependent on the prevailing geological conditions and their availability and suitability of the purpose with various exploratory investigative methods being used to gain the required scientific verification that host rocks are suitable for constructing the necessary or proposed facilities.

References • • •

Author references can be found on the full length article on TunnelTalk.com Waste management at Yucca Mountain – TunnelTalk, May 2002 In search of resilient cities – TunnelTalk, December 2011

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Akademik Lomonosov, the world’s first floating nuclear power plant, will permit decommissioning of the Bilibino power plant site in the Chukotka region

Russia to improve nuclear waste management

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he Russian Government is designing a package of measures aimed at improving the current system of nuclear waste management and reducing the volume of accumulated nuclear waste. According to statements by senior officials of the Russian Ministry of Energy and industry analysts, implementation of these plans is part of the existing Federal program entitled Ensuring Nuclear Radiation Safety for implementation during the period to 2030.

The end of World War II, and the beginning of an active development of nuclear power generation in the USSR, and later Russia, resulted in a significant increase of the volume of accumulated nuclear waste in the country. Most of this waste has never been the subject of any disposal or treatment in the country. The present volume of accumulated nuclear waste in Russia is estimated at a total 500 million tonnes.

According to Dr Olga Ulybina, a senior researcher at the German Center for Social Research (WZB), management of nuclear waste is complicated by the variety of civil, military and experimental nuclear reactors which were used in Russia and the earlier USSR. The existing program involves the establishment of at least 10 sites of final radioactive waste isolation in Russia by 2025. These sites will be designed for the disposal of about 80,000m3 of solid radioactive waste material. One of the largest of the sites is on the base of the Mayak plant, a facility established in 1945 in Ozersk, a closed city in the province of Chelyabinsk Oblast, for the production of weapons-grade plutonium. The new complex will have the design capacity of 2,000m3 of waste/year and will be capable of recycling solid nuclear waste of all categories.

The national program also involves the complete suspension of the release of radioactive effluent and the closure of at least six of the existing sites for their storage.

At present, the storage of nuclear waste in Russia is carried out mainly in temporary storage facilities. The total number is currently estimated at 140 industrial sites and 1,466 temporary storage points located in 43 regions of the country. Most of the waste is stored in metal or concrete containers or tanks, at ground level or underground, and in outdoor pools for liquid radioactive waste.

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Spent fuel is usually stored at power plants, in reactor storage pools, as well as on vessels servicing nuclear icebreakers. There are also a number of on-shore facilities. The majority of these facilities are operated by the Russian Government monopoly of the nuclear industry Rosatom.

A spokesman for Alexander Novak, the Russian Minister of Energy, said a significant part of nuclear waste in the country is stored on the seashore in a number of special naval bases built along the Russian coast from the 1960s. Most of these specialize primarily on the storage of spent fuel from nuclear submarines, as well as liquid and solid radioactive waste. Currently Rosatom is working on the reconstruction of some of these coastal bases and the decommissioning of old ones. The situation, however, is complicated by the fact that many of these nuclear submarines, reactors and containers were flooded in the Kara Sea and the Pacific Ocean during the Soviet times.

As the presence of long-lived isotopes is associated with the need of extremely long-term storage of nuclear waste, up to hundreds of thousands of years, Russia plans to continue the practice of pumping liquid nuclear waste into rock formations as an alternative method of waste disposal.

The method was first introduced more than 50 years ago and was practiced also in the USA until 1984.

One of the sites operating the practice currently is located within the city of Zheleznogorsk, a closed town in the Krasnoyarsk Krai region, where such nuclear waste is pumped into porous sandstone layers and blocked by clays at up to 400m deep.

There are also plans for the development of new, more advanced methods for the management of nuclear waste and its disposal. These include deep geological disposal facilities in stable rock masses at between 250m and 1,000m deep for mined repositories, and between 2,000m and 5,000m deep for blast-holes.

As part of these plans, Rosatom is establishing an underground laboratory at more than 500m depth in the Krasnoyarsk Territory. Implementation of these plans is scheduled for the period of 2021–2030.

The repository is being where scientists will be able to implement a control for the compliance of these works with safety requirements.

Eugene Gerden for TunnelTalk In the meantime, other options for the long-term storage of nuclear waste in Russia are being considered. For example, in the case of remote nuclear power plants such as the Bilibino plant located in Chukotka, there are plans to build a special terminal for the final isolation of radioactive waste. It is planned that these works, and the future storage of nuclear waste at the site, will be carried out in the conditions of permafrost. According to experts of the Russian Ministry of Energy, in the short term, permafrost ensures the lack of water movement and slows down chemical reactions, which increases the design life of engineering barriers. However, with climate change the effectiveness of such storage facilities will significantly decline.

At the Bilibino power plant site, there is a possibility of the beginning of the gradual decommissioning of the plant. That will be mainly due to the recent commissioning of the world’s first floating nuclear power plant the Akademik Lomonosov by the Rosatom Corporation in the Chukotka region. The new plant is comprised of coastal infrastructure and a floating power unit, which is equipped with two KLT-40S reactors with a capacity of 35 MW each.

The thermal capacity of the new plant is 50 gigacalories/hour. In the long-term, the new plant will become the main source of energy for the Russian Chukotka Republic.

In addition to State plans to build facilities for storage and disposal of nuclear waste, there is the beginning of the re-use of at least part of the waste for various purposes in Russia. Advance of the technology will establish a closed nuclear fuel cycle in Russia.

According to State plans, investments in the implementation of the existing State program in Russia is expected to reach RUB 399 billion (US$6.6 billion), the majority of which will be provided from the Russian Federal Budget with extra-budgetary sources and private investments.

There is however, a possibility that implementation of the plans may be prevented by the plans by Russia to resume imports of nuclear waste after a pause period of almost 10 years. According to recent announcements in German and Russian media, imports will take place on the basis of fuel lease agreements for the purpose of their further processing, storage or disposal. n

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Disposal programme for UK radioactive waste

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Ashley Marsh, Department of Materials, Professor Laurence Williams OBE, Department of Materials, Dr James Lawrence, Department of Civil and Environmental Engineering, Imperial College London at various stages of the programme.

These include cut-and-cover, TBM, roadheader and drill+blast techniques.

The lining required for excavations is an important safety consideration.

Excavation support is required to be maintained and serviceable for up to 160 years throughout construction and operation. Steel mesh and rock bolts are likely to be employed in all three settings.

In HSRs and LSSRs, shotcrete has been developed for incorporating into the lining, which exhibits low accessible gas porosity and permeability of ~10-17m2.

The process to search for a suitable GDF site has been launched in England and Wales. In 2020 RWM released its guide as to how it will evaluate potential host sites in England. This guide addresses: • legal concerns, • siting process and land use planning requirements, • siting factors, and • evaluation considerations.

It also shows how RWM plans to move through the siting process with interested parties. The process is built on the premise of voluntarism whereby only those communities expressing an interest in hosting a GDF will engage in the process of site identification and selection.

Initial discussions with interested parties will be informed by data gathered as part of the National Geological Screening process. It is expected that RWM will form a number of working groups, along with willing interested parties, to identify the geographical areas suitable for a GDF. At present RWM is engaging with a number of communities in the hope of developing working groups in multiple locations from which community partnerships will emerge. n

FOCUS: NUCLEAR WASTE MANAGEMENT

either England or Wales. For each geological setting RWM has developed or adopted a number of generic repository designs.

Each design considers the challenges in excavating that particular geology along with the waste streams to be emplaced. Both considerations are reflected in the respective GDF footprints. The maximum extent of a GDF in HSR is anticipated to span an area of approximately 7.6km2. In evaporites, the area is up to 10.6km2 and in LSSR, the illustrative design has a footprint of 15.3km2.

This assumes that at some time in the future spent nuclear fuel (SNF), as the irradiated fuel removed from a nuclear reactor at the end of its useful life, is declared as a waste.

The illustrative designs developed and/or considered by RWM consider the disposal of high heat generating wastes (HHGW), namely HLW and SNF and low heat generating wastes (LHGW), including ILW and LLW, in the same facility. This is reflected in the minimum separation of the disposal galleries for the concrete ILW zone of the repository and vitrified HLW and SNF zones. Irrespective of the geological setting, this minimum separation is set at 500m.

The heat output of HLW may be of detriment to a number of the GDF engineered barrier materials. In the case of concreted ILW the chemical conditions promoted in the ILW zone, as the wasteform and its container breakdown, could impact on the long-term behaviour of vitrified wasteforms. These potential interactions raise questions as to whether the co-location of multiple waste streams in a single repository, as opposed to the construction of multiple GDFs, is a viable solution. Though RWM’s current preferred policy is to build only one GDF, the possibility of having single facilities for particular waste streams has not been ruled out.

The geological disposal of HAW is a long-term programme of more than 100 years and will involve the construction of surface and sub-surface facilities.

A combination of construction and excavation methods are likely to be used

References • •

Short sighted Yucca Mountain shutdown – TunnelTalk, June 2011 Waste management at Yucca Mountain – TunnelTalk, May 2002

Overview of the UK process for siting a GDF

Credit: © NDA, 2020

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he UK has been a nuclear nation for more than 70 years and first embarked upon its radioactive waste disposal journey more than 40 years ago. It is yet to decide upon a location for its underground geological disposal facility.

In April 2019, the UK radioactive waste inventory stood at 133,000m3. It is forecast that following the decommissioning of all current facilities, it will stand at more than 4 million m3.

The UK classifies its waste according to its radioactivity and heat generation and in the categories: high-level (HLW), intermediate-level (ILW), low- and very lowlevel (LLW/VLLW). Of these, high level and intermediate level waste are known as higher activity waste (HAW). In England and Wales the policy for the long-term management of this type of waste, along with a small proportion of low-level waste, is disposal in a deep underground geological disposal facility (GDF). Conversely, Scottish Government policy favours near-surface disposal of waste. In Northern Ireland, where no higher activity radioactive waste exists, there are currently no plans to site a GDF. HLW results from the vitrification of fission products from the reprocessing of spent nuclear fuel. ILW currently arises from nuclear fuel cladding, a wide range of nuclear power plant items, equipment, materials and flocculants, all of which are encapsulated in concrete. A small amount of LLW that is deemed unsuitable for near surface disposal is also to be disposed of in a GDF. The GDF will be constructed at a depth of between 200m and 1,000m below the ground surface. It will be designed as an engineered facility, within a stable geological setting, to provide containment and isolation of radionuclides from the biosphere for upwards of 100,000 years.

The GDF will be designed to contain the waste and enable the radioactivity to decay to very low levels. Within the GDF, the goal is for the radionuclides contained within the radioactive waste to be surrounded by a number of engineered barriers designed to inhibit the release of radionuclides.

In England and Wales three principal geological settings have been identified in which the GDF could be located. These are higher strength rocks (HSR), lower strength sedimentary (LSSR) rocks, and evaporites.

HSRs generally exhibit high compressive strength but demonstrate a propensity for the formation of fracture networks and include lithologies such as intrusive and extrusive igneous rocks and low-grade metamudstones. LSSRs are fine grained sedimentary rocks formed by the deposition of grains, generally underwater, and are mechanically weaker than HSRs, but have self-sealing or creep tendencies. Evaporites are water soluble mineral salts that resulted from the evaporation of saline bodies of water. This geology creeps readily and provides an extremely arid, low permeability and low porosity environment.

Radioactive Waste Management Ltd (RWM) was created by the UK Government to be responsible for delivery of the GDF in

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Aerial of north end of Yucca Mountain crest

USA nuclear waste options undermined by politics

FOCUS: NUCLEAR WASTE MANAGEMENT

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uclear energy in the USA generates about 2,000 metric tonne of used fuel each year, with a total of 84,000 metric tonne since the 1950s stored at more than 70 sites in 34 states. The country has yet to build a permanent disposal location for the spent fuel, despite the fact that a specific site for disposal on Federal Government owned land at Yucca Mountain, about 130km northwest of Las Vegas, Nevada, was written into Federal law in 1987.

The Nuclear Waste Policy Act of 1982 stated that the Federal Government would accept responsibility for spent nuclear fuel disposal from all civic energy production when a repository is operating. Politics and geological concerns, however, have prevented issuance of the licenses needed to start work on a permanent disposal facility at Yucca Mountain.

The Nuclear Energy Institute trade group said in May 2020 that taxpayers continue to pay some US$800 million annually because the Federal Government fails to meet disposal mandates. The funds pay for on-site storage of waste at reactor sites.

Plans to store 70,000 metric tonne of spent fuel at Yucca Mountain halted in 2010 when President Barack Obama canceled the project. Politicians from the State of Nevada have opposed the plan, further delaying construction. Some politicians at the County level have taken a more open-minded position. Meanwhile, spent nuclear fuel is currently stored temporarily in water-filled pools and above-ground dry storage facilities.

The area of Nevada has experienced some seismic activity, which naysayers of the Yucca Mountain facility say raises doubts about the safety of storing spent fuel at the site. The area experienced a 6.5 magnitude earthquake in May 2020, the third in the past two years within 150 miles of Yucca Mountain. Nevada officials have also gone so far as to challenge various assertions by the Federal Government about geology, hydrology and transportation risks associated with the project.

The site has two large tunnels excavated by the Department of Energy in the 1980s.

The main tunnel is U-shaped and spans five

miles x 25ft in diameter (about 8km x 7.6m) and the other is two miles long, branching off the main tunnel. The Yucca Mountain area is semiarid and has little surface water, with strong, low-permeability volcanic rock and with low levels of seismic activity. None of the earthquakes near the site damaged below ground facilities and the proposed repository has been designed to withstand much stronger seismic activity.

The proposed repository calls for a complex at about 1,000ft (300m) below the top of the mountain and about 1,000ft above an aquifer in the area (Fig 1). The mountain is formed of at least 6,000ft (1,800m) of volcanic tuff, which is volcanic ash compressed by gravity and intense heat to form solid rock.

Below the tuff is carbonate rock formed from sediments laid down at the bottom of ancient seas that existed in the area. A mix of natural and engineered barriers would isolate the waste from the surrounding environment.

“Because the Yucca Mountain site is considered unsafe for long term nuclear waste storage and disposal, and because there has been decades of bipartisan opposition, Yucca Mountain will never become the nuclear waste repository for the USA,” said Geoff Fettus, a senior attorney at the Natural Resources Defence Council nonprofit environmental advocacy group.

He continued: “If leaders in Washington want to come up with a durable solution for radioactive waste, they need to start over and provide a durable framework that gives the EPA and State decision makers a say in where, how, and how much waste is stored at various sites.” Moving the permanent storage site from Yucca Mountain, however, would require an Act of Congress.

In this stalemate of national policy making, private companies in the USA have developed their own proposals including new temporary storage sites in New Mexico and Texas, which need a license for temporary nuclear waste storage for construction to start. Federal law however may need changing to allow for the Federal Government to own the waste and pay for development costs.

Holtec International has proposed an interim storage facility, known as HI-STORE,

Wade Tyler Millward, USA Correspondent, TunnelTalk in southeastern New Mexico, about 35 miles from Carlsbad and about 12 miles from the existing Waste Isolation Pilot Plant (WIPP).

When Holtec began the application process, then-Governor of New Mexico Susana Martinez endorsed the project, which is now opposed by the current Governor, Michelle Lujan Grisham.

The HI-STORE consolidated interim storage facility, or CISF, would occupy 288 acres and stand less than 2ft above ground, storing up to 100,000 metric tonne of spent fuel about 40ft (12m) underground (Fig 2). The project would cost about $3 billion in capital investments, with construction expected to start as soon as late 2022. Opponents say such a facility would not be ready until 2048 at the earliest.

Interim Storage Partners, a joint venture of Waste Control Specialists and Orano CIS, has proposed a site in Andrews County, Texas, on the border with New Mexico. The facility would store an eventual total of 40,000 metric tonne of spent fuel on 332 acres.

The site is atop a 600ft (180m) thick bed of red clay that is ten times less permeable than concrete and limits any horizontal groundwater travel to about 1ft (30cm) per 1,000 years.

Like the Holtec facility, the project has faced political opposition. Local residents and officials have spoken out against the planned site because nuclear waste would be transported to the facility on local railways.

But the area has stored low-level nuclear waste since 2012.

Former Texas Governor and former USA Energy Secretary Rick Perry has long supported interim nuclear waste storage in the State. The current Governor of Texas, Greg Abbott, has voiced opposition to more spent fuel at the site.

A previous attempt by Private Fuel Storage for an interim storage site on Goshute tribal lands about 45 miles from Salt Lake City, Utah, was abandoned in 2012.

The Goshute people sought $3 billion for the project. Local politicians and Utah residents

Credit: Holtec;

Fig 1. Proposed Yucca Mountain nuclear waste repository; Fig 2. Rendering of the proposed Holtec facility

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Fig 3. Proposal for disposal in deep horizontal directional drilling boreholes opposed the project. The USA Bureau of Indian Affairs declined to approve the lease agreement and the USA Bureau of Land Management refused a project needed to transport waste to the site.

Final environmental impact statements for the Holtec and Interim Storage Partners concepts in New Mexico and Texas are expected from the USA Nuclear Regulatory Commission (NRC) in Summer 2021.

Opposition groups argue that the plans violate Federal law by possibly making the Federal Government own the nuclear waste before operation of a permanent repository.

The NRC continues to move towards providing licenses for 40 years for the Holtec and Interim Storage Partners facilities, with an opportunity to renew the licenses in 40-year increments. The NRC states that the USA Congress could change the law in the meantime to allow spent fuel to be stored in locations other than Yucca Mountain, making the proposals legal.

As an alternative to tunnel and cavern repositories, a startup company, Deep

Isolation, has a proposal to dispose of nuclear waste, contained in canisters, in deep directional drilling horizontal boreholes.

The corrosion-resistant canisters would be placed into carbon steel-encased boreholes and sent about a mile underground and then up to two miles horizontally (Fig 3).

The horizontal section of the boreholes would be about 18in diameter and the canisters about 18ft long x 13in diameter. A 3,300ft long disposal section would hold about 150 canisters, with an array of 10 parallel disposal sections, holding a total of 1,500 pressurized water reactor assemblies, which would accommodate the waste produced by a 1,000 MWe nuclear power plant during 30 years of operation.

The horizontal section of the boreholes could extend for up to two miles in sedimentary, igneous or metamorphic host rocks. These repositories could be installed at or near commercial reactor sites or at regional repositories in different locations. The company has raised $14 million of private

investment and has signed agreements with NAC International, Schlumberger and Bechtel to develop the technology.

Potential sites would be identified through a stakeholder and community engagement process. After a community has shown interest in moving forward, a sitespecific study of the geology, hydrology, geochemical and seismic activities of a potential host site would follow. Once the necessary license, permits and agreements with the community and State Governments are in place, placement of waste canisters in drilled boreholes could start within a few years.

While the borehole technology is considered a promising alternative to cavern repositories, the Deep Isolation team would need an Act of Congress to allow for alternatives to Yucca Mountain to be licensed. n

References •

Waste management at Yucca Mountain – TunnelTalk, May 2002

Excavation and operation of Hungary repository

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ungary is one of the first countries of the world to operate a purpose designed and built underground repository for low- and medium-level nuclear waste. The Bátaapáti complex has started the fully entombed longterm storage of low- and medium-level radioactive waste generated by the operation of the Paks nuclear power plant.

The underground repository has a planned six emplacement chambers and will have a capacity of up to 20,000m3. This waste is comprised of tools and personal protective equipment used by employees. The facility will also store waste created by the eventual decommissioning of the Paks reactors and some ion exchanger resin.

The repository at Bátaapáti is some 60km from Paks. Excavation began in February 2005 and placement of the containerised waste began in 2012. Since then, the first entombing chamber has been filled; the second is being filled; the third and fourth chambers are excavated; and excavation of two further chambers is being prepared.

The facility is established in an outcrop of granite. It has two access decline adits of about 1.7km long to about 250m below the surface where the repository chambers are aligned. One adit is used for access by the excavation operations and the other for

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vehicles that transport the prepared waste.

Bátaapáti has received international recognition for its design, construction and method of permanent waste encasement and storage.

In a 2011 paper, authors provided detailed information on the design of the Bátaapáti repository. The paper describes the excavation criteria, the rockbolt and shotcrete support requirements and the grouting regime to comply with the hydrogeological criteria.

Fully grouted 4m long IBO bolts were installed on a 4m x 4m pattern and steel fibre reinforced shotcrete with a minimum dosage of 40kg/m3 was specified.

Water inflow criteria was set at 5 litre/min/100m for the access tunnels and 5 litre/min for the full length of an emplacement chamber. Pre-grouting technology was developed to ensure that installed rock

Shani Wallis, TunnelTalk support does not reduce the efficiency of pre-grouting. Grouted zones are determined with sufficient overlap and to ensure that they cannot be punched through by rockbolts.

Both for the excavation and for the long-term design life of the facility, an array of monitoring instrumentation has been installed and applied. The monitoring results in the emplacement chambers in particular has provided valuable information for design of the additional chambers of the facility.

Development of the project at Bátaapáti is well documented in a video presentation. n

FOCUS: NUCLEAR WASTE MANAGEMENT

Credit: Deep Isolation

Credit: USA Nuclear Regulatory Commission

View of the first curve in the main drift of the exploratory studies facility at Yucca Mountain, Oct 1995

References

1. Ágnes Vááró, Botond Benö, Alun Thomas, Mott MacDonald Magyarország Kft, Hungary.

Using Underground Space Symposium, Croatia, April 2011

Layout of the storage facility and concrete emplacement structure

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Lower reservoir of Snowy 2.0 pumped storage scheme

Global review of hydropower developments

FOCUS: HYDROPOWER DEVELOPMENTS

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ydropower developments added almost 22 GW of installed capacity worldwide in 2018, according to the International Hydropower Association (IHA).

Total capacity in 2018 stood at 1,292 GW with most activity taking place in the fastgrowing and emerging economies of East Asia and the Pacific (Fig 1).

Growth was also strong in North and South America with several major projects underway in Canada. Elsewhere in the world, pumped storage is a focus with major projects including the Snowy 2.0 installation in Australia and Ataqa in Egypt.

East Asia and Pacific

East Asia and the Pacific region continue to be the drivers for global hydropower development, adding 9.2 GW of capacity in 2018. China accounted for the majority of that, adding 8.54 GW to pass 350 GW of installed capacity.

Leading the Chinese development is the 16,000 MW Baihetan project on the Jinsha River, which includes two underground caverns to house 16 x 1,000 MW generating units. Developed by the China Three Gorges Corp, the first group of units are expected to come online in 2021 followed by full commissioning by the end of 2022. Also under construction on the Jinsha River is the 10.2 MW Wudongde plant, which includes two underground powerhouses housing 6 x 850 MW turbines each.

Baihetan and Wudongde form the second phase of hydroelectric development on the Jinsha River, following phase one development of the Xiluodu and Xiangjiaba facilities. In total, the scheme will have a combined generating capacity of more than 46,000 MW. China is also investing in smaller-scale hydro and pumped storage projects as part of a nationwide shift to renewable generation and away from coal generating installations, long the dominant fuel for Chinese power generation.

Beyond China, development of the Greater Mekong region of Myanmar is advancing. The Myanmar Government has issued notices to proceed on both the 1,050 MW Shweli 3 project led by the French utility company EDF, and the 60 MW Deeoko project. Indonesia is also developing its hydropower resources with up to 6 GW under construction or in planning.

In Australia there are several pumped storage projects, notably the Snowy 2.0 project by Snowy Hydro and the Battery of the Nation initiative in Tasmania. Snowy 2.0 is expected to be complete by 2025

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to provide an additional 2,000 MW of capacity. Hydro Tasmania selected three sites in March 2019 to develop the Lake Cethana, Lake Rowallan and Tribute Power Station projects. Hydro Tasmania is now undertaking feasibility studies to determine the first site for development.

Hydro developments are being investigated in Papua New Guinea, the Solomon Islands, and on Fiji.

North and Central America

In Canada, the largest of a number of hydro projects under construction is the 1,100 MW BC Hydro Site C project on the Peace River, which requires the construction of two 10.3m i.d. concrete-lined diversion tunnels of 700m and 800m long to allow construction of the dam. Excavated using two Sandvik 115 tonne MT 520 roadheaders, the first tunnel broke through in June 2019 after 10 months of excavation, and the second followed in July. Focus is now on lining and finishing the tunnels.

The CAN$1.75 billion civil works package is being undertaken by Peace River Hydro Partners, a joint venture between Acciona Infrastructure and Samsung C&T and is expected to be complete by 2024.

Work is also continuing on the La Romaine project for Hydro-Quebec with the final 245 MW La Romaine 4 element due for completion in 2021 bringing the total capacity of the facility to 1,550 MW. The 824 MW Muskrat Falls project on the Lower Church River in Labrador and the 695 MW Keeyask project on the Nelson River in Manitoba are also in the works. In Alberta, construction of the 75 MW Canyon Creek pumped storage project, including a 7km x 2.5m i.d. long headrace, has been approved. Renewable energy accounts for about two-thirds of power generation in Canada, based largely on its significant hydro resources.

Although the USA remains one of the largest producers of hydropower, new projects are slow to progress with investment mostly focused on retrofits of existing facilities, despite the Department of Energy saying 50 GW of new capacity could be added by 2050. Some 35 GW of this would be pumped storage, such as the planned 400 MW Gordon Butte project in Montana.

New developments in Mexico have also been slow to materialise, despite ambitious goals by the Government to promote renewable energy.

In Central America, several smaller projects are underway with a number of governments developing ambitious

Jonathan Rowland, TunnelTalk plans. The Government of Honduras, for example, is planning several projects as part of a target to achieve 95% renewable energy in its power generating strategy by 2027. Throughout the region, projects face challenges from legal obstacles and security concerns. Cancellation of the 631 MW Diquís project in Costa Rica at the end of 2018 after objections from indigenous communities is a leading example.

South America

South America is one of the fastest growing regions for hydropower development in the world, adding close to 4,855 MW in 2018, despite the growing challenge posed by climate variability.

Brazil accounts for about two-thirds of installed capacity. One of the largest dams in the world, the Belo Monte Dam complex on the Cingu River in the north of the country, recently commissioned a new turbine, number 18, to bring the capacity of the installation to 11,233 MW. Belo Monta could be the last mega project in Brazil, according to the IHA, as the country moves towards a more decentralised network of renewable energy.

The 2,400 MW Ituango project in Columbia is the largest in the country and, when complete, will meet about 18% of electricity demand in the country. The project was hit by a major flood disaster in 2018 (see p31).

Projects are underway in Peru, as part of a Government commitment to become energy self-sufficient by 2024, as well as in Paraguay, Ecuador, Bolivia and Guyana.

In Chile, the 531 MW Alto Maipo project is the largest in the country and will be one of the largest underground hydropower facilities in the world with more than 70km of tunnels and two powerhouse caverns. It comprises a cascade of two run-of-river plants – the 264 MW Alfalfal 2 and 267 MW Las Lajas installations. A financial restructuring in 2018 saw the signing of a new construction contract with Strabag, after termination of the original contract with Hochtief and CMC di Ravenna. The new contract includes the excavation of 18.5km of tunnels as well as construction of the intake structures and a 5km steel pipeline. Strabag had previously been contracted in 2012 to excavate two-thirds of the underground watercourse and powerhouse works, totalling 46km of tunnels and shafts.

Four open gripper TBMs were used to

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Africa

While Africa continues to rely on oil, gas and traditional biomass combustion for power generation, hydropower is expected to grow by about 4,700 MW over the next two to three years as major projects come online in Angola, Zambia, Nigeria, and Uganda.

The 2,070 MW Lauca project in Angola, constructed by EPC contractor Odebrecht, includes excavation of six 2,000m long penstock tunnels to the underground powerhouse and six tailrace tunnels with gate structures. Construction is progressing also on the China-financed 2,172 MW Caculo-Cabaça project. The US$4.5 billion facility is being built by the China Gezhouba Group and is expected to be completed in 2022.

In Zambia, the current status of the 750 MW US$2 billion Kafue River facility is unclear. Reports in September 2019 indicated that construction had been suspended by contractor Sinohydro after the Zambian Government failed to pay.

Underground elements of the project include a flood release tunnel with a maximum capacity of 1,018m3/sec, a 4.4km power tunnel, and a 980m diversion tunnel.

Sinohydro of China is also constructing the 750 MW Zungeru plant in Nigeria, the 600 MW Karuma plant in Uganda, and the 1,400 MW Ataqu pumped storage scheme in Egypt.

The Zungeru project is on track for its scheduled completion date of December 2021. The project is financed by the Exim Bank of China, alongside the Nigerian Government. The EPC contract was awarded in 2013 to a consortium comprising China National Electric Engineering Co and Sinohydro. Design and technical services were provided by

Kunming Survey and Design Institute, a subsidiary of China Hydropower Engineering Consulting Group.

At Karuma in Uganda, underground work has been extensive and included six 238m long x 7.7m diameter tunnels, six 7.7m diameter pressure shafts, six tailrace branch tunnels, two 12.9m diameter x 8.7km tailrace tunnels, and three 12m diameter x 2km long surge tunnels.

Elsewhere in Africa, construction of the controversial 6,000 MW Greater Ethiopian Renaissance Dam continues. Mozambique, the Democratic Republic of Congo and Cameroon have also seen interest in developing hydropower plants with the 420 MW Nachtigal project in Cameroon being the largest independent hydro project in Africa. Along with the 1,800 MW Grand Ewing, the 485 MW Kpep and the 365 MW Makay projects, Cameroon has the potential to add about 3,000 MW of hydropower capacity by 2025.

Europe

With the rapid growth of renewable energy, combined with the phasing out of nuclear and traditional generating fuels, such as coal, the onus is on hydropower to maintain a secure, affordable and sustainable energy supply under the European Union Framework Strategy for the Energy Union.

Outside of the EU, recent development has taken place in Norway and Turkey.

One major project nearing completion within the EU is the EDF 92 MW RomancheGavet underground hydropower plant in France, which will replace six existing powerhouses and five dams in the valley, and increase production by 30%.

South and Central Asia

In South Asia, major projects have been commissioned in Pakistan, Nepal and Bhutan, while in India, major policy developments have been supportive of hydro. Cross-border trade agreements could

boost hydro development in the region.

In Central Asia, construction of the US$3.9 billion 3,600 MW Rogun project in Tajikistan by Salini Impregilo continues after commissioning of the second turbine in September 2019. Featuring what is reportedly the tallest dam in the world, facilitated by two diversion tunnels on the Vakhsh River, work on Rogun also includes headrace, powerhouse, tailrace, and access excavations.

There are plans to develop new stations in Uzbekistan by UzbekHydroEnergo, as well as modernising the existing installations, most of which are between 30 and 80 years old.

Modernisation work is also underway in Russia and across the South Caucasus. PJSC RusHydro announced the inauguration of the 246 MW Zaramagskaya-1 plant on the Ardon River in North Ossetia in Russia to include construction of a 14km headrace.

Across the border in Georgia, there is a portfolio of assets in the planning stage, including the 433 Namakhvani project under development by Enka Renewables, formerly the Clean Energy Group Georgia.

This follows development of the Dariali hydro project on which two 5.5m diameter Robbins main beam TBMs excavated the 5km long headrace.

Hydro installations currently produce almost two-thirds of global renewable energy, according to the IHA. It concludes that hydropower is making a major contribution to delivering on the ambitions of the United Nations Sustainable Development Goals and that without its contribution, the objectives of limiting climate change to 1.5 or 2 degrees above pre-industrial levels would likely be out of reach. n

References • •

Snowy Mountains adds long planned element – TunnelTalk, May 2019 Bhutan seeks bids for next major hydro tunnels – TunnelTalk, November 2018

Fig 1. Hydropower capacity and generation by region

FOCUS: HYDROPOWER DEVELOPMENTS

excavate the long tunnels with drill+blast used for the caverns, access tunnels and additional waterways.

Source: IHA

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Hydroelectric waterway inspections and failures Dean Brox, Consultant, Canada

FOCUS: HYDROPOWER DEVELOPMENTS

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he costs associated with the inspection of hydropower tunnels are not small, but the consequences of serious problems can escalate rapidly in terms of costs, environmental compliance and public safety if issues are not addressed quickly and efficiently. Waterways of many hydroelectric plants are now ageing beyond 40 years and while routine maintenance can be performed during short outages, more effort is required for online inspections to overcome access constraints.

The greatest risk posed to the safe longterm operations of hydroelectric tunnels is the stability at the locations of geological faults or other weak geological features as encountered during construction. Collapses occur because of inadequate support and the non-recognition of non-durable or scoursusceptible conditions.

A first inspection of older installations is typically performed as a result of detected or inferred problems after many years of operation. Hydroelectric tunnels operated under peaking conditions are subjected to highly variable internal operating pressures with associated cyclic loading of the support and linings. Peaking operation of waterways warrant a higher frequency of tunnel inspections (Fig 1).

Advances in robotic and data acquisition technologies with remote operated vehicles (ROVs) are able to capture information to perform more comprehensive condition assessments. The manoeuvrability of ROVs enables them to access also complex geometries of surge shafts and intake gate slots. The condition of rock traps is also to be confirmed during an inspection to ensure they have capacity to prevent debris passing over the rock trap and into the penstocks.

The longest single pass ROV inspection was 12km at the Snowy Mountain scheme in Australia and the longest total inspection completed was for the 120km Paijanne drinking water supply tunnel for Helsinki, Finland. ROVs have operated at depths of more than 600m with some capable of operating at up to 2,000m.

In low turbidity clear water ROVs can provide high-resolution photographs and video imagery. In high turbidity conditions, profiling sonars are used to provide continuous 360° data for a high-resolution 3D point cloud model and associated visualisations.

Part of the overall condition assessment

Fig 1. Recommended frequency of inspections (left); Fig 2. Qualitative risk matrix of aged linings is to detect if there is any deteriorations or voids forming. To date there are no standard approaches for the investigation and inspection of the integrity of shotcrete, concrete or steel linings or the presence of voids behind linings. The use of modified forms of ground penetrating radar, seismic reflection and acoustic emission techniques may be developed in the future for ROV inspections to provide this crucial category of information.

A dewatered inspection should only be considered in the event that an unwatered ROV inspection indicates serious concerns.

Dewatering of the watercourses for physical inspection incurs loss of generation and its revenue and may also cause a negative impact to the integrity of the tunnel.

Dewatered inspections however have the benefit of direct observations and the obtaining of concrete lining samples and local testing for durability and strength.

The condition of concrete and shotcrete linings are typically of most interest.

Numerous 3D visualisations prepared from ROV inspection data will identify the geometry of the transitions in linings where scour can occur and create significant changes in the geometry of the profile.

Since 1995, more than 300km of lowpressure hydropower tunnels have been excavated using TBMs in conjunction with precast concrete segmental linings. These have been completed successfully with no problems reported to date.

Asset risk assessment

The risk assessment for a hydroelectric waterway represents a complex engineering challenge and is based on the age, hydraulic

ROV with 360° hovering manoeuvrability (left); Visualisation during an ROV inspection

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operations, and type of linings (Fig 2).

Following an inspection, an updated or new risk assessment should be performed with both qualitative and quantitative risk assessments. A qualitative risk assessment is based on historical and recent inspection observations, historical problems including leakage failures or instabilities, and historical and normal hydraulic operations.

A quantitative risk evaluation should be based on optimistic and pessimistic assumptions to indicate the remaining life of the tunnel. One assessment approach is based on accumulating the probabilities of failures due to identified instability or failure mechanisms that are deemed plausible.

A formal risk workshop with hydroelectric engineering experts is recommended to perform a comprehensive risk assessment.

Watercourse failures

Investigation of recent collapses in the waterways of hydro schemes, after start of operation as well as during construction, make it apparent that the main causes are due typically to design errors – not construction defects. Given that hydropower tunnels are subjected to internal and dynamic loading during operations, their design is significantly different to the design of other tunnel infrastructure.

Design of a hydropower tunnel should be based on a thorough review of the possible worst case operating conditions.

Reservoir schemes typically maintain constant pressures with run-of-river schemes subjected to seasonal fluctuations and their associated significant pressure variations. Projects with multiple intakes can be expected to result in significant pressure oscillations. Hydraulic transient analyses should be performed by the hydraulic designers to confirm the magnitude and variation of internal operating pressures to be expected during normal and non-normal operating periods.

In the last decade, a set of five notable hydropower tunnel collapses have occurred at the Glendoe installation in Scotland, the Rio Esti project in Panama, the La Higuera project in Chile, the Shuakhevi project in Georgia, and the Ituango project in Colombia (Table 1). Along with insurance investigations, legal proceedings resulted for most of the

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Ituango project disaster

Collapse of the diversion tunnel system around the construction of the dam and underground powerhouse for the Ituango hydroelectric power project in Colombia has the potential to be the largest insurance loss in international civil infrastructure construction history. Two root cause reports into the disaster, one for the project owner and one for the re-insurer, provide details of the catastrophic event.

Located on the Cauca River, the project comprises a 235m high earth core rockfill dam and a 2,480 MW generating station sited in the right abutment. The scheme comprises a large cavern with eight short headrace tunnels, eight 495m deep shafts and four 1km tailrace tunnels (Fig 3).

Construction of the project started in 2010 with excavation of two 1km long x 190m2 diversion tunnels, with a cast concrete invert in each. The diversion tunnels were completed in 2013 and diversion through them commenced in early 2014.

After the first two years of construction, the project was running 20 months behind schedule due mainly to delays in securing access and permits. An acceleration plan was adopted to not install the control gates in the two original diversion tunnels and to instead build a third diversion tunnel, referred to as the auxiliary diversion tunnel (ADT) for the entire duration of dam construction. Its excavation started in mid-2015 and was completed in late 2017. This decision was a major design change during the early stages of the project and was proposed by the project designer based, as they claim, on previous project examples.

The project is being developed by the Public Company of Medellin under a buildoperate-own-maintain and transfer approach whereby the project design was prepared by a consultant for the project client, construction is by an engaged contractor, and progress is audited during construction by a separate supervision consultant.

The ADT was designed as a single, drill+blast horseshoe-shaped excavation of similar size of each of the original twin diversion tunnels at 14m high x 14m wide (about 190m2) and about 2.3km long.

The ADT operated successfully for about nine months until late April 2018 when it collapsed. At that time, the project was 87% complete and eight months from

Table 1. Hydropower waterway collapses in the past decade Project Year Diameter Length Operations period Repairs prior to collapse Glendoe 2009 5m 8km 8 months Bypass Rio Esti 2010 10m 5km 9 years Concrete lining La Higuera 2011 6m 16km 9 months Bypass Shuakhevi 2017 6m 18km 3 months Injection and additional support Ituango 2018 16m 2km During construction Unknown start of power generation.

Heavy rainfall during April 2018 caused the reservoir level behind the partially completed dam to increase steadily and submerge the ADT intake causing high velocity, high pressure flow conditions. Actual flows during April varied from 1,400m3/sec and increased to a maximum of 2,800m3/sec. A second peak of up to 2,400m3/sec for multiple days resulted in flow velocities of almost 15m/sec during a 15-day period.

In late April, the flow through the ADT suddenly decreased. This was followed by the formation of a large circular crater shaped sinkhole along the slope immediately above the ADT intake.

With the one diversion tunnel blocked and the water level continuing to rise, the decision was made to open four of the power intake tunnels to bypass the flood flows through the nearly completed powerhouse and prevent overtopping of the nearly completed dam. This resulted in significant erosion along the floor of the unprotected power intake tunnel inverts, as well as significant damage to the electro-mechanical equipment being installed.

The estimated volume of the crater shaped hole was 120,000m3 extending over a lateral distance of about 100m at the surface. With overbreak of about 7m in the ADT, the minimum cover of rock over it is about less than 70m. The crater shaped hole revealed highly altered and discoloured poor quality rock of soil-like conditions extending to a depth of possibly 50m.

Both of the root cause reports appear to have focussed on identified technical factors contributing to, or responsible for, the tunnel collapse, rather than highlighting the fundamental reasons for the collapse, which are deemed to have been: • the high flood flows that occurred during the diversion period, • the inadequate hydraulic capacity design of the ADT, and • the absence of a hydraulic concrete lining in the ADT. In fact, many of the technical factors listed in the reports as reasons for the collapse,

are not of primary importance, as the ADT would have functioned acceptably if these factors had been adequately addressed in the design. The main conclusion of both reports is that the root cause of the collapse was due to erosion of a discrete shear/ weakness zone. This is considered to be entirely speculative, with reference in the client’s report to a single example in Norway.

Overall, both reports do not categorically state that the collapse was the responsibility of any particular party involved. However, based on standard practices, it is quite obvious that there were multiple and serious shortcomings with regards to the engineering design of the ADT. Also, the technical expert board that was involved during the construction of the project recommended not to build the ADT. The ADT operated successfully during non-flood flow periods and under only limited durations of pressure flow conditions. The actual design of the ADT with traditional rock support and a shotcrete lining with an irregular profile and large overbreak, would have resulted in highly turbulent flow conditions and the development or build-up of overpressures within the surrounding rock during the flood period. This overpressure would have migrated to as high as 35m above the top of the ADT for a period of three weeks and occurring under relatively low cover near the portal. This caused saturation of the rock, lubrication, and loss of integrity along weak fractures with an imbalance between the hydraulic and geotechnical conditions leading to instability and formation of a collapse extending upwards for more than 100m to the surface.

After review of the root cause reports, together with additional information, the following alternative and additional factors are considered to be the primary reasons for the collapse of the ADT: • Unacceptable portal location with the initial tunnel section under low cover of fractured rock; • Single, under sized tunnel for hydraulic operations of high flood flows (only 50% of necessary design capacity);

FOCUS: HYDROPOWER DEVELOPMENTS

tunnel collapses due to the substantial repair costs and the loss of power generation revenue. Most of these collapses resulted in financial costs exceeding US$250 million and a loss of generation for up to 24 months.

Fig 3. Schematic of the Ituango project (left) and the 100m diameter crater and sinkhole above the failed auxiliary diversion tunnel

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• Unacceptable tunnel profile with large overbreak for hydraulic operations, and; • Deficient final tunnel lining for hydraulic operations under high pressures and velocities.

All of the above are related to the design of the ADT. None of them are the responsibility of the contractor as the applicable geotechnical and hydraulic conditions were previously known by the project designer and unprecedented critical design decisions were made by the project designer. The actual high flood flows that occurred should have been correctly mitigated through ongoing risk management practices for the project.

Collapse of the ADT set back completion of the project to 70%. In late 2018 the dam spillway was completed to allow flows to pass over the dam safely and permit safe inspection of the damage caused to the intake tunnels and underground powerhouse. Recovery of the underground works continues with the start of energy generation currently planned for late 2021.

To date, Mapfre insurers have provided payments of USD$250 million in covered claims. The insurable limit for damages is $2.56 billion along with $628 million for loss of generation. The project client has declared its intention to commence litigation against the project designers, construction supervisors and contractors.

Causes and consequences

Upon review of the details, it is apparent that the main causes of collapses have been due typically to design errors due to the incomplete identification of weak geological zones before and during excavation. The hydropower industry has often relied upon the judgement of site geologists to make the final lining design decisions without fully appreciating and understanding the nature of future hydraulic operations and imposed loadings for the tunnel. In addition, there appears to be no independent checking of the final lining designs.

The use of shotcrete for long-term stability and support of major geological faults within hydropower waterways is not adequate, particularly for peaking power plants and where highly variable internal pressure oscillations can cause preferential scour, saturation, and deterioration of such final linings. New tunnel support design standards comprising the use of concrete linings are considered necessary for the longterm stability and support of major geological faults in hydropower watercourses.

The following must be considered to prevent hydropower tunnel failures;

• Adequate geotechnical information is required to form the basis of a coherent design and contract documentation.

• Programme realistic construction schedules that are site-specific for constructability and not subjected to the deadlines for energy delivery agreements.

• Avoid EPC or design-build approaches to allow total design control by the client to prevent any compromising of construction quality.

• Perform comprehensive tunnel mapping with detailed descriptions of suspect weak zones.

• Use methods other than rock mass classifications for application of final support and linings.

• New support design standards are required to consider appropriate longterm stability and support of major geological faults within hydropower waterways.

• Stop hydropower operations at the onset of any detectable headloss to prevent damage.

• Independent external technical reviews, as applied to other critical infrastructure projects including bridges and dams, should form part of the design and construction of hydropower installations.

Feedback from Fabrizio Bove, Project Manager, Seli Overseas Thank you for the interesting analysis carried out and good suggestions shared.

Since I had the challenging opportunity to work for the rehabilitation of the Estì headrace tunnel in Panama, I would like to add and share some issues for further considerations.

In the case of Estì, the failure occurred mainly because horizontally bedded weak layers ran parallel to the tunnel axis in several areas and were not visible during excavation. In other words, during the face inspections the rock mass had been recorded as self-stable and sound with high value rock mass indexes, thus leading to a choice for a softer lining of shotcrete. As a result, only a complete overview, focusing on the stabilization of the on-going advance core and fully appreciating the in-situ 3D geology and the nature and pace of future hydraulic loading for the tunnel, could improve the choice of the permanent lining and stability.

Where the biggest collapse of about 14,000m3 occurred, at least three factors could have hampered the situation: • A steep geometrical change of the tunnel alignment, • Low overburden and

Collapse of the Glendoe unlined TBM headrace; Collapse in Rio Esti headrace

• Parallel alignment of the soft/weak strata with the tunnel axis.

An EPC contract was used for the main project procurement and also for the Estì rehabilitation phase in 2011 and 2012 and with good achievements. Obviously, however, stronger control by the Engineer is needed in these cases.

In the case of unforeseen and unforeseeable events, a contractual risksharing approach between Employer and Contractor can be the best option, both in terms of cost control and timely reaction and application of solutions.

Feedback from Nick Barton, Independent Consultant In his interesting and well-illustrated review, Brox has suggested using “other than rock mass classification methods” for application of final support and linings. This ignores the contribution of such methods to thousands of kilometres of hydropower tunnels and considerable cost savings for owners. If mistakes are made in application of the methods due to oversight, especially in the case of faulted rock, then lessons need to be learned by those involved. Incidentally, for the Ituango case, the failure erosion cone is much larger than described and is a special case of optimism in diverting water with a peak velocity of up to 10m/sec around a remarkably tight bend. Design for velocities of 1.5-2.5m/sec have been and are the basis of Q-system case records.

Secondly, Brox recommends independent checking of waterway tunnel designs. I have reservations based on what is available outside of the use of more careful rock mass characterization and use of empirical methods, like the Q-system which probably has the most relevant database.

It should not be forgotten that there are thousands of kilometres of such waterways, and many hundreds (actually thousands) of economic projects as a result of the singleshell type of support, which, as pointed out by many, needs to consider the intended use of the tunnel.

Having reviewed many projects over the years, and having experience of a specific international court case, it is evident that numerical modelling is frequently too much relied upon. These experiences have also demonstrated the severe limitations of popular numerical modelling methods.

Of course, it is also possible to misuse the more reliable codes and their longer track records by, for example, modelling with exaggerated joint continuity. There are hundreds of examples of this. In fact, it is found that a super-simple empirical model, linking deformation, tunnel span and the Q-value, provides a far more accurate check of potential deformation, as monitored subsequently at the completed project, than the exaggerated models. n

References • • • • •

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Author references can be found on the full length article on www.TunnelTalk.com Repairing damaged hydropower pressure tunnels – TunnelTalk, March 2014 Panama awards urgent Esti headrace repair – TunnelTalk, December 2011 Recovery contract for failed headrace at Glendoe – TunnelTalk, February 2010 Tough excavation for clean energy in Georgia – TunnelTalk, May 2017

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First TBM components on their journey into the Snowy mountains

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Alternative design for Snowy 2.0

Fig 1. Alternative design changes a deep pressure shaft to an inclined alignment which the 9.8m i.d. x 6km tailrace tunnel contractor, as well as for working out fair connects to the Talbingo reservoir. Maximum compensation for time and costs during rock cover is almost 450m above the actual construction. headrace and 800m above the tailrace.

The project has had to manage Primary access to the power station bushfires in the area in 2019-2020 as well as is provided by the main access and the the Covid-19 pandemic. In a statement from emergency egress, cable and ventilation Snowy Hydro Ltd, both were managed with tunnels, both of which are about 2.5km long. minimal disruption to operation and minimal The three TBMs will include two open impact on the project timetable. mode and one dual-mode machine. The Although the bushfires came through CREG machine will drive the tailrace and main the construction site, damage was limited as access tunnels with one of the Herrenknecht a result of good preparation, including heat machines excavating the headrace and the barrier fencing around the main compound, other progressing first the emergency egress, and contractors were able to return within cable and ventilation decline tunnel and then weeks. Work has also continued through onto the inclined pressure shaft.

Covid-19 with strict safety protocols in place A AUS$55 million factory for production and schedule and shipping adjustments of the lining segments is also established. made to minimise any impact on the overall Operated by Future Generation, it will project schedule. manufacture more than 130,000 segments In addition to construction of the Polo over the course of the project and will employ Flat precast segment factory, exploratory 125 people. A steel lining will also be installed works have been underway since March at locations where leakage or confinement 2019 at the Lobs Hole construction site. Also issues are identified. advanced during 2020 was construction of The project faces challenging geological access roads and support infrastructure, and hydrogeological conditions with the including two bridges and temporary worker alignment passing through several highly- camps and a range of earthworks to prepare variable alpine formations with a wide range the portals for launch of the TBMs. n of rock types and geological structures.

Excavation is likely to face frequently References • Snowy Mountains adds long planned element changing mixed ground conditions – TunnelTalk, May 2019 with regular transitions through different • Global review of hydropower developments – lithologies, faults and weak zones. High TunnelTalk, March 2020 groundwater inflow may also impact construction and will Two Herrenknecht TBMs will bore the require pre-excavation grouting headrace, inclined pressure shaft and ECVT

FOCUS: HYDROPOWER DEVELOPMENTS

C

onstruction of the Snowy 2.0 hydroelectric scheme in the Snowy Mountains of New South Wales, Australia, has started with new innovative design alternatives offered by the engaged Future Generation consortium. With a high head differential of more than 700m, the construction JV, led by Salini Impregilo (now Webuild), alongside partners Lane Construction and Clough, has proposed an inclined pressure tunnel in place of the 800m vertical pressure shaft of the designbuild contract design (Fig 1).

Snowy 2.0 will provide an additional 2,000 MW of fast-start, dispatchable energy and provide 350,000 MW hours of largescale storage. The Snowy Scheme already generates about a third of the renewable energy in the national electricity market in Australia. The new project will expand the Snowy Hydro Limited network of hydro power stations and support the transition to a low-carbon emissions future.

The project features about 27km of precast segmentally lined waterways, a deep underground power house, and 430m of vertical shafts. When complete, the pumped storage scheme will link the existing reservoirs of Tantangara at an elevation of 1,231m, and Talbingo at 546m.

According to project owner, Snowy Hydro Ltd, the project takes hydro design and construction to a new level, involving several geological and hydromechanical challenges for the waterways.

Three TBMs of 11m diameter, two supplied by Herrenknecht and one by CREG are to be used on the project. The CREG machine is the first on site and components for the two Herrenknecht TBMs have also arrived on site. The first two TBMs to launch will operate at a descent of 9% to excavate the 2,660m access tunnels to the powerhouse and will continue onto the tailrace and pressure shaft drives.

Loaded on long trailers hauled by heavy trucks from Port Kembla, shipments of the TBM components for the first two machines passed through the town of Cooma in the Snowy Mountains to arrive at Lobs Hole, for excavation of the two access tunnels to the powerhouse.

From large water intake structures of up to 90m high in both reservoirs, the 9.8m i.d. x 17km long headrace will run from Tantangara to the 25m o.d. x 250m high headrace surge shaft. In the contractor’s design alternative to the traditional vertical pressure shaft of the initial design, water will then flow in a 1.6km long x 25° inclined TBM excavated pressure shaft. This leads to three penstocks that bifurcate to feed six 340 MW Francis pump-turbines in the 30m x 55m x 250m machine hall at about 800m below ground. A 20m x 50 x 200m transformer hall is located alongside the machine hall. Three of the single-stage, reversible Francis pumpturbines will be conventional synchronous machines, while the other three will be variable-speed asynchronous.

On the downstream side of the machine hall, the six draft tubes combine into three collectors that meet at the bottom of the almost 200m-high tailrace surge shaft, from

Credit: Snowy Hydro Ltd

Jonathan Rowland, TunnelTalk

in critical areas.

Although a geotechnical baseline has been defined, a more thorough understanding of the ground conditions will only become evident when construction begins. As a result, a contractual risksharing mechanism has been developed to allow for a balanced distribution of risk between the project owner and

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Nepal prepares for second TBM waterway drive

FOCUS: HYDROPOWER DEVELOPMENTS

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xcavation of the second TBM project in Nepal is awarded to the same contractor as the first. After completing the Bheri Babai segmentally lined TBM water project in 2019, COVEC, China Overseas Engineering Co, is awarded the 13.3km long Sunkoshi Marin diversion tunnel, which is also specified as a segmentally lined TBM excavation.

The new 6.4m o.d. (5.5m i.d.) tunnel will divert 67m3/sec of water from the Sunkoshi River to the Marin Khola, a tributary of the Bagmati River, to augment the Bagmati irrigation scheme and generate 30 MW of electricity in a hydroelectric installation.

The overall contract period is 75 months, including a 24-month defect notification period. The conditions of contract are the FIDIC Pink Book: The Multilateral Development Bank Harmonised Edition (2010).

The COVEC bid, at NPR10 billion (about US$84 million), is the lowest of bids received and nearly a reported NPR 6 billion ($50 million) below the official Government estimate of NPR15.84 billion ($134 million). Its proposal to reuse much of the equipment procured for the Bheri Babai project including the Robbins double shield TBM, together with the experience gained and the skilled managers and workers moving from the first to the second project, accounts for the bidding advantage. The TBM shield and cutterhead and the segmental lining casting equipment will require modification to adjust from the 5.06m o.d. (4.2m i.d.) of the 12km long Bheri Babai project to the 6.4m o.d. (5.5m i.d.) of the Sunkoshi

Marin project. COVEC is in discussions with Robbins to manage the TBM rebuild.

The re-engineered machine must have a minimum 7,500 hours remaining design life of the main bearing.

The moulds and steam curing facilities for the precast segment production factory will cast the lining of about 300mm thick and will require up to 85,000m3 of cement, 13,000 tonne of steel reinforcement and 45,000m3 of pea gravel and annular grouting.

Progressing from the Marin River outlet portal, the 6.4m o.d. TBM is anticipated to pass through the series of competent and incompetent rock masses of the Siwaliks and the Lesser Himalaya and is expected to encounter conditions typical of young, high overburden geology including shear zones, squeezing, slabbing, bursting, high water ingress and fault zones (Fig 1).

The geology along the alignment, separated by a low angle reverse fault known as the Main Boundary Thrust, was further described in details provided by Ajay Raj Adhikari, Senior Geotechnical Engineer for the project. To one side, the drive passes through fluvially originated, relatively young Siwaliks that consist mostly of interbedding sandstone, siltstone, mudstone and conglomerate under a maximum cover of about 550m.

Except for about 1km in a slate formation that belongs to the Lesser Himalaya Region, the majority of the remaining alignment, or about 8.3km, passes through the relatively old Higher Himalaya Region composed mostly of medium to highly metamorphosed schists, quartzite, granite and gneiss with occasional calcareous beds of limestone

Fig 1. Geological profile of the 13.3km x 6.4m o.d. water transfer drive

The Robbins TBM will require a new shield and cutterhead for its larger diameter second project

TunnelTalk reporting and dolomite. Because of the long stress history of the mountain range, this region consists of several minor and major folds, faults and shear zones with the alignment passing through the major syncline of the Nepal Himalayas known as the Mahabharat Synclinorium. The TBM will have to bore through the core of the Synclinorium where the overburden is at its highest of about 1,320m, and through the anticipated granite rock type (Fig 1).

As the rocks are dipping north or south at different angles, mixed face conditions of competent and incompetent strata are anticipated. Systematic probing is a specification and ground engineering methods including cement/chemical pregrouting, forepoling and umbrella pipe roofing, are to be anticipated. Squeezing conditions may require profile overexcavation and, in extreme cases, TBM bypass headings.

Having one highly successful double shield project to its credit, in the Bheri Babai project, and with a second now in procurement, Nepal is also to use TBM excavation for the 10km second phase of the Melamchi water supply for the city of Kathmandu. The 27km tunnel of the Melamchi Phase 1 project was excavated by drill+blast. Despite working from eight headings (the two portals and in both directions from three intermediate adits) the project suffered serious difficulties, major delays and changes of contractor.

The benefits of a robust TBM in the hands of an experienced contractor are the advantages that Nepal is now seeking to repeat for its new long-distance tunnels, under high overburden and into geological conditions that are anticipated to hold serious challenges.

Where TBM advance rates of more than 1,000m/month were achieved in more favourable ground conditions than expected on the Bheri Babai project, geological risks to the Sunkoshi Marin TBM drive are higher with high water ingress and fault zones. With its experience in hand, COVEC is equipped to manage the conditions as encountered providing the contract has the contingency funds and the mechanisms to cover the time and costs that will be required to overcome these anticipated challenges.

Feedback from Siba Prasad Sen, Independent Consultant, India It is very unlikely that the Sunkoshi Marin TBM diversion project in Nepal will be a repeat of the Bheri Babai TBM experience, due mainly to the expected presence of high pressure water ingress and distressed rock.

Also, I do not think that the suggestion of provision of a contingency fund can alone take care of such risks in the absence of advance planning.

While assisting in the preparation of the feasibility report for the Bheri Babai multipurpose project and in association with Nepal irrigation engineers, two things were in mind: First, it was to be the first TBM

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project in Nepal, and secondly we did not know whether there was a good probability of presence of ground water in high pressure and high volume in the form of either or both perched or pressurised aquifers.

Investigation study data, drill hole information and a walk over the Bheri Babai alignment did not indicate that high-pressure, highvolume water issues would be so.

It has been the general experience that the presence of water in high pressure along an alignment has been a recipe for disaster, especially for excavation by TBMs in the Himalayas. The Dulhasti and Parbati II projects are examples. The current Tapovan and Vishnugad hydro projects have also experienced the presence of high-pressure ground water.

With limited information on geology and geotechnical data being available for the Tapovan Vishnugad project I understand that the alignment had some kind of syncline rock strata, which should have been taken as a red signal for ground water. It is true that further development of geological and hydrological investigation methodology in the Himalayas is required.

In the Himalayas, the presence of substantive water can change the engineering behaviour of rock. I am not sure whether high-pressure ground water is accounted for while designing the TBM and planning for the excavation of projects in the Himalayas. Many owners and contractors use the excuses of difficulty in conducting site investigations, lack of sufficient experience of the complexities, and a rush to start the work in a hurry and without doing any investigation at all.

In case of Bheri Babai in Nepal and the Kishanganga hydro scheme in India, the presence of water was not high, though the geology was as complex as it has been on other projects.

For the proposed Sunkoshi Marine project in Nepal, the TunnelTalk report on the proposed project, though brief, gives a good idea of the complex geology. The most important point is that the alignment crosses the Main Boundary Thrust of the Himalaya Massif and that it has to pierce through the major syncline of the Nepal Himalayas. Experience confirms that such a syncline will have high stress and the presence of quartzite bands and must also anticipate to have the presence of high pressure and high volume ground water.

As I am not aware of the detailed geology and investigation data of the Sunkoshi Marine project, I can only say that in planning the TBM technical specification and the excavation processes, provision should be made for large quantities of water flow. It may be advisable to try some investigation for the presence of high pressure, high volume water along the tunnel path. n

References • • • • •

Nepal proving TBM applicability in Himalayas – TunnelTalk, February 2019 TBM rescue for Tapovan hydro challenge – TunnelTalk December 2016 Vishnugad Pipalkoti TBM finally set to start– TunnelTalk October 2019 New award follows Seli Kishanganga success (with video) – TunnelTalk May 2014 Breaking excavation records in the Himalayas – TunnelTalk December 2012

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Lesotho Phase II procurement TunnelTalk reporting

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re-qualification and procurement of contracts to build the Polihali dam and Polihali transfer tunnel for the Lesotho Highlands Water Project Phase II in southern Africa is back on track. The process initiated in 2019 that had identified a shortlist of six groups from 12 prequalified applicants for the transfer tunnel and eight for the 165m high Polihali dam and appurtenant works was cancelled in July 2020 after it was established that some of the requirements of the funding lenders had not been adequately addressed in the prequalification process. The principal lenders are the New Development Bank and the African Development Bank.

The 2019 process by LHDA, the implementing and management authority of the Lesotho Highlands Water Project on behalf of the Government of Lesotho, shortlisted groups from around the world. These included contractors from South Africa, Lesotho, many from China and others from France, Italy, Brazil and Portugal. The shortlisted teams for the dam and the tunnel included groups led

by Webuild of Italy, which is currently excavating the two diversion tunnels around the Polihali dam construction site on the Senqu River.

Masilo Phakoe, Public Relations Manager of LHDA explained that the new open tender process for the two contracts of the main Phase II works will invite all interested parties to participate.

LHDA is also in the process of procuring professional services of an independent Probity Auditor to provide independent scrutiny of the Phase II contract procurement processes. “This is in line with the LHDA procurement policies that requires all procurement processes to foster competitiveness, transparency, cost effectiveness and quality,” said Phakoe.

Meanwhile, excavation is advancing to divert the Senqu River ahead of construction of the concrete-faced rockfill

The new Polihali dam reservoir will be linked to the Katse reservoir by the 38km long transfer tunnel Polihali dam. Drill+blast excavation of the twin diversion tunnels of 7m and 9m diameter and 1km long is advancing from the outlet portals and at about 6m/day in each heading.

Excavation of the intake and outlet portals has been completed and work on the concrete lining is underway.

Work on site got off to a slow start in early 2020 due to Covid-19 restrictions that restricted shift work and reduced the number of workers to enable social distancing. Continued border restrictions between Lesotho and South Africa also posed travel challenges for South Africanbased technicians and the movement of equipment and supplies.

The LHDA Phase II project augments the Phase I system which has been delivering specified quantities of water to South Africa since 2004 via an 85km long transfer and delivery tunnel system to an outlet on the Ash River in South Africa and at the same time generating hydroelectric power in an underground powerhouse at ‘Muela in Lesotho. The Governments of Lesotho and South Africa are the owners of the bi-national treaty that governs the delivery of water from the Lesotho to the Gauteng region of South Africa. Phase II will increase delivery under the international water delivery treaty from the current 780 million m3/year of Phase I to 1.37 billion m3/year. n

FOCUS: HYDROPOWER DEVELOPMENTS

Polihali diversion excavations

References • •

Lesotho Phase II dam and tunnel shortlists – TunnelTalk, January 2020 Lesotho appoints experts and calls prequalifications – TunnelTalk, January 2019

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Melamchi watering-up gate failure

FOCUS: HYDROPOWER DEVELOPMENTS

Credit: Rising Nepal National Daily

T

he 27.5km long Melamchi raw water supply tunnel to bring fresh water to Kathmandu city in Nepal was close to being finished. Excavation was complete, the upstream run-of-the-river diversion weir and intake structure was about 70% complete and work was progressing at the downstream end on a sedimentation facility before directing raw water into a new treatment plant. Drill+blast excavation of the 27.5km long tunnel progressed, in addition to works at the portals, from 18.4m2 intermediate adits, the main ones at Ambathan, Gyalthum and Sindhu.

At this stage of progress, it was decided to water-up a limited section of the tunnel from the Melamchi River to the Ambathan adit to test its hydraulics and operating mechanical equipment. The aim was to complete the long awaited and urgently needed project by the end of 2020.

There are a total of 29 control gates for the operation of the water supply tunnel including five 12.5m2 adit bulkhead gates with a radial gate at the intake and a control gate at the downstream end. The gates for the project are designed, supplied and imported to Nepal and installed by a company from India. The project contractor, Sinohydro of China, completed the civil works associated with the installation of the gates including

Adit location after watering up accident the rock support around the doors and the shotcrete support of the adit junction with the main tunnel. All the adit gates were closed ahead of the watering-up test. On 5 July 2020, Sinohydro released water into the tunnel via a temporary pipeline and the temporary dam erected on the Melamchi River to begin its filling.

In mid July, Gate 17 at the end of the Ambathan adit failed, bursting open and flooding the adit. At the time, four project workers – a project engineer for Sinohydro, a site engineer, a project worker and the driver of the pickup truck that drove the men into the adit – were coming back to the portal

TunnelTalk reporting

when the bulkhead gate failed. The men and the vehicle were swept out of the adit and into the Melamchi River. The site engineer and the project worker were rescued but the project engineer and the driver lost their lives.

General Secretary of the Ministry of Water Supply, Ramakant Dawadi, said that the accident was caused due to error in the knot bolts used to lock the adit bulkhead door: “The door had been tightened with 30 knot bolts that slipped due to the water pressure and unbolted the door.”

At the time of the accident, the Ambathan gate had about 2m of static water head and about 1.6 bar or about 16m of pressure acting on the door. The gate is designed for 50m of water pressure.

A main reason for the failure of the gate is that the door opened into the adit, rather than into the main waterway. Had it been installed to open into the waterway, it would have been self-locked by the water pressure.

Failure of the rock around the gate mount is not suspected or known at present as being contributory to the failure. An investigation committee was convened by General Secretary Dawadi to investigate further technical reasons behind the accident. n

References •

Urgent infrastructure needs in Nepal – TunnelTalk, November 2018

Fatal flood hits Himalayan hydro works

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estruction and many fatalities were the aftermath of a devastating flood on the Alaknanda River high in the Himalayas in India. The flood hit several hydropower construction sites and their dams and underground headings further downstream on the Dhauliganga River (Fig 1). The cause of the flood is reported as being failure of a glacier that caused a landslide as it crashed into the river causing the deluge downstream. Given the volume of sediment and boulders carried by the flood, others have said the cause might have been the bursting of a glacial lake.

Four hydropower plants were affected by the disaster with dams damaged and tunnel portals in the river valley inundated, burying workers many of whom were rescued as the underground headings were cleared.

Rescued workers reported how they held onto support features in the crown of the tunnels and climbed down mounds of rocks and rubble as the water receded.

Tapovan was the project most affected with the cofferdam ahead of main dam construction washed away and the portal of the tunnel headings blocked by the inundation.

TBM operations by Seli Overseas on the Tapovan-Vishnugad project are at different

locations and were not affected. Teams from the TBM works joined the rescue efforts.

The disaster is being seen as the latest in a string of events that call for caution in awarding infrastructure projects in the high mountain areas. In Switzerland in 2010, TunnelTalk reported completion of an emergency drill+blast heading to drain a dangerously filling glacial lake to avert a potential disaster. Glacier releases are predicted to become more common with acknowledged global climate change, as the glaciers melt and their mountain slopes give way resulting in large slides.

Feedback from Dr Gyanendra Lal Shrestha, Chartered Engineer, MICE President, Nepal Tunnelling Association It was with great concern and distress that we learned of the glacial activity deluge that hit the Alaknanda and Dhauliganga River valleys in the Himalayas, and of the devastation, damage and deaths that it caused.

Glacial lake outburst floods have been a clear and present danger in the countries of the Himalayas where glaciers and glacial lakes are also major sources of freshwater. It is known that the cryosphere in the Himalayas is vulnerable to climate change and glaciers have been melting at an unprecedented rate

Fig 1. Rivers high in the Himalayas are known to be prone to flash floods and landslides

TunnelTalk reporting

since the mid-20th century. This leads to expansion of existing glacial lakes, formation of new lakes, and an increase in the risk of glacial lake outburst floods. Nepal has experienced several such outburst floods in recent decades.

A 2011 study by the ICIMOD International Centre for Integrated Mountain Development of the United Nations Development Programme (UNDP) reported 24 glacial lake outburst flood events in the past in the Himalayas.

In 2015, the ICIMOD, based in Nepal and funded by the Government of Norway and the Swiss Agency for Development and Cooperation (SDC), began a study of the threat of glacial lake outburst floods (GLOF) in the Koshi, Gandaki, and Karnali River basins.

The study report published in late 2020 found that there are 47 potentially dangerous glacial lakes in these basins. Of these, 21 are located in Nepal, 25 in Tibet and one in India.

The water levels of four lakes, two in Nepal and two in Tibet had been lowered in the past to reduce the risk. The water level of Tsho Rolpa Lake in the Rolwaling Valley in Nepal was lowered by more than 3m in 2000, and in 2016 the level of the Imja Tsho Lake in Nepal was lowered by 3.4m.

Since the late 1980s, we have been including a GLOF study report in most of the snow-fed hydro projects under development and feasibility study in Nepal. The recent incident in Uttarakhhand in the Himalayas in India has further alarmed us. n

References •

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Swiss glacier drainage tunnel in full flow – TunnelTalk, April 2010

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Underground spaces created by SCL ready for construction of the inner architectural and M&E finishes

Intricate excavation upgrades London metro station • Development of a sprayed concrete radial joint, without connecting reinforcement, to eliminate the need of workers entering the face; • Optimised SCL lining thicknesses to reduce the risk of fallouts and improve construction cycles; • Change of proposed hand mining operations to sprayed concrete linings for improved workability; • Application of 3D ground modelling; and • Adoption of a risk-based approach to design and construction.

During excavation, the exterior of several existing London Underground assets were exposed. No internal propping within existing assets was required.

The Option A SCL sprayed radial joint between the top heading and bench excavations eliminates the requirement for the installation of reinforcement bars.

The joint is formed fully using mechanised means, eliminating the need for the

Sebastian Kumpfmueller, Senior SCL Engineer & Senior Associate, Dr Sauer & Partners Donal Kelly, Tunnel Manager, Dragados SA UK & Ireland workforce to access close to the face and avoiding the need for a temporary SCL sealing layer of the face. The stepped SCL lining application used the robotic concrete spraying equipment with the excavator breaking out the SCL lining toe for the joint preparation and cleaning (Fig 2). This innovation is a significant advancement for the SCL tunnelling industry by making the works considerably safer.

The 19m2 heading of the new Northern line running tunnel progressed as a fullface excavation on 1.2m advances. It was a pilot heading for the platform tunnel and was enlarged to full platform cross section of 10.5m wide at spring line x 9.6m high.

Fig 1. Plan (left) and 3D image of working site and access shaft

F O C U S : N AT M / S C L / S E M

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pgrade of interchange Bank Station on the London Underground network in the UK has been an exercise in intricate design and construction of underground structures in the heart of the financial centre of the city and within a complex of existing underground infrastructure, all of which had to remain in operation throughout the works.

In a successful collaboration between Dr Sauer & Partners, Dragados and the London Underground project management team, the upgrade project began with award of the £642 million design-build contract in July 2013 and had progressed to substantial completion of the civil works in July 2020. With the aim of boosting capacity of the underground station by 40%, the new structures include a new Northern line platform and running tunnel to convert the existing centre-island platform to two separate platform tunnels.

To complete the complex SCL (sprayed concrete lining) works, several technical achievements to improve constructability and protect the workers were developed and implemented successfully. These have included: • Uphill and downhill excavation of 30 degree inclined escalator barrels in a top heading and combined bench/invert sequence; • Removal of load bearing foundation piles of four high-profile stakeholder buildings; SCL advances through London Clay

Fig 2. Design of a fully mechanised joint between top heading and bench eliminating need of workers in the face

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Dr Roberto Schuerch, Pini Swiss Engineers and Roland Herr, Technical Journalist

A Working from the SCL canopy between exposed operating platform tunnels

F O C U S : N AT M / S C L / S E M

Load transfer of piles

During excavations, four 20m deep x 1.8m diameter end bearing foundation piles supporting an existing 1970s office building required interception.

A load transfer structure was designed to transfer the load of up to 10MN of each cut foundation pile to an arched reinforced concrete structure bridging over the new tunnel to deliver the loads to a reinforced concrete invert and diffused to the ground.

A set of intricate excavations was required to create connecting adits to existing and operational parts of the station. The preliminary design of handmined timber headings was redesigned to a sprayed concrete lined access tunnel and canopy. During excavation, the narrow space between operating platform tunnels was opened up, with the lean squareworks ground support system maximising the space between the back of the platform linings. Movements to both platform structures during adit excavation were as predicted and below 40mm on the diameter.

Escalator barrel excavations

Escalator barrels of about 7m x 6m high and on a 30 degrees decline progressed top down in a sequence of top headings and combined bench/inverts. Excavators and spraying machines were hooked to a winch at the top and personnel wore harnesses to ensure health and safety. The

Option A sprayed radial joint was especially beneficial on the escalator tunnels.

Escalator 4 required uphill excavation between the existing and operational Central line platform tunnel assets and with no access from the top. Close collaboration between design and construction was required to complete excavation successfully.

The construction works at Bank posed unprecedented risks and pushed the limitations of tunnelling equipment and the use of the SCL technique. In the end, five different types of excavators and four different types of SCL spraying robots were required. Due to the complexity of the works, the excavation advances were drawn as graphical images for the workers.

Following primary supported excavation the underground structures were finished with either a spray applied or a plastic sheet waterproofing membrane and steel fibre reinforced sprayed or cast concrete secondary linings.

In July 2020, after approximately 1,200m of SCL excavation, 1,840 advances, 1,195 daily review meetings and 995 required excavation and support (RES) sheets, the SCL excavation works for the Bank Station upgrade were successfully completed. n

References •

Optimised design wins Bank Station upgrade – TunnelTalk, July 2013

Unavoidable uphill excavation of escalator 4; Downhill excavation of escalator 2

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remarkable project of special design and excavation is under construction under the city of Jerusalem, Israel, as the first phase of the Gateway project to create an underground traffic access and parking facility for the modern quarter of the city and its business hub, close to the historic Temple Mount area and at the start of a terminus for a rail connection to the Tel Aviv airport. Following a presentation at the 2020 Salzburg Geomechanics Colloquium, Roland Herr spoke with Dr Roberto Schuerch about progress of the project, its design and construction challenges.

Two parallel caverns of 20m wide x 30m high x 270m long lie beneath Shazar Road in the Temple Mount area of Jerusalem with just 3m to 12m overburden, passing within 4.5m of the new Hauma train station and within 7m of the planned K convention centre.

Excavation of the parking and road caverns by the contractor Electra Group for owner Moriah Jerusalem Development started in April 2017 to designs prepared by Pini Swiss Engineers. Opening of the facility is planned for end of 2022.

Each cavern has a three-lane road in the upper part and about 700 parking places distributed over five floors beneath.

The distance between the parallel caverns is 3.8m at the top and 5m in the lower area.

With the start of the operation, traffic will be connected by six cross passages between the caverns and five vehicle exits and eight pedestrian connections to the Convention Center of Jerusalem, the Hauma railway station and other nearby structures. The caverns were excavated by drill+blast and simultaneously from both the east and west portal, under shallow cover and through weak sedimentary rock. The size of the caverns, the narrow distance between them, the limited overburden, the difficult ground conditions, awareness of nearby structures, and the intense potential earthquake activity of the area, make the Shazar project technically very challenging.

The geology consists mainly of dolomite and dolomitic limestone of the Bina-Weradim formation. The upper portion of the rock mass is highly weathered with extensive karst features. Above is a 3m layer of fill.

The weathering of the 3m to 7m layer had it classified as soft ground. Below 7m, both intact and poor jointed, fractured and crushed rock has been encountered. Sound dolomitic limestone appeared at about 30m to 40m below ground surface. Major karst cavities, both empty and filled with clay, have been encountered with one of the largest having to be filled with more than 750m3 of concrete.

Due to the limited overburden, the poor ground conditions and the large cavern span, large settlements and, in the worst case, crater formation at ground surface were identified as the major geotechnical hazards during excavation of the top heading. A pipe umbrella presupport system in combination with full face excavation was applied over the majority of the 270m length of the caverns.

Partial excavation of the top heading, with

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Car parking excavations in Jerusalem

Fig 1. Cross section of the caverns in relation to Hauma Station of the caverns (Fig 1). It was part excavated by drill+blast, starting from a circular shaft, and part from the surface outside the Jerusalem hill. Previous analyses by others identified that the excavation of the caverns may create unacceptable stresses in and around the narrow rock pillar between the cavern and the station. These stress levels, combined with the fact that the station walls are unsupported over a height of 8.5m on the vertical span, was judged unacceptable for the serviceability and ultimate state of the station, thus questioning the technical feasibility of the entire project.

The final design consisted of an intervention in the station, reinforcing the station wall using steel plates. This solution was combined with sequential excavation of the top-heading in the area and a risk management plan based on intensive

monitoring of the wall behaviour during excavation. Deformation measured in Hauma Station during cavern excavation remained within the expected ranges and no cracks appeared in the station walls.

Excavation of the top-heading in both caverns started in April 2017 and was completed in August 2018. Benching in both caverns started in February 2018 and was completed in July 2019. Casting of the final lining started in August 2019. Value of the construction contract and the total investment in the project was withheld and works are in the final stages for the parking caverns to start operation at the end of 2022. n

F O C U S : N AT M / S C L / S E M

a central drift enlarged with two side drifts, was added and applied over the most critical areas. The primary support of the top heading consisted of a combination of steel ribs and a 45cm shotcrete lining.

The instability of the rock mass below the top heading was another significant hazard. To mitigate this risk, a 1m2 longitudinal foundation beam reinforced with a longitudinal coupled reinforcement was installed at the base of the topheading span on both sides. Each beam was interrupted only by the junctions of shafts and cross-passages. During the casting of the in-situ final lining, the beams were used as the foundation for the gantry crane. Prestressed rockbolts were installed beneath the top-heading foundation beams to reduce further the risk of vertical settlements of the top heading.

Due to the narrow distance between the caverns and between the caverns and the new Hauma Station, the instability of the rock pillar presented a major hazard during bench excavation. To mitigate this risk, the maximum height of bench excavation was limited to 3m. Four rockbolting patterns were designed to cope with all possible geological scenarios. The patterns included cross-bolting between the caverns using Gewi bolts with a preload of 110kN. Primary support of the walls consisted of 30cm thick shotcrete reinforced with two layers of steel mesh. Additional strengthening was applied in the areas of the connection passages and exit shafts.

The final lining was designed without taking into account the favourable effect of the primary lining and support. To face all hazards and load combinations, the final lining is a 45cm thick cast in place steelreinforced concrete arch in the crown, a 90cm thick concrete slab across the top heading invert, 30cm cast concrete and installation of precast parking slabs designed to support the ground pressure under both static and dynamic conditions.

A sheet membrane waterproofing is placed behind the final lining. The final lining was cast from the bottom up after completion of cavern excavation.

The potential of earthquake activity was investigated thoroughly for both the construction and operation phase of the caverns. During excavation the behaviour of the caverns was monitored by installed optical prisms total stations and prism arrays, load cells and extensometers, and by monitoring the force in the prestressed bolts. Systematic probe drilling was carried out to identify the presence of karst features in the pillar and beneath the benches. Detected voids were filled with cementitious grouting. The longitudinal foundation beams were designed to cope with the worst-case scenario of a badly filled karst cavity extending underneath the top heading foundation.

One of the most critical sections of the project was in the area adjacent to the new underground Hauma Railway Station where, for a length of 90m, the north cavern runs within 4.5m proximity to the station. The station was not part of the contract and was built before the cavern. The platform level of the station is lower than the bottom

Excavation of the 30m high x 20m wide caverns

References • •

Controlling blast vibrations – TunnelTalk, December 2020 Explosives for blasting in civil excavations – TunnelTalk, November 2020

Excavation of the 30m high x 20m wide caverns

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High altitude location of the project taxed construction phase men and machinery

Rohtang pushed NATM to the limits

Roland Herr for TunnelTalk

F O C U S : N AT M / S C L / S E M

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xtreme working conditions at an altitude of more than 3,000m above sea level, water ingress of more than 250 litre/sec, high rock pressures with extreme deformations and rapid changes in geological conditions presented major challenges during excavation of the Rohtang road tunnel in the Himalayas in India. At the 2020 Salzburg Geomechanics Colloquium, Peter Reichenspurner and Thomas Riedel of contractor Strabag, in joint venture with Afcons, explained how conditions pushed the NATM excavation method and the crews to the limit during the 10-year construction period from 2009 to 2020.

The 8.9km long, single-tube tunnel was constructed under a contract of about €250 million to avoid the dangerous route over the Rohtang Pass, shorten the ManaliLeh Highway by about 50km, and provide an all-season route between Himachal Pradesh State and the State of Jammu and Kashmir. The 13m wide excavation accommodates two traffic lanes, two footpaths and an emergency egress beneath the carriageways with entry points every 500m. The 50cm thick unreinforced in-situ final lining was designed with no systematic waterproofing system and an intermediate ceiling provides for transverse ventilation and smoke control. (Fig 1).

The high altitude and its rare atmosphere that affected personal health as well as a loss of equipment performance. Excavation was planned to progress using drill+blast from both portals however getting to the job site was a challenge with load restrictions on bridges and with landslides, falling rocks and extreme weather conditions a regular occurrence on the local roads. Under

these conditions, construction work at the north portal was only possible for about six months per year.

Drill+blast excavation started in 2010 and progressed on a top-heading, bench and invert sequence on a cross section that ranged from 140m2 to 205m2 depending on the excavation class.

With the rock formations unsuitable for determining designed excavation classes, a change to the NATM processes was incorporated into the design and ground behaviour was stipulated as an additional criterion. This meant that monitoring was an essential part of the NATM excavation process.

At about 1.93km, horizontal deformations combined with severe cracking resulted in initial failure of the heading. Water ingress increased, with up to 150 litre/sec inflow recorded from the top-heading face alone.

At 2.05km a major collapse occurred causing an inflow of about 400m3 of water-saturated material. Several further collapses occurred as the drive progressed. The largest inflow of loose saturated material was about 1,000m3.

The high level of water ingress created cavities primarily in the crown area. At 2.4km the pipe umbrella pre-support collapsed with deformations in excess of 800mm recorded in the crown. The area was recovered with timbers and shotcrete.

The conditions were subsequently linked directly to a watercourse on the surface.

As the heading approached the main identified fault zone, new excavation classes were defined to increase the support resistance. Additional anchors were installed and drainage pipes were inserted to manage water ingress. Pipe umbrella pre-support was installed on 15m rounds at the start of

Largest influx of material (left) and chain reaction collapse towards the face (right)

Fig 1. Design of the two-lane road link

the main fault zone. As geotechnical and geological conditions deteriorated, the presupport pipes were lengthened, the pipe diameter was increased from 76mm to 114mm, the pipe rows were doubled and the spacing reduced to skin-to-skin with internal reinforcement added.

After various trials, the top-heading was eventually advanced in sequential drifts with shotcrete and spiles used also in the face. In some cases, longer face spiles with microfine cement grouting and micro piles in the crown were required together with consolidation and sealing pre-grouting.

In some areas of the north drive, the primary steel fibre reinforced shotcrete behind the face flaked off. This was caused by the biotite schist encountered and was largely mitigated by switching to steel mesh reinforcement.

In addition to shotcrete cracking and spalling, squeezing rock conditions caused rockbolt plates and lattice girders to buckle.

In areas of more than 1,500m overburden, stress release rock bursts occurred at up to 200m behind the face.

To manage deformations, adjustments of the design excavation and support classes were undertaken, sometimes within an advance cycle. The largest deformations were checked by providing deformation slots along the tunnel axis and inserting lining stress controllers.

The completed tunnel opened to traffic in October 2020 with extra effort to continue the final construction phases while dealing with the coronavirus pandemic. n

References •

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Geotechnical concerns for deep mountain drives – TunnelTalk, May 2012

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Spraying ultra-high performance FRC Catherine Larive, Sebastien Bouteille and David Chamoley, CETU, Bron.

France, Bertrand Petit, Alain Huynh and Francois Teply, Freyssinet, Rueil-Malmaison, France, Sebastien Bernardi and Julien Derimay, Ductal LafargeHolcim, Paris, France, LafargeHolcim R&D Center and IFSTTAR, France

FOCUS: CONCRETE LININGS

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ltra-high performance fibrereinforced concrete (UHPFRC) is usually a self-compacting material.

For pumping and spraying UHPFRC on vertical surfaces or overhead a new formulation was required. LafargeHolcim redesigned its Ductal concrete mix to this end and new onsite pumping and spraying equipment was developed by significantly modifying traditional equipment.

Since UHPFRC was developed in France in the 1980s, a broad variety of mix designs have been used, all with a fluid and often self-levelling consistency that made spraying UHPFRC a real challenge.

The aim was to make sprayable Ductal concrete without adding any accelerator or activator. The challenge was to create the cohesiveness necessary to successfully apply a significant thickness on the substrate without any risk of slipping or tearing.

Steel fibres in the plane perpendicular to the substrate contribute to the adhesion by artificially increasing the yield stress of the fresh product. As soon as setting begins, the suction effect significantly increases adhesion between the sprayed product and the substrate.

Cohesiveness is obtained due to a significant yield stress when the mixing phase is finished. The viscosity however must remain suitable for pumping over long distances. A relatively low viscosity of 20 Pa·s to 40 Pa·s at a shear rate of 15s-1 and a yield stress of >300 Pa at a shear rate of 0.07s-1 enabled adhesion of the fresh product on the support. Water and admixture quantities had to be adjusted for a viscosity compatible

with pumpability requirements.

Proportions of cement, cementitious additives and sand were optimised to create an adapted skeleton. Several dosages of steel fibres of diameter 0.2/L 14mm and up to 3.25% in volume were tested.

A rheometer was indispensable for understanding the behaviour of the fresh mix as a function of the shear rate and simple, robust and affordable field equipment was necessary to check and adjust the targeted yield stress on site. A tailor-made blade for a hand-operated vane shear achieved an adequate range of yield stress.

Dry ingredients were premixed and delivered in bags with water, admixtures and steel fibres added at the batching plant on site. For a high viscosity mix, the planetary mixer with a hydraulic motor required specific modifications of the blades and adaptations of the motor.

The mixing sequence and method of introducing the steel fibres were adapted so that it was feasible to pump the wet concrete in 50mm diameter hoses. After modifications to the hydraulic accessories, a piston pump allowed pumping and spraying at a rate of 2m3/hr to 6m3/hr. The capacity of the compressor was greater than 10,000 litres/min with a pressure of 7 bar. The spray nozzle was adapted so the air flow could homogeneously disperse the UHPFRSC. To verify the mix and the spray performance, a sample of fresh UHPFRSC was sieved under water and the fibres on the sieve removed with a magnetic tool and dried. Calculations ranged from 5% to 10% rebound or loss.

Introduction of steel fibre concrete in the UK Colin Eddie, UK consultant, and Marc Vandewalle, a pioneer in the field of steel fibre reinforced concrete in the tunnelling industry, speak of the introduction of steel fibre reinforcement for shotcrete and precast concrete lining segments in the UK and across the world. They speak of scope for further development of the technology and the state of codes, standards and tests for the successful design, production and application of SFRC shotcrete and for precast concrete lining segments. n

Spraying inside a corrugated pipe After spraying trials and laboratory tests, Freyssinet used the UHPFRSC to rehabilitate metal pipe culverts under highways and to line corrugated pipes. Bending tests on corrugated flat sprayed samples confirmed that the French standard for a structural UHPC with a characteristic compressive strength higher than 150 MPa can be achieved. For load tests on the reinforced corrugated metal culvert, deformations versus applied loads were measured.

INCA2 software made it possible to calculate the equilibrium of a section following a nonlinear stress deformation law.

The shape of the load-displacement curves shows that the maximum load reached during the test should be very close to the ultimate strength of the structure.

The potential application field for UHPFRSC is wide. Although the material itself is expensive, savings are expected in terms of total construction and maintenance costs, since less material is needed, less time is required and the expected lifetime of the repair is longer than for other methods. n

References •

Critical analysis of FRS durability study – TunnelTalk, March 2015

Face to Face with Marc Vandewalle, pioneer of steel fibre reinforcement

References

• • •

SFRC durability in a chlorinated environment – TunnelTalk, April 2016 20 years of fibre concrete linings in the UK – TunnelTalk, October 2010 Heathrow Baggage Tunnel – TunnelTalk, October 1994

Watch the video  The research, introduction and continuing development of steel fibre reinforcement for shotcrete and precast concrete segments is described by Marc Vandewalle, a recognised pioneer and chief advocate of the technology. n

References • • •

Watch the video 

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Lee Tunnel wins prestigious concreting award – TunnelTalk, December 2016 SFRC durability in a chlorinated environment – TunnelTalk, April 2016 Fibre-reinforced concrete for precast segments – TunnelTalk, May 2014 20 years of fibre concrete linings in the UK – TunnelTalk, October 2010

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Shotcrete best practice recommendations

Spraying shotcrete overhead

Spraying shotcrete overhead is challenging.

Propelled at high velocity against the overhead surface, the dynamic energy compacts the concrete in place. However, plastic shotcrete has no immediate strength. The weight of a single layer or multiple layers of shotcrete can be enough to pull the shotcrete down and cause local or large scale fallouts. In addition, improper application of overhead shotcrete and other circumstances can lead to delamination and voids in the installed shotcrete.

During the plastic shotcrete phase, the adhesion of the plastic material to the ground surface in combination with the cohesion of the plastic shotcrete material to itself are the forces acting against the self-weight of the plastic shotcrete.

Because the chemical reaction of the cement in the mixture is still in progress and has not yet created significant strength, the plastic shotcrete sticks overhead only if the conditions for adhesion and cohesion are right.

Another important factor is the interlocking effect during the shotcrete installation on irregular, blocky, or porous ground surfaces. The shotcrete interlocks mechanically, allowing the shotcrete material to fill and bridge over irregularities.

The use of this interlocking effect is a major aspect of controlling the shotcrete bond.

Experienced underground nozzlemen take advantage of ‘reading the rock’.

The ASA provides guidance for the proper application of shotcrete overhead by covering mixture design, surface preparation, the thickness of each pass, utilization of anchors, lattice girders, and reinforcement, as well as challenges with waterproofing membranes. It also highlights the importance of overhead shotcrete only being applied by qualified shotcrete nozzlemen.

One of the key questions for overhead shotcrete operations regarding safety is the definition of a re-entry criteria, allowing the crew movement beneath the newly installed overhead shotcrete.

The position statement notes that it is generally preferred to develop re-entry criteria based on actual early-age strength development, rather than a predetermined time period. However, it is emphasized that neither a strength- nor a time-based re-entry criterion provides a guarantee against fallouts, as these are influenced by a multitude of factors.

There is a need for a project-specific definition and evaluation of the re-entry criteria. Typical values for an early

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compressive strength-based re-entry criteria range between 150psi to 500psi (1MPa to 3.5MPa) and are typically measured with a penetrometer or end beam tester. Re-entry criteria for those other than the crew should be significantly higher.

Recommending that the contractor follows the guidelines provided by the American Concrete Institute Committee for Shotcreting (ACI 506), the position statement notes that preconstruction testing and mockups are essential to test the mixture design, strength development, equipment operation and in particular the accelerator dosing pump calibration and project conditions. The tests are seen as a beneficial tool to avoid safety hazards and rework during execution and not simply a contractual obligation.

Shotcreting on membranes

Applying shotcrete for final linings against synthetic sheet waterproofing membranes has become more common. However, the smooth surface and potential pillowing or vibrating of the waterproofing membrane poses a challenge compared to a shotcrete application against a stiff and rough surface. Improper application of shotcrete against waterproofing membrane in a double shell system, with a separate temporary lining at the extrados and the final lining at the intrados of the membrane, can lead to poor-quality shotcrete due to delamination and voids, local or large-scale fallouts, and can be the subject of technical disputes about cause and effect responsibilities.

The ASA position paper discusses the basic elements of the adhesion of overhead and vertical shotcrete on a waterproofing membrane, the proper application techniques, and emphasizes the use of mockups. It also provides recommendations for contractors and owners on how to properly specify, apply, and inspect shotcrete against waterproofing membranes.

The key technical challenge is the weight of the plastic shotcrete before it gains sufficient strength to support itself.

Axel Nitschke, Chair, ASA Underground Committee Adhesive forces of the plastic shotcrete can only be transferred into the initial lining at the fixation points of the membrane or where the membrane is supported by a self-supporting reinforcing bar cage.

Reinforcement and lattice girders provide an important element during the installation of shotcrete. It is important to ensure that either the self-supporting rebar and/or the anchoring system is strong enough. However, the weight to be carried strongly depends on the shotcreting procedures and patterns as well as the strength development of the shotcrete over time.

The potential for damaging the membrane by fibers is a frequent question.

There are two different scenarios. The first deals with fiber-reinforced shotcrete in the substrate. To avoid damages to the membrane, typically a non-fiber-reinforced smoothing layer is installed. The second scenario is applying fiber-reinforced shotcrete as a final lining on top of the membrane.

Spraying steel fiber-reinforced shotcrete does not damage or puncture the membrane because the forces acting on the fiber are not strong enough to push the fiber into the membrane, and typically the fibers tend to orient parallel to the membrane on impact.

Coordination between the membrane installer, the reinforcement installer and the shotcrete contractor is another key element. An improperly installed membrane can lead to performance issues for the shotcrete lining.

The ASA position papers provide guidance in areas that are currently not well covered by other guidelines or generally accepted literature, and it is a goal of the ASA to support the industry by filling these gaps. Both position papers are available for free download on the ASA website. n

FOCUS: CONCRETE LININGS

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wo critical topics of underground shotcrete application – the application of shotcrete overhead and shotcreting on synthetic sheet waterproofing membranes – are covered in two American Shotcrete Association (ASA) position statements, aimed at providing industry guidance on the best practices and a common technical understanding of the topics covered.

References •

Testing durability of PVC membranes – TunnelTalk, October 2018

ASA guidance for achieving quality initial and final shotcrete lining

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Single-shell lining design and advantages

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excavation and drill+blast overbreak.

Significant over break is inevitable if the Q-system parameters show a ratio of joint sets (Jn) to surface roughness (Jr) equal to or more than 6. When using the NMT single-shell S(fr) lining option, overbreak is less of an issue. The area of the excavation perimeter is greater with overbreak, but the over-break is not and should not be filled. The rock mass, assisted by systematic bolting and shotcrete, takes the major load.

NMT based tunnels and caverns are made stable via application of the Q-system of rock mass quality estimation that encompasses a rock mass quality scale from 0.001 - equivalent to a serious fault zone where NMT may also need a local concrete lining - to 1000, which is

Credit: Right images courtesy Vandewalle

FOCUS: CONCRETE LININGS

ost, construction time, and the CO2 implications of concrete consumption are significant concerns regarding tunnel lining options. For many decades, NMT (the Norwegian Method of Tunnelling) has effectively minimized cost and time and the use of concrete. It is based on application of the Norwegian Q-system to design the rock support and emphasizes a single-shell shotcrete final and permanent lining. Its characteristics distinguish it from doubleshell options that include final load-bearing and often steel-reinforced concrete linings as the permanent finish. Such a method is more expensive, uses more concrete, can take longer to build, and usually requires a larger labour force.

A common problem in underground excavation is the incidents of profile over

Fig 1. Top: Single shell fibre reinforced shotcrete S(fr) with pre-excavation grouting with permanent CT-bolts applied close to the face; Bottom: Wire mesh reinforcement demonstrates the difficulties caused by overbreak Fig 2. Relative time (max 10:1) and relative cost (max 12:1) of Q-based tunnel support and reinforcement

Fig 3. Relative cost when applying Q-System support recommendations

Nick Barton, Independent Consultant equivalent to massive unjointed rock where careful blasting can remove the need for shotcrete, but in practice is applied perhaps with one layer of S(fr).

In typical rock masses, rock mass quality will be closer to Q = 1, which is described as poor quality with an associated mid-range bell-shaped distribution of RQD. These conditions would need combinations of corrosionprotected rock bolts and high-quality fibre-reinforced shotcrete, with stainlesssteel or polypropylene fibres. Systematic high-pressure pre-injection grouting using micro-cement and micro-silica may be required to control water inflow to create essentially dry tunnels with limited inflow of approximately 1-2 liters/min/100 linear metre of tunnel which can be dried out by the ventilation air in ventilated facilities.

Systematic pre-injection grouting may add 20-25% to the starting cost of the NMT excavations. A note is that a central value of Q = 1 or poor, often correlates with approximately 1 Lugeon or a permeability of 10-7m/sec. In such cases inflow would be unacceptable and would require injection grouting.

In support of single-shell designs, S(fr) has a lower matrix permeability compared to mass concrete and much lower single or double-layer permeability than cast concrete linings, due to the absence of radial joints in the S(fr). To achieve high impermeability of S(fr), tight quality control and good quality additives are required. Highest unit prices for additives and fibres ensure the fastest, cheapest and safest tunneling.

The relative time and costs of Q-value based, good quality S(fr) + high quality rock bolting, such as systematic patterns of bolting using corrosion-protected CT bolts with a PVC sleeve, can be illustrated, based on the analysis by Professor Steinar Roald of 50km of Norwegian and Swedish tunnel projects (Fig 1). The lower plateaux are due to minimal support and reinforcement.

Whatever the rock mass quality the doubleshell cost level is high in the left corner of the graph due to the processes involved and the materials used. The systematic double shell concept will be faster, per meter, than non-systematic local zones of cast concrete in NMT projects, since this local heavy support has to be applied where rock conditions are challenging, hence the approximately estimated lowered time box in the left diagram of Fig 2.

The same trends of relative cost versus Q as in Fig 2 are found when directly applying the Q-system support recommendations, for a range of road tunnels, of varied cross-section, with material costs, blasting and 4km of muck transportation included (Fig 3). n

References • •

44

TunnelTalk ANNUAL REVIEW 2020

Author references can be found in the full length article on www.TunnelTalk.com Pre-excavation grouting – a Nordic focus – TunnelTalk, June 2017

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Integrated engineering for quality segmental linings

C

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Sam Simons, Independent Concrete Segmental Lining Consultant

Top: Accurate ring build in as-built segmental lining is possible Middle: Ring build and TBM operation must integrate precisely to avoid lining damage and defects Bottom: Process accuracy and reliable unit production must be repeated many thousands of times to reduce defects to below 0.5% of steel fibres with accurate methods of production, dosing and distribution, and reliable performance verified by sample and full-scale laboratory testing.

Despite these proven specialist materials and the different codes developed

for design methodology, the performance of SFRC (steel fibre reinforced concrete) is more likely than ever to be compromised by adoption of fibre options that do not provide reliable distribution or long-term creep properties. Specifications continue to require minimal SFRC performance.

TBM build conditions present both possible and predictable deviations placing demands on precast unit joints between interconnected rings with submillimeter accuracy of segment body dimensions, connection components and seals. All elements must perform to an expected range of build tolerance without compromise in the macro world of the TBM. Component detailing, including bolts, dowels and gaskets, must respect segment size and shape, and construction must respect the component design limitations. Improved solutions cannot be based solely on component cost or demands on progress rates without fully exploring the higher cost impacts of poor tunnel build.

In addition, the speed of tunnel advance must not compromise annulus grouting without which segmental linings will have irregular support and will almost certainly compromise build shape and tolerance.

A single ring does not make a tunnel. Process accuracy and reliable unit production must be repeated many thousands of times to reduce segment fabrication defects to below 0.5%.

Integrated component design, must address, for example, gasket displacements limited by the designed jointing system to a much lower degree than standard specifications. Otherwise the design anticipates breaches of ring geometry caused by poor build quality.

Correctional packing should not be required with accurate segment tolerances and rolling ring design. Reliance on packing and its effect on dowels and gaskets becomes ignored at the tunnel face during the ring build. Packing used only to decrease contact stress and corner damage from solid gasket corners also just introduces more costs rather than addressing the latent problem.

EPDM cast-in gaskets development, with compliant compressible corners, provide uniform stress and seal contact through the gasket without overstress to the concrete. Gasket selection should not be made based on historical design and unit price alone. The cost savings during segment manufacture and reduced damage in ring build should be taken into account.

A more integrated approach is needed to properly manage tunnel lining defect and delay risks to create the achievable objective of defect free tunnel construction in the coming decade. n

FOCUS: CONCRETE LININGS

oncrete segmental lining practice has undergone major development over the last 40 years and should be considered as significant as the advancement of TBM design to the success of the tunnelling industry in the same period. Rejects in the casting yard and costly repairs of damage during construction, however, are still adding high extra cost to projects. Without segment production knowledge, the costs, the schedule and delayed availability of the lining on site can increase segment supply contracts by 50-100% over procurement assumptions. But zero defects and high quality can be achieved with an integrated engineering approach.

The task of manufacturing concrete segments appears easy to the inexperienced and the process can become centrally managed by commercial spreadsheets with low technical input.

The result however is frequent repetition and re-learning of common difficulties with failure to deliver a quality tunnel product at reliable cost. Project management needs technical appreciation of history, research, advancements and past mistakes to avoid repeated failure to deliver the expectation of defect free segmentally lined tunnels.

Today, segment manufacture requires aerospace accuracy, delivering a prefabricated lining solution on the limits of physical processes. Without detailed knowledge, procurement decisions are made on simplified commercial costs, without regard for design and production details that will determine the success of the final tunnel asset long into the future.

Specialist concrete is essential to justify segment manufacturing outputs at the limits of process quality and speed.

Reliable outputs are vital for cost control and top-quality mixes are required for low permeability, high durability concrete, capable of vibration, finishing and segment production in 10 hours or less. High performance production of thousands of units requires process engineering timed in seconds, through repeated activity.

Segmental construction requires concrete units with exceptional dimensional precision cast from highly specialized moulds to manage the contact loads exerted from the TBM during tunnel build and prevent cracking and leakage associated with long term maintenance.

When reinforcement is included, damage increases the risk of long-term corrosion and the additional costs of attempted repair and extended program time. Segment damage and repair is commonly accepted as ‘normal’ but causes of defects can be eliminated with application of concentrated experience. Risks must be addressed from project concept, as during construction there are few options to change strategy.

The elimination of steel rebar reinforcement cages should be a determined objective wherever possible to de-risk lifetime maintenance issues in subsurface conditions. Decades of development have engineered a range

References •

Monitoring segment production and installation – TunnelTalk, October 2018

TunnelTalk ANNUAL REVIEW 2020

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Choosing right fibre for SFRC precast segments

FOCUS: CONCRETE LININGS

T

46

here is nothing new about strengthening concrete with steel. One hundred years ago a patent was filed to incorporate steel shavings into a concrete mix to increase strength and stability. In the 1980s SFRC began to be used for underground applications, after the realisation that the cracking tensile strength of concrete, one of its main drawbacks, could be significantly improved by adding fibres, initially in shotcrete and later in concrete segments. Choosing the right fibre for segment lining application is essential but should be done in a structured way to achieve the full benefits in terms of performance, quality and cost of the project.

Fibre reinforced concrete (FRC) is a composite material characterised by a cement matrix and discontinuous discrete fibres, which can be steel, polymers, carbon, glass or natural materials. The characteristics of the materials used, and their dosage, affect the final properties of the FRC. FRC is also influenced significantly by a range of other factors such as the geometry, the volume fraction and the mechanical properties of the fibres, the bond between the fibres and the concrete matrix, and the mechanical properties of the matrix.

As it is a composite material, the behaviour of FRC is impacted also by the interaction between the matrix and the fibres, which means the transfer of load from the concrete matrix to the fibre system.

For efficient load transfer, the following three conditions must be satisfied: • Sufficient exchange surface achieved through the number, length and diameter of fibres • The nature of the fibre-matrix interface should allow for proper load transfer • The intrinsic mechanical properties (Young’s modulus, anchorage and tensile strength) of the fibre should allow the forces to be absorbed without breaking or excessively elongating the fibre For steel fibre reinforced concrete (SFRC), a fibre geometry should always be chosen that is relative to the compactness of the matrix, as characterised by its compression resistance, to avoid rupture of the fibre when the matrix cracks. Brittle fibre tensile strength failure of SFRC can occur at any age of the concrete, from one day to 10 years, and is a consequence of selecting an incorrect fibre type for the concrete, not the age of the concrete.

The ductility and post-crack strength of SFRC is determined by many different aspects, including concrete composition, fibre aspect or length to diameter ratio.

A major driver of performance is also a balanced combination of anchorage design, wire strength, wire ductility, and optimum network or distribution.

Mix design is also key. Mixing the right amount of sand and gravel aggregate can achieve an optimal density with the lowest volume of pores between the fine and coarse material, with less mortar required to fill these pores and glue everything together. The aim should be for a sufficient fine material to mortar mix with this importance increasing for higher fibre dosages.

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Benoit de Rivaz, Global Technical Manager, Bekaert Underground Solutions In accordance with Bulletin 83 from the Fédération Internationale du Béton (fib), the accepted recommendation for the design of SFRC for structural precast tunnel segments in underground construction is based on the post-crack residual tensile strength provided by the steel fibres. Nominal values of the material properties can be determined by performing a flexural bending test. One of the most common tests refers to EN 14651, which is based on a 3-point bending test on a notched beam. To obtain statistically reliable results, a minimum of 12 beam tests are recommended.

Results of beam bending tests conducted by Roma University show how a low variation provides a performance class type 5e according to Model Code 2010. The results of such a bending test are expressed in terms of force (F) vs crack mouth opening displacement (CMOD) measured in millimetres (Fig 1).

Two kinds of tests were performed on segments used typically in water tunnels: • A test simulating point load effects produced by the back thrust of the TBM during excavation, and • A flexural test simulating the behaviour of the segments when loaded under bending.

The tests were performed on two segments reinforced only with 40kg/m3 of Dramix® 4D 80/60BG steel fibre of 60mm long. This mix design is typical in segment production in terms of cost and performance.

The tests were carried out on precast segments of 250mm thick, about 1,670mm long and 1,200mm wide. Segments were made from the same batch of concrete, as were the beams and cubes for the material characterization tests (Table 1).

The average compressive strength of the fibre reinforced material, measured on eight 150mm cubes, was equal to 61.20 MPa.

Beam test procedure

The tensile behaviour was characterized through bending tests on nine 150mm x 150mm x 600mm notched specimens according to the EN 14651 code: To classify the post-cracking strength of FRC a linear elastic behaviour can be assumed, by considering the characteristic flexural residual strength values that are significant for serviceability (ƒR1k) and ultimate (ƒR3k) conditions.

In particular, two parameters, namely ƒR1k (representing the strength interval) and a letter a,b,c,d, or e (representing the ƒR3k/ƒR1k ratio).

The material can be classified as 5e according to Model Code 2010. In fact, the characteristic value of ƒR1k is higher than 5 MPa and the ratio between ƒR3k and ƒR1k is equal to 1.37, so higher than 1.3.

For the bending tests, one point load and one flexural test was carried out. The test was performed by adopting a 1000kN electromechanical jacket, with a PID control and by imposing a stroke speed of 10µm/sec.

During the test, the following measures were continuously registered: • the load F, measured by means of a 1,000kN load cell with a precision of 0.2%; • the midspan displacement, measured by means of three potentiometer wire transducers placed along the transverse line; and • the crack opening at midspan, measured by means of two LVDTs. The crack pattern was recorded at different intervals using a 100mm x 100mm grid plotted on the intrados surface.

The bending test was carried out in displacement control, using an electromechanical jack, up to the collapse.

The cracking phase is highlighted during the test. No appreciable torsion was found, as the three wire transducers measured almost coincident displacements. The maximum load was about 254kN. The point load test was performed by applying two point loads to the segment, using the same type of thrust jack shoes as used on a TBM. A uniform support is considered, as the segment is placed on a stiff beam suitably designed. Every jack, having a loading capacity of 2,000kN, is inserted in a closed ring frame made with HEM 360 steel beams and 50mm diameter Dywidag bars.

Four potentiometer transducers, two located at the intrados and two at the extrados, measured the vertical displacements, while one LVDT transducer, applied between the load pads, measured the crack openings.

The first crack for the bending test on the segment and as measured by the three wire transducers, appears for a load value of about 170kN at the intrados surface close to the midspan of the segment and propagates on the lateral surfaces. The maximum crack width is about 0.05mm For a load level of 200kN a new crack

Fig 1. Results of the beam bending tests according to EN 14 651 with CMOD in mm

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Table 1. Concrete mix design Component kg/m3 Cement 42.5 R

480

Natural sand (0-4 mm)

422

Crushed sand (0-4 mm)

423

Crushed aggregate (4-16 mm)

519

Crushed aggregate (16-25 mm) 350 Plasticiser

4.8

Water

170

Steel fibre

40

forms at the intrados surface and propagates on the right lateral face. Furthermore, a widening and lengthening of the already formed crack takes place. The maximum crack width is about 0.25 mm For the point loading test, load was applied through time. For this report it is worth noting that the term load refers to the single shoe.

During the test, the first crack appeared for a load level of 1,000kN for each steel pad, between the two shoes and at the top and extrados surface. This spalling or splitting crack propagates through the extrados and intrados surfaces with: • a maximum crack width of lower than 0.05mm under a load of up to 1,750kN and • a bursting crack opening under a load level of about 2,000kN and extending for a length of about 80cm at the intrados and about 100cm at the extrados.

The maximum crack width measured with a crack gauge during the test was equal to about 0.35mm. The maximum crack width at the end of the test, after complete unloading, was about 0.05mm (Table 2).

The technical report shows that:

Table 2. Measured crack widths during the point load test Name Crack width [mm] 1000 1150 1350 1500 1750 2000 2250 [kN] [kN] [kN] [kN] [kN] [kN] [kN] 1 <0.05 <0.05 <0.05 0.05 0.05 0.10 0.30 2 <0.05 <0.05 <0.05 0.05 0.10 0.10 3 <0.05 0.05 0.10 0.20 4 <0.05 <0.05 5 0.05 6 0.15 7 <0.05 Table 3. Maximum crack widths comparison Load [kN] 125 160 180

210

222

2500 [kN] 0.35 0.10 0.20 <0.05 0.10 0.20 <0.05

0 [kN] 0.05 0.05 <0.05 <0.05 <0.05 0.05 0

250

270

Crack width SFRC <0.05 0.25 0.35 0.60 1.00 n/a* n/a* SFRC-GFRP <0.05 0.10 0.15 n/a* 0.35 0.45 0.70 n/a*= measure not available since the crack width was not recorded at this load step, or the segment did not reach this load value Table 4. Comparison of maximum crack widths Load

Maximum crack width [mm] SFRC

SFRC -GFRP

1st crack [kN]

1250

0.05

<0.05

Service load [kN]

1580

0.10

0.05

Unblocking thrust*[kN]

2670

0.40

0.25

Unload [kN]

0

0.15

0.10

*For metro tunnelling, TBM pushing capacity coincides with unblocking thrust • hardening post crack behaviour at the section level allows for immediate cracking control to the SLS (serviceability limit state) design, and • validates a maximum crack opening for design approach based on the Model Code 2010 and includes the

new generation of high performance fibre, with high tensile strength (> 1,800MPa), optimized anchorage and a high length:diameter ratio of greater than 80 and at a dosage that provides a minimum network of 10,000m of reinforcement per m3 of concrete.

Dramix® Hardening post-crack behavior at a low total cost

Steel fibre concrete reinforcement Using steel fibre reinforcement for tunnel applications assures an easy handling process and optimal crack control. This results in: • A safer, more durable concrete structure • A reduced carbon footprint • A lower total cost

Abu Dhabi, STEP

Go to www.bekaert.com/underground and get in touch with your local underground expert.

BEK-3694_Ad Tunnel talk_Crea 1.indd 1

1/06/2021 11:08

FOCUS: CONCRETE LININGS

The standard deviation of the test results could be influenced by many parameters such as mix design, casting, and testing, and is also strongly influenced by the fibre number and network effect. A higher fibre network leads to a lower standard deviation, which is key to achieving the required characteristic value for design.

For the classification of the post-crack strength of FRC, a linear elastic behaviour can be assumed, by considering the characteristic residual flexural strength values that are significant for serviceability limit state (SLS) and ultimate limit state (ULS) conditions. Two parameters are especially important, and need to be specified by the designer, namely: fR,1k, the minimum value for SLS; and fR,3k, the minimum value for ULS. Hardening post-crack behaviour at section level through a beam test immediately allows for crack control and for serviceability limit state design.

In recent years, demand has increased for higher compressive strengths for the precast segment from C40 to C70. This is driven by the need for more structural requirements to address durability issues and early age demolding for increased production capacities. On the down side, the increase in concrete strength with age, and hence better bond to the fibres, leads to fibre failure in the cracks, rather than bond failure, resulting in a much more brittle behaviour.

Fibres provide a more ductile behaviour when they are gradually pulled out, and for this, hooked ends are essential to generate the ductility and post-crack strength of concrete.

A correct network effect of the fibres in the concrete is key to optimised cracking control, post-crack behaviour, fibre homogeneity and dispersion in combination with glued fibre, and low dispersion in the result.

Keeping the same network effect is essential to ensure consistent behaviour and cracking control. For example, a fibre with a length to diameter ratio aspect of 80 (60mm length x 0.75mm diameter) offers a network higher than 11km of fibre/m3 of concrete with a fibre content of 40kg/m3. A minimum network of 10km/m3 is recommended. For this a fibre length to diameter ratio of 65 (60mm length x 0.9mm diameter) will need a fibre content of about 55kg/m3. This means that using a fibre diameter of 0.9mm vs 0.75mm adds about 40% more kg/m3 to achieve the same minimum network (Table 1).

After many years of experience, Bekaert designed its Dramix® 4D 80/60BGP specifically for precast segments. It has a nominal tensile strength of 2,200 N/mm2, a Young’s Modulus of 200,000 N/mm2, and a strain at ultimate strength of 0.8%.

It is supplied with a fibre length of 60mm and diameter 0.75mm, giving a length to

diameter aspect ratio of 80.

Dramix® 4D 80/60BGP offers a hardening post-crack behaviour in terms of crack width control and SLS design, and low variation in the result to guarantee a highperformance class according to the Model Code 2010 classification.

Hybrid segment design

The adoption of fiber reinforced concrete (FRC) segments, without any reinforcement rebar, provides advantages in terms of cost and precast production operations.

Nevertheless, in some parts of a segmentally lined tunnel, particular loading conditions, typically under prevalent bending actions such as in cross-passage breakout or under particularly shallow alignment, the FRC solution can not satisfy the requirement.

Adopting glass fiber reinforced polymers (GFRP) reinforcement rebar in concrete segments can be an alternative to traditional steel rebar when a high resistance to environmental attack is required since GFRP reinforcement does not suffer corrosion problems. From the mechanical point of view, GFRP rebar is characterised by an elastic behaviour in tension.

Compression strength is often neglected, due to its low value. GFRP is also electrically and magnetically non-conductive.

This type of reinforcement is not suitable for all applications, but it appears appropriate for precast segments, both for provisional and permanent applications.

To evaluate the potential applications, FRC segments of a typical metro tunnel geometry were cast with and without GFRP rebar and tested. Both bending and point load tests were carried out.

Four 1.4m wide x 300mm thick steel fibre reinforced test segments were produced for a 6.4m o.d. ring. Dramix 4D 80/60BG steel fibre was added to the concrete matrix with a content of 40kg/m3. The average compressive strength, measured on six 150mm cubes, was equal to 62.35 MPa. The tensile behavior was characterized through bending tests on eight 150mm x 150mm x 600mm notched specimens according to the EN 14651 code. Nominal stress versus the crack mouth opening displacements (CMOD) were plotted (Fig 2).

The two hybrid SFRC-GFRP segments were further reinforced with a perimetric GFRP cage. The GFRP rebar had a nominal diameter of 18mm and was characterized

by Young’s Modulus of about 40 GPa and ultimate tensile strength equal to 1000 MPa. Both segment types were subjected to full-scale flexural and point load tests for evaluation of structural performance, in terms of structural capacity and crack pattern evolution, under bending and TBM thrust conditions.

Bending tests

The bending tests were performed by adopting a 1000kN electromechanical jacket, with a PID control and by imposing a stroke speed of 10 µm/sec. The segments were placed on cylindrical supports with a span of 2,000mm and the load, applied at the midspan, was transversally distributed be adopting a steel beam and measured by three potentiometer wires and two LVDTs. The behaviour of the SFRC and SFRCGFRP segments are compared where the average value of the displacement, measured by the three potentiometer wires, is plotted versus the load. The first cracks appeared for a load value of about 125kN for the SFRC and 120kN for the SFRC-GFRP segments. In both cases the first cracks were opened on the lateral surfaces close to the midspan and propagate on the intrados.

After a first comparable response, the SFRC-GFRP segment presented a peak load about 63% higher than the SFRC segment at 367kN compared to 225kN. The obtained results, including the maximum crack widths measured at different load steps, show clearly the synergic effects of the two materials in reducing the crack widths (Table 3).

Point load tests

The point load test was performed by applying three-point loads on each segment and adopting the same steel plates as used by a TBM, each jack having a loading capacity of 2,000kN. The load was continuously measured by pressure transducers with six potentiometer transducers (three located at the intrados and three at the extrados) measuring the vertical displacements and two LVDTs transducers, applied between the load pads, measuring the crack openings.

Two cycles were performed, with the chosen reference load levels equal to 1,580kN and 2,670kN (for each pad) referring to the service load and unblocking thrust of the TBM. The final crack pattern is similar for both the SFRC and SFRC-GFRP segments. The first cracks appeared for a load level of 1250kN between two pads at the top and lateral surfaces in both the cases.

Besides the splitting cracks (between the pads), a bursting crack (under the point load) formed in both the cases. The addition of the perimetric GFRP cage halved the crack width under the service load, and reduced the crack width by about 37.5% under the unblocking thrust force (Table 4). A reduction of the crack width of about 33% was measured after the complete unloading. n

References • • •

Review of FRC brittle failure considerations – TunnelTalk, March 2015 SFRC durability in a chlorinated environment – TunnelTalk, April 2016 Cracking of segmental lining under investigation – TunnelTalk, September 2019

Fig 2. Results of the beam bending tests (left) for hybrid segments comprising SFRC and GFRP cages (right)

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TunnelTalk ANNUAL REVIEW 2020

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S

election and design of the machine for a TBM project is a task more complex than might be expected. Discussions about who is best equipped to design, specify, or choose the TBM for a project can be a controversial decision given the three issues of technical specification, cost and liability.

Those who make the decision on the type and specification of the TBM also take on the liability of that decision. In many cases, interested parties including the Owner, the Owner’s Engineer or its Program Manager, and the Geotechnical Engineer, want to make or influence the decision but are often hindered by the risk and liability. The Contractor and the TBM manufacturer want to make the decision yet minimize their liability exposure created by the decision.

In reality, everyone should be involved in making the decision and in a collaborative manner. Too often, however, commercial and legal issues get in the way leading to a decision that is a compromise and not necessarily the best choice.

Without ground information the choice of tunneling means-and-methods, including the choice of TBM, is very speculative. Ground information from bore hole interpretation is still very limited, with the ground profiles and characteristics seen in geotechnical reports derived from small samples of ground taken from a small vertical bore or core. Everything between each bore hole is educated guess work based on interpretation and knowledge of the regional geology. But this is the best information available for the TBM selection with respect to the geology, and who is most suited to address this issue other than the Geotechnical Engineer for the project.

For most of many tunnel projects these days, the GBR (geotechnical baseline report) has become the document of choice to share the risk of variation in the ground.

It is based on the Owner’s interpretation of the ground conditions and provides a level platform for ground risk on which all contractors can bid. This has resulted in less variance in bids and provides a clear basis for ground related claims.

But for TBM selection the reliance on the GBR is ill advised. It is a risk sharing mechanism in which, if certain provisions are encountered, the contractor will be entitled to additional compensation. If the TBM selection is based on the GBR and the machine is then considered not fit for purpose or underdesigned, how can remedial measures be quantified on a GBR risk management basis? Remedial measures may not be easily implemented in the field and any significant modifications to the TBM may be at high cost and with damaging schedule impacts.

The Design Engineer working for the Owner will try to maximize its input and control on the project and in many cases, this leads to extensive prescriptive specifications and design documents on construction means-and-methods. This will typically include all the calculations, modeling and specifications for the permanent works and may include some design of shafts and temporary ground support.

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There is a wide variance worldwide in the detail of a bid TBM specification document.

Some are highly prescriptive documents, verging on the edge of a TBM design. Other performance specifications may state that, based on the geotechnical information, the TBM to be supplied has to excavate and build the tunnel as per the drawings and without causing adverse settlement or damage to nearby structures. In this case the contractor submittal requirements tend to be more extensive. In some cases, the TBM specifications in the bid document are quite prescriptive but based on limited geotechnical information provided in the tender package and acquired from a few widely spaced borehole logs. In such situations it is essential, and normally a contract requirement, for the contractor to carry out additional in-depth ground investigations to determine the ground profile and value of ground parameters to allow for modelling for the design of the permanent ground support and to determine the parameters of the TBM type and specifications. Due to schedule pressure, the TBM is frequently ordered before the additional ground investigation is complete.

“The advance rate is never baselined in a GBR” Basing the TBM type and specifications on the GBR is complicated further in that there is a wide variation in the way GBRs baseline the expected conditions. A typical example is rock strengths that may test at a maximum strength of 10MPa in the majority of boreholes along the excavation alignment, but 80MPa in one borehole in the middle of the drive length. The baseline value of the rock strength could be provided in the GBR simply as 10MPa to 80MPa. The contractor and the TBM manufacturer could provide a TBM capable of excavating mainly 10MPa rock with some 80MPa strengths. If during excavation, strengths of much higher than 10MPa rock is encountered for much of the drive and the cutter tools wear out and progress is slower than anticipated, the contractor would have no chance of a differing site condition (DSC) claim as the maximum rock strength of 80MPa is not exceeded.

Alternatively, if the contractor considers only the high 80MPa value and designs the cutterhead for this rock strength, it is likely to have lower production in the softer ground.

Since the baseline covers the strength range found in the borehole cores, the contractor would have no basis for a DSC claim based on the percentage of any given rock strength excavated.

Some GBRs would not only baseline a strength range, but also the percentage of the alignment for the various strength bands of rock. In this case, the contractor would have the basis for a claim for differing site conditions if the amount of hard or soft rock exceeded the baseline. The value of the change order then becomes debatable as the advance rate is never baselined in a GBR.

Paul Nicholas, AECOM Tunnel Practice Leader - West Co-Author Nasri Munfah, AECOM Tunnel Practice - Director Competent contractors will interpret the geotechnical data, the geotechnical interpretive report, and the GBR if they expect to submit a competitive bid.

The geotechnical data and interpretive reports are sometimes not provided to the contractor and, if provided, are often not contract documents. Most contractors do not have a geotechnical engineer as part of their permanent staff and often do not have available time during the bid process to analyze the geotechnical data extensively.

Some contractors, knowing the importance of understanding the ground conditions, will engage a local geotechnical engineer to provide a better appreciation of the ground conditions to be expected.

In some cases, the tender documents, with the geotechnical information and the GBR are passed directly to the TBM supplier with the request to provide a TBM of the required size and suitability for the ground conditions indicated in the supplied documents. In this case, the contractor is trying to pass the risk, and the liability, to the TBM supplier who is unlikely to accept the role and opt instead, to providing an advisory role only.

When the tender documents are more performance orientated and for designbuild projects, there is always the risk that a contractor will use the lowest cost TBM to arrive at the lowest bid. This may include an optimistic view of the suitability of the selected TBM and the production rates in the ground conditions that may have been misinterpreted. The contractor may also own a TBM of the required diameter, and bids with that machine which may not be entirely suitable for the project conditions.

So, who should choose the TBM? It should be a collaborative effort!

The main interest of the Owner is to build the project for the lowest cost, safely and on time. Providing a conditional performance specification for the TBM – which may include diameter of the finished tunnel, possibly the type and design of the permanent tunnel support system and providing detailed geotechnical information so that the TBM and tunnel liner performance can be properly estimated – is likely to achieve this end.

A well-qualified tunnel contractor with experience in similar ground conditions for a tunnel of similar diameter, supported by an experienced TBM supplier that has supplied TBMs for tunnels in similar ground conditions, is a team most qualified to provide the most technically suitable means-and-methods solution. It may not however result in the least expensive TBM or the lowest bid. n

FOCUS: TBM SELECTION

Who should choose the TBM?

References • • • • •

Tailor-made TBMs for Norwegian hard rock – TunnelTalk, February 2019 In search of the ideal TBM specification – TunnelTalk, June 2018 Rebuilt TBMs - are they as good as new? – TunnelTalk, May 2018 Slurry or EPB for conditions in Bangalore – TunnelTalk, January 2016 Equipping TBMs for tough conditions – TunnelTalk, November 2019

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TBM risk assessment and selection Dean Brox, Consultant, Canada

FOCUS: TBM SELECTION

I

n the process of selecting the TBM for a given project, the parties that are most familiar with the inferred ground conditions are typically the Client and its project designer. For a design-build approach it may be that very limited ground investigations have been completed prior to overall procurement, and this is a key risk that should be imparted to the Client very early in the planning or conceptual design stage.

While no level of ground investigations can provide a guarantee against differing site claims, Clients should be fully informed and fully understand that their liability increases at the end of the day if limited ground investigations are undertaken and provided. They should not attempt to limit the opportunity and time for additional investigations in the project schedule or transfer this risk to bidders.

During the early stages of a project the project designer should complete a TBM evaluation/risk assessment which is being proposed as part of the TBM Guidelines of the International Tunnelling and Underground Space ITA Working Group 14 on Mechanized Tunneling. This evaluation should be updated regularly throughout the project stages, prior to procurement, when new ground information becomes available, and made available, as information only, to bidders and TBM suppliers during project tender stages.

If the project designers are well experienced in TBM tunneling, and particularly if they have experience from a previous project in similar ground conditions, they should be well able to prepare an appropriate TBM specification that addresses the minimum requirements without being overly prescriptive and excluding a TBM supplier from quoting.

In reality, and as with current GBR practice in the industry, project designers are typically preparing overly prescriptive TBM specifications. Then, if there is a dispute about the TBM being fit-for-purpose during excavation, they attempt to avoid any liability on the subject.

It is easy for the project designers and consultants to be overly prescriptive on TBM specifications without recognising what they have prepared. A dispute is currently underway on a major project in the industry that focuses on this issue,

whereby the project consultants specified the requirement to install rock support in front of the TBM grippers but did not actually specify an open gripper type of TBM. However, it can be inferred from this requirement that this situation can only apply to an open gripper TBM. Another very important aspect is that the GBR should be prepared based on a means and method of excavation by the project designer that is based on their best judgement. The designers and consultants have had the greatest amount of time to review and appreciate the anticipated ground conditions. However, if the preferred bid is based on a means-and-method alternative, then it is critical that the GBR is revised to be consistent with the new alternative, especially for ground behaviour baselines and parameters. Failure to modify the GBR accordingly creates a terrible situation for the resolution of differing ground conditions and behaviours and represents a key shortcoming of good industry practice. For a design-build project, the final GBR should be the product of input by the preferred bidder as per typical design-build practice.

It appears to date that the majority of disputes questioning whether the correct TBM was in use has been due to situations where more adverse ground conditions were actually encountered and therefore defaults to claims of differing site conditions based on a comparison to the baselines presented in the GBR. The preparation of good quality GBRs with clear and concise baseline statements and parameters that can be confirmed during construction remains the greatest challenge for any project, as this is where the greatest uncertainty in any project exists.

There are several typical examples of where an open gripper TBM has been selected and used, but a higher than expected amount of geological faults and fractured ground has been encountered, requiring more ground support and inhibiting TBM progress, or where a shielded TBM was selected and used in alternating open and closed modes, but higher than expected groundwater pressures were encountered, preventing good TBM production. Both examples relate to situations where more optimistic ground conditions were presented in the GBR than were actually experienced.

Long and deep tunnels are inherently

of high risk since they present geotechnical uncertainties and access challenges. The assessment and selection of a TBM for long deep tunnel drives should be based primarily on a comprehensive technical evaluation of all geotechnical and construction risks.

Secondary aspects, including project economics, site access, and availability of used TBMs. The primary geotechnical aspects to be considered include: • Potential for squeezing; • Potential for overstressing, including rockbursting; • Strength, quality and abrasivity of the main rock units along the tunnel alignment; • Number and nature of major, moderate and minor geological faults and shear zones anticipated to be intersected; • Number and nature of geological folds as synclines and anticlines anticipated to be intersected; • Number and nature of geological contacts between different rock units anticipated to be intersected; • Durability of the rock units; • Anticipated groundwater pressures and storage; and • Final tunnel lining requirements necessary for long-term uninterrupted operation of the infrastructure.

Geotechnical and construction risks

Geological fault zones and associated conditions represent the greatest risk for TBMs. The identification and characterisation of geological faults and weak zones is therefore critically important, and a detailed geological map should be prepared as part of the design to present the locations of all field-confirmed and inferred geological faults.

Squeezing is one of the highest risks for TBMs and influences the most appropriate type of TBM to be considered.

The identification and characterisation of geological synclines and anticlines is also important to confirm through a comprehensive structural geological assessment of the entire tunnel alignment.

High risk rock types and conditions for TBMs include young volcanic bedrock of tuffs, breccias, agglomerates, lahar, mudstones (clay shales and siltstones), karstic and disturbed or highly fractured limestones, as well as mining areas with mineralisation that commonly include highly

From left: Example of a geological section based on available investigation boreholes; Example of a TBM utility pie chart

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Types of TBM and applicability

Open gripper TBMs are most commonly selected for the risk of overstressing. While they pose the lowest risk for becoming trapped due to squeezing conditions, they have elevated levels of risk since workers are exposed within the forward L1 area for the installation of ground support. If the risk of overstressing is limited, it is considered appropriate to select an open gripper TBM, as long as mitigation measures are included during construction.

Single shield TBMs are typically used for deep and long tunnels in bedrock where there is the anticipated risk of squeezing conditions.

Single shield TBMs offer increased protection of workers against overstressing as they are most commonly used in conjunction with precast concrete segmental linings.

The impact of overstressing to single shield TBMs is associated with cuttability, whereby overstressed rock fragments can cause jamming within the cutterhead and lead to a reduction in production.

Double shield TBMs are typically used for deep and long tunnels where there is a very limited risk of squeezing, overall limited poor-quality ground conditions, and where there is the requirement for precast concrete segmental linings. Double shield TBMs offer enhanced production of as much as 30m/day in comparison to the 15m/day of single shield TBMs, and also offer increased protection of workers. The impact of overstressing to double shield TBMs is similar to that for single shield TBMs.

“The Project Designer/ Client should take ownership for any shortcomings in the GBR and TBM specifications.” drives at the Pando hydropower project in Panama and at the Lake Mead No 3 Intake in the USA. The TBM diameter for the Pando project was limited by the project client to 4m and so could not include a manlock and was unable to complete the tunnel under the extreme conditions. The TBM at Lake Mead with a diameter of 7.2m, included a manlock and successfully completed the 4.8km intake tunnel.

In summary, all parties must take their fair share of liability, even in this increasingly litigious industry. Parties must not cross boundaries or confuse their responsibilities.

These can be summarised as: • Client/Project Designer: Responsible for the GBR and TBM specifications from ground investigations • Contractor: Responsible for selection of type of TBM from interpretation of GBR and TBM specifications • TBM supplier: Responsible for TBM design in accordance to TBM specifications and/or requirements of the Contractor.

Under current good industry practice the selection of a TBM is in fact a collaborative effort whereby the project designer provides its input via a GBR and a set of TBM specifications; the TBM supplier provides its insights based on its experiences; and the contractor likewise. So, if an appropriate GBR and TBM specification is prepared, there does not appear to be any requirement for any change in the practice, and no party should be looking for greater input to the overall process. In particular, the Project Designer/Client should take ownership for any shortcomings in the GBR and TBM specifications.

Given the extensive use of TBMs in the industry, all of the TBM suppliers

have acquired extensive experience and knowledge about which TBMs work well in certain ground conditions from their detailed analyses of productivity, and therefore typically have relevant opinions and advice to offer to bidders. In many cases, TBM suppliers also offer additional features in the TBM design for reducing the risk of reduced TBM production.

Feedback from Siba Prasad Sen, Tunnel Engineer, India India has been pursuing hydropower development for the past seven-or-so decades and today has about 45,000 MW of large and medium capacity installed. Some 90% of the capacity is in the Himalayas.

Here, the high mountain peaks, monsoondriven hydrology, seismic vulnerability, steep slopes and many geological faults are a real challenge for planning, designing and constructing long tunnels for hydro projects.

To add to the woes, there are high ground water tables with large aquifers, innumerable shear zones, squeezing rocks, and very hard rocks that cause rock bursting.

For such terrains, to plan a hydro tunnel of more than 5km requires extensive geological investigations and detailed probing of the actual ground is very much required. Constraints in investigations beyond surface mapping by geologists, which itself is very difficult due to the hostile terrain, leads to poor understanding of the ground conditions. That is why planners and designers in India prefer to use drill+blast technology for tunnelling. That way, the long tunnels can be aligned in a zigzag manner along the side slope of the mountain valley.

The 510 MW Teesta hydro project has a 17.5km headrace tunnel. This tunnel has been aligned along the mountain slope as close as possible to the road and there are three obtuse bends in the tunnel. This has helped to reduce the rock cover, which helps investigations and enables better geological mapping. Such a layout also reduces overburden and the hydro-static pressure of the ground water table and

FOCUS: TBM SELECTION

altered and associated weak rock conditions.

TBMs do not offer the effect of de-stressing at the tunnel face, as with drill+blast methods, but rather concentrate in-situ stresses at the face and in the immediate L1 area behind the cutterhead.

Furthermore, elevated in-situ stresses, namely high horizontal in situ-stresses, can be expected in close proximity to plate tectonic margins.

Overstressing in deep tunnels can have a serious impact on worker safety, as well as causing damage to TBMs. Clients and project designers have a fundamental responsibility to thoroughly evaluate the potential for overstressing on any deep tunnel and to fully disclose all relevant information in the GBR. The potential for high groundwater levels and any fluctuations, as well as in-situ rock mass permeability, should be confirmed as part of early design studies to prepare for maximum groundwater pressures and inflows. Developers of long deep tunnels are strongly encouraged to allocate adequate budgets and schedules for geotechnical investigations during the project designs.

Practical constraints

High groundwater pressure, in excess of 6-7 bar, will require a manlock to access the TBM cutterhead for maintenance and the changing of cutters. To include a manlock, a larger TBM size and diameter is required. This constraint should be considered if such adverse groundwater conditions are anticipated.

Very high groundwater pressures of 11 to 15 bar were realised during the TBM

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Safety risk and TBM damage from rockbursting

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reduces the probability of squeezing and rock bursting. But the availability of such a road cannot be assured, particularly with concerns surrounding the environment and wildlife. Permission for such an intermediate approach is being regularly denied by the Environmental and Forest Authorities.

In the Parbati Stage II project, the tunnel was designed partly by drill+blast with a zigzag alignment and partly by TBM for 9km of the total 32km length.

The project is ready for commissioning in all respects except the TBM is struggling to complete the job. The TBM portion of the tunnel has very high cover and a high ground water head of 10 to 12 bar. There are many major and minor faults along the alignment along with high ground water inflows and very hard quartzite. There is very slow progress due to many contractual issues, including inappropriate choice of TBM, which is an open gripper machine and of insufficient capabilities. Risk sharing for such projects by the Government owner is almost impossible. I was wondering whether in the near future it will be possible for a TBM to excavate a tunnel in zigzag alignment. The Himalayas are waiting for it.

What makes the situation worse in the Himalayas is the presence of high-pressure geohydrology. With long experience of the Himalayas during my engineering career with NHPC, the absence of high ground water tables and the absence of artesian wells along the tunnel alignment is a good sign for less trouble from water. But it is rare.

For Parbati II, where the TBM is still stuck, the owner NHPC was able to construct successfully the two 30 degree inclined pressure shafts, each of about 1.1km long, using an inclined TBM. NHPC was also successful on the Kishanganga hydro project in the western Himalaya State of Jammu and Kashmir, to excavate about 10km of the headrace by TBM in about 24 months.

Here cover was very high, at up to 1,400m, but ground water was not the troubling force.

But all these are exceptions and not the trend. There are some TBM tunnels for different projects which are unfinished, causing huge loss to the owner and also to the construction agencies. Until a reasonable method is found to undertake a satisfactory geological and hydrogeological investigation and plan for a sustainable excavation procedure for TBM applications, we are caught in Hobson’s choice with only one option on offer. n

References • • • • • •

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Author references can be found on the full length article at TunnelTalk.com Nepal proving TBM applicability in Himalayas– TunnelTalk February 2019 TBM rescue for Tapovan and Parbati hydro challenges – TunnelTalk December 2016 In search of the ideal TBM specification – TunnelTalk June 2018 Equipping TBMs for tough conditions – TunnelTalk, November 2019 Lake Mead TBM designed for the extreme – TunnelTalk, November 2009

TunnelTalk ANNUAL REVIEW 2020

TBM procurement, risk, and technology advancement John Reilly, Consultant, former President, American Underground Construction Association

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rocurement of TBMs involves a combination of referencing technology, machine type and capability, contracting procedures, clarity of responsibilities, risk allocation, commercial issues, competition, and geotechnical baseline reports. The balance between the roles and responsibilities of the Owner, Engineer, Contractor and TBM supplier are constants in these regards.

The TBM procurement environment includes complex technical requirements, cost and schedule constraints, unknown ground conditions and risk. The basic requirements of the project owner include an environment that: • Maximizes contractor competitiveness, • Results in a machine that will perform reliably, safely and productively in the prevailing geology; • Has necessary face control to avoid settlement and damage to adjacent buildings; • Addresses all essential design requirements and is deemed fit for purpose; and • Protects the interests of the owner, all stakeholders and political representatives.

To achieve these requirements, many and varied procurement options have been introduced and adopted over the decades.

Prescriptive models are where the Owner and its design engineer, geotechnical engineer and other engaged experts, fully define the type and characteristics of the TBM, the tunneling processes and the ground support operations required. The Owner maintains control of key parameters and specifies minimum technical requirements to avoid the shortcomings of a low-bidder-wins environment when contractors may select the least expensive machine that they believe is capable of constructing the facility.

A performance-based procurement requires that the Contractor meets defined performance requirements, with freedom of choice regarding machine type, components, means and methods.

It is selected on the basis that the Contractor is best able to determine the most appropriate equipment, methods and techniques to meet the specific geotechnical and other requirements. It is a method that is susceptible to the low-bidwins syndrome. In practice, the approach is often a combination of performance and prescriptive methods such as in the design-build or turnkey model.

Direct procurement by the Owner of the TBM, the lining system and other ancillary equipment and materials is an extreme prescriptive approach. The process specifies and procures the type of machine that the Owner, with its

advisors (design engineers, geotechnical experts, TBM manufacturers), believes is necessary to control the ground and meet project requirements. Advantages include the ability to accelerate the construction schedule and avoidance of inappropriate TBM selection and other low-bidder-wins concerns.

The design-build and turnkey approaches are a combination of a performance approach with prescriptive elements. Application of the method has been increasing since the mid 1990s and examples of projects that have adopted the method include the SR99 Alaskan Way Viaduct replacement highway tunnel in Seattle, recent contracts for the Los Angeles Metro Purple Line, and the DC Water CSO program of interceptors in Washington DC. An early example was the Tren Urbano transit project in Puerto Rico, which was authorized under the 1991 Turnkey Demonstration program of the USA Federal Transportation Administration.

Experience with these procurement methods has led to an evolution of variants including Engineering, Procurement and Construction (EPC), Progressive Design Build (PDB), Early Contractor Involvement (ECI), General Contractor/Construction Manager (GC/CM), Target Cost, and Alliancing methods.

These procurement methods, with a combination of performance and prescriptive elements, offer a middle way which aims to preserve schedule and financial benefits, but structures the contract documents to reflect a higher level of tunneling machine technology and procedural requirements. The goal is to limit the prescriptive details to fundamental elements and leave those that are best left to a knowledgeable and capable contractor in order to foster innovation and identify better alternatives.

Projects, including the SR99 Alaskan Way Viaduct Replacement highway tunnel in Seattle, have used this procurement method to structure the contract documents with technical input from a shortlist of contractors to reflect the input from those contractors regarding means and methods and TBM technology.

The Progressive Design-Build (PDB) procurement method uses a qualificationsbased or best-value selection, followed by a process whereby the Owner then progresses towards a design and construct price with the team. Through this process, PDB brings integration of the Owner, Engineer, Contractor, subcontractors and suppliers to assist in the application of technology and pursuit of best value. For a tunnel project, this would include a more integrated

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evaluation of performance and risk issues related to the type and technology of the TBM to be used.

With this growing range of procurement alternatives, how to choose the best approach for a particular project might now be the more difficult decision for an underground construction project.

An example of how to choose is the structured method that was adopted in 2012 to select the most suitable approach for the Los Angeles Metro Purple Line tunneling program, which considered the owner’s requirements, procurement precedents of the owner’s organisation and applicable California State and USA Federal legislation. Legislative restrictions limited Metro, the Owner, to design-bidbuild or design-build. Working with the Federal Transit Administration, the method adopted was the USA Transit Cooperative Research Program (TCRP) Procedure 131.

The method considered: • Agency goals and objectives; • Risks related to the contracting and delivery method; • Characteristics of the contracting and delivery methods in terms of key attributes; and • A checklist of elements related to the contracting and delivery method.

The TCRP Procedure 131 includes consideration of key factors, some of which take precedence. These generally include: • Schedule, with design-build generally resulting in a compressed schedule, which is often a priority; • Owner control of design details, which lends a bias towards design-bid-build; • Risk tolerance of the owner and contractual risk transfer methods, with the focus on improving the chance of success; and • Political and other considerations including insurance and bonding requirements.

For the Los Angeles Metro Purple Line, the resulting decision was to use design-build, with substantial technical input and involvement of the agency and the agency’s design engineer to include a significant prescriptive element.

The above procurement alternatives do not completely address the characteristics of the TBM to be selected or who decides

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those characteristics. In practice, the actual process is usually somewhere between the extremes of full owner specification and procurement versus full performance specification with detailed decision and procurement of the TBM by the contractor. The middle way is based on some prescriptive Owner requirements of the TBM, such as minimum face control method or convertibility, and some performance requirements, such as settlement limits and protection of adjacent properties. Collective treatment of risk and related compensation of any damages, such as allowances and shared contingency, must also be included.

“In general, more technologically capable machines are better at avoiding delays and could be considered similar to an insurance policy.”

In soft ground, the selection of a TBM is often the choice between a slurry or EPB TBM or a convertible machine that combines both modes. In hard rock, the decision is between an open gripper TBM or a single or double shielded machine with a precast segmental lining. The differentiating factor is the tension between desired technical requirements and capabilities versus cost. In general, it can be argued that the more technologically capable machines are safer and better at avoiding delays due to difficult driving conditions. The additional costs may therefore be justified and considered similar to an insurance cost.

Many of the procurement decisions also involve risk considerations. Good progress has been made in risk management processes and capabilities since the mid1990s. Discussions continue with regard to the Owner’s risk register, where risk identification and management is required for major projects, and for the inclusion of that risk register in the contract documents.

Nevertheless, identification, analysis and evaluation of significant risks related

to TBM capability and operation should be a normal process in TBM procurement, both pre-bid and in the initial phases of design in a design-build contract.

Several key topics such as ground conditioning, settlement control, thrust and advance, mechanical breakdown, and the operating impacts on seals and bearings while operating in the ground to be encountered would be essential areas for specific risk assessment. This assessment was undertaken in the prebid project development by the Owner for the SR99 Alaskan Way Replacement highway tunnel in Seattle, as part of the owner’s CEVP® risk identification process.

An area for development would be to use such a process to evaluate bids prior to construction contract award. Best value determination is an accepted process, however, a case is not known where a quantified risk profile, added to base cost, has been used to determine contract award. It could be that such an analysis would show that a more sophisticated and costly TBM would have a probable outturn cost which would be lower than a simpler less expensive machine.

The above considerations can be viewed in the light of several factors.

• The evolution of increasing TBM capability and technology which is driven by competition, value, safety and reliability.

• The increasing awareness of owners that safety, performance and avoidance of risk is reasonable and necessary and that additional costs in this regard are justified, and • Risk management as a process of risk sharing, rather than risk transfer.

Fundamentally, a good answer to the question of who should choose the TBM may require use of another management process – the alignment of the full project team, including owner, designer, contractor, TBM manufacturer and suppliers, to meet key goals and objectives. n

FOCUS: TBM SELECTION

Left: Probable cost of TBM selection where [1] is base TBM cost [2] costs of probable risks [3] probable outturn cost; Right: Low bid contracts for early Los Angeles Metro resulted in machines that were unable to control excavation and settlement

References • • •

Author references can be found on the full length article at TunnelTalk.com Alaskan Way mega-project procurement – TunnelTalk, October 2010 Alternative contracting and delivery methods – TunnelTalk, September 2011

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Crossover XRE for navigating fault zones D Harding, The Robbins Company, USA and Y Alpagut, ATES Engineering Construction, Turkey

FOCUS: TBM SELECTION

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n the mountains outside of Ankara, a Robbins 5.5m diameter hybrid-type single shield/EPBM Crossover XRE TBM completed the final 9km leg of the 31.6km long Gerede Water Transmission Tunnel in Turkey by navigating 48 fault zones and hydrostatic pressures of up to 26 bar. The notoriously difficult conditions had previously caused two non-Robbins double shield TBMs to become stuck in massive inrushes of mud and water.

Preliminary geologic testing and borehole samples showed a mix of volcanic rock including tuff, basalt, and breccia, giving way to sedimentary formations like sandstone, shale, and limestone, all punctuated by fault zones.

After two of the three original TBMs on the 31.6km long tunnel became irretrievably stuck or damaged, the Kolin/Limak JV contacted Robbins, who suggested a Crossover dual-mode type TBM that could effectively bore conditions in both rock and mixed ground under water pressure, by converting between modes. Kolin/Limak needed a machine that could effectively bore in wide-ranging conditions, but also statically hold water pressure up to 20 bar in the event of an emergency flow – a failsafe that none of the standard stuck double shield TBMs were equipped with.

The Crossover cutterhead has the face and internal structure of a hard rock machine with the open rear structure of an EPB. This machine has a screw conveyor at the bottom of the chamber to aid in cutterhead cleaning in the event of a fault zone. Rocks entering the cutterhead thus have the entire height of the machine to fall. To reduce damage from large falling rocks, the pedestal was specially designed with multiple deflector plates to slow the fall (Fig 1). The cutterhead buckets were also designed to direct the muck from the face by pushing it backward into the cutting chamber. Because of the open back design, this cutterhead can also be converted to an EPB head if conditions require it.

A new feature on the Gerede machine, which will also be supplied on all subsequent Crossover machines, is the two-speed gearbox. With the ability to shift into two speeds, the machine can easily bore through different types of ground.

For hard rock, the machine can run in high rpm/low torque and for EPB mode, it can

Table 1. Best & Average TBM Advance Rates Best Day 29.4m Average Day Best Week 134.6m Average Week Best Month 484.0m Average Month shift into a low rpm/high torque. The low rpm/high torque allows the machine to bore through fault zones and soft ground without becoming stuck like an EPBM. In order to protect the machine from high water pressure, an extensive sealing system has been put into place. Around the main bearing, there is an outer row of six seals and an inner row of three seals. Between each seal, the cavity is filled with pressurized grease to ensure a constant pressure in each of the cavities. In the event that the machine is shut down and an inrush of water overtakes the machine, a pressure sensor will detect this and pressurize each cavity with grease to continually protect the seals from the pace pressure. The articulation joint, gripper, stabilizer shoes and tail seals are sealed off in the same manner.

Perhaps one of the most important parts of the Gerede TBM design is the screw conveyor, which has the ability to seal itself off so that in a fault zone with large amounts of water, the machine will still be able to continue excavation. In this case, the screw can be used in a sequential operation. First, the rear discharge gate is closed, sealing off the interior of the machine from the incoming water. The screw extension cylinders will then push the rear of the screw back, pulling the screw out of the cutting chamber and inside of the screw casings. Next, the bulkhead gate is closed and the screw conveyor is dewatered.

The rear discharge gate can be reopened and the screw conveyor can run, emptying the casings of muck. A catchment basin, under the hopper of the bridge conveyor, can be filled with leftover water coming from the screw. The water is then pumped out via the back-up system. Once the screw has been emptied, the rear discharge gate can be sealed. The bulkhead gates can be reopened and the screw extended into the cutting chamber. Boring can then commence until the screw conveyor is once again full.

Due to unpredictable ground conditions, it was necessary to detect and grout off zones of concern wherever possible to protect the machine from flowing ground and water

From left: Two original TBMs became stuck and damaged amid massive mud and water inflows; Fig 2. Robbins Crossover cutterhead for Gerede with deflectors to prevent damage from rocks falling into the excavation chamber

9.49m 71.14m 284.54m

pressure. The Gerede machine achieved this using a standard array of twelve 100mm diameter ports angled at 7° and spaced equally around the rear shield. Each port is sealed by a ball valve until it is needed for probing. There are also ten of the same sized ports straight through the forward shield for probing and grouting. Six additional hatches are built into the pedestal at the front of the machine, equipped to mount an optional pneumatic percussive drill that can be used in the center section of the cutterhead.

The probe drills on the Gerede machine also had an extra feature for emergency cases.

The drills are designed to pull back behind the tail shield and at an angle of 16°, so they can drill behind the shields and into the segment lining. If water has filled the cutting chamber and the pressure is great, drilling a hole in the roof of the tunnel will allow the water to spill out, relieving the buildup of pressure on the machine and the segment ring.

The Crossover machine began boring at a slight angle to the rest of the tunnel and in a fault zone, bypassing the stuck machine before gradually meeting up with the original tunnel alignment. The machine was required to be used in EPB mode as it encountered water pressures up to 23 bar, alluvium, flowing materials, and clay. Water pressure was lowered by draining the ground water through the rear shield probe drill ports, which were equipped with normally-closed ball valves.

Probe drilling became routine after advancing 50m past the section that buried the original double shield TBM. The Crossover machine bored at about 30mm/min through the first bad section of ground, with any limitations in speed the result of the existing tunnel belt conveyor, which tended to have spillage issues resulting in significant clean-up. Despite the challenges, crews were able to bore 80m to the side of where the original machine is currently buried and pass it.

Systematic probe drilling was maintained as the machine continued. By the end of tunnelling, the TBM had crossed 48 fault zones and statically held back 26 bar water pressure. Each time a zone was encountered, exceptional thrust was used to keep the machine from becoming stuck combined with dewatering to lower the water pressure.

The rear discharge gate was sealed at these times and the machine was operated in a sequential fashion. By keeping the TBM advance rate, rpm, and screw conveyor at an optimal level, the machine was able to navigate the squeezing conditions in clay and achieve constant rates through exceptional conditions (Table 1). n

References • •

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XRE TBM conquers toughest drive in Turkey – TunnelTalk, February 2019 Equipping TBMs for tough conditions – TunnelTalk, November 2019

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Sydney’s underground highway network continues to expand

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fter opening of the M4 underground highway in 2019 and the M8 in July 2020, drivers in Sydney will travel 23km underground on the longest portal to portal route of the AUS$16.8 billion WestConnex project when the M4-M5/M8 link and Rozelle Interchange open in 2023.

North of the city, the 9km NorthConnex route opened in October 2020.

These projects add to existing underground roadways in Sydney including the existing Harbour immersed tube crossing, the Lane Cove project completed in the early 2000s and the Eastern Distributor double deck highway completed in the late 1990s.

Sydney will remain an underground highway capital with proposed new routes including new immersed tubes under Sydney and Middle Harbours for the Western Harbour and Beaches Link and the 4km M6 Stage 1 route to connect south of the city from the M8 to the wider southern highway network (Fig 1).

In addition to immersed tubes for reasonable gradient harbour crossings and drill+blast where needed, most of the highway excavation through the favourable selfsupporting Hawkesbury Sandstone of the Sydney area is by roadheader on large three and four lane rectangular cross sections.

Fifty machines have been in use concurrently excavating the 7km twin tubes of the WestConnex M4-M5/M8 link and the Rozelle interchange complex, which comprises up to 25km of various cross section headings for traffic lanes, cross passages, ventilation and access (Table 1). Previously a total of 55 roadheaders were used on the recently opened WestConnex M4 and M5/M8 routes and on the NorthConnex highway. The M6 Stage 1 project presents the first opportunity to introduce large diameter TBMs to the highway network excavation with bidders given the option to deploy TBMs or stay with the roadheader contract design.

Fig 1. Sydney’s underground highways and proposed Western Harbour and Beaches Link (right) Table 1. Sydney underground highways and the roadheaders engaged Project Status Length Roadheaders NorthConnex Complete 9km 20 WestConnex M4 and M8 Complete 14.5km 35 M4-M5/M8 Link In construction 7km 28 Rozelle Interchange In construction 20-25km 22 Western Harbour Tendering 6.5km For landfalls immersed tube Beaches Link with Middle EIS released 7.2km For landfalls Harbour immersed tube M6 Stage 1 Tendering 4km TBMs an alternative St Peters Interchange (Fig 2).

The M8 will initially feature four lanes of traffic, with capacity to expand to six, and comes into service about a year after the first stage of WestConnex, the new M4 tunnels, opened in mid-2019.

AUSTRALIA/NEW ZEALAND

TunnelTalk reporting

The two remaining stages of the 33km WestConnex network are: • The twin two-lane 7.5km tunnels to link the M4 at Haberfield and the M8 St Peters Interchange, known as the M4-M5/M8 Link and

Vertical alignments of existing and planned highway tunnels in Sydney

WestConnex

The M5 underground highway, now known as the M8, is the second element of the WestConnex network to complete.

The AU$4.3 billion route comprises twin 9km alignments from Kingsgrove to a new

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Above: Fig 2. M8 new link from M4 at St Peters Interchange Right: Fig 3. Intricacy of Rozelle interchange on the M5-M5/M8 Link • The underground Rozelle Interchange linking WestConnex with the City West Link and the proposed Western Harbour Tunnel.

Excavation of the M4-M5/M8 link is on schedule to complete in mid-2021, after the first of six breakthroughs on the project occurred in January 2021. The Lendlease-Samsung-Bouygues JV is using roadheaders at various locations at depths of between 25m and 50m. Total excavation of the $3.2 billion M4-M5/M8 Link comprises almost 20.8km of mainline traffic lane drives, on and off ramps, and stub tunnels to the Rozelle Interchange.

With the twenty-eighth roadheader beginning operation in May 2020, the project is now reportedly operating the largest number of roadheaders ever used concurrently in Australia. Each roadheader operates continuously, 24 hours a day, seven days a week, and is capable of progressing at an average of 25m/week. More than 7.5 million m3 of spoil will be excavated for reuse in the Sydney area. The M4-M5/M8 Link is expected to open to traffic in 2023, when it will provide a western bypass of the Sydney central business district.

Fig 4. NorthConnex links the M1 and M2 highways and bypasses 21 sets of traffic lights on the congested Pennant Hill Road

Excavation of the twin tube NorthConnex underground highway

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The alignment of WestConnex runs through relatively uniform Hawkesbury Sandstone, briefly passing through Mittagong Formation, Ashfield Shale with residual soils and weathered rock at the portals. Primary support consists mostly of shotcrete and patterned CT rockbolting with heavier support solutions, including canopy tubes/lattice girders, canopy tubes/steel sets, and lattice girders/spilling bars, required in some areas of shallower rock cover. A secondary lining is installed to ensure the 100-year design life. The project is expected to use more than 400,000m3 of concrete, for shotcrete and cast concrete, and 25,000 tonne of reinforcement steel.

The fourth and final element of WestConnex is the complex multi-level underground Rozelle Interchange to connect with City West Link and the proposed Western Harbour Tunnel. Construction began in December 2019 by the John Holland-CPB Contractors JV. The project is being managed directly by Transport for New South Wales, rather than the WestConnex consortium led by Transurban, which is managing development of the other three elements.

Twenty-two roadheaders are working

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on the Rozelle Interchange, progressing from four sites for the 22km of road tunnels, caverns, ventilation structures, passages, substations and temporary access declines (Fig 3). Excavation is on track to complete in 2022.

Running at between 35m and 65m deep, the $3.9 billion Rozelle alignment is through unconsolidated sediments and Hawkesbury Sandstone. Ground support comprises a combination of double corrosion protected rockbolts with a layer of shotcrete as required by conditions encountered. The interchange is expected to open to traffic in 2023.

NorthConnex

Opened in October 2020, NorthConnex features 9km of twin tunnels to link the M1 Pacific Highway at Wahroonga to the M2 at West Pennant Hills. Opening of the underground highway was delayed, according to Transurban CEO Scott Charlton, as the commissioning was complicated by Covid-19, which has caused issues around supply and overseas workers, as well as to the working environment.

Construction by the 50:50 designbuild JV of Lendlease and Bouygues began in 2015.

The AUD$3 billion route links the M2 Hills highway around the north of the city with the M1 Pacific route north to the Central Coast, Newcastle and Hunter regions of New South Wales, adding capacity to the upgraded surface Pennant Hill Road (Fig 4).

The project includes underground ramped interchanges at north and south portals and 88 cross passages. In total 21km of underground headings were excavated through Hawkesbury Sandstone and Ashfield Shale between May 2016 and the end of 2018 by 20 roadheaders supplied by Sandvik and Mitsui, as well as two Vermeer surface miners for bench excavation. At an average 60m deep, and with a 90m underpass of the Sydney Metro Northwest alignment at the deepest point, NorthConnex is reportedly the deepest road tunnel in Australia.

Primary support through the Hawkesbury sandstone is provided by rockbolts and steel/ synthetic fibre-reinforced shotcrete, followed

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Fig 5. Landfall and immersed tube construction for Western Harbour link and proposed construction sites of the harbour crossing

Western Harbour, Beaches Link

A second highway crossing of Sydney Harbour is planned to the west of the famous bridge and its existing immersed tube crossing. The AUS$14 billion Western Harbour crossing is part of the wider Beaches Link to the northern beaches of Sydney, under Middle Harbour and connecting to Gore Hill Freeway and the Warringah Freeway.

Unlike other highway projects in Sydney that are delivered by a toll road operator, the Western Harbour crossing and its northern Beaches Link are New South Wales State Government led projects. After engagement with industry, the NSW Government decided on a State-led procurement and delivery process.

The Western Harbour link is proposed

by NSW Transport in its reference design as an immersed tube crossing with mined tunnels at the landfalls (Fig 5). To the south, the crossing will link to the underground

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Rozelle interchange and WestConnex highway routes and the M6 underground Stage 1 alignment. To the north there will be a connection to the North Beaches extension and its immersed tube crossing of Middle Harbour and also to an upgrade of the Warringah Freeway that links to the Harbour Bridge and Tunnel crossing.

The Warringah Freeway is one of the busiest roads of the city and its upgrade is designed by NSW Transport to increase safety for motorists and provide seamless connections to the Western Harbour Tunnel and Beaches Link. Procurement of the 4km Warringah Freeway upgrade is a separate call for expressions of interest process with NSW Transport.

In creating a western bypass of the Sydney city centre, the Western Harbour Tunnel is designated as a nationally significant project to transform the way motorists move around the city and provide for faster and more reliable journeys under the harbour. Preliminary planning for a western crossing of Sydney Harbour began in 2015 with an initial design completed in March 2017 and the application for status of State Significant Infrastructure submitted in November 2017. Community engagement progressed from July to December 2018.

Planning permission for the Western Harbour crossing was granted despite concerns over potential damage to property and the environment caused by potential drill+blast excavations on the landfall routes and marine dredging for the immersed tube.

According to the EIS, the main underground landfalls of the immersed tube crossing will be excavated by roadheaders at up to 109m deep. The State Department of Planning and Public Spaces concluded that these issues had been adequately addressed and that the impact of the project to the community and environment could be appropriately managed, minimised or offset to an acceptable level. The project was approved as being in the public interest.

Three groups have been shortlisted to tender as development partner for the 6.5km western immersed tube crossing: • Bechtel Infrastructure (Australia) • Harbour West Partners, comprising Macquarie Capital, Jacobs and RPS • Laing O’Rourke Australia.

Contract award is expected in 2021.

The appointed development partner will assist with the procurement and delivery of the project and will be expected to leverage industry expertise, innovation and value for money to achieve the best outcomes for New South Wales.

At Middle Harbour the geological profile on the Beaches Link of the immersed tube requires that the units sit on supporting piles

in soft sediments. Temporary cofferdams will allow construction of the interface with landfall alignments.

The environmental impact statement (EIS) for the Beaches Link was released in late 2020 and construction is anticipated to begin in 2023, subject to planning and procurement processes, with completion at the end of 2027.

M6 Highway

Providing better connectivity to the south of the city, the M6 is classified by the New South Wales Government as a State Significant Infrastructure project and will be delivered in three stages with the underground section in Stage 1.

The estimated AUD$2.6 billion Stage 1 section will deliver a missing link to the south and towards Illawarra with more than 2,000 trucks a day removed from local streets and 23 sets of traffic lights on the Princes Highway bypassed.

The project was approved for construction in December 2019 based on consideration of the EIS and responses via community feedback. As a result, conditions have been set to enhance public space, cycling and pedestrian connectivity, and to improve environmental outcomes.

The new 4km long twin tube tunnels will link the new M8 underground motorway at Arncliffe, south to President Avenue at Kogarah (Fig 6). Roadheaders are proposed in the design documents, although TBM

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by a spray-on waterproof membrane with a final lining of synthetic-fibre reinforced shotcrete. Through the poorer-quality Ashfield Shale, canopy tubes and steel sets were used as primary support, with a waterproof sheet membrane and a final reinforced cast in-situ concrete lining. A 250mm-thick continuous reinforced concrete slab forms the road deck, which is designed to withstand the up to 5,000 trucks that are expected to use NorthConnex every day.

More than 2.3 million m3 of excavated material was removed by vertical conveyors at each of four production shafts, eliminating the need for access adits and helping to reduce the surface footprint of the project. Conveyors were also used to transport 1 million m3 of the spoil, at a rate of 2000 tonne/hr, into the nearby Hornsby Quarry, where it was used for restoration work. Sustainability was a key element of the NorthConnex project, winning it several awards.

According to Transport for New South Wales, the new highway will allow motorists to drive between Melbourne and Newcastle, a distance of more than 1,000km, without passing a set of traffic lights, as well as easing congestion on Pennant Hill Road, one of the most congested in Australia. Initially opening with two lanes in each direction, and with capacity to carry more than 100,000 vehicles/day, the tunnels allow for future expansion to three lanes in each tube.

NorthConnex is the first in Australia to incorporate a series of internal lighting features designed to keep drivers engaged as they drive through. These include backlit silhouettes of native birds, trees, and starry skies, placed strategically along the alignment to stimulate driver attention and improve safety.

Warringah Freeway leading from north to the Harbour Bridge and Tunnel crossing, one of the busiest traffic routes in Sydney

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Fig 6. M6 Stage 1 extends the underground M8 highway south to Kogarah excavation is also permitted in proposals from the three shortlisted contractors: • Gamuda-BMD • CPB Contractors-Ghella-UGL • Acciona-Samsung The design-build contract for the twin tubes is expected to be awarded in 2021 with construction anticipated to begin by early 2022 toward the new project opening to motorists by the end of 2025.

Feedback from Dr John L Goldberg, Former Honorary Associate, The University of Sydney Safety during operation of the 9km NorthConnex highway tunnel in Sydney, connecting the M2 and M1 motorways is of concern. After reviewing the reports that approved the project for construction, there is no mention of a quantitative risk assessment being undertaken in the 3,600 page environmental impact statement submitted by toll road operator and project owner Transurban or in the New South Wales State Department of Planning Assessment report. This is contrary to international practice and raises concerns, given that the highway is designed to carry up to 5,000 heavy trucks/day in mixed vehicle traffic.

Claims of a 15-minute transit time for vehicles through the 9km NorthConnex tunnel route are also subject to scrutiny. The claim does not take into account the delays that occur to multi-combination vehicles at signaled intersections at the entrance and exit of a tunnel that can cause queues backing up into the tunnel and delays passing into the tunnel. A report by Ramsay and Brunker (2003) at the Queensland University of Technology, shows that MCVs have poorer acceleration capabilities which will lead to a lower acceleration for all vehicles in the traffic queue.

These road safety findings raise a number of serious implications for the operation of the NorthConnex tunnel: • The failure to carry out an assessment of road safety means that no guidance is available to tunnel users as to how a tunnel accident can be avoided; • The claimed travel time savings will not be achieved, which means that the trucking industry will be paying tolls for no gain while submitting to the risk of accidents; • The risk of accidents to toll paying passenger car drivers from collisions with heavy vehicles is shown to be much greater than that for truck drivers. n

References • • •

Sydney opens new underground highway – TunnelTalk, August 2019 WestConnex Rozelle underground interchange awarded – TunnelTalk, December 2018 WestConnex awards the underground M4-M5 (M8) Link – TunnelTalk, June 2018

West Gate TBMs remain idle in Melbourne

T

BM excavation of the West Gate highway in Melbourne remains on hold with a range of issues still to be resolved, admitted project owner Transurban in its 2020 financial results. Launch of the two 15.6m diameter TBMs has been delayed since assembly of the machines in 2019.

The outstanding issues include a lack of approved disposal sites for contaminated ground identified during the site investigation and classified as hazardous after award of contract and assembly of the TBMs. A tender process underway by construction JV CPB Contractors-John Holland involves securing planning and environmental approvals for potential disposal sites.

Some 1.5 million m3 of muck will be excavated by the twin tube TBM drives, with

low levels of contamination by carcinogenic chemicals known as per- and polyfluorinated alkyl substances found at a number of points along the drive alignments.

Transurban, which is developing the project in partnership with the Victorian State Government, confirmed that a revised target opening date in 2023 will not be met and that it is unable to set a finishing date on the project. The scheme was originally scheduled to open in 2022.

The two TBMs are sitting in the Footscray launch shaft at the northern portal in Yarraville, west of Melbourne (Fig 1). A maintenance schedule has been developed in partnership with the manufacturer to ensure the machines remain operable and ready to be fully commissioned when a launch date is confirmed.

Contaminated ground holds up launch of the TBMs Current activity at the portal sites includes installation of the final lining and roof deck beams. Crews are also

Jonathan Rowland, TunnelTalk undertaking slipform work around the TBMs to prepare for construction of the surface roads that will connect the underground drives to new bridges over the Maribyrnong River to the north. Production of the precast segmental lining is also continuing at a facility in Benalla, about 200km and two hour’s drive northeast of Melbourne.

The ongoing challenges will result in substantial cost overruns, said Transurban CEO Scott Charlton on a call with business analysts in February 2021. How much more than its original AUS$6.7 billion estimate is unknown, but could run to billions of dollars.

In late 2020, the Victoria State Environmental Protection Authority rescinded three permits to dispose of contaminated muck at landfills in Bacchus Marsh, Ravenhall and Bulla, admitting it had not met State Government regulations when approving the Bacchus March site. While it remained satisfied the two other permits met the strict conditions designed to protect human health and the environment, for avoidance of doubt, new applications for all three sites need to be submitted. A fourth site in Wyndham Vale is also being investigated as a potential temporary back-up site.

The news is a further blow for stock exchange listed Transurban, after its toll revenues slumped during the Covid-19 pandemic, leading to a AUS$448 million loss in the six months to December 2020.

Average daily traffic on the Transurban network of toll highways in Australia was down 17.8% in 2020. n

References •

Mega TBMs arrives in Melbourne – TunnelTalk, March 2019

Fig 1. New highway with underground and elevated sections

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www.TunnelTalk.com

Sydney Metro buildout

Jonathan Rowland, TunnelTalk

W

ith excavation of the new Metro City & Southwest Line in Sydney complete, attention is focusing on the new Metro West Line and the Metro Western Sydney Airport link as part of substantial metro expansion for the city over the coming decades.

Metro West

Fig 1. Sydney Metro West will link Paramatta to the city centre in 20 minutes

Impressive caverns create mined underground stations for the metro stations

tunnelling will be undertaken in two sections: the first between The Bays and Olympic Park, to begin in mid-2022, and the second, between Westmead and Olympic Park, starting in late-2023. The design plan is for TBMs to launch from Westmead and The Bays and for all four to breakthrough at Fig 2. Link to new Western Sydney Airport Olympic Park.

Three consortia are shortlisted for delivery of the first two major tunnelling packages: • John Holland, CPB Contractors and Ghella Australia • Gamuda and Laing O’Rourke Australia • Acciona Australia and Ferrovial Australia The JVs will first tender for the 11km of twin running tunnels of the Central Tunnelling Package from The Bays to Sydney Olympic Park.

Once awarded, the remaining two tenderers will bid for the 9km of twin tunnels of the Western Tunnelling Package from Westmead to Sydney Olympic Park.

To drive greater competition in the delivery of Australian tunnelling infrastructure, the successful tenderer for the Central Tunnelling

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The first EIS for Sydney Metro West was released in April 2020 as one of three that will be published to cover the three stages of the project to construct 24km of twin running tunnels between the city centre and the major commercial district of Paramatta (Fig 1).

The new infrastructure investment will target a travel time of about 20 minutes between Parramatta and the city centre.

Under current design specifications, the twin tube alignment will have a 6m segmentally lined i.d. and will run between 22m and 32m below ground. At least four TBMs are expected to excavate the route. Roadheaders will excavate the caverns, stub tunnels, and connectors to the Rosehill transition to the above-ground Clyde stabling and maintenance facility.

According to geological mapping, the Sydney Metro West will run through a mixed geology, including Ashfield shale, Hawkesbury Sandstone, and quaternary deposits, such as silty-to-peaty quartz, sand, silt and clay. Machine selection will be made by the successful contractor.

Stage 1 covers all major civil construction works between Westmead Station at the western end of the line to The Bays, including station excavation and tunnelling, while Stage 2 comprises fit-out of all stations and installation of the rail systems. The final stage covers all major civil construction works between The Bays and the city centre, including station excavation and tunnelling, as well as fit-out of stations and installation of rail systems.

According to the EIS, Stage 1

Package will not be eligible to be awarded the Western Tunnelling Package.

Stage 1 stations include cut-and-cover stations at Westmead, Paramatta, Olympic Park, North Strathfield, Burwood North, and The Bays with a binocular cavern-type station at Five Dock.

Additional stations may also be added at Rydalmere and Pymont, with investigation work underway to determine their potential.

The final project budget will be confirmed when all contracts have been awarded, following the same procedure used previously for the Sydney Metro Northwest and Sydney Metro City & Southwest projects.

Metro Western Sydney Airport

Adding to metro development in the New South Wales capital is the Metro Western Sydney Airport, which will run 23km between St Marys and the new Western Sydney International Airport and Western Sydney Aerotropolis (Fig 2). According to its scope, the route will be a mix of surface, underground and elevated alignments, with underground elements at either end.

Linking at St Marys with existing Sydney trains network for services to the Sydney Central Station, additional

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• Bouygues Construction Australia • John Holland Gamuda Joint Venture • Acciona Construction Australia “The civil works contract is expected to be awarded by the end of 2021, with the first of an expected four TBMs anticipated to launch by the middle of 2023,” said Andrew Constance, New South Wales State Minister for Transport and Roads.

The contract will be awarded on a fixed price design-build basis and the estimated budget for the line and the value of the contract is yet to be disclosed.

The underground works are in two sections of about 4.3km of twin tube excavation from St Marys to a portal at Orchard Fig 3. Metro City & Southwest route under Sydney Harbour Hills and for 6.3km of twin stations are planned at Orchard Hills, running tunnels from the Luddenham, at two locations at the new airport to Bringelly. About 3.3km and Western Sydney International Airport, two underground station of this section and at the Aerotropolis. The objective is lie under the airport precinct. An elevated to have the project operational in 2026, section will take the line through an when the Western Sydney Airport is elevated station at Luddenham. scheduled to open.

The Australian and New South Wales Three consortia are shortlisted to bid Governments are jointly delivering the project for delivery of station boxes and 10km of with the final budget for the project confirmed underground infrastructure for the project: when all major contracts are awarded.

Excavation and concrete lining of station caverns at Martin Place and Victoria Cross

Metro City & Southwest

On the Metro City & Southwest Line, TBM excavation of the 15km long twin tube alignment was completed in March 2020 when the Herrenknecht Mixshield slurry TBM broke through at the Blues Point reception shaft at the end of the second 885m drive under Sydney Harbour (Fig 3). Four additional double shield TBMs had already been shipped back to the Herrenknecht in February 2020, after the last of these completed its drive between Marrickville and Barangaroo in January 2020.

The second drive under the harbour took a month less to complete than the first, after modifications were made to the cutterhead and tunnelling processes to better deal with the higher than expected amounts of clay encountered on the first drive.

Work now continues on the stations with drill+blast excavation of the cavern and service tunnels at Victoria Cross Station. The impressive underground space is reportedly the largest rail cavern in Australia at 265m high x 25m wide x 20m high. Focus is currently on installation of the permanent concrete lining and construction of the southern shaft, which will be one of the entrances into the new station. About 151,000 tonne of a total 262,000 tonne of rock for the shaft had been removed by early July 2020 with excavation expected to continue until November 2020.

The tunnels, stations and excavations works package for the project was won by a John Holland-CPB Contractors-Ghella JV in June 2017 at a contract value of AUD$2.8 billion.

Major excavation is also nearing completion at Martin Place Station.

Design-build contractor Lendlease is delivering the complete integrated station project for developers Macquarie Group.

The works include a 39-storey over-station development above the northern entrance to the underground station.

Excavation of the cut-and-cover extension to the city’s main Central Station

by Laing O’Rourke is also progressing and a 80m long x 6m wide tunnel has been excavated to allow construction of a 19m wide Central Walk underground concourse to connect the Chalmers Street entrance with suburban rail and metro platforms, and to new light rail and bus services. The construction tunnel runs parallel to the planned Central Walk alignment and will provide access for excavated rock to be removed without impacting existing station services.

Excavation broke through into two ghost structures that were built last century as part of the Eastern Suburbs Railway but never completed. These platform structures will now be used to house 17 new communications and power rooms for the new metro line. n

References • •

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Two more breakthroughs on Sydney Metro – TunnelTalk, December 2019 Slurry TBM makes five on Sydney Metro – TunnelTalk, September 2019

www.TunnelTalk.com

Melbourne Metro rail excavations TunnelTalk reporting

Rail Loop planning

Meanwhile, expressions of interest are invited by the Victoria State Government for a package of early enabling works to prepare for Stage 1 construction of the planned 90km long Melbourne Suburban Rail Loop.

The works will prepare for construction of six underground stations and launch of TBMs for excavation of the 26km Stage 1 twin running tunnels underground route to the south east of the city (Fig 1).

Early works will also prepare for detailed site investigations that will include ecology and geotechnical studies. Initial site investigations started in the second half of 2019 to identify and confirm the broad alignment and general precincts of station locations. Almost 300 boreholes were drilled as part of geotechnical investigations.

Procurement of the project began when the State Goverrment allocated AUD$2.2 billion to buy the land required for the construction sites.

The Suburban Rail Loop is an investment in the long-term rail service infrastructure of Victoria to support continued growth of its State capital city of up to a projected nine million people

Fig 1. Proposed underground Stage 1 of the Rail Loop and Metro route (inset) by 2050. Following Stage 1, future stages will continue the line through the northern suburbs to connect major railway lines and the Melbourne international airport.

Rail Projects Victoria is leading the design development and has engaged the AureconJacobs-Mott MacDonald Joint Venture (AJM) as technical adviser and KPMG as commercial adviser. The project will allow people to travel by train around Melbourne without having to connect in and out of the central city rail station hubs.

Premier of Victoria Daniel Andrews is championing the project and stated that “we are not wasting a minute getting this

vital project started.” Minister responsible for the project Jacinta Allan said: “The $2.2 billion investment for Stage 1 early works are to start in 2022, which will help drive our State’s recovery from the coronavirus pandemic.” n

References •

Melbourne awards its PPP metro contract – TunnelTalk, July 2017

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M

etro excavations in Melbourne are into final stages ahead of an opening of the line in 2025, a year ahead of the original schedule.

The first of four 7.2m diameter Herrenknecht Mixshield TBMs broke through into a 13m deep shaft in February 2020 after its launch at the Arden Staton site in September 2019.

The second TBM completed the parallel tube and the third and fourth TBMs launched from the new Anzac station site in mid-2020 and progressed under the Yarra River towards breakthrough at a 19.5m retrieval shaft at the eastern portal of the underground section of the line.

Trinocular caverns of spectacular scale create the mined stations at State Library and Town Hall, with cut-and-cover excavations at Arden, Parkville and Anzac Stations (Fig 2).

Cross Yarra Partnership, the designbuild-finance concession comprising Lendlease Engineering, John Holland, Bouygues Construction and Capella Capital, is completing the AUS$6 billion PPP contract with Melbourne Metro Rail Authority. Work began in 2018 at the Arden Station site.

Trinocular caverns (Fig 2) create the mined stations at State Library and Town Hall

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Brisbane advances Cross River Rail link TunnelTalk reporting

E

xcavation of the Cross River Rail twin tube route began in Brisbane, with TBMs and roadheaders deployed to excavate the 5.9km underground section of the 10.2km rail link between Dutton Park in the south of the city and Bowen Hills in the north (Fig 1).

The Pulse consortium of the CIMIC Group companies, Pacific Partnerships, CPB Contractors, and UGL, with international partners DIF, BAM, and Ghella, was awarded the AUD$5.4 billion contract to deliver the underground section and its four new underground stations at Boggo Road, Woolloongabba, Albert Street and Roma Street and their ongoing maintenance.

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Fig 1. Twin TBM drives will progress 5.9km under the Brisbane River and central business district

The CPB Contractors-Ghella-BAM International JV is delivering the design, construction and underground excavations; with UGL delivering the mechanical and electrical works and providing maintenance services for a 24-year period.

Two 115tonne roadheaders, previously used to excavate the new Woolloongabba Station cavern, are 30m into excavation of the 870m twin tubes between Woolloongabba and the new Boggo Road Station site. The 22m-long machines will excavate at a rate of 60 tonne/hour to remove 86,000m3 of muck.

In total, six roadheaders are working on the project, excavating the station caverns at Roma Street and Albert Street, three cross passages at 240m intervals and the southern portion of the twin alignments from Woolloongabba.

Woolloongabba is also the launch site for the two 7.2m diameter refurbished

Herrenknecht TBMs that will drive the northern 5km of the route. Previously used to excavate the City + Southwest Metro in Sydney, the TBMs will drive under the Brisbane River and the central business district, through the Roma Street and Albert Street Stations, before emerging at the northern portal.

Work began in July 2020 at the Wagners precast facility at Wacol, to produce the segments to line the twin tunnels in 1.7m long x 270mm thick rings.

Excavation of the 5.9km route is expected to be complete within twelve months, with the roadheaders and TBMs breaking through by the end of 2021. M&E and rail systems are to be installed by end 2023 before commissioning and planned start of public train services in 2024. n

References •

Brisbane Cross River Rail mobilises for construction – TunnelTalk, August 2019

Roadheaders began excavation south from Woolloongabba

Graphite iron joins concrete segments on Perth link

A

fter consultation with international experts, project owner Metronet decided on the repair method for the damaged section of the 8km long twin bored tunnels of the Forrestfield and airport rail link in Perth, Western Australia.

A 26m long section of one of the running tunnels was damaged in September 2018 when excavation of the first cross passage collapsed and the groundwater pressure and associated loading caused localised distortion to the tunnel and its precast concrete segmental lining.

Spheroid graphite iron lining on the Perth airport route repair

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A spheroid graphite iron lining was installed by main contractor Webuild (Impregilo) and its local JV partner NRW. The structure will correct the tunnel alignment and ensure the required strength, durability and water tightness of the lining. The failed cross passage was re-excavated to complete rectification work and free up the last section of running tunnel for track laying.

Ground freezing has been applied for excavation of the final cross passage.

The 8 km long twin tube alignment has 12 cross passages and three emergency and maintenance access shafts.

At the tunnel portal at Bayswater, about 11m below ground level, works are ongoing on waterproofing the tunnel sealing rings.

The sheeting of the lower roof of the portal building is complete and installation of the upper roof structure is ongoing.

Excavation of the TBM running tunnels was completed in April 2020 when the last TBM drive broke through at the Bayswater transition ramp to the surface rail alignment that connects services to the city centre railway station.

Salini Impregilo and NRW spent more than 900 days tunnelling through varied and

Metronet News Release sometimes challenging conditions, including under Perth Airport and under the Swan River. The two Herrenknecht 7m diameter variable density machines installed 9,000 tunnel rings of precast concrete segments with a 120-year durability.

The AU$1.86 billion rail line is scheduled to become operational in the second half of 2021. The line will cut the journey from the east to the central business district of Perth from 45 minutes by car to 20 minutes by underground rail.

Transport Minister Rita Saffioti said that first operational trains are expected to run on the service in the first half of 2022.

While this is later than anticipated, the delay was unavoidable in the wake of the pandemic and cross passage repair works.

Despite the extended timeframe the WA Government states that the original budget of $1.86 billion remains unchanged. n

References • •

Cross passage sinkhole halts work in Perth – TunnelTalk, September 2018 TBMs push on for Perth Airport Link – TunnelTalk, August 2018

www.TunnelTalk.com

Auckland centre of underground activity TunnelTalk reporting

T

wo major projects are currently underway in Auckland, New Zealand, one to create a new rail link to improve public train services though and around the city and the other to intercept combined sewer overflows and protect the city’s waterways.

For the NZ$ 4.4 billion City Rail Link, the Link Alliance JV of Downer, Vinci Construction and Soletanche Bachy, has mobilised a 7m diameter Herrenknecht TBM to complete the 1.6km twin running tunnels between three new underground stations (Fig 1). Progressing from the Mt Eden Station launch site, the TBM will advance southward to Aotea Station where the drives will connect to cut-and-cover tunnels built earlier to link the reconfigured Britomart Station from a terminus to a through station.

The first 1.6km TBM drive is expected to breakthrough towards the end of 2021 when it will be retrieved and reassembled at Mt Eden Station for the second drive.

The full 3.4km City Rail Link at up to 42m below the streets of Auckland includes a fully grade-separated junction in mined caverns to connect with two cut-and-cover connections east and west to the existing North Auckland Line.

The 32m deep Karangahape Station is a mined cavern design. The 15m deep Aotea Station is a 300m long cut-andcover excavation and the Mt Eden Station is a partial underground structure with a 7m deep open trench to provide interchange between the City Rail Link and the existing Western Line.

When opened in 2024, the project will double the capacity of the rail network in Auckland.

Interceptor project

For its contract with owner Watercare, the Ghella Abergeldie JV (GAJV) procured a 5.45m diameter EPBM from Herrenknecht to excavate the 14.7km long x 4.5m i.d. alignment of the NZ$1.2 billion Central Interceptor project. Starting from a working site and access shaft at the Mangere wastewater treatment plant, the TBM will progress at depths of between 15m and 110m and will pass under Manukau Harbour at about 15m below the seabed. Protection against surface settlement will be a priority as the alignment passes also under private residential property.

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TBM begins City Rail Link journey

Fig 1. Route and elevation of the new railway to provide a looping rail service Watercare specified an EPBM and the GAJV with Herrenknecht, designed the machine to operate at up to 9 bar EPB pressures. The cutterhead is designed for both soft ground and hard rock.

Along the route will be 17 shafts reaching depths of up to 80m. Two link sewers of 1.1km long x 2.4m i.d and 3.2km x 2.1m i.d., will be excavated with two pipe-jacking machines.

The TBM has passed its factory acceptance testing and is expected to

TBM ready for journey to New Zealand for the Central Interceptor project (right)

arrive and launch before end of 2021. The project is programmed to be completed and commissioned in 2025.

Underground heritage

The two new projects follow on from previous TBM and underground projects in New Zealand including the twin mega-TBM drives for the Waterview highway project completed in the 2010s, the Hudson Bay sewer and Rosedale outfall projects for Watercare in the early 2000s using Lovat TBMs and the Manapouri tailrace project completed in the late 1990s using a Robbins gripper TBM that went on to excavate the Niagara hydro scheme diversion tunnel in Canada in the early 2000s as the largest diameter main beam hard rock TBM to date. n

References • • • • •

www.TunnelTalk.com

Auckland calls for rail link proposals – TunnelTalk, October 2018 Preferred contractor selected for Auckland interceptor – TunnelTalk, November 2018 Managing progress of mega TBM at Waterview – TunnelTalk, March 2015 Hobson Bay underwater works and designbuild responsibility at Rosedale – TunnelTalk, February 2009 Niagara plan of attack – TunnelTalk, December 2006

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Rebar for final insitu concrete lining at Belleview

Underground developments for Seattle LRT

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ith the Northgate and East Link light rail extensions in Seattle on schedule for completion in 2021 and 2023, the city is planning its next phase of light rail expansion. Known as ST3 and following voter approval of funding in 2016, the programme includes plans for a significant new underground section on the planned West Seattle-Ballard Line, which will run from Alaska Junction in the southwest, through the Chinatown/International District and under the city centre to Ballard in the north (Fig 1).

The West Seattle-Ballard Line will total about 12 miles (19km) of underground and surface alignments with nine new stations (Fig 2). The exact route is yet to be confirmed and all options currently under review in downtown Seattle are for underground alignments. “There are further reaches of underground alignment being considered near the north and south terminals of the line,” said David Jackson of Sound Transit.

“Some of these underground options would require additional funding beyond that approved by voters,” he added.

Construction of the West Seattle-Ballard line is to be in two phases for a start of services scheduled for 2030 on the West Seattle element and 2035 for the Ballard link.

“The project is in the environmental impact statement study period at present and it is from these studies that the final routes will be decided,” Jackson said. Following public review of the draft environmental impact study, design work is expected to progress between 2022 and 2026 with construction beginning in 2025 on the West Seattle element and 2027 on the Ballard section.

The remaining more than 50 miles (80km) of light rail included in the ST3 programme is likely to be at-grade or elevated with the choice of guideway reflective of the service area of the project, said Jackson. The West Seattle-Ballard route will run under the downtown area, where space is at a premium, while the remaining routes will be constructed in more suburban locations, where space allows surface development.

The ST3 programme is scheduled to be complete by 2041.

bench and invert sequence through the first half of the alignment, which ran through more competent glacial till. It then changed to a more controlled excavation through the more complex outwash material in six stages dividing the heading with a single sidewall drift.

The 38ft o.d. excavation is supported with an initial 1ft thick macro-synthetic fibre reinforced (MSFR) shotcrete and lined with a 1ft thick cast-in-place concrete lining to a finished i.d. of 34ft. A Normet Spraymec 8100 robot applied the macro-synthetic fibre shotcrete as well as the spray waterproofing membrane supplied by Mapei.

In addition to the Belleview tunnel, the route includes two additional underground sections that will run through the existing Mount Baker and Mercer Island road tunnels.

Northgate Link extension

Running through some of the most congested neighbourhoods of the Seattle region, excavation of the 4.3 mile (7km) 22ft o.d. TBM-bored Northgate Link alignment was completed in 2016 (Fig 4).

The project included excavation of Fig 1. Current and planned LRT in Seattle

Jonathan Rowland, TunnelTalk 23 cross passages, of which 11 required ground freezing support. Five of these used vertical drilling from the surface, while horizontal drilling from within the completed tunnel was used at six locations where ground conditions, including unexpectedly permeable soil and unstable running silt, made the original dewatering plans infeasible.

The remaining 12 cross passages were supported by dewatering and local ground control. At 17ft wide x 18ft high and varying from 15ft to 25ft in length, excavation of the cross passages was by SEM on 3ft headings.

Ground freezing was used also to create a support canopy for TBM breakthrough into the University District Station.

Two new Northgate Link underground stations at University District and Roosevelt were completed under a separate contract.

With a total taxpayer budget of $1.99 billion, with US$1.4 billion for construction costs including $500 million for the underground element, work has so far been completed on schedule and within budget, said Davis. n

References •

$200 billion for transit funding on US ballot – TunnelTalk, November 2016

Fig 3. $1.6 billion 14 mile East Link

Fig 4. Despite a TBM breakdown, NorthgateLink excavation finished in 2016 Fig 2. Ballard extension route and options

East Link update

With a budget of US$121 million for the underground work within the project total of $1.6 billion, excavation of the 2,235ft (681m) Belleview SEM section of the 14 mile (22.5km) East Link to serve the communities of Mercer Island, Bellevue and Redmond is complete and finishing works are underway (Fig 3). The Belleview alignment will also form part of the planned 11.4 mile South Kirtland-Issaquah Link of the ST3 programme, which is currently scheduled to go into service in 2041.

SEM progressed on a full top heading,

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www.TunnelTalk.com

Rehabilitation option for Hudson rail links in New York TunnelTalk reporting

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www.TunnelTalk.com

Fig 1. Route of the existing and new Hudson River rail underpasses recommends a conceptual approach to repairing the tunnel lining and sealing leaks first, and considers alternatives to the existing concrete bench walls for protecting cables, such as combinations of racks, troughs, and metal strongboxes that have been used successfully elsewhere.

The LBA approach prioritizes the root causes of unreliability evidenced by train delay data attributed to track conditions, overhead power and signal problems, and recommends accelerating work to correct these issues as quickly as possible.

LBA noted that further design and contractor outreach would be required to determine, develop, test and practice the means and methods that would allow continuation of the current levels of service as the rehabilitation works progressed.

The report has been received with a mixed reception. Governor of New York State Andrew Cuomo has received the report saying: “We have a report that says the tunnels can be rehabilitated. There is also a desire by Amtrak and many people to build new tunnels, which I think is a good idea. One is not the enemy of the other.” New Jersey Governor Philip Murphy is less enthusiastic, saying the proposal would make commuters “more miserable,” because it would require nighttime and weekend service reductions. “We need four tunnels under the Hudson and we need to do it in a way that does not disadvantage and further impact the lives

and the experience of the commuters from New Jersey,” he said.

Steven Cohen, New York Trustee and Chair of GDC, said, “We are all saying the same thing: we need the new tunnels to add access, but that is a decade away and we do not want the current systems in the existing tunnels to fail in the meantime.

So it is worth looking at whether we can rehabilitate the old tunnels while we build the new ones.”

Tony Coscia, Amtrak Trustee and Vice Chair of GDC, said, “Construction of a new Hudson River Tunnel is the fundamental reason GDC was created and that is our top priority. As we await Federal environmental approval to begin construction, a full review of the very best means, methods and practices to preserve the existing tunnels is an important part of stewardship by Amtrak of this critical infrastructure. The concepts suggested by LBA are being evaluated to determine feasibility, cost, and schedule impacts, so that we can determine the best ways forward.”

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nline rehabilitation of the existing twin rail tunnels under the Hudson River in New York, which bring Amtrak and local train services into Pennsylvania Station in Manhattan, is an option that has introduced a rethink of the current planning of the Gateway project.

The objective of the project is to increase rail capacity and carry out needed upgrade and renovation of the existing twin rail infrastructure.

The Gateway project has been in development for several years and is based on excavating and having in service the first of two new under river rail tunnels to allow for the first of the existing 110-year-old tunnels to be taken fully out of service for a refit. The operation would be repeated for the second of the existing running tunnels, once the first renovated tunnel is back in service and as the second new drive under the river is progressing.

The Gateway Development Corporation (GDC), a New Jersey notfor-profit entity with Board members representing Amtrak, which owns the existing Hudson River tunnels, and the States of New York and New Jersey that govern and fund rail service agencies including the New Jersey and New York Transit organisations, is developing the currently estimated $11.4 billion project.

In a study, commissioned by the GDC and carried out by London Bridge Associates (LBA) of the UK, an alternative proposes rehabilitation of the old tunnels during night and weekend engineering hours when normal train services are suspended. This would allow rehabilitation of the tunnels without delay and could save money.

The old tunnels are not in fear of failure, as they are built in the hard Manhattan Schist of the region. It is upgrade and replacement of outdated operating systems and reconstruction of deteriorating concrete linings and structures that is required, due to severe damage caused by flooding during superstorm Sandy in 2014.

Analysis of the LBA study confirms that the rehabilitation of the project includes reconfiguring and rebuilding the concrete bench walls; replacing high-voltage electrical cables and other cables currently inside the bench walls; a 360 degree repair of the concrete lining, including areas behind the bench walls and beneath the ballasted track bed; replacing the outdated ballast and wood tie track-bed with a direct-fixation concrete system; and upgrading and replacing the catenary overhead system and dated cables and signals with stateof-the-art equipment. Existing levels of Northeast Corridor train services must be maintained throughout construction.

Inline rehabilitation of old rail tunnels is an operation that is well established and used for rehabilitation of several aging rail tunnel infrastructure. With knowledge of these experiences in hand, the LBA report

In-service rebuild

In-services rehabilitation of road and rail infrastructure is a proven methodology, as contributing journalist Roland Herr reports of a project in Germany. The 451m singletube double-track Kuckuckslay railway tunnel built in 1871 was refurbished while maintaining train services. The EKT joint venture of Porr and Alfred Kunz

Existing rail tunnels in need of extensive rehabilitation

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From left: Enlargement working platform unit and protective shield ready for launch; Services continued as drill+blast enlargement and rebuild progressed; Breakthrough at the North Portal of the Kuckuckslay tunnel in July 2020 was commissioned by Deutsche Bahn DB Netz in 2018 to refurbish the facility.

Construction began in February 2019 and was programmed to be completed by Summer 2021. The €19.15 million contract includes enlargement of the cross-section, and the finishing of the construction work.

The in-tunnel rehabilitation method is a tried and tested process by Deutsche Bahn using a movable construction rig installed on its own set of rails to enclose the operating track and allow train traffic to continue as the work progresses. Outside the protective unit, work takes place concurrently to demolish the existing lining, expand the cross section using drill+blast and install immediate support. A new inner concrete lining was then cast as a follow-on operation. Stefan Vetter of DB Netz, Mario Galli of EKT JV and Peter Steiner of Laabmayr Consulting, explained the details of the process.

At Kuckuckslay the JV used a 36m long x 160 tonne enlargement unit consisting of three sections – a shield, the main unit and a backup gantry running on rails mounted on temporary reinforced concrete foundations at either side of the rail tracks. The shield has hydraulically adjustable support plates and is always within the existing rail envelope,

preventing the existing lining from breaking ahead and falling to the operating track. The main working unit is fitted with demolition hammers and drilling equipment for drilling charge holes and rock support anchors and for spiling presupport as required.

The supply devices, such as hydraulic and power units, ventilation equipment and laydown areas for supplies were mounted on the backup gantry. Excavators removed the demolished lining and excavated enlargement rock from the tunnel.

Once the working unit was launched, demolition, excavation and primary support work progressed continuously, 24 hrs/7 days a week. Excavation blasts took place during possession outages of the operating track and after close coordination between the construction supervision managers, railway operators and the construction management.

Track possessions depended on availability and were as short as possible. As many as 45 trains/day ran on the one bi-directional operating track during the works.

In the enclosed and limited working area, a suction ventilation system was provided, as well as a pressure ventilation system for the main cross-section.

Due to a requirement of the fire

department that any haze, especially from smoke, had to be taken away from the main approach direction of the emergency services, the ventilation plan had to be designed from south to north. This was achieved by installing jet fans on the working unit which generated a vacuum in the main cross section into which dust was sucked from the working areas. Air quality was supplemented by the use of waterspraying devices to suppress dust.

Removal of the existing lining, expansion of the cross-section from 24.10m to 25.47m i.d., and installation of primary support took about 200 days, working two 12 hr shifts/day, and achieving an average advance of 2m/day.

For the Gateway project in New York, a major cost reduction exercise for the project in September 2019 reduced the budget of the new under river tunnel works to US$9.5 billion from previous estimates of US$11.1 billion. n

References • •

New York on the brink of a rail tunnel crisis in aftermath of Superstorm Sandy – TunnelTalk, November 2014 Budget trimmed to advance Hudson Gateway – TunnelTalk, September 2019

BART to San Jose options and shortlisted bidders

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everal design configurations have been studied for the BART heavy rail extension to Silicon Valley through the city of San Jose in Northern California.

In the latest rethink, the larger diameter single-bore tunnel with center platform stations in a TBM bore of 49.5ft i.d. and 56ft o.d. (15.1m i.d. and 17m o.d.) and side-by-side double tracks throughout is replaced with a combination of station and running tunnel configurations.

Following several months of developing the single-bore option, BART, the Bay Area Rapid Transit organization as the operator of the new 6-mile (10km) extension with 5 miles (8km) and one surface and three underground stations beneath San Jose, agreed to the large single-bore concept with side-by-side tracks and a 24ft (7.3m) wide center platform at each of the underground stations. In July 2019, VTA began advancing the larger single-bore design with its Program Management Team, a joint venture between HNTB and WSP, and its General Engineering Consultant MMW, joint venture between Mott MacDonald and PGH Wong Engineering.

A particular undertaking by VTA, the

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Valley Transportation Authority that will fund, design, build and own the infrastructure, is to limit construction disruption particularly on the route that runs under Santa Clara Street in the downtown retail, business and residential area of San Jose (Fig 1).

The traditional twin-tube running tunnels between open cut station boxes, in the central area, has been ruled out, as has twin tube running tunnels between SEM mined

Shani Wallis, TunnelTalk stations, which are considered high risk in the saturated sandy soils of the area under a high groundwater table.

However, as design of the large singlebore, double-track option with a central in-tunnel platform and overhead mezzanine concourse at stations progressed, higher projected risks were identified and preliminary

Fig 1. Considered reconfigurations of the extension

www.TunnelTalk.com

References • •

Funding and single-bore secured for BART to San Jose – TunnelTalk, May 2018 A slow road for BART to San Jose – TunnelTalk, May 2007

www.TunnelTalk.com

Acciona-Ghella selected for Broadway Subway project

Top: Broadway City Hall interchange station with the Canada Line at Cambie Street Below: Fig 1. Twin tube EPBM drives will link six underground stations

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design, construction and partial funding proposal from the Acciona-Ghella JV for the CAD$2.83 billion Broadway Subway project in Vancouver is selected by the Government of British Columbia from two shortlisted proponents for the 5.7km westward extension of the Millennium Line SkyTrain from VCC-Clark Station to Arbutus Street and with a connection to the underground section of the Canada Line at Cambie Street (Fig 1).

Designers with the JV proposal are IBI Group of Canada; Dialog BC Architecture Engineering Interior Design Planning; Mott MacDonald; and Acciona Ingenieria Especializada Obra Civil e Industrial of Spain with systems integration contractor Parsons.

The project is funded and delivered by the Government of British Columbia, with contributions from the Government of Canada and the City of Vancouver and an element of funding from the construction group. Acciona is the 60% leader of the JV with Italian partner Ghella at 40%.

The new 5.7km public transit line is aligned 5km underground in twin tube running tunnels connecting six new underground stations, with a 700m section of elevated guideway linking to the existing VCC-Clark Station of the elevated Millennium Line. The 6m o.d. (5.2m i.d.) tunnels, will be excavated through sandstone geology, below the water table and through zones of glacial till. “We plan to use two EPB TBMs,” said Fernando Vara, Business Development Director for the Railways & Tunnels Unit for Acciona, “and are in discussions with TBM providers for the procurement of the machines. We will also design the segmental lining and procure the moulds and the carousel and other equipment to produce the segments in a local facility in collaboration with a local Canadian company.”

The six stations are planned as topdown excavations beneath the main street of the Broadway Corridor. The first cut will be completed in two halves with each decked over to reinstate traffic for excavation to continue beneath and down to base level. All the traffic staging will be developed with minimum impact on the surrounding communities and stakeholders. Interior construction of the

Shani Wallis, TunnelTalk stations will then progress from the bottom up. The new extension is expected to open in 2025. Once in service, the trip from VCCClark to Arbutus Station will take 11 minutes, saving the average transit commuter almost 30 minutes a day and relieving congestion along Broadway.

This is the fifth extension of the Vancouver Metro system since the first element of the elevated Millennium Line was inaugurated in 1986. This was followed by the elevated Expo Line; the Canada Line link from the international airport with half of the line underground in cutand-cover and bored tunnels under the city streets; and most recently the underground Evergreen Extension.

Competition for the contract was presented by the second shortlisted proponent, the Broadway Connect JV of Dragados and Aecon of Canada, with designers Hatch, WSP, and Dr Sauer & Partners, VIA Architecture, Wood Environment & Infrastructure Solutions and Sener. The JV proposed an alternative to design and build three of the underground stations as mined operations without disrupting traffic.

A third group, the SNC-Lavalin led West 9th Partners, withdrew from the process.

There are studies ongoing also for an underground extension of the Broadway Subway of the Millennium Line west from the Arbutus terminus to the University of British Columbia (Fig 2). n

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cost estimates began to exceed available funding. BART also raised concerns regarding ventilation, the proposed uncustomary train operations, and provisions for emergency egress facilities.

Feedback from tunneling contractors at an industry forum add to the discussion, indicating that the higher risks of operating such a large TBM may reduce the interest in bidding for the project and possibly increasing the cost of prospective bids. A re-evaluation of current estimates for the project at about US$6 billion, was needed.

The complexity arises in that the owner and future operator of the extension are different with VTA building and owning the infrastructure and BART operating the train services.

Two separate authorities are involved because Santa Clara County opted out of becoming part of the Bay Area Rapid Transit District when first formed in the 1960s and County residents have not contributed tax revenues to previous builds of the San Francisco Bay area metro system. VTA therefore secured the funding to build the extension and will manage construction of the infrastructure for the extension to be operated by BART. Having previously had reservations with the stacked single-bore concept, BART has agreed to an optimized, smaller diameter, single-tube, doubletrack running tunnel concept with stacked platforms at stations and enhanced emergency egress at two mid-tunnel ventilation structures. The current combination strategy is a larger singlebore diameter to accommodate side-byside trackways from the west portal to the western enhanced mid-tunnel ventilation and emergency egress facility. East of the eastern enhanced mid-tunnel facility, and through a cut-and-cover station at 28th Street/Little Portugal Station, the trackways are required to be side-byside either in twin tubes or in a single tube configuration which is yet to be confirmed.

Only the central section between the midtunnel ventilation and emergency egress facilities, will a smaller diameter single tube contain stacked tracks to stacked platforms at the Diridon and Downtown Stations (Fig 1).

Managing the variables for delivery of the project is the task of Takis Salpeas who joined VTA in February 2020 and has worked for the Washington DC WMATA Transit Authority, the Los Angeles Metro, and for BART, to manage its San Francisco Airport extension. Under the Salpeas leadership, VTA will advance the design and assess any environmental, right of way and utility considerations.

VTA will also be preparing documents to submit for Federal a funding allocation from the FTA Expedited Project Delivery Pilot Funding Program.

There is still design and planning work to be done before construction can begin. n

References •

Revised shortlist for Vancouver Broadway Subway – TunnelTalk, August 2019

Fig 2. Proposed extension west to the University of British Columbia

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Toronto advances phased metro expansion Jonathan Rowland, TunnelTalk

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our major projects with a combined investment of CAN$28.5 billion are in the procurement phases to expand the public transit infrastructure in Toronto. Project owner Infrastructure Ontario and regional transport agency and metro operator Metrolinx are together advancing the Scarborough Subway, the Eglinton Crosstown West extension, the Ontario Line and the Yonge North Subway extension to add up to 30km of metro service to the city’s metro network. The majority of the new lines are aligned underground (Fig 1 and Table 1). All four projects are in procurement to have the last of them in service by the early 2030s.

Following a prequalification process, preferred bidders have been selected for Table 1. Details of Line Ontario Line Yonge Subway extension Scarborough Subway extension Eglinton Crosstown West extension

the two design-build-finance TBM running tunnel contracts for the Scarborough Subway and the Eglinton Crosstown West metro extension: • Strabag for the fully-underground

the four metro line priorities in Toronto Cost (CAN$) Length Completion Date $10.9 billion 16km, 9km underground 2027 $5.6 billion 7.4km, majority 2029-2030 underground $5.5 billion 7.8km, all underground 2030 $4.7 billion

7.8km Scarborough Subway with the design team Arup Canada and Brian Isherwood & Associates; and • West End Contractors JV of Aecon-Dragados-Ghella for the 9.2km Eglinton Crosstown West extension design-build-finance TBM running tunnel contract with lead designers TYPSA and EXP Services with ACS Infrastructure Canada, Aecon Concessions, Scotiabank Capital, and Ghella Investments & Partnerships as the financial advisors.

Procurement for construction of the stations, and installation of the rail and systems contracts are yet to be confirmed for both projects.

The preferred bidders for the tunnelling contracts, known as first negotiations proponents, were the highest ranked of three shortlisted groups on each contract. Evaluation was based on design and construction methodology, project management approach, and the collaborative behaviours of key individuals in the bid teams. The process was overseen by a third-party fairness monitor. The two groups are now working with Infrastructure Ontario and Metrolinx to finalise best value proposals with a financial close for the running tunnel contracts is scheduled for later in 2021 when work will enter the construction phase.

For the new 15.5km Ontario Line, shortlisted prequalified bidders have been announced for the southern 6km long underground civil works with six underground stations, and for supply of rolling stock, systems, operations and maintenance (Fig 4 and Table 2). The contract is expected to be awarded in 2022 when procurement of a third package for the northern section civil works will also begin.

Procurement of the 7.4km Yonge North extension is to begin in the second half of 2021. To reduce costs from about CAN$5 billion to $4.5 billion and maintain the financial viability of the project, plans for a fully underground extension with five underground stations have been amended to have the northern part of the route and two stations at-grade. A second costsaving and fully underground alternative, comprising a large twin-track single-bore running tunnel option, with station platforms in the single-bore in a stacked configuration, is also being investigated.

In a change to previous metro projects, the new tunnelling contracts will include procurement of the TBMs and segmental linings. For previous projects, the TBMs and the segmental linings were procured by the owner and provided for used to the engaged contractors. Four EPBMs were supplied for the Spadina Line extension and another four for the Eglinton Crosstown Line. n

Fig 1. Four new metro lines planned for Greater Toronto

9.2km, 6km underground 2031

Table 2. Shortlist for the Ontario Line south package Community Transit Link Applicant Lead Aecon Infrastructure Management, Dragados Canada, Strabag Design Team Arup Canada, Hatch ON-Linx Applicant Lead Webuild, Astaldi Canada Enterprises, Amico Infrastructures, Saipem Design Team IBI Group Professional Services Canada, Arcadis Canada Ontario Transit Group Applicant Lead Ferrovial Construction Canada, Vinci Construction Grands Projets Design Team AECOM Canada, COWI North America, GHD, SENER Group From left: Fig 2. Scarborough Subway extension; Fig 3. Eglinton Crosstown West extension

From left: Fig 4. Southern section of Ontario Line; Fig 5. Three options for Yonge Subway extension

References • •

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Final breakthrough for Toronto Crosstown LRT – TunnelTalk, August 2016 Wrapping up Spadina Line southern tunnels – TunnelTalk, March 2013

www.TunnelTalk.com

Mobilizing for the Los Angeles outfall drive Jonathan Rowland, TunnelTalk

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www.TunnelTalk.com

Top: Fig 1. Route to the ocean; Mixshield TBM selected for challenging conditions Below: Fig 2. Fault zones, squeezing ground and high water pressures are anticipated Precast in Littlerock, California, which is a truck journey of about 80 miles and 1.5 hours north of the job site. Segments will be delivered to the TBM in sets of two rings by rubber-tired multi-service vehicles. Each ring of 5ft wide x 1ft thick (1.5m x 300mm) comprises six segments, including the key and counter key, and weighs about 21 ton/ring. About 7,350 rings will be required to complete the lining.

Reinforcement is dependent on the ground conditions with 60lb/yd (36kg/m3) steel fibre-reinforced segments specified through the alluvial reach and in a short section at the junction with the outfall manifold structure. Rebar cage steelreinforced segments are to be used through the hard rock drives with a reinforcement content of 205lb/yd3 (122kg/m3).

Through the alluvial reach and for a 740ft (226m) section of low-cover at the southern end of the alignment, where net internal operating head during peak wet weather periods exceeds the hydrostatic head of the natural groundwater, a pre-tensioned design has been specified for the segmental lining. The design involves two sets of ducts and pockets cast into the segments with up to four steel tendons inserted.

Post-tensioning will take place 500ft (152m) behind the TBM on two dedicated gantries and the pockets and ducts will be backfilled with nonshrink grout.

A 3/8in (19mm) thick welded steel secondary lining with cellular grout backfill is

required in reaches of weak ground where the alignment intersects with the Palos Verdes Fault and at both ends of the drive. These add to a total of some 1,450ft (442m), the longest section of which is 500ft (152m). n

References • •

Los Angeles effluent outfall bid result – TunnelTalk, November 2018 Breaking new ground on LA outfall tunnel – TunnelTalk, June 2015

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BM excavation of the 7 mile x 18ft i.d. (11.25km x 5.5m i.d.) effluent conveyance system in Los Angeles is underway. Main contractor Dragados took delivery of its Herrenknecht slurry machine in November 2020 and assembly of the machine and its slurry treatment plant was ready for launch shaft in May 2021.

With no intermediate shafts, the drive will be managed from the 114ft (35m) deep x 55ft (17m) diameter launch shaft, with a starter and tail heading to support TBM launch and assist with logistics. The starter and tail headings were excavated by mechanical excavator inside a block of jet grouted ground. Zones of jet grouting will provide also safe havens for free air cutterhead inspection and tool replacement in the alluvial deposits across the first 3.7 miles (5.8km) of the 11.25km alignment.

Injected from the surface, the three blocks are about 60ft long x 40ft wide x 40ft high and at up to 75ft below ground surface.

The TBM is equipped with two personnel and one material locks for hyperbaric interventions, as required. With the entire alignment below groundwater level and with up to 10 bar hydrostatic pressure expected, there is also provision for pre-excavation grouting, as needed.

The 21.6ft (6.5m) diameter slurry TBM is designed to withstand complex ground conditions expected in the southern half of the alignment. In this section, the TBM will progress under the Palos Verdes Hills and reach depths of up 460ft (140m) through sequences of calcareous, diatomaceous and dolomitic siltstones, mudstone and claystone, interspersed with breccia, limestone, shale, and some basaltic intrusions. These units are heavily folded with north-south trending anticlines and synclines on the east side of the Palos Verde Hills and with an east-west anticline paralleling the alignment. Under the hills, there is evidence of faulting throughout and highly variable bedding orientations.

Significant squeezing conditions are anticipated with convergences of up to more than 12in (30cm) occurring within six hours of excavation.

To drive through the squeezing ground, the TBM features an additional hydraulic circuit that increases nominal thrust force from 79,128 kN to 158,256 kN when activated. A tapered shield, plus shield circumferential flushing ports and strain gauges built into the shield will also assist through squeezing conditions.

The Mixshield slurry circulation system comprises nine 600hp (447kW) slurry boosters and four 600hp (447kW) slurry feed pumps at the longest reach, with the slurry treatment plant capable of handling 5,283 gals/min (1,200m3/hr). Screened muck, dewatered through a filter press, will be trucked for offsite disposal. Gas vapour and hydrocarbon monitoring instruments installed at the treatment plant will detect contaminated muck for separate disposal.

The segmental lining is being cast at the production plant of subcontractor Traylor

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USA CSO projects continue in a challenging year One of the greatest streams of national and state investment in the USA in 2020 was the continuation of CSO network buildout to protect the rivers and shorelines of many major cities. While coping with the challenges posed by the pandemic, CSO projects advanced in Missouri, Rhode Island, Kentucky, Ohio, Washington DC and Indiana, and faced a variety of setbacks including a trapped TBM in St Louis, rock fallout and methane gas encounters in Louisville and hydrogeological inrush events in Fort Wayne.

Progressing Project Clean Lake in Cleveland

Jonathan Rowland, TunnelTalk

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wo deep storage tunnels are under construction in Cleveland, Ohio, with two completed and three more in planning as part of its USD$1.37 billion Federallymandated Project Clean Lake. When fully completed in 2035, the project will comprise a CSO interceptor network of more than 22 miles (35km) to reduce combined sewer overflow events into Lake Erie by 4 billion gallons/year.

In June 2020, the project marked the completion of the 2.8 mile x 24ft i.d.

(4.8km x 7.3m i.d.) Dugway storage tunnel.

Completed under its $153 million budget, Dugway follows completion of the 3.4 mile x 24ft i.d. (5.5km x 7.3m i.d.) Euclid Creek tunnel, which was finished in 2015 (Fig 1).

Four of the seven projects including the Dugway and Euclid Creek alignments are located in the easterly service area of the Northeast Ohio Regional Sewer District, NEORSD. Dugway and Euclid Creek run at about 200ft below grade through Chagrin Shale and were constructed using a single-pass (300mm) thick fibre-reinforced precast segmental lining. The method was specified

by NEORSD and project designer Hatch Mott MacDonald to limit gas infiltration and overbreak. The method has been used on all the main project drives and will be used on the remaining deep tunnels.

The Euclid Creek and Dugway projects were constructed by different contractors, using the same Herrenknecht TBM. After excavation of Euclid Creek by the McNallyKiewit JV in August 2013, the machine was purchased by the contractor Salini-Impregilo Healy DST JV. It was refurbished with the support of the manufacturer and relaunched in early March 2016. Breakthrough to complete excavation was achieved two years later in mid-March 2018.

The two remaining projects in the easterly service area are the Doan Valley system, which is currently in construction, and the Shoreline project. Both will connect to the Dugway alignment.

The Doan Valley system with six shafts, comprises the main 1.9 mile x 18ft i.d. (3km x 5.5m i.d.) storage system, plus two shorter 2.6m i.d. connectors. Excavations on the $142.3 million contract were completed in 2020 by contractor McNally-Kiewit JV using two TBMs. A new 21.5ft (6.6m) diameter single-shield Herrenknecht TBM completed the main Doan Valley alignment in September 2019. A Robbins machine, first manufactured in the 1970s and subsequently refurbished in 2009, completed the connectors in December 2018 and January 2020. The open gripper TBM tunnels are finished with a cast-in-place final lining.

TunnelTalk ANNUAL REVIEW 2020

Fig 1. Project Clean Lake deep storage tunnels All three Doan Valley drives were constructed from a single site within the University Circle neighbourhood. This posed several design and construction challenges that included protection of trees and sculptures, as well as the use of a small-diameter helicoidal shaft excavation method to minimize impact. The contractor has also had to deal with several utilities in the TBM launch site that could not be relocated, due to a prohibition on service disruption. The project is due to begin capturing CSO overflows in 2021.

The planned 2.7 mile x 23ft i.d.

(4.3km x 7m i.d.) Shoreline project is the fourth and final tunnel within the easterly service area and is likely be constructed

by EPBM through softer ground conditions and under the watertable. The Dugway TBM broke through in 2018

project includes three online shafts, with two drop shafts. The third will feature an upper and lower gate to help control dewatering of the tunnel.

Currently in design by McMillen Jacobs, bidding for the construction contract is expected in 2021 with completion in 2025.

The estimated project cost includes US$18 million for the design and $204 million for construction.

Flows from the easterly tunnels system are pumped by one of the largest CSO pump station projects in the USA, to the easterly wastewater treatment plant.

Designed by MWH, now part of Stantec, and constructed by the Walsh-Atkinson JV, the pump station is located 230ft underground, 22ft below the Euclid Creek and Dugway tunnel storage system invert, in a cavern of 185ft long x 45ft wide x 60ft high (56m x 14m x 18m). Nine pumps provide a capacity of 160 million gallons/ day to entirely dewater the storage tunnels.

The pump station was completed in 2018.

Three additional tunnels comprise Project Clean Lake.

Construction of the 1.8 mile x 25ft i.d.

(2.9km x 7.6m i.d.) Westerly storage tunnel began in 2018 by the Jay Dee-Obayashi JV and is about halfway complete. Running at 200ft-250ft (61m-76m) below grade, the alignment is being excavated by a 28.1ft (8.56m) diameter Lovsuns TBM. Construction is expected to be completed in 2021 at a cost of $135 million.

The Southerly and Big Creek tunnels are currently in planning with bidding for construction expected in 2023 and 2026 respectively. n

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A shorter retrieval shaft than originally planned

Challenging hydrogeology on Fort Wayne Jonathan Rowland, TunnelTalk

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ith hydrostatic pressure at up to 6.5 bar and groundwater inflows in the range of 5,000-10,000 gal/min, construction of the 4.6 mile x 16ft i.d.

(7.5km x 4.9m i.d.) CSO interceptor project for Fort Wayne City Utilities in Indiana has faced tough conditions. Main contractor Salini Impregilo-Lane JV launched a 19ft (5.8m) diameter Herrenknecht slurry TBM in April 2019 to complete the alignment at 200ft-240ft (61m-73m) deep.

The interceptor project is part of a US$240 million Federally-mandated programme of works and will reduce discharge from CSOs into the St Marys and Maumee rivers by 94% or 1 billion gallons.

The City of Fort Wayne contracted Black & Veatch for tunnel design and Jacobs as construction manager.

“The high groundwater inflow and pressure is the main reason a slurry machine was selected,” said Francesco Chiappalone, Technical Manager at Salini Impregilo-Lane. “We are driving through dolomite limestone formations, which is not typical geology for a slurry TBM, but it has been a good choice.”

The use of a slurry TBM has also helped with muck removal on a drive with only one working shaft and that started heading west, before curving slowly through 90° and will complete the drive heading south (Fig 1).

In addition to the hydrogeological challenges, the TBM has also had to excavate through changing stretches of massive dolomite and a reef-type limestone formation with some mixedface conditions of both (Fig 2). “This has affected penetration rates and advance speed, as well as causing some impact damage to the cutting tools, although general wear on the cutterhead has not been high,” said Chiappalone.

To reduce the time and risks involved with cutterhead interventions, the contractor decided to perform cutterhead maintenance at atmospheric pressure.

With no hyperbaric locks in the machine, there is a design in place for pre-excavation grouting to allow man entry under atmospheric conditions.

The drive is lined with steel fibrereinforced concrete segments, each 1ft thick x 5ft wide (300mm x 1.5m wide), with 35.6kg/m3 of reinforcement. Each ring comprises four trapezoidal segments, weighing up to 4 ton, plus a key and counter key. Segments are manufactured in Ohio by the CSI Tunnel SystemsForterra JV. The 33ft (10m) diameter x 240ft (61m) deep working shaft is one of three largediameter shafts on the US$188 million project and is adjacent to the 69ft (21m) x 240ft (61m) deep pumping station shaft.

The connection between the two shafts was excavated by drill+blast and lined with a steel pipe backfilled with cellular grout.

The 29ft (8.8m) diameter retrieval shaft will function as one of eight drop shafts on the scheme and was originally designed to be 180ft (55m) deep. It was shortened to 120ft (36.5m) to reduce the risk of high water inflow similar to that experienced during the excavation of the working and pump shafts.

The main shafts were constructed with diaphragm walls through the 70ft (21m) overburden, followed by drill+blast to depth and supported by rock bolts and shotcrete. A final cast-in-place concrete lining will be installed after the TBM has broken through and the adits are complete.

The additional drop and vent shafts range from 2ft (600mm) to 8ft (2.4m) in diameter and are excavated by blind bore drilling with a ductile iron or spun fibreglass-reinforced polymer mortar pipe lining.

The drop shafts will be linked to the main alignment by drill+blast adits of a cross section of 9ft x 9ft (2.7m x 2.7m) and vary in length between 50ft and 180ft (15m-55m). “The original design of the adits and deaeration chambers included a cast-in-place lining but this was redesigned to be a spun fibreglass pipe similar to the drop shafts, to further mitigate project risks due to water inflow,” said Lance Waddell, Project Manager for Salini Impreglio-Lane.

Due to the hydrogeological conditions, pre-excavation grouting will be required to construct the adits with any residual groundwater inflow pumped out via the main alignment.

Despite the challenges posed by the high hydrostatic pressure and groundwater inflows, the conditions have been managed by the project team to keep TBM excavation progressing.

Another challenge for the project team has been working through the pandemic.

This has required changes to working patterns, particularly at shift change, to help keep people separated, as well as monitoring worker health status before they enter the site. “Thus far we have had about nine days of delay due to the pandemic, but we are through that and back on track,” said Project Manager Waddell.

Construction is now progressing to meet the mandated completion deadline of December 2023. n

Fig 1. Route (left) and Fig 2. Geological profile (right) through mixed face conditions and under a high watertable

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TunnelTalk ANNUAL REVIEW 2020

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Narragansett Pawtucket contract awarded

TunnelTalk reporting

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xcavation of the 11,600ft (3.5km) Pawtucket tunnel as the start of the final phase of the Narragansett Bay CSO control program in Rhode Island is awarded to the CB3A JV of CBNA (the Bouygues Travaux Publics subsidiary in USA) and Barletta Heavy Division. Notice to proceed has been granted under a design-build contract worth $450 million, with CBNA as the majority partner and AECOM the engaged design engineer. GZ Gall Zeidler Third and final phase (in blue) of the CSO program

THE AMERICAS

Completed Phase 1 storage tunnel is sub-consultant for design of the larger diameter shafts and the SEM elements.

Stantec and its partner Pare Corporation, is Program Manager for Phase III of the project for the Commission Located in the Rhode Island Delta, about 75km south of Boston, the Pawtucket project is the first part of Phase 3 of the Narragansett Bay Commission water management modernization program. The 3.5km x 9m (30ft) i.d. tunnel drive will follow the Seekonk River and will be excavated by TBM (Fig 1).

The TBM will be designed specifically to cope with the varied geology anticipated along the route. Excavated at up to 180ft

Kentucky celebrates final breakthrough after tough drive

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6.7m (22ft) o.d. Robbins main beam TBM and conveyor system completed the 6.5km (4 mile) long tunnel for wastewater storage below Louisville, Kentucky. The TBM had to cope with overstress in the crown that resulted in significant rock fallout in seven Celebrating the breakthrough

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(55m) deep, the tunnel is designed with a single-pass, gasketed, precast-concrete, segmental lining.

The new CSO tunnel will collect, store and convey wastewater and stormwater to an existing water treatment plant.

As well as the 3.5km TBM drive the construction contract includes three main shafts, one of which will serve as a pumping station, and four collector drop shafts and connecting adits.

Carried out in the heart of an urban residential area of Pawtucket city, the project will be subject to measures designed to protect the environment and minimize the impact of the work on local residents. n

TunnelTalk ANNUAL REVIEW 2020

different areas, as well as methane gas infiltration. Breakthrough was celebrated in September 2020.

The tunnel was originally planned to be 4km (2.5 miles) long, but after a change order, 2.1km (1.3 miles) was added. The extension was ordered by the owner, Louisville Metropolitan Sewer District (MSD), and its Engineer-of-Record Black & Veatch to eliminate four surface CSO storage basins, one of which was located at the site of the TBM breakthrough.

“The original CSO site was located in close proximity to Beargrass Creek and had flooded multiple times. It was decided to extend the tunnel to that site in order to use the tunnel as storage instead, and connect it to the sewer system,” said Shemek Oginski, Project Manager for the contractor, a joint venture of Shea/Traylor.

Much of the crown overstress was encountered in the 2.1km (1.3 mile) extension, essentially a bifurcation of the main tunnel. “The longest section of overstress was 700m (2,300ft) and took two and a half months to get through,” said Oginski. The crew changed the prescribed rock bolt pattern of four to six bolts at 1.5m centers, to six bolts at 1m centers, which was two rows/stroke. They also installed wire mesh mine straps, and channels in the crown. Extra time was needed to install additional steel support, and remove loose rock. Overbreak varied from a few inches

Robbins News Release above the machine to 1ft and more.

“At first glance, this seemed like a straightforward project, but it turned out to be a lot more challenging,” said Oginski. “Shortly before holing through we encountered natural methane gas.” The methane was discovered as the crew was probing 150ft ahead of the machine, as they did continuously throughout the drive, using one, two or four probe holes depending on the geology. “We were down for about two weeks and were able to contain the methane within the cutterhead, where concentration spiked at 100% LEL. We were able to resume work after ventilating, probing and grouting multiple times.”

Despite the challenges, the refurbished TBM with a brand new cutterhead from Robbins and completely rebuilt electrical and hydraulic systems, was able to achieve up to 658m (2,159ft) in one month and 192m (630ft) in one week. This was made possible by using a Robbins continuous conveyor with a 68.6m (225ft) long vertical belt in the shaft. “The conveyor is definitely the way to go, especially for longer drives.

There was quite a difference in performance between the extension tunnel, which we excavated with lift-boxes, and excavation with the conveyor. Our best month in the extension tunnel with the boxes was 221m (725ft),” said Oginski. n

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he last of the large tunnel contracts in the Washington DC Clear Rivers CSO project received environmental approval from the National Parks Service to permit construction of the project mostly on and under its lands.

The 5 mile (8km) long x 18ft (5.5m) diameter tunnel will run along the east shore of the Potomac River passing beneath parks and gardens of the Washington DC riverside and alongside famous landmarks including the Lincoln Memorial and the Kennedy Centre Concert Hall.

The new tunnel along with diversion facilities, drop shafts and support structures, will intercept combined stormwater overflow outlets on the Potomac and divert flow southwards, under the confluence with the Anacostia River, to join the first tunnel of the Clear River project for conveyance to the Blue Plaines wastewater treatment plant (Fig 1). An estimated 654 million gallons of CSOs currently enter the Potomac River in a year of average rainfall. The Potomac tunnel will reduce that volume by 93% and reduce the frequency of overflow events from about 74 events a year to four. Green infrastructure options are also being studied as part of the overall Clean Rivers CSO control project.

According to Brandon Flora, a Project Manager with DC Water, the utility owner of the Clear River project, the tunnel will run 100ft to 150ft deep and will be a TBM drive with a precast concrete segmental lining along the same design as the previous Blue Plain, Anacostia, First Street tunnels and the current Northeast Boundary tunnel project.

If green infrastructure is determined practicable, the project will require construction of four shafts, according to Flora. If green infrastructure is determined impracticable, the tunnel will be extended to include CSO number 029 and with a total of seven new shafts.

A request for qualification is planned for late 2021 with an anticipated date for inviting the shortlisted groups to tender in mid-2022 and a start of construction in Summer 2023. The current budget for

Fig 1. Full scope of the DC Water CSO Clean Rivers project

New CSO tunnel will pass under the Memorial Bridge and past the Lincoln Memorial landmark the Potomac tunnel project is between US$450 million and $550 million.

With most of the construction taking place on Nation Parks Service (NPS) land, an environmental assessment was completed to evaluate two alternatives: a no-action option and an action alternative for the tunnel. A finding of no significant impact was signed by the NPS Acting Director of the National Capital Area in March 2020, selecting construction of the Potomac River tunnel as the preferred alternative and concluding the National Environmental Policy Act (NEPA) process. The Clean Rivers project by DC Water is developed to comply with the 2005 Federal Consent Decree and as amended January 2016 to have the full

Replacement TBM to finish St Louis network

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second, refurbished Robbins TBM is to be procured to complete the Jefferson Barracks CSO storage tunnel in St Louis, Missouri, after the original machine became trapped in a karst formation. Jefferson Barracks is the third of eight alignments that form the 32 mile (46km) network of deep CSO tunnels in the St Louis Project Clear program (Fig 1).

SAK has been the contractor on the five contracts awarded in the program to date, and in joint venture with Goodwin Brothers for the Maline Creek drive. SAK began the Jefferson Barracks drive in early 2017.

As with all eight of the Project Clear drives, the 3.5 mile x 11ft (5.5km x 3.6m) Jefferson Barracks alignment was designed as a hard rock drive with the original 11ft diameter Robbins TBM approved for the project by the Metropolitan St Louis Sewer District (MSD). MSD told TunnelTalk

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that excavation had stalled about 1.3 miles (2.2km) into the drive with the TBM unable to excavate through the geological conditions encountered. At its December Board meeting, trustees of the MSD approved a plan to procure a 14ft (4.3m) diameter Robbins TBM, designed and equipped for probing and pre-excavation grouting, to complete the drive.

In the meantime, work is progressing to retrieve the trapped TBM. Work began in April 2020 with exploratory borings for excavation of an emergency recovery shaft and access adit. Drill+blast construction of the 205ft deep x 40ft diameter (62.5m deep x 12m diameter) shaft started in July 2020 and was completed in October with hand-mining of the 200ft long x 40ft wide (61m long x 12m wide) recovery adit beginning soon after. To counter the karstic ground conditions and allow excavations to reach the trapped

TunnelTalk reporting

project in operation by 2030.

DC Water began its $2.6 billion Clean Rivers Project in 2011 to construct 18 miles (near 30km) of deep, large diameter CSO and stormwater storage tunnels to deliver all captured flow to the Blue Plains treatment plant (Fig 1). Within the Program Consultants Organization for the overall project for DC Water, McMillen Jacobs Associates is the general consultant overseeing tunnel and geotechnical engineering.

In addition to the Blue Plains, Anacostia and Potomac CSO tunnels, the Northeast Boundary flood prevention project began in 2012. A new storage tunnel under First Street was completed in October 2016 and the new 27,000ft long x 23ft diameter (8km x 7m) Northeast Boundary trunk sewer was awarded in mid-2017 to the Salini Impregilo/Healy (Lane Construction) JV, after the same JV was awarded the Anacostia River tunnel of the CSO program in mid 2015 with designbuild engineering partner Parsons. After completing excavation of the 3.8km x 7m i.d. Anacostia River tunnel in November 2016, the team refurbished the 8m diameter Herrenknecht EPBM for reuse on the Northeast Boundary tunnel.

After launch in September 2018, the TBM excavated more than 15,600ft (4.75km) and broke through into the W Street shaft in April 2020. It resumed excavation of the final 11,000ft (3.25km) in early May. The project, including construction of the diversion structures and drop shafts, is to meet the in-service operating date of the Northeast Boundary and the Anacostia tunnels in 2023.

The 7km x 7m i.d. Blue Plains tunnel was completed by the Traylor/Skanska/Jay Dee JV with design engineer CH2M-Hill and using an 8m diameter Herrenknecht EPBM. The completed tunnel was placed into operation in 2018 and has captured more than 7 billion gallons of combined sewage since then.

Upon completion in 2030, the Clean Rivers Project will reduce the volume of combined stormwater overflows by 96%. n

THE AMERICAS

Potomac River alignment approved in Washington DC

Jonathan Rowland, TunnelTalk machine, the contractor proposed grouting together with spiling and steel sets.

The replacement TBM will be installed and launched via the recovery shaft and adit after retrieval of the trapped machine. It will be attached to the existing backup and Fig 1. The eight deep alignments of Project Clear

TunnelTalk ANNUAL REVIEW 2020

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Jefferson Barracks recovery shaft and adit

continuous muck hauling conveyor, from the original working shaft for continuing to the planned reception shaft.

Elsewhere in the programme,

construction of the Maline Creek facility, a 2,640ft x 28ft i.d. (800m x 8.5m) concretelined cavern was substantially completed in September 2020 with full operations

expected to begin by the end of 2020.

Excavation of the 4.3 mile x 19ft i.d.

Deer Creek sanitary tunnel was completed in January 2020 when a Robbins TBM broke through into the Haddington retrieval shaft. The 12in (30cm) unreinforced castin-place secondary lining was anticipated to be completed in March 2021. Final works and the dewatering pump station for the contact are scheduled to be complete

by September 2022.

Construction of the 6.8 mile x 8ft i.d.

Lower Meramec drive was due to start in January 2021 after SAK Construction was approved as the contractor in November 2020. Procurement of three further contracts will follow in the late 2020s and 2030s with the Upper River Des Plains deep storage tunnel concluding the project when it opens in 2039. n

DigIndy progresses to final bore

THE AMERICAS

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xcavation is now complete on all but one of the six deep CSO storage tunnels of the DigIndy system in Indianapolis, Indiana, after the project TBM finished excavation of the 6.1km (3.8 mile) Fall Creek drive in April 2020 (Fig 1). The Robbins machine was retrieved by contractor JF Shea-Kiewit JV and transported to the launch site of the final 11.9km (7.4 mile) Pleasant Run drive,

Fig 1. Five phases of the DigIndy program complete End of the White River spur

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TunnelTalk ANNUAL REVIEW 2020

where it is being repaired and refurbished before relaunching in early 2021.

The total 45km x 5.5m i.d. (28 miles x 18ft) DigIndy network will intercept most of the 134 combined sewer overflows in the city and have a capacity of 1 million m3 (270 million gallons). Two sections, the Deep Rock connector and the Eagle Creek alignment, have been in operation since December 2017, capturing more than 7.6 million m3 (2 billion gallons) of overflow in that time.

Despite difficulties posed by the Covid19 pandemic, the project remains on track to meet the 2025 completion deadline set by the USA Environmental Protection Agency, said Mike Miller, Construction Manager for owner, Citizens Energy Group. “We were slightly impacted, mostly by supply-chain issues early on in the pandemic,” explained Miller, “but overall, we are about where we expected to be.”

Drill+blast adit and deaeration chamber excavation is now underway on Fall Creek, as well as continuing on the White River and Lower Pogues Run alignments. “Nine adits on Fall Creek total 1.7km (1 mile),” said Miller. “One is 500m long and expected to take five months to excavate.” Adits will be lined with precast concrete pipe, while the deaeration chambers will have a reinforced cast-in-place lining. Unreinforced cast-inplace lining of the 9.3km White River and 2.9km Lower Pogues Run alignments is currently underway.

According to the Federal mandate, the White River and Lower Pogues Run alignments are to be in service by the end of 2021, while Fall Creek and Pleasant Run must be operational by end 2025.

The same Robbins TBM has completed all drives of the project. For the final Pleasant Run alignment, the second longest after the Deep Rock connector, the machine cutterhead has been refurbished, a new main bearing installed, and the majority of the mechanical, electrical and hydraulic systems have been replaced. A large amount of the steel frame and decking also needed reinforcing or replacing.

The launch shaft is located at the end of a spur excavated as part of the Deep

Jonathan Rowland, TunnelTalk Rock connector/Eagle Creek project. Two bulkheads, installed at the connection with Pleasant Run, allowed the Deep Rock/ Eagle Creek phases to go into service ahead of Pleasant Run excavation. An opening cut through the upstream bulkhead and three valves installed through the second bulkhead allow for dewatering inflow during the Pleasant Run excavation directly into the Deep Rock connector.

Excavation of Pleasant Run is expected to take about 20 months with completion at the end of 2022/early 2023. Two additional large diameter shafts are being constructed on the alignment: an intermediary shaft at about the mid-point and a retrieval shaft about 1,000m from the tunnel end, which lies under a golf course. After reaching the end of the drive, the TBM will be backed up to the retrieval shaft for recovery.

Backing up of the TBM has been a feature of the project. It was backed-up after excavation of the Eagle Creek, Lower Pogues Run, western White River spur, and Fall Creek drives. “By the time we have finished, we will have backed up the machine along 9 miles – more than some projects go forward,” said Miller.

In addition to the deep tunnel network, about 6km (3.8 miles) of shallow sewers will be installed to consolidate the CSO points into eight drop shaft locations. Solicitation for the consolidation sewer work contract will occur in mid-2021 and work will progress concurrently with the Pleasant Run drive.

“The impact of this project,” said Miller, “will fundamentally change the condition of Indianapolis rivers and streams by capturing more than 97% of combined sewer overflows into these water bodies, all while remaining on schedule, under budget and with no violations of the consent decrees.” n

References • • • • •

CSO solution goes underground in Louisville – TunnelTalk, November 2019 One TBM for two-diameter Mill Creek alignment – TunnelTalk, October 2019 Breakthrough at Cleveland clean-up operations – TunnelTalk, April 2018 Final push for cleaner waterway in Washington DC – TunnelTalk, July 2018 Cleveland awards second CSO storage tunnel – TunnelTalk, November 2014

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Argentina begins Agua Sur drives

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fter passing its site acceptance test, the first of two 4.66m diameter Terratec EPBMs was launched by Italian contractor CMC di Ravenna for excavation of the 13.5km long Río Subterráneo a Lomas water supply project in Buenos Aires, Argentina.

A cutterhead lowering ceremony in June 2020, witnessed by President of Argentina Alberto Fernández and several government officials, marked start of the multi-billion-dollar Agua Sur system that will bring fresh water for 2.5 million inhabitants in the southern metropolitan area of Buenos Aires.

At an average depth of 25m, the EPBMs will work through the variable soft ground geology of the alignment, which ranges from silts to sandy silts, with some cobbles expected. The machines are

equipped with high-torque spoke-style soft ground cutterheads with a 49% opening ratio. Cutting tools consisting of fixed and back-loading knife bits will ensure rapid advancement with minimum interventions.

Each TBM cutterhead has eight hydraulic motors with a total power of 792 kW. As they advance, the TBMs will install the 3.9m i.d. precast segmental lining with each ring comprising six 250mm thick x 1.4m wide segments.

The first TBM was launched from the 45m long x 12m wide x 25m deep shaft composed of four circular sectors interconnected at the base. “As the machines are launched from a shaft, we have made full use of a modular design and umbilical launching system to work in the confined space, which is why the hydraulic drive solution was

Terratec News Release chosen,” said Emilio Saraniero, Terratec Project Manager.

The new Agua Sur system is the largest water infrastructure project to be carried out in Argentina during the last 40 years and includes a raw water intake and expansion of the water treatment plant to increase its capacity from a current maximum of 1,950,000m3 to 2,950,000m3/day.

The 23km water conveyance tunnel will be built in two stages and consist of two pump stations and 46km of pipe connections. The whole project is expected to complete in 10 years. n

References • •

Second EPBM for water project in Argentina – TunnelTalk, August 2019 Agua Sur project receives first EPBM – TunnelTalk, November 2018

President Fernández visits to see the first of two TBMs launched; The water tunnels will be lined with a 3.9m i.d. segmental lining

From top: Fig 1. Overview of the Woodsmith Mine; Fig 2. Route of the MTS and its TBM drives by two machines

Driving MTS progress at Woodsmith Mine Roland Herr for TunnelTalk

EUROPE

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aving been awarded the first 13km long section of the 4.9m i.d. segmentally lined mineral transport system (MTS) for the Woodsmith polyhalite potash mine in the UK, the design-build contract with the Strabag-led JV was subsequently extended to include the second and third TBM drives to complete the full 37km long system from Wilton to the mine site via the intermediate access shaft at Lockwood Beck (Figs 1 and 2). The Strabag team will also engineer, procure and fit-out the mineral transport system for operation.

Following a period in design and mobilisation, Strabag started excavation of the MTS in early 2019 with launch of the first of two 6m o.d. TBMs in June 2019.

The polyhalite resource is located 1,500m beneath the North York Moors National Park and the mineral once extracted will be lifted to an underground cavern for transport to the Wilton Teesside processing plant and export shipping harbour via the 37km long 4.9m i.d.

x 37km long MTS. The first TBM, a machine supplied by Herrenknecht, is proceeding on a 3.5 to 0.9% down gradient slope from the Teeside portal in Wilton to the intermediate shaft cavern at Lockwood Beck. The same TBM is planned to progress from the Lockwood Beck shaft towards the mine head with a second TBM, on a third drive, progressing from the mine head towards an in-tunnel junction to complete the remaining reach of the MTS. The second TBM is due to be procured and launched in 2022.

In a presentation to the virtual Salzburg Geomechanics Colloquium in October 2020, Ernst Gschnitzer, Julian Wenger and Andy Raine of Strabag AG, UK Branch, explained that excavation of the MTS started at Wilton with a 300m long open cut area into a 100m long shotcrete lined SCL heading. Originally the SCL heading was to be 800m long through the upper mixed face geological deposits, but the distance could be shortened to 100m due to slightly better than anticipated rock conditions. The SCL tunnel was completed in April 2019 and

Fig 3. Geotechnical profile along the TBM drives of the mineral transport system; Below: VSM excavation of the Woodsmith Mine MTS shaft by DMC Mining Services

in June 2019 the walked in TBM reached the rock face to begin full-face excavation in favourable Redcar Mudstone. By early October 2020, 10km of this first 13km long drive was complete.

Geological data, geophysical borehole surveys, seismic traverses, surface mapping and 12 borehole samples along the MTS route were studied to confirm the alignment. Data from historical and recent mining activities were also available and studied. During excavation, fault sensors on the TBM, shape arrays and triaxial nodes to detect movements, probe drilling in certain areas, in-situ stress measurements and face scanning data are adding to the understanding and control of the geological conditions.

The 6m diameter single-shield Herrenknecht rock TBM has an installed power of 2,900kW, a cutterhead power of 2,100kW delivered via six 350kW motors, and a maximum cutterhead rotation of up to 9 rev/min. Cutterhead torque is 3,281kNm at 5.81 rev/min to a maximum of 4,758kNm. Thrust is between 62,068kN and 73,890kN. The 6m o.d. tunnel is lined to 4.9m i.d. with five 350mm thick segments and a universal large key in each 1.5m long ring. A 200mm annular gap with overcut allows for any potential squeezing and rock blocking interaction with the shield beneath the 370m deep cover. The lining is of three types with strong segments, reinforced with 125kgm³ steel rebar cages and a concrete grade C50/60, designed to take the overburden pressure and up to 29 bar of hydrostatic pressure.

Within the single service rail track heading, logistics rely on movable and fixed California crossings. After completion of excavation, the track system will become the permanent infrastructure, requiring only small modifications and maintenance. The permanent fit-out includes the MTS mineral haulage conveyor system which is divided into two reaches: the 24km reach from the mine head to the Lockwood Beck cavernand a 13km long conveyor from Lockwood Beck to the Teesside processing plant.

Advance rates to date have been high with a best excavation day of 52.65m in 24 hours and the best month of 1,012m in October 2020. n

References •

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TunnelTalk ANNUAL REVIEW 2020

More funding and first TBM ready for UK potash mine – TunnelTalk, January 2019

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Scope of Oslo raw water project

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roject New Water Supply Oslo, a second raw water treatment and delivery project to secure potable water supply for the city of Oslo, has started the construction phase with award of a NOK2.8 billion (USD$330 million) contract to Skanska for the excavation of the underground treatment plant. Contract E8 includes 5km x 25m2 of drill+blast for three access adits and excavation of the caverns at Huseby for the underground water treatment plant and pumping station (Fig 1).

The contract includes a 70m2 cavern for the assembly and staging area for one of two double-shielded TBMs that will excavate the 19km long x 5.2m o.d.

(3.6m i.d.) segmentally lined raw water transmission tunnel from an intake at Vefsrud on the shores of the Holsfjord lake, to Huseby (Fig 2).

There are a total of eight major contracts in the raw water project, of which the main tunnel is one of the three largest.

The first contract was awarded early in 2020 to Skanska for the rock work and access tunnel at the Huseby site.

Contract E1 is for all concrete works in the mountain halls of the Huseby treatment plant. It also includes the operational buildings on the surface and their associated works.

Contract E5 is for the segmentally lined raw water transmission tunnel from an intake at Vefsrud on the shores of the Holsfjord lake, to Huseby. The tunnel will be excavated using two TBMs of 5.2m diameter, launched from each end, and progressing towards an in-line junction. As well as a laketap intake, the lake side work includes excavation of an access tunnel, an entrance hall with instrumentation, an inlet station, and a TBM assembly hall. It also includes facbrication of the segments.

Contract E6 is on the treated water side of the project and includes an 11.3km supply tunnel from Huseby to Trosterud that is being planned as TBM excavation.

Access tunnels of about 1.5 km long will be excavated to the underground pumping station and clean water pools at Trosterud.

Another 3km tunnel is needed to OsetDisen. The contract includes the laying

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of pipes in the clean water tunnel and the establishment of a connection to the existing water distribution network.

Contracts E2, E3, E4 and E7 cover installation of pumping equipment, electrical systems, dosing systems, and control systems.

Design of the NOK12.5 billion (USD$1.3 billion) project has been procured by the client for award for design-bid-build contracts. There is no prequalification process for the contract and any bidders that meet the qualification criteria will be assessed.

The new capital works project establishes a reserve water supply to Oslo city to ensure access to drinking water in a situation where the water supply from the main water source is interrupted or depleted. Project New Water Supply Oslo will ensure an adequate reserve water supply for the city by 2028. n

References •

Oslo selects TBMs and segments for new water project – TunnelTalk, October 2019

From left: Fig 1. Scope of the underground treatment plant; Fig 2. Eight contracts will complete the new raw water infrastructure

Political interference on the Helsinki-Tallinn plan Jonathan Rowland, TunnelTalk

feasibility report in 2018. The environmental impact assessments (EISs) include three evelopment of a rail link under the possible alignments on the Finnish side Baltic Sea to link Finland with Estonia and five on the Estonian side (Fig 1).

In another unusual turn, the long and mainland Europe hit a political snag when local politicians in Finland term plan would result in development published a 2020 long term regional plan of two underground rail links between to 2050. The Uusimaa Regional Council Helsinki and the airport. “The two would decided to support only one alignment be on top of each other,” said Vestebacka.

“The decision by the city regional for the link passing through the centre of Helsinki. The decision is taken before council also complicates work on the environmental impact assessments and Estonian side,” said fellow cofounder, geological investigations in both Finland and Kustaa Valtonen. “If you fix the route on the Finnish side, it has implications on Estonia have been completed.

“There is not enough information yet the Estonian side, as you cannot freely to make a decision about alignments,” mix and match potential alignments.”

Work on the project continued in the said Peter Vestebacka, a cofounder of project developer FinEst Bay Area meantime. The EIA is well underway in Development.

Privately-owned FinEst Finland, although the Covid-19 pandemic Bay Area Development is currently the during 2020 slowed the process. In Estonia, only organisation to be developing a fixed preparatory work to begin the EIA was sea link, after the two-year government- taking place. “Legislation in Estonia has backed FinEst Link project produced its final been going through some changes,” said Valtonen. “Our understanding is that it Fig 1. Route options for the Helsinki-Tallinn TBM bored link will make the process smoother and more like the process in Finland. As a result, we actually withdrew our original application and will now re-apply under the new system, when that is available.”

Detailed design work is also ongoing with design contractors, AINS of Finland, AFRY, and Chinabased CRIG, China Rail International Group, a subsidiary of China Railway Engineering Company, CREC. The project design includes twin TBMbored 100km rail tunnels for dedicated passenger and freight trains, as well as an artificial island off the coast of Finland. When complete, it would be the longest rail tunnel in the world, with high-speed rail services linking the two cities in 20-25 minutes.

At the national level, political

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support appears to be growing for the project. “Estonia Prime Minister, Jüri Ratas, mentioned the tunnel as an example of the type of project that his country needs for the post-Covid recovery,” said Vestebacka.

The Governments of Finland and Estonia are also due to sign an memorandum of understanding (MoU) endorsing the project.

This MoU is particularly important for the Estonian Government as a sure sign that the political will is there to back the project. It does not however translate into financial support. Funding for the €15 billion project, of which construction is expected to be some €12.5 billion, is being provided

by London-based firm TCP, TouchStone Capital Partners, which has both major Chinese state-owned enterprises and private companies as investors. Under the structure agreed in 2019, 30% of the funding will be provided by TCP in exchange for equity, with the remaining 70% provided as a loan.

Although the project is fully funded by TCP, “we have the possibility to bring on board additional investors,” said Valtonen.

This was agreed to at the request of politicians in Finland and Estonia to balance concerns over Chinese investment in the project. Additional private investment is likely, as there are currently no plans to apply for public funds from either of the two countries involved or the EU. Earlier in 2020, a representative of the Estonian Government Transport Development told TunnelTalk that it would support adding the connection to the EU TEN-T Core Network. “This would create both visibility for the project and would enable applications for certain EU funding.” n

References • •

Chinese onboard for bored Helsinki-Tallinn link – TunnelTalk, August 2019 European connectivity masterplans – TunnelTalk, April 2015

Construction phase initiated for Fehmarnbelt Link

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anish state-owned company Femern AS activated the main construction contracts with Femern Link Contractors (FLC). With effect from 1 January 2021, FLC will construct the 18km immersed Fehmarnbelt tunnel to link Germany with Denmark across the Baltic Sea, which is expected to be completed by 2028. The link comprises a dual-track railway and a four-lane motorway. Activation of the main contracts starts construction of

Plan of Rødbyhavn showing tunnel portal location

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the immersed tube casting factory and the tunnel portal and ramp structures at Rødby harbour (Rødbyhavn) on the Danish side.

The concrete casting factory will be one of the biggest factories in Denmark and the overall construction site at the harbour will be the largest of its type in Northern Europe.

Dutch consortium Fehmarn Belt Contractors (FBC) started construction on the harbour in November 2019 and expects to complete it by the end of 2021.

Activation of the contracts is being carried out with due respect for the ongoing German approval process of the project.

In February 2019, Femern received the signed approval from the authorities of the German state of Schleswig-Holstein. The German Federal Administrative Court is currently processing the complaints about the approval. In the meantime, Femern AS is engaged in a number of construction site preparation activities for the tunnel on the German side at Puttgarden. Further progress can be made as soon as the German legal proceedings allow.

Femern News Release In other news, Atkins, a member of the SNC-Lavalin Group, signed an eightyear agreement with Femern AS to provide consultancy services for the railway element of the new 18km link.

Atkins will deliver multidisciplinary railway consultancy services throughout the project, which will include the track, overhead catenary system, power supply, signalling, train control system and telecommunications.

Atkins will also collaborate with German engineering firm GAUFF, who will focus on the German elements of the new railway.

Designed for speeds of up to 200km/hr, the dual track line will see sevenminute journey times between Denmark and Germany that currently take an hour by ferry.

The link across the Fehmarn Belt in the Baltic Sea will connect the Danish island of Lolland and the German island of Fehmarn. n

References •

Objections filed as Fehmarn prepares for construction – TunnelTalk, June 2019

www.TunnelTalk.com

From top left: First indication of a problem in February 2020; Fig 1. South portal and the karst zone as the source of the water inflow; Right: Fig 2. Overburden in the area is about 400m

Lötschberg inflow through lining system failure During original excavation, 80m long exploratory drill holes were drilled in the crown and ahead of the face in the 500m long karst zone (Fig 3). One of these drill holes (R37) encountered a karst spring, which drew large quantities of water.

Since this borehole could not be sealed, the water was collected in a separate pipe through the sealing system and the in-situ concrete lining into the interior of the tunnel. The decision to the capture of the karst water spring for supply to a village community in the area that had suffered a lowering of the ground water table and its water sources by the tunneling activity, is noted by a geologist in a geological report of the Lötschberg base tunnel published by the Swiss Geological Survey.

“To use the water, an attempt was made in early 2005 to drill out the former borehole and to recapture the water,” explained Dr Stefan Irngartinger, Construction Officer and Project Manager for the Lötschberg Baseline for BLS. “The system now consists of two separate drains at a distance of about 5m, which collects the water at the crown and drains it to a valve chamber in the sidewall on the west side of the east running tunnel. From this valve chamber, the water pipe leads to a cross passage and from there to the portal of the pilot gallery (Fig 1).

BLS estimated water inflow during the first ingress event of about 14 days in

Shani Wallis, TunnelTalk February 2020, and during the seven days of the second breech in March 2020, at about 50 litre/sec to 100 litre/sec, at an estimated 5 bar pressure, and that about 1,000m3 and 700m3 of sand and silt came in with the water, respectively. The full 34.6km of the base tunnel is fitted with a waterproofing system, 19.7km with a sealing membrane and drainage layer, and with a drainage layer only in geological units where no water was found during excavation.

In assessing the failure and its repair, Irngartinger said: “It is probably not possible to call on the construction warranty, as the maximum warranty period was ten years, and, since there is probably no systematic defect in the sealing membrane, no product liability can be claimed.”

The permanent solution proposed by the owner of the infrastructure, BLS, the Bern-Lötschberg-Simplon railway company, and as submitted to the Swiss Federal Office of Transport (BAV), the Government authority that approves all new-build and rehabilitation transportation project applications in Switzerland, was to breakout

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ngress of water and mud into the 13-year old Lötschberg baseline railway tunnel raised serious alarm in Switzerland.

The situation started in February 2020 when a water inflow, rising to more than 100 litres/sec, broke through the final cast concrete lining in the crown of the east tube of the twin tube railway, carrying with it significant fines. The water ingress became evident when a passenger train emerged at the south portal covered in mud.

Some 37 days later, a second inrush occurred at the same location. A camera installed at the failure zone alerted the control room and train traffic in both tunnels was stopped. On this occasion, the closure of the affected east tube was for about six weeks with traffic diverted to bidirectional operation through the west tube while initial reparation measures were upgraded.

The inflow occurred at about 2.5km in from the south portal of the twin tube tunnel through a known reach of karst limestone conditions and under an overburden of about 400m (Figs 1 and 2).

Water broke through also into the west operating tube but to a lesser degree. At this point, the tunnel is designed and built with a drained waterproofing system using a plastic membrane in combination with a geofleece layer and is finished with an unreinforced in-situ concrete final lining, with the membrane directing water to the invert drainage system.

Point of the lining breech (top) and the temporary sedimentation tanks (bottom) installed ahead of a permanent works solution

Fig 3. Graphic of how the existing drainage system failed

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Feedback from Dr Trevor G. Carter, Golder Associates, Toronto, Canada Mud migration in karst systems can lead to very major inflows, and possibly damage to the lining. At high cover, water pressure on the back of the lining will be significant, but mud impact dynamic pressures can be many times greater, as commonly considered in the design criteria for deep mining bulkhead plugs.

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Fig 4. Design of the permanent management works of the existing east tunnel at two points and excavate a parallel cavern to house a set of water and sedimentation settling tanks.

Under a negotiated contract of about CHF12 million, contractor Frutiger completed about 10,000m3 of drill+blast excavation and the casting of the internal concrete works of the cavern from early September 2020 to end of January 2021 (Fig 4). Design consultants for the works were srp engineers, Emch + Berger and Pini Swiss Engineering, with geotechnical consultant Kellerhals + Haefeli.

The cavern, with its sloping invert, is 89m long x 11.40m wide x 5.7m to 11.50m deep and the settling basin has a capacity of more than 2,000m3 from which settled water will continue to be channelled out via the south portal for on-going commercial resale and reuse in the district, and sediment will be cleared regularly as it builds up. Works included excavation of a cavity of about 8m x 4m x 2m above the crown of the east running tunnel, in which karst water is to be collected and piped to the sedimentation basin. About 2,700m of 400mm diameter steel pipework has been installed as part of the works, with another 300m of 250mm diameter Inox-tubes in the crown cavern above the operating running tunnel. The cavity in the vault above the running tunnel will remain accessible for on-going monitoring and maintenance.

During the preparation works, the east tube of the railway was closed to permit a 24hr/day, 7 day/week working programme.

Drill+blast vibrations had to be well controlled to permit train operations in the west tunnel at about 40m parallel. There are no doors in the two adit openings so that the cavern is ventilated by the train traffic.

With completion of the excavations works, questions remain about the long term draining of the ground water and washout of sediment from the mountain and the potential consequences. The permanent works also raise queries about the environmental

regulations for management of natural water regimes around excavation projects both in Switzerland and internationally. Regulations to protect the natural environment have been strengthened in recent decades and complying with these regulations are expensive processes to be managed by owners and developers of new underground infrastructure.

Feedback from Heinz Ehrbar, former Chief Construction Officer for the St Gotthard Baseline railway Switzerland, currently an independent consultant and lecturer at the ETH Zurich university This event is a clear failure of certain elements in the lining system. Such a water inflow in a tunnel, sealed with a high technology sealing and drainage system, is not expected by anybody and that must be investigated in combination with a welldefined risk management process. All underground facilities in the world using the same final lining design should know the reason of this failure in order to be able to assess their own risks. As a civil engineer, and as a public servant who was involved on the AlpTransit projects in Switzerland since 1996, I believe these investigations are critical for the benefit of all long and deep tunnel projects. Safety must be guaranteed always. Railway systems are only safe when the basic principles of risk management are respected without compromise.

Feedback from Dean Brox, Consultant, Canada I note that the maximum overburden in the karst zone is actually 900m since it goes to the top of the rock unit to the surface (Fig 2). A tunnel lining with a membrane cannot withstand 90 bar external pressure. Open boreholes allowing groundwater inflow will be subject to the full hydrostatic pressure with the rock unit providing unlimited storage. The current drainage solution will require ongoing maintenance.

Feedback from Nick Barton, Independent Consultant, Norway The list of possible causes emphasises the hydrogeological risks, especially in the case of karst. There are also risks with choice of method. The leakage of water, and mud, serves to warn us of the questionable longlife performance of an easily clogged drainage fleece. There are also the many kilometres of welds in the membrane and the radial joints in successive concrete pours. These are actually absent when using sufficiently thick longitudinally sprayed shotcrete. There are no radial joints, and steel fibre shotcrete has extremely low permeability, in the panelsprayed range of 10E-10 to 10E-12m/sec.

It is not felt that the double-shell systems is the right answer. Another choice is systematic high-pressure pre-injection grouting, with pressure suited to the rock and rock mass. There are literally millions of kilometres of drill-holes used for construction of large dams where grout curtains are permanent and designed for a 100-year+ life. Pre-grouting umbrellas ahead of the face for high-speed rail tunnels of more than 100m2 in cross section, take 24-30 hours/cycle and provide for a guaranteed almost 20 hours/week of fullface excavation. Pre-excavation grouting is known, and has been 3D-measured, to cause rotation of the 3D permeability tensors, and their magnitude reduction, and modulus and velocity increase. The risk during construction is reduced dramatically by drilling 1-1.5km of holes every 15-20m of tunnel advance. Any damp spots in the shotcrete signal where local post-injection is needed. This is not the case with the double-shell solution. n

References • • • • • •

Lötschberg inflow through lining system failure – TunnelTalk, April 2020 Lötschberg water inflow explained – TunnelTalk, May 2020 Sealing and drainage experiences in Swiss tunnels – TunnelTalk, December 2018 Testing durability of PVC membranes – TunnelTalk, October 2018 Grand opening of world record Gotthard Baseline – TunnelTalk, June 2016 Assessing the effects of environmental impact assessments – TunnelTalk, September 2011

From left: Works begin with breakout of the east tube lining; Crown cavern above adit junction with main running tunnel; Completed parallel cavern and its pipework and settlement basin

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High speed rail excavations begin for UK HS2 Jonathan Rowland, TunnelTalk

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TunnelTalk ANNUAL REVIEW 2020

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f the new 225km High Speed 2 rail project in the UK to link Birmingham and London, 45km is to be in twin tube bored tunnels with a further 11km in cut-and-cover and short under pass structures (Fig 1). Ten TBMs will excavate the bored alignments in three contract packages. Two will take the line through the VariableChiltern Hills for the Align JV, of Bouygues density Travaux Publics, Sir Robert McAlpine and TBMs for VolkerFitzpatrick for the CI central contract Chiltern drives package. A third will drive under ancient woodland near the village of Long Itchington in Warwickshire for the BBV Balfour Beatty/Vinci JV together with another that will excavate the 5.6km Bromford alignments on the approach to Birmingham Curzon Street Station. The remaining six are required by the SCS, Skanska-Costain-Strabag TBM components JV for the total 21km Northolt arrive at Long Itchington East and Euston alignments that complete the HS2 approach into Euston Fig 1. About 56km of the 225km HS2 Phase 1 route is underground (in black) Station in London. In contract packages C2 Procurement of the TBM for the 5.6km Tunnel Engineering Lead, and Michael and C3 by the EKFB, Eiffage, Kier, Ferrovial, long Bromford twin drives in Birmingham Greiner, Tunnel Manager, for SCS. BAM Nuttall JV, there are cut-and-cover is underway. Also in Birmingham, the twoSix TBMs of different diameters will tunnels to build. stage design-build contract for the Curzon excavate the London running tunnels (Fig 2): Components of the first two TBMs on Street Station is awarded to the Mace/ • Two for the 8km x 8.8m i.d. Northolt West the project - the 10.26m diameter variable Dragados JV. HS2 Ltd worked with WSP tunnel between the West Ruislip portal density machines for the 16km x 9.1 i.d. and Grimshaw Architects on a station and the Greenpark Way ventilation shaft; Chiltern drives - began arriving in the UK design that will be net zero carbon in • Two for the 5.5km x 8.1m i.d. Northolt from the Herrenknecht factory in Germany operation and will capture rainwater and East tunnel between Greenpark Way in December 2020. Designed for the have more than 2,800m2 of solar panels on and Old Oak Common Station; and mix of chalk and flints under the Chiltern platform canopies.

• Two for the 7.2km x 7.5 m i.d. Euston Hills, the machines feature a range of tunnel between Old Oak Common innovative technologies, including a robot Station and Euston Station.

London tunnels to automatically remove the wood spacers A seventh TBM will excavate a Of the 45km of bored alignment, just between segments when stacked and under half, or about 21km, is located 1km x 6.1m i.d. logistics tunnel that will transported, and to insert the connecting under west London, between the HS2 provide access from the main Atlas Road dowels. Known as Krokodyl, the robot southern terminus at Euston Station and construction compound to the Old Oak works in a similar manner to the robotic a portal at West Ruislip, just inside the Common open cut station box as the arms used on car assembly lines. In orbital M25 highway. The 21km route launch site for the Northolt East and Euston addition, a mini annular grout batching presents a complex engineering and TBMs. It will be used to bring in construction plant located on the backups will remove logistical challenge for the £3.3 billion materials, including the precast concrete the need to pre-mix and transport grout to design-build contract awarded to SCS lining segments, and for muck removal. the working faces.

The first TBMs procured for the in 2017. Details of the project were Once launched, the machines will provided to TunnelTalk in an interview contract are two Herrenknecht EBPMs to operate almost continuously, 24 hr/day, with Eddie Woods, Head of Tunnelling excavate the Northolt West drives and the 7 days/week, for 3.5 years, to complete and Underground Structures for project longest of the three sections. These will be the Chiltern drives. Each TBM will be delivery partner HS2 Ltd and Dave Terry, followed by procurement of the Northolt operated by a crew of 17 with another 30 in each shift on the surface and in the Fig 2. Launch and retrieval of the six London TBM drives tunnel behind the machine.

The seven segments in each 2m wide x 400mm thick ring of precast steel fibre reinforced lining for the drives are being produced on site near the south portal and transported by multi-service vehicles directly from the production stockpile into the tunnel.

Together with the long TBM drives, there are five associated ventilation shafts and cross passages on the Chiltern tunnel.

The Long Itchington Wood machine, also delivered from Herrenknecht, will launch from a north portal of the twin tube alignment and will take about five months to complete the first 1.6km drive. The TBM will then be retrieved and transported back to the north portal to drive the parallel tube.

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Fig 3. Stacked-drift construction of the Euston Station approach turnout

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East TBMs in early 2021 and finally of the pressure is mitigated by the increasing or two machines for the Euston drives in late decreasing internal diameter. In the Chiltern 2021. The main TBMs will be procured new tunnels, trains will run at up to 320km/hr and will be designed specifically for the and the larger 9.1m i.d. will mitigate the project, while a refurbished TBM is likely to aerodynamic pressure. be used for the logistics tunnel. Delivery of Although not within the SCS contract, the Northolt West EPBMs is expected by there is significant interaction with the Old the end of 2021 for start of excavation by Oak Common station works by Balfour mid-2022.

Beatty Vinci Systra JV and at Euston by the Advancing from the West Ruislip portal, Mace/Dragados JV. the Northolt West TBMs will excavate From the open cut station box at Old through mixed-face conditions of the Oak Common SCL stub tunnels will allow Seaford Chalk with water pressures up to full assembly of the Euston drive TBMs 3 bar. To assist excavation, the EPBMs before launch. At the other end of the box, will have a spherical bearing to allow for the Northolt East TBMs will launch from an translation or tilting of the cutterhead, ancillary shaft connected to the station box providing a greater degree of accuracy in by SCL headings. The Atlas Road logistics terms of steering and better control of face TBM tunnel will also break through into the pressure, cutter load, and settlement.

Old Oak Common Station box.

The TBMs will also feature automated At Euston, SCS is responsible for unloading of the segments to the segment construction of the 16m wide x 12m high feeder and a robot for removal of the wooden cavern to accommodate the turnout that will spacers and insertion of the segment enable HS2 trains to run with the required connector dowels. Sensors and cameras will frequency alongside what is already one assist one operator to build the rings. of the busiest mainline rail stations in the In addition to breakthrough of the UK. The cavern will be constructed using Northolt West machines, the Greenpark Way a stacked-drift method of SCL headings working site will receive the Northolt East to control full section excavation and TBMs at the end of their twin 5.5km x 8.1m settlement (Fig 3). i.d. drives from Old Oak Common (Fig 2).

The geology along the Northolt East Track and systems contracts alignment is mostly London Clay. The 7.2km As its contractors prepare to launch the x 7.5 m i.d. Euston drives between Old Oak TBMs, project owner HS2 Ltd announced the Common Station and Euston Station also shortlists for procurement of the track systems run entirely through London Clay. and tunnel and lineside M&E contracts. Worth The 52 cross passages on the London almost £2.5 billion, the contracts cover HS2 tunnels are to be SCL excavations, with Phase 1 and the Phase 2a extension from a waterproofing sheet membrane and a Birmingham to Crewe (Fig 4). secondary in-situ concrete lining.

These will be constructed as the main TBMs proceed. Innovative openings will allow breakout of the segmental lining without the need to prop the running tunnel. With most of the route located under an operational railway, any ground treatment to construct the cross passages will need to be applied from inside the main drives.

The seven segments in each ring of the 8.8m i.d. Northolt West drives are 350mm thick x 1.9m wide, while those for the 8.1 m i.d.

Northolt East segments are 340mm thick x 1.9m wide, and for the 7.5 m i.d. Euston drives are smaller again at 325mm thick x 1.8m wide.

The varying internal clearance of the running tunnels is needed for aerodynamics. As trains Fig 4. Planned UK high-speed rail development; accelerate out and decelerate in to inset: HS2 Phase 2a underground sections at Euston Station, the aerodynamic Whitmore Heath and Madeley

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Supply of the track systems is divided into four lots: • Lot 1 - Urban London and Birmingham - £434 million • Lot 2 - Open Central - £526 million • Lot 3 - Open North - £566 million • Lot 4 - Birmingham to Crewe £431 million Four teams have been shortlisted to bid for the contracts that are expected to be awarded in 2022: • BBVT JV of Balfour Beatty, ETF, TSO • Ferrovial-BAM Nuttall JV • Colas Rail • Strabag-Rhomberg Sersa JV Three teams have shortlisted for the £498 million contract to deliver the design, supply, manufacture, installation, testing, commissioning and maintenance until handover of the M&E services, which will include tunnel ventilation systems and services in shafts, tunnels and crosspassages. The shortlisted teams are: • Alstom Transport UK • Balfour Beatty NG Bailey, BBB, JV • Costain Group The Phase 2a extension of the route from Birmingham to Crewe, a principal rail hub that lies at the gateway to northwest England and Scotland, was given legislative approval in early 2021. The 56km route will not rely as heavily on underground sections as Phase 1, but will include construction of 2km of 8.8m diameter twin TBM bored tunnels in two sections at Whitmore Heath and Madeley, with an additional 200m cutand-cover excavation at the southern end of the Whitmore alignment. An alternative for a continuous 6.4km twin underground alignment between Whitmore Heath and Madeley was rejected in 2018 as being too costly.

The £250 million-£500 million design and delivery partner contract for Phase 2a is underway and a £100 million£250 million early civil works package will tender in late 2021.

Continuing the full £106 billion scheme north under the western leg of Phase 2b will connect Crewe to Manchester and upgrade the existing network to enable high-speed trains to serve Glasgow, Liverpool, Wigan, Preston and Carlisle.

UK legislation to cover construction of this section is to be introduced in early 2022.

The future of an eastern leg of Phase 2b to Leeds is currently paused and awaiting further planning studies.

The £35-45 billion Phase 1 project has a target completion date of 2028-2031 with a programmed phased opening of the full line between 2029 and 2036. n

References • • • • • • •

Civil contract awards for UK HS2 Phase 1 – TunnelTalk, July 2017 HS2 prepares to excavate 21kn route under London – TunnelTalk, February 2021 HS2 prepares TBMs, shortlists systems and M&E bids – TunnelTalk, February 2021 Notice to proceed granted for HS2 construction – TunnelTalk, April 2020 HS2 will run late and well over budget – TunnelTalk, September 2019 Speed up delivery to cut costs of HS2 – TunnelTalk, March 2014 High-speed rail pitch for the UK – TunnelTalk, August 2009

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Fig 1. Route of the 118km long Crossrail railway and its central underground section and undercrossing of the Thames

Yet more money agreed to complete Crossrail of the mechanical and electrical equipment and railway line operating systems by the same Tier 1 contractors as for the excavations works.

There were cost increases on the underground civil engineering works. The total value at contract award of £3 billion was revised as a turnout cost in a report by the UK National Audit Office in January 2019 to £4.3 billion. Delays occurred particularly at Bond Street Station, where a major upgrade of the existing London Underground station for TfL took place at the same time. This combination of work being progressed from restricted work sites in the heart of London was complex and its completion will not be ready in time for the revised mid-2022 opening of Crossrail.

Completion of the civil works contracts however was substantially within the project programme with all civil excavation completed in approximately four years.

An opening date now in mid-2022 is more than six years in finishing and railway-wide systems installation and commissioning.

“There is often too much emphasis on civil works at the expense of complex M&E systems integration” There have been official investigations into the delay and increasing costs of the project including a presentation by the Crossrail Ltd Chair Tony Meggs and Deputy Chair Nick Raynsford to the All Party Parliamentary Rail Group of Members of Parliament in September 2020. As reported in International Railway Journal, Meggs, who took up his position in January 2019, explained that the original December 2018 deadline caused “mayhem” and that “as things slipped and slided a bit, as is almost inevitable,” the immovable end date meant that a huge amount of finishing work was compressed into the schedule. “Every year

Shani Wallis, TunnelTalk the schedule was revised,” he said, “but the end date was never moved and, as a consequence, two or three years’ worth of work was ultimately squeezed into a few months and of course, led ultimately to a failure to meet the delivery date.”

He further explained that a consequence of the fixed deadline was the premature disbanding of 35% of the Crossrail Ltd delivery organisation, adding that the management team spent much of 2019 rebuilding a team with the capability and capacity to deliver the finishing work.

He warned that there is often too much focus on the civil engineering aspects of major projects, such as Crossrail, at the expense of the complex M&E operating systems integration process, suggesting that there should be a change of thinking with greater emphasis on programme rather than project management.

Meggs told the Parliamentary hearing that Crossrail did not need to be as complicated as it became, encouraging Government, as the procurement agency of major infrastructure projects, to emphasise simplification, standardisation and minimum viable product.

In this regard, Crossrail Ltd Deputy Chair Raynsford said there was a lack of coordination between contractors carrying out vertical contracts at individual sites and horizontal contracts by firms working on systems used across the railway. This is exemplified, he said, by the use of three different signalling systems across Crossrail. The central section relies on communications-based train control (CBTC); the eastern and western reaches to Shenfield and Reading, which use Network Rail infrastructure and operate on the train protection warning system (TPWS); and the branch from Paddington to Heathrow is fitted with the European train control system (ETCS).

Raynsford added that the integration of software between the Crossrail Bombardier

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elays and cost overruns have plagued the finishing works of the Crossrail project in London, detracting from the exceptional work achieved to complete running tunnels and stations under the heart of the city and under the Thames. The capital cost of the project now stands at £18.6 billion, from £14.8 billion in 2010, and the anticipated opening date for the central underground section of the 118km long railway is extended to the first half of 2022.

Crossrail services on the overground section from Paddington to Reading and Heathrow in the west, and from Liverrpool Street Station to Shenfield in the east started in December 2019. The project is funded almost entirely by public taxpayer money with some private capital invested in the stations at Woolwich and Canary Wharf.

Work on the 118km long project started in early 2009 with the establishment of the private sector Crossrail Ltd Project Delivery Partner of Bechtel, Halcrow Group (now Jacobs) and Systra, and Programme Partner of AECOM, CH2M Hill (now Jacobs) and the Nichols Group.

Work on the underground sections began in August 2009 with start of design-build contract awards for 24km of segmentally-lined twin running tunnels (48km in total) and seven new underground stations, two open-cut and five SCL mined excavations (Fig 1). The design-build contract for the twin tube section under the River Thames in the east was awarded in April 2011 and the last of the underground station contracts for Bond Street Station was awarded in February 2013.

The first of a total eight TBMs was launched at the Royal Oak portal to the west in May 2012. The last TBM broke through at Farringdon in May 2015.

With underground work for both running tunnels and stations substantially completed by end 2015/early 2016, the delay and cost overrun has been largely on the installation

From left: Last TBM breakthrough at Farringdon Station in May 2015; Fitout of underground stations and system wide installations have caused extensive delay

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class 345 rolling stock and Siemens CBTC equipment has proven particularly problematic. Meggs is reported as describing the decision to proceed with such an arrangement between two competing companies in the first place as a “really, really bad idea.” Unravelling the difficulties is a large part of the work undertaken by the new management team.

Another problematic phase of the project has been the transfer of ownership of the railway from Crossrail Ltd as the Delivery Partner to ultimate governance, ownership and operation of the system by Transport for London, TfL. The transfer had started in October 2020 with Crossrail Ltd gradually being dissolved and absorbed as a direct subsidiary of TfL. Meggs said the current Crossrail Ltd leadership team will remain to manage a closer working relationship with TfL and “help to simplify responsibilities and ensure seamless and fully aligned decision making at this crucial stage”. A special purpose committee of the TfL Board has been established to provide high-level oversight of this process.

In his presentation to the Parliamentary Group, Raynsford said that the technical

challenges of completing the works through shafts and portals, which house all signalling and communications cables, are considerable. He added that “London Underground would normally do two new station handovers in a year; we are trying to do eight in a similar period. It was going to be technically difficult to do that without rescheduling and re-sequencing the station works.”

By September 2020, five of the six station sites, apart from Bond Street, were complete and ready to support trial running of trains. Dynamic testing of signalling and train systems was scheduled to complete by the end of 2020. Systems integration would then commence ahead of the start of trial running at the earliest opportunity in 2021. This planned schedule has had the caveat of the impact of the Covid 19 pandemic. In September, less than 50% of the pre-Covid workforce was on site limiting the capacity to scale up productivity. Despite this, Raynsford said that if the revised works programme and schedule goes well, “it might be possible to do better than” the mid-2022 projected opening date.

The current agreement for an extra £825 million in funding finalises a round of political push-pull between the different public bodies involved in the project, including the current Mayor of London, TfL, the DfT and the UK Treasury, as to who is actually responsible for completing the project and who should provide the funds in the immediate term.

While the agreed £825 million is less than the £1.1 billion anticipated by Crossrail Ltd in August 2020, TfL Transport Commissioner Andy Byford said: “I have been crystal clear, and I’ll say it again, no further slippage, no further recourse to public funding over and above what has previously been identified by the outgoing Crossrail Board. Let’s get this railway finished and opened.”

When fully open, the Elizabeth Line will increase rail capacity in central London by 10% with its ability to carry more than half a million passengers/day. n

Lyon-Turin rail link advance

The consortium will start work with excavation of four ventilation shafts from the Villarodin-Bourget-Modane access tunnel. The 500m deep x 5.2m diameter shafts will be excavated as raise bores.

Also in the contract is excavation of seven caverns of up to 22m high x 23m wide that will be used for assembly of TBMs that will excavate the base running tunnels towards Italy. The preparatory works contact has a 36-month period.

The €8.6 billion cross-border link will replace the 150-year-old mountain railway that includes the 13.7km single-tube Fréjus rail tunnel, which was opened in 1871.

The new base tunnel will have 204 cross passages at 333m intervals, four intermediate accesses, five central ventilation systems and three underground security areas.

All four of the access tunnels, three in France and one in Italy, have been completed and work began in early 2019

on the portal structure to the base tunnel on the French side. In September 2019, the first of eight TBMs finished excavation of the first 9km of the southern tube of the main base tunnel, reaching the La Praz access adit. The 11.25m diameter hard rock single shield NFM TBM started its journey in the summer of 2016 from the Saint-Martin-LaPorte access adit and managed to maintain an average speed of 15-20m/day. This first €390 million lot was constructed by a joint venture of Batignolles TPCI, Eiffage TP, Ghella, CMC, Cogeis and Sotrabas. Egis and Alpina provided project management.

“The drive encountered several challenges,” said Mauricio Bufalini, Deputy CEO of TELT. “At about 300m in, the TBM entered a geological fault that stopped excavation for several months.” The TBM then crossed the Briançonnais Houiller zone, and safely negotiated faults of carbonaceous deposits under overburdens of more than 700m. “A similar fault was crossed in less than one month,” said Bufalini.

After completing the first contract, TELT launched procurement for the remaining four contracts with a total value of €3.3 billion for the remaining main lots between Saint-Jean-de-Maurienne in Savoy, France, and Susa in Piedmont, Italy. According to TELT, companies have submitted bids for the three main tunnel construction lots on the French side and for the 12.5km section on the Italian side.

“More than 100 companies from all over the world are competing for the four main contracts,” said Bufalini. “We are expecting the next project TBM to be launched by the end of 2021, with the goal to complete all excavations by 2026.” The new railway line is expected to be operational in 2030. n

Armand van Wijck, TunnelTalk Europe correspondent

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€220 million preparatory works contract is awarded by the FrenchItalian project developer TELT to start construction for the 57.5km long Mont Cenis base tunnel of the 270km Lyon-Turin railway line. Awarded to a consortium led

by Vinci with Dodin Campenon Bernard, Bergteamet and Salini Impregilo (now Webuild), the contract encompasses works needed to prepare for excavation of the 21.9km twin tube Lot L1 of the alignment between Villarodin-Bourget and Modane on the French side of the bi-national project.

PARIS

CROSS-BORDER SECTION SEZIONE TRANSFRONTALIERA

65 km

Ambérieu-en-Bugey

LYON

Route and design of the Base tunnel

Saint-Exupéry

Saint-Priest Vénissieux

CONTOURNEMENT FERROVIAIRE BYPASS OF THE LYON DE L’AGGLOMÉRATION METROPOLITAN AREALYONNAISE

Grenay

BurgoinJallieu

Avressieux

Chambery

Aiton

TGV Ligneline TGV Paris / Marseille

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BASE TUNNEL TUNNEL DI BASE 57,5 km

Linea AV/AC Torino / Milano

Saint-Jean-de-Maurienne

Grenoble

Modane

Susa

Bussoleno

Chiomonte Historical line Linea storica

Outside section Linea all’aperto

Tunnel section Linea in galleria Areas of intersection Aree di incrocio between the historical tra la linea storica line and the new line

e la nuova linea

France

Italia

MILANO

Caselle

Avigliana

Orbassano

Settimo Torinese

TORINO Terzo Valico dei Giovi

GENOVA

References • • • •

Crossrail mobilized – TunnelTalk, May 2009 Launch of first TBM – TunnelTalk, May 2012 Crossrail nears excavation half-way landmark – TunnelTalk, September 2013 Crossrail prepares for 2018 grand opening – TunnelTalk, March 2018

References • •

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Progressing the Lyon-Turin base rail link – TunnelTalk, August 2013 Bi-national safety codes for Lyon-Turin rail link – TunnelTalk, August 2013

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From left: Record of 860m/month by a 10.65m diameter double shield TBM; Gripper TBM completes 16.63km exploratory tunnel

Records being set on Brenner Base line

TunnelTalk reporting

Extensions into Italy

In early 2021, the Webuild-Implenia JV submitted the first-ranked proposal for a 22.5km high-speed rail line from the southern end of the Brenner Baseline at Fortezza to Ponte Gardena in Italy.

The new €1.07 billion line will be mostly underground and is a part of plans by Italian rail infrastructure management company, Rete Ferroviaria Italiana, to

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xcavation of the underground works for the 55km long Brenner Base railway beneath the Alps between Innsbruck in Austria and Franzensfeste/ Fortezza in South Tyrol, Italy, have continued a pace during 2020 and into 2021.

On the Mauls/Mules 2-3 contract, the Astaldi-Ghella JV is continuing drill+blast excavation southward and operating three Herrenknecht TBMs on the two main running tunnels drives and the exploratory heading northwards from the Mules adit in Italy. In March 2021, a new record was Fig 1. Major works on all lots of the Alpine baseline railway are progressing set by one of the 10.65m diameter double shield TBMs excavating the main tunnels, upgrade the 180km line between Fortezza TBM breakthrough was celebrated for the achieving a peak advance of 860m in one and Verona. It is expected to come into Terzo Valico dei Giovi high-speed railway month. The machine achieved an average service at the same time as the Brenner by Webuild. The breakthroughs were daily advance of 27.7m with a daily best of Baseline connection under the Alps to achieved along two underground sections of the railway: the Valico Tunnel (Galleria di 36.75m. By early April 2021, the two main Innsbruck in Austria.

The design-build contract includes twin Valico) and the Serravalle Tunnel (Galleria running tunnel TBMs, launched in April and May 2019, had completed more than bore single-track alignments of 15.4km dei Serravalle). Once completed, the 50% of their 20km drives and are expected and 6.3km, connected by a viaduct over Valico will be the longest railway tunnel in Italy. With a total length of 53km, 36km of to reach their contract and lot boundary the Isarco River.

Located on the Munich-Verona rail which is underground, the Terzo Valico dei by early 2022. Double shield TBMs were chosen to erect the one-pass 450mm axis, the Fortezza-Ponte Gardena project Giovi will reduce the time to travel between thick precast segmental lining in 1.75m forms part of the 9,400km Scandinavia- Genoa and Milan from one hour and 39 long rings as they progress through mainly Mediterranean Corridor of the Trans- minutes to 50 minutes.

Also in Italy, on the Milan to Verona calcareous schists and gneiss geology European Network, TEN-T to improve rail route of the TEN-T Mediterranean highbeneath the mountainous overburden of connections across the EU. Included on the TEN-T project is the speed rail corridor, a 10.03m diameter between 590m and 1,750m.

Other works underway on the project Terzo Valico dei Giovi high-speed line EPBM manufactured by CREG in China, will for the Austrian Italian BBT SE owner between Genoa, Turin and Milan, on the excavate the 4.75km long twin tube Lonato organisation are for the Pfons-Brenner Lot Rhine Alpine Corridor to link the ports of tunnel. The TBM will be operated by Seli by the Porr-Hinteregger-Condotte-Itinera Rotterdam and Genoa. In 2020, a double Overseas for main contractor Cepav Due JV. Comprising Saipem, Pizzarotti and ICM, JV, and on the Tulfes-Pfons Lot and the JV is main contractor for the 48km the Isarco Underpass Lot by the From left: Genoa-Milan breakthrough; CREG long Brescia East to Verona section of Webuild/Strabag JV. The excavations TBM ready for Lonato drive the line, after award of the Lot 2 by Rete include drill+blast and TBMs for Ferroviaria Italiana in 2018. running tunnels and exploration/ Following resumption of work service tunnels and drill+blast for after Covid-19 limitations in Italy, work large caverns for emergency stop progressed to assemble and launch complexes and their cross passages. the TBM. The machine is designed Works also began in August 2020 with a double screw and a boulder on the H21 Sill gorge Lot to link the trap arrangement and a specification base tunnel to the central station in to withstand up to 6 bar operating Innsbruck. This €59.5 million contract pressure. A segmental lining of 450mm awarded to the Porr Kematen JV and thick x 2m long rings will line the 8.8m scheduled to be completed at the end i.d. rail drives. n of 2024, involves about 600m of cutand-cover and earthworks and Sill References River engineering works.

Brenner Base project fuels exploratory drive debate – TunnelTalk, September 2019 Brenner contract award, progress advances – TunnelTalk, April 2018 Brenner project marks progress milestones – TunnelTalk, August 2017 Brenner prepares final procurement push – TunnelTalk, September 2016 TBM launched for Brenner exploratory tunnel Italy – TunnelTalk, October 2015 European connectivity masterplans – TunnelTalk, November 2015

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Plans for increasing Trans-Siberian rail capacity Eugene Gerden for TunnelTalk

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our new tunnels are being planned for excavation on the Eastern Range sections of the Baikal-Amur Mainline (BAM) and Trans-Siberian railways in Russia.

At present, BAM and the Trans-Siberian railways remain the only transport routes connecting Russia with the attractive markets of Asia Pacific through the Far Eastern ports. Still, the routes have problematic bottlenecks, which significantly slow export traffic to foreign markets. The solution is to build a tunnel to eliminate single-track bottlenecks. Of these, perhaps the most likely to progress is excavation of a second tube for the Kuznetsosvky Tunnel in the east. Construction could start in early 2022 and would include new tracks and new bridges over the Amur and Yenisei Rivers. The new works will be part of the existing rail routes to the ports of Vanino and Sovgavan, the largest seaports in the Russian Far East basin (Fig 1).

Preparatory works for the project have started with leading analysts in the field of engineering in Russia considering

the planned tunnel as one of the most technically sophisticated in Russia. It will be located in the area of Vysokogorny in the Khabarovsk Territory, close to the existing Kuznetsovsky tunnel, and will be 4km long.

The project will significantly expand eastern direction traffic potential on the BAM railway and increase cargo traffic on this section of the route by 100 million tonne/year.

Prior to 2012, the Kuznetsov Pass was considered the narrowest point on the BAM railway, which limited the development of new ports at Vanino and Sovetskaya Gavan on the coast of the Tatar Strait (Fig 1). The first Kuznetsovsky tunnel in 2002 partially solved this problem.

The new tunnel is estimated to cost RUB 50 billion (about US$649 million). During tunneling works there are plans to use the same 9.5m Lovat TBM and Robbins TBM that were first used during the building of the first Kuznetsovsky Tunnel with the Robbins TBM designed specifically for the anticipated mixed rock formations of the region.

According to Mikhail Zaichenko, a former head of the Far Eastern branch of the national RZD rail network, construction

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Fig 1. Planned doubling of the Kuznetsovsky, Severomuiski and Baikal Tunnels

will be carried out in harsh climatic conditions, with winter temperatures reaching 54 degrees and snow cover in some places reaching more than 2m deep.

Implementation of the project is personally controlled by Oleg Belozerov, a divisional head of RZD. Other projects are planned also for the eastern rail network. There are plans to resume a project to build a parallel tube for the Severomuisky Tunnel on the BAM railway that should increase its carrying capacity by five or six times. In April 2020 the Russian Government decided to suspend implementation of the project due to the pandemic and its negative consequences on the domestic economics. This may be revised in 2021 or 2022.

RZD has plans also for the 1.8km long Dusse-Alin tunnel on the BAM railway in the Verkhnebureinsky District of the Khabarovsk Territory. A tender for the estimated RUB7 billion (US$93 million) construction works has been announced and the new infrastructure is expected to be commissioned by December 2025.

The parallel Baikal Tunnel on the BAM railway is planned to open by mid-2022. The 7km tunnel has been under construction since 2014 using a Lovat TBM that was first used during the building of Moscow Metro in 2010. The machine achieved average daily rates of between 7m to 12m at Baikal. The works were complicated by large volumes of groundwater, which were managed via two drainage adits of 1.7km and 1.5km long. The tunnel is located on the border of the Irkutsk region and the Republic of Buryatia and its opening will increase throughput capacity on the BAM Lena-Severobaikalsk section from 17 pairs of freight trains to 25 pairs. n

References • •

Doubling Severomuisky to add rail capacity in Russia – TunnelTalk, June 2019 Overcoming adversity in Siberia – TunnelTalk, April 2002

Kiev Metro prepares plans for expansion

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wo new lines are being prepared to expand the Kiev Metro system by 25km by 2025 and with all 23 planned stations aligned underground.

According to representatives from the regional government of the capital city of Ukraine, the new lines are the Podilsky-Vygurovskaya Line and a new Podolsk-Levoberezhnaya Line (Fig 1). Oleg Tokarev, a Chairman of Kyivmetrostroy, the major metro construction in Kiev, said there are plans also to extend the existing Syretsk-Pecherskaya Line to the Vynohradar historical neighbourhood of the city.

Following a series of expansions of the Metro in the 2000s, a change of political power and a series of economic and political crises in 2013 and 2014 in Ukraine resulted in the suspension of further works. Construction was paused for almost four years, until implementation of the project resumed in Spring 2017 with the aim to extend the network to the Troeschina residential area, one of the largest districts in the city, situated on the left bank of the Dnepr River.

In November 2018 the Kiev Government received an official letter of interest from the China Railway International Group to construct the metro line to Troieschina. With the a feasibility study completed, construction works are yet to begin. The reason for the delay was not disclosed by the Kiev regional authorities.

The new underground line with 14 underground stations is 7km long and will be constructed in two phases, each lasting three to four years. The

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Fig 1. New lines and extensions to Kiev Metro

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Moscow Metro ready for further expansion for excavation of single-track tunnels, with another four machines at 10m diameter for single-bore, twin-track running tunnels.

In June, China Railway Construction Corporation (CRCC), joined JSC Mosinzhproekt for start of construction on the eastern section of the BKL. The two companies are working on the project on the basis of an agreement between CRCC and the Moscow Regional Government.

For excavation of the eastern section, CRCC recently completed delivery of an almost 11m diameter TBM via the Northern Sea Route from China to Moscow. The machine is designed

•

Ambitious project planning in Kiev – TunnelTalk, October 2005

www.TunnelTalk.com

to operate in Moscow construction conditions and at temperatures of down to -30°C. This is the fourth large diameter TBM supplied by CRCC, together with four 6m diameter machines, for working on the BKL project. A similar TBM is also working on the eastern section of the Line, while two similar machines are employed on the western section.

Completion of BKL construction is scheduled for the end of 2023. n

References •

China assists Moscow Metro expansion – TunnelTalk, Aug 2019

Route of the 69km Moscow Metro BKL Circle Line

cost of the project is estimated to be more than UAH30 billion (about US$1.2 billion). The majority of the funding for the project is expected to come from the Kiev regional budget and the Ukranian State budget. Some funding will be provided also by private investors as well as international financial institutions that may include leading banks in the EU and Asian region.

The Kiev Metro opened in 1960 and currently has three operating lines with an overall length of 68km. Of the 52 stations, 20 are deep underground, 26 are subsurface and the other six are at grade. The Arsenalnaya Station on the Svyatoshinsko-Brovarskaya Line is currently recognised as the deepest station in the world at 105.5m deep.

According to the Mayor of Kiev, Vitaly Klitschko, expansion of the Metro is part of the existing general plan for development of the city within the next decade. The overall length of the Metro will increase to 130km, and the number of stations will increase from 52 to 100. Each 41km of the network serves one million inhabitants of the city.

It is planned that Kyivmetrobud will remain as general contractor for Metro works in the city with the company likely to continue using its 6m diameter Herrenknecht TBM purchased in 2008. The new stations on the new lines will be built using the open cut method.

The Kiev regional government estimates the overall investment in the expansion of the Metro will amount to UAH50 billion (about US$2 billion). n

References

Eugene Gerden for TunnelTalk

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oscow authorities plan to maintain the current pace of metro construction across the next several years, amid the evergrowing demand for its use from local citizens. Marat Khusnullin, Deputy Prime Minister of the Moscow City Government, said that at present, more than 70% of Muscovites use the Metro, which makes it the most popular transport mode in the city. The plan of further expansion of the network in coming years will make it one of the largest metro systems in Europe.

Current construction works are concentrating on building the Bolshaya Koltsevaya Line (BKL) as the priority project for Moscow authorities. Moscow Mayor Sergei Sobyanin recently announced that tunnelling works for the BKL is currently 80% complete.

Khusnullin added that “building of the BKL is the largest project in the history of metro construction.” The new line will have a length of 69km with 31 stations and two depots, giving it the status of the world’s longest metro circle line.

In mid-June, general designer and contractor JSC Mosinzhproekt completed excavation of the northeast section of the BKL. The 3.5km section was excavated using a 6m diameter TBM at a depth of almost 70m. The drive is one of longest sections of the Moscow Metro and took JSC Mosinzhproekt several years to build.

Andrei Bochkarev, Deputy Mayor of Moscow for Urban Planning and Construction, said that despite the impacts of the coronavirus pandemic of early 2020, Moscow may set a new record this year in terms of the volume of ongoing construction works and the number of TBMs operating on the metro works. He reported that there are 33 TBMs in Moscow at present, of which 22 are in operation. Of these, 18 machines have a standard 6m diameter

Eugene Gerden for TunnelTalk

Arsenalnaya Station, the deepest metro station in the world

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Settlement after 2009 Cologne Metro disaster TunnelTalk reporting

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ore than 10 years after the fatal metro works collapse in Cologne in March 2009, the years of legal processes were brought to a close with an out of court settlement. The settlement will draw a line under any further court actions and permit a long-awaited section of the North-South Line for the city to be completed.

It was during excavation of a sump facility in the bottom of an open-cut line junction that the structure was undermined, bringing surrounding ground into the collapsed area and demolishing an adjacent apartment block and the historical archive building. The collapse cost the lives of two residents in the apartment block and destroyed records in the archive building dating back to medieval times.

Civil works for the new 4km long twin tube North-South underground line for the Cologne tram system were complete at the time and the open-cut junction was the last

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Fateful day of collapse in March 2009

element progressing towards opening the line to services in 2010. The line and stations either side of the collapsed zone eventually opened in 2014 with buses carrying passengers across the incomplete section to continue their journeys. At the time, costs to recover the collapsed zone and complete the line were estimated at between €620 million and €1 billion.

Given the devastating and deadly circumstances of the collapse, criminal prosecution proceedings began in 2018 against individual defendants charged with involuntary manslaughter. In its judgment, the Cologne District Court determined that the catastrophe was unequivocally and unquestionably caused by an error in the underground line junction construction.

A construction supervisor of project owner KVB, Kölner Verkehrs-Betriebe, was sentenced to probation for negligent homicide, another was acquitted and in a second criminal trial, the senior construction manager of the construction JV received a one-year suspended sentence. The ARGE Los Süd JV of Bilfinger Berger, Züblin, and Wayss & Freytag was working on the 3km southern section of the new line with five underground stations, and a consortium lead by Hochtief and including Strabag, Keller, Brueckner and Bauer, was completing the 1km northern section with the sixth underground station.

In press release statements distributed by the three equal-partner companies of the JV, each agreed to an out of court settlement with the City of Cologne and KVB, to pay a total of €600 million, €200 million each. This will be in final settlement of all civil lawsuits against the JV, after which the parties will

Breakthrough on Istanbul Metro Terratec News Release

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fter launch on its 1km long drive in mid-March, the first of four new 6.56m diameter Terratec EPBMs currently working on the Ümraniye-Atasehir-Göztepe Metro line in Istanbul completed its first Istanbul Metro expansion routes

Intermediate breakthrough at Atasehir station

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intermediate breakthrough in May 2020. Its sister machine in the parallel drive, launched a month later, has been achieving consistent advance rates of up to 42m/day for the Gulermak, Nurol & Makyol JV. “We have made rapid progress on the project, achieving an average of 20 rings/day across a period of 10 days for both machines,” said Mesut Emre Aymir and Ihsan Yagcıoglu, Tunnel Managers for the Gulermak, Nurol & Makyol JV. This is despite the difficulties posed by Covid-19 and the relative lockdown of the city, which have seriously affected all activities and organisation of the site. “The outbreak has especially affected the commissioning of the second two machines where we have had some delays. Generally, however, we are satisfied with the performance of the Terratec machines, which have exceeded our expectations.”

The 13km-long Ümraniye-AtasehirGöztepe Metro (UAG) line with 11 underground stations and NATM-built connections, will form a second north to south rail corridor under the denselypopulated Anatolian side of Istanbul.

The Terratec TBMs have mixedface dome-style cutterheads with an opening ratio of about 35% as well as

dismiss further claims against each other.

Under the settlement agreement, the JV partners have agreed to complete, at its own expense, the refurbishment and extended completion of the structural shell of the track switching facility.

The three JV partners explained in their press statements that the €200 million payments each are covered largely by company insurance payments and that they will have no impact on the earnings estimate of the publicly listed companies for 2020. BAM on behalf of its operating company Wayss & Freytag stated that the remaining part of the payment, not covered by insurance, it will take as an exceptional charge in the 2020 accounts for an amount of about €40 million. Ed Züblin AG has been a subsidiary of Strabag since 2005 and Bilfinger civil construction became part of the Implenia Group of Switzerland in 2015.

“In view of the extremely complex issue regarding the cause of the damage, which has kept all involved parties occupied for more than 11 years, and would probably have kept them occupied for another 10 to 15 years, and after intensive consideration of all options, we consider the agreement reached to be reasonable for all project participants including our shareholders,” said Thomas Birtel, CEO of Strabag SE and Chairman of the Supervisory Board of Ed Züblin AG. “The time has come to draw a line under the past and to focus on the future. Still, the third of March 2009 will remain a deeply tragic day that we will never forget.” n

References •

Fatal collapse on Cologne’s new metro line – TunnelTalk, March 2009

VFD electric cutterhead drives, tungsten carbide soft ground cutting tools, that are interchangeable with 17in disc cutters, high torque screw conveyors and active articulation systems. The machines have worked effectively through the mixed faces of low-strength sandstones, siltstones, limestones and shales.

As the machines progress north and south from the mid-point Finans Merkezi Station, they install 1,500mm wide x 300mm thick precast concrete lining rings of five segments and a key.

Mucking is via continuous conveyor with TBM segments and materials supplied by multi-service vehicles.

The UAG project is one of a number of metro lines under construction in Istanbul that will increase the current 145km metro network to more than 480km. In 2020, Terratec had nine machines working concurrently in the city. Four 6.56m diameter EPBMs were progressing for the Halkali-Yeni Havalimani Metro JV (consisting of Cengiz Insaat, Kalyon and Kolin) on the HalkaliIstanbul New Airport metro line and elsewhere other Terratec machines completed their work on the expanding network. n

References •

Record advance for the Istanbul Metro – TunnelTalk, March 2018

www.TunnelTalk.com

Bidders shortlisted for large-diameter Thames crossing

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The twin tubes are expected to advance from the north portal. It is a good position for muck disposal with the adjacent landfill currently receiving muck from the Tideway CSO project in London.

From the north end, the geology comprises made ground over alluvium, followed by a layer of gravels and Seaford and Lewis Nodular Chalks.

• BFV JV of BAM Nuttall, It is through these chalk deposits Ferrovial Construction and Vinci that the majority of the alignment Construction Grands Projets, lies, making slurry machines the likely supported by Atkins, Tecnica y choice by the contractor.

Proyectos and Stantec UK; As the bores reach the river • BMJV of Bouygues Travaux Publics crossing, the TBMs will be operating in and J Murphy and Sons, a full face of chalk. At the deepest point supported by Mott McDonald of 55m below high-water level, “we and Ove Arup and Partners; have the potential for 5.5 bar of water • DH JV of Dragados and pressure, as well as the presence of Hochtief Infrastructure. flints,” said Bowers.

In addition to excavation of As the TBMs move beyond the the twin tubes, the design-build river on the south side, the alignment contract includes construction cuts through the surface of the of the portals, the north and south chalk and back into the gravels, Figs 1 and 2. Route and design of the twin tube approach roads and design and raising again the challenges of crossing under the Thames installation of the finishing and mixed face conditions and relatively operating systems. It is one of three low cover. “The priority in this area studies and laser imaging, detection and main contracts of work on the project to ranging (LIDAR) surveys. More than 10km will be to protect the wetlands from any build a new 23km linking highway between of core samples were collected. environmental disturbance,” said Bowers. the existing junction of the A2 and M2 When complete, the tunnels will have The exact length of the under river twin highways in the south, and the A13/A1089 tubes will be determined by the contractor an internal diameter of 15m (Fig 2) with and M25 highways in the north (Fig 1). during detailed design. The number of space under the road deck for equipment When complete, the project will almost cross passages is likely to be 27 based and systems that might usually be placed double road capacity across the Thames on the required 150m spacings. Short in the cross passages, allowing for east of London. elements of cut-and-cover create the maintenance without the need to close The procurement process is expected to portals at either end. traffic lanes. It also reduces the necessary run until contract award in mid-2022.

The large 16.4m o.d. of the drives is size of the cross passages to 5m diameter.

Proposals for two further contracts determined by the requirement to house a The Lower Thames Crossing is were also invited for the £600 million three-lane 110km/hr highway in each tube. expected to open to traffic between 2027 design-build Kent Roads contract of the “There are few projects to-date that have and 2028. n surface route south of the river and the used larger diameter TBMs than those we £1.3 billion design-build Roads North anticipate,” said Bowers, “although the global References • TBMs specified for critical Thames highway contract to link to the M25. trend is towards larger diameter machines.” crossing – TunnelTalk, January 2016 Technical support through the development and construction phases of the project is being provided to Highways England by the LTC CASCADE joint he largest TBM ever used in Europe venture between COWI, CH2M, now part Herrenknecht News Release successfully completed its drive in of Jacobs, and Arcadis. In a more unusual approach to the procurement process, Italy. The supersized 15.87m diameter References the design-build contract is designed to Herrenknecht EBPM excavated the • Mega-EPBM for Italian highway tunnel – incorporate all foreseeable delivery risks 7.5km Santa Lucia highway route through TunnelTalk, September 2016 within the target budget. “The aim is to the Apennines in 2020. Working with set up an environment where all parties contractor Pavimental the new 15.87m Completion of the mega EPBM mission are working together to deliver within the diameter TBM was designed in particular budget, rather than wrestling each other to protect the site crew from the expected over the usual issues,” said Keith Bowers, methane gas deposits in the ground. After Tunnels and Systems Director for the the start of tunnelling in July 2017, crews operated the mega machine at progress Lower Thames Crossing.

An extensive programme of ground rates of up to 122m/week and excavated a investigation work was carried out by total of about 1.5 million m3 of rock and soil.

The three-lane Santa Lucia tunnel geotechnical investigation contractor Perfect Circle. In addition to geophysics, is a key project in the expansion of the the work included investigation of Autostrada A1 between Bologna and unexploded ordinance (UXO) left as a Florence. The new underground highway result of WWII bombings. The investigation will minimise the likelihood of accidents, programme also included ultra-high improve travel times and reduce resolution seismic studies, bathymetry and consumption of gasoline and diesel by the Tromino surveys, as well as laser scanning tens of thousands of cars and trucks that of flints, pumping tests, geomorphology use the highway each day. n

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Jonathan Rowland, TunnelTalk

onstruction of a new 4.3km highway link under the River Thames in the UK entered its construction procurement stage with the twin 16.4m o.d. tubes to be among the largest bored highway tunnels in the world and the longest underground road links in the UK. Three prequalified bidders have been shortlisted to present proposals for the £2.3 billion Lower Thames Crossing and approaches contract:

Santa Lucia mega TBM breakthrough

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Stonehenge progress despite legal challenge Jonathan Rowland, TunnelTalk

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egal action brought by a campaign group is asking a judge to quash the granting of planning permission for the proposed £1.7 billion upgrade to the A303 highway in the southwest of England that includes a 3.3km twin-tube section alongside the ancient monument of Stonehenge (Fig 1). The legal bid by the Save Stonehenge World Heritage Site group was launched after the UK Minister for Transport formally approved the development consent order for the scheme in November 2020.

The campaigners conclude that the project would substantially and permanently harm the integrity of the heritage site and that the harm would not be offset by the

benefits of the scheme. The comments echo concerns raised by UNESCO, which in 2019 urged the UK Government not to proceed with the project in its current form.

The campaign group further argues that the decision by the Secretary of State is unlawful because he underestimated the overall impact by averaging it out and offsetting the purported benefits before appreciating the true extent of the damage. In doing so, they say, the Secretary failed to follow national policy and breached international law under the World Heritage Convention.

Alongside the legal process, work continued toward announcement of the main contractor with project owner Highways England currently engaged in competitive dialogue with three shortlisted bidders:

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Main features of the proposed twin tube highway scheme

• Bouygues Travaux Publics, • HDJV of Hochtief Infrastructure and Dragados, • MORE JV of FCC Construcción, Salini Impregilo and BeMo Tunnelling UK. Highways England is being advised by technical partner AECOM, in partnership with Mace and WSP, and legal advisors Gowling WLG, confirmed to TunnelTalk that announcement of the preferred bidder is expected later in 2021.

Procurement for other elements of the project is also continuing. A £75 million tender for a delivery assurance partner was launched in December 2020 and contractors for preliminary and archaeological works were announced in October 2020.

Wessex Archaeology will lead efforts to survey, excavate, record and preserve any archaeological finds during the project, under a contract of £35 million.

The company was previously involved in the evaluation phase of the project, during which a number of finds were uncovered from the Neolithic and Bronze Ages.

Meanwhile, a £8.5 million preliminary works contract awarded to Osborne is progressing to prepare the sites for the main excavation construction. These works include preparation of the site compound and road access, and wildlife protection work. n

References •

UK revives Stonehenge road tunnel proposal – TunnelTalk, November 2014

TBM selected for Swinoujscie road link Jaroslaw Adamowski for TunnelTalk

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Chinese TBM manufactured by CREG is to be used to excavate the subaqueous road link in Swinoujscie, Poland, a city located on several dozen islands. Austrian contractor Porr, as the lead of a joint venture with Gülermak of Turkey and Energopol Szczecin of Poland, will excavate the road link under the Swine River to connect two of the largest islands of the city.

The central 1.5km length of the 3.2km long, two-lane bi-directional tunnel will be excavated by the 12m diameter CREG slurry TBM at up to 38m below sea level at its deepest point. It will pass through fine sand and fine-medium sand with gravel at the landfalls, while below

the Swine River the main deposits are fine-medium sand with gravel and overconsolidated sandy clay with gravel and chalk. To better cope with the geology, the machine design includes a cutterhead structure with a large opening ratio, a device for continuous wear detection of the cutterhead and cutters, a pipe extension system with zero slurry spilling, and a special articulation structure and cutterhead retraction for ease of steering.

“Despite the coronavirus pandemic, the machine was produced according to the plan,” said Lucyna Roszyk, a spokesperson for Porr. “The TBM will be shipped as 129 components, with a total weight of 3,176 tonnes, taking about 60 days to complete the journey, of which 45 days will be at sea. Once arrived, assembly

From left: China-made TBM for Swinoujscie road link; Preparation of the TBM launch

will be in the 23m deep x 120m long x 19m wide launch shaft. From a launch in March 2021, and according to our schedule, the TBM should take about six to seven months to complete the 3.2km drive.” Under the plan, construction is to be completed in September 2022.

Production of the lining segments is in an on-site casting yard about 400m from the TBM launch shaft. “There are two types of segments, said Roszyk. “Shorter 1.5m wide rings, will be used through a curve of 300m radius with rings of 2m wide used on the straight sections and through an exit curve of 500m radius.” Segments will be cast using rebar cage reinforcement and C50/60 concrete.

Currently, transportation between the two largest islands of Uznam and Wolin is by ferry which employ outdated vessels. Due to this, Swinoujscie is periodically cut off from the rest of the country. Swinoujscie has obtained funding from the European Union which will finance 85% of the €411 million project. n

References • • •

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Poland commissions new TBM road link - TunnelTalk, January 2019 Lodz to host Poland’s first TBM railway tunnel – TunnelTalk, May 2018 Gdansk accepts TBM for vital river crossing – TunnelTalk, October 2012

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Chambers Wharf job site on the Thames Fig 1. The 25km Tideway route

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xcavation of the main 7.3m i.d.

Tideway CSO interceptor under the River Thames in London was focused on the 65m deep x 20m i.d. Chambers Wharf shaft in late 2020 with one TBM breaking through and another preparing to launchAn NFM EPBM finished the second 7.6km Central Contract drive from Kirtling Street, the longest of the Tideway main drives, for the Ferrovial-Laing-O’Rourke FLO JV and remained in place, while a Herrenknecht slurry machine prepared for launch on its 5.5km drive to Abbey Mills pumping station for the Costain-Vincy Bachy Soletanche (CVB) East Contract JV (Fig 1).

Breakthrough of the NFM machine at the Chambers Wharf completed 19km of the main interceptor with only the East Contract, through the Seaford Chalk and under water pressures of up to 5 bar, remaining.

The first NFM TBM on the 5km drive in the opposite direction between Kirtling Street and Carnwath Road on the Central Contract completed its drive in November 2019. This was followed in August 2020 by breakthrough of a Herrenknecht EPBM at the end of the 7km drive of the West Contract from the launch shaft at Carnwath Road to Acton Storm Tanks for the BAM NuttallMorgan Sindall-Balfour Beatty (BMB) JV. The main 25km x 7.2m i.d. Tideway alignment extends from Acton in the west to Abbey Mills, where it connects with the existing Lee Tunnel for conveyance of combined storm water to the Beckton sewage treatment works (Fig 1).

Two further TBMs worked on the connectors for the sewer project. In July 2020, a refurbished Lovat EPBM completed the 1.1km x 2.5m i.d. long Frogmore connector between King George’s Park and Carnwath Road on the West Contract while on the East Contract, a second 6.5m diameter Herrenknecht slurry machine was launched in December 2020 to bore the 4.6km x 5.5m i.d. connector between Greenwich pumping station and Chambers Wharf.

By early 2021, 19 of the 21 shafts on the project were also complete and work continued on other short connectors to the main interceptor. In November 2020, excavation of the 147m long Cremorne Wharf SCL connector reached the segmental lining of the main interceptor on the Central Contract with breakthrough waiting until construction of the main line is complete.

SCL excavation of the 300m Hammersmith

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Tideway continues and counts cost of Covid

Jonathan Rowland, TunnelTalk

From left: Tideway main TBM drive complete, Connector reaches main Tideway segmental lining

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alignment was completed in early 2019.

Casting of a 250mm thick secondary concrete lining inside the primary segmental lining of the main 25km long interceptor is a major part of the project. Reducing the i.d. to 7.3m, the secondary lining will account for high internal operating pressures and provide resistance to abrasion to ensure the 120-year design life of the infrastructure.

Sewage in Tideway will flow by gravity eastward with no need for intermediate pumps until lifted by pumps into the Beckton sewage treatment works at the end of the Lee Tunnel.

The lining is being cast using full round shutters supported on travellers (Fig 2).

First part of two shutters lowered into Kirtling Street shaft for reassembly

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Tideway and the pandemic

Work on Tideway was suspended in March 2020 as required by UK Government regulations to control the coronavirus pandemic. Following a restart in May, work continued despite a resurgence of Covid infections in the UK that led to a second and third nationwide lockdown in November 2020 and early 2021.

Although unavoidable, Tideway is counting the cost of the pandemic shutdown and released ‘plausible’ and ‘severe’ downside scenarios. Under the plausible downside scenario, the costs to complete the project are 9% higher than forecast, taking the total cost to £4.1 billion. Under the worst-case scenario, costs increase by a further 24%, taking the total to £4.3 billion.

Resuming activities at all working sites involved implementation of new safety measures, including staggered shift patterns, one-way walkways, contact-free entry to

Fig 2. Two 12m shutters on a single traveller will form the secondary lining sites, social-distancing in welfare facilities, and encouraging workers to avoid public transport. “Every member of staff who was able to, began working from home,” said Andy Mitchell, Tideway CEO. “We gave assurances to our supply chain that we would continue to pay them, so they in turn could protect their own workforce.”

Start of commissioning is now expected in September 2021, later than originally forecast, with handover in March 2025, a nine-month delay that Tideway blames entirely on a slowdown in productivity due to the essential Covid-safe measures on sites. Further delay is considered unlikely, as the safety measures taken have allowed production to increase to near pre-Covid levels, ultimately mitigating significant

potential cost and schedule increases above those forecast.

In its late-2020 quarterly report, Tideway confirmed that Covid would add £233 million to completion of the project, which now totals £4.1 billion from an initial £3.4 billion estimate at start of construction (£3.1 billion in 2014/15 prices). The predicted budget for the project had already increased from an initial £3.4 billion in 2014/15 prices to £3.9 billion. n

References • • •

Preparations to start London supersewer excavations – TunnelTalk, August 2017 Tideway TBMs well into excavations – TunnelTalk, September 2019 Connection construction underway for Tideway – TunnelTalk, September 2017

London Main Ring inspection and maintenance Jonathan Rowland, TunnelTalk

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nspection and maintenance work on a 35km section of the 80km London Water Ring Main and relining of 1.9km of inlet and outlet tunnels at the Waltonon-Thames QEII Reservoir is part of a £22 million programme of inspections and repair work awarded to UK contractor Barhale.

The fresh water supply Ring Main at up to 50m and more deep was completed during the 1980-90s using several TBMs, many of them supplied at the time by Lovat of Canada.

Depending on the criticality of the asset, regular inspection of the Ring Main is required said to Phil Cull, Southern Region Director at Barhale. The work involves the isolation and draining of the tunnels to allow access for a line-and-level survey, as well as any required repair or replacement of pressurised assets from within the access shafts or tunnels. Sections of the Main Ring between Battersea and Park Lane, New River Head and Barrow Hill, and Hogs Mill to Raynes Park are among those in the current works programme.

Work on the Brixton to Honour Wood section is already complete.

Barhale is also refurbishing one high integrity gate valve at New River Head, and three at Barrow Hill, while all existing

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80km London Water Ring Main (top); Unbolted reinforced concrete wedge block lining will be relined at QEII white caps – the lifting eye sockets for each plate – on the 14.4km stretch of the Ring Main between Ashford A4 and Kew via the Kempton shaft, and on the 12.7km stretch between the shafts at Kew and Barrow Hill, via Barnes and Holland Park, are being

replaced. In total 220,000 new white caps will be installed.

In addition to work on the Main Ring, 12 raw water tunnels of various diameters and constructions, including brickwork, cast iron, steel and wedge block, totalling 9km in length, will be inspected. This will again require isolation of the tunnels, at both upstream and downstream ends, and draining using temporary drop-in pumps.

Necessary repairs will be made and any debris, such as silt will be removed.

At the QEII Reservoir, the 1.1km inlet and 0.8km outlet tunnels will be fitted with an in-situ concrete lining. Both 2.5m i.d. alignments are lined currently with precast unbolted reinforced concrete wedge block linings dating back to the reservoir’s original construction in the 1960s.

Barhale has completed similar relinings, at the Queen Mother, Wraysbury, and Datchet reservoirs.

The award of the contract to Barhale builds on more than three decades of work by the company for Thames Water. n

References • • •

Second of four main Tideway drives breakthroughs – TunnelTalk, October 2020 London Water Ring Main feeder – TunnelTalk, December 1992 Geared up for London Ring Main drive and beyond – TunnelTalk, December 1990

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Cooling systems at Hinkley Point

Power cables to move underground across Snowdonia National Park Jonathan Rowland, TunnelTalk

TunnelTalk reporting

E Ten pylons will be removed and the cables replaced underground ground conditions, the planning application allows for the use of conditioning additives.

Excavation is anticipated to progress from the western shaft and take 17 months to complete the 3km drive.

Shaft diameters will be up to 15m for the western TBM launch site and up to 12.5m on the eastern retrieval site.

Water inflows during excavation of the shafts of 137m3/day and 268m3/day are expected for the western and eastern shafts, respectively. According to the planning documents, it is not currently known whether the water inflow will be fresh or saline, due to the proximity of the two shafts to the estuary. Fresh water could be discharged to surface waters close to the shafts. Saline water would need to be contained and piped to locations where it could be discharged to brackish waters. n

xcavation of the SCL onshore cooling water systems for the nuclear power plant at Hinkley Point in the UK is complete. Contractor Balfour Beatty for owner EDF Energy reported successful breakthrough of the longest and final onshore cooling-water tunnel to complete 600m of sprayed concrete lining works for the project. The five onshore SCL tunnels will be finished with a secondary rebar reinforced insitu concrete lining.

At the same time, Balfour Beatty crews are managing excavation of the marine cooling water system TBM headings. The first TBM launched at the end of August 2019 and has progressed more than 2.5km into the first of three 3.5km x 6m i.d. segmentally lined drives, 33m out under the Bristol Channel. The cooling water system will transfer more than 120,000 litre/sec of water to and from the new power plant. n

References •

Nuclear deal paves way for 11km of subsea tunnels – TunnelTalk, October 2015

Last of five SCL on-shore cooling water headings now complete

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endering is underway for construction of a project to move underground a 3km section of 400kV overhead power lines across Snowdonia National Park in north Wales.

The project is one of several by owner National Grid to remove the visual impact of electricity cable pylons from national parks and areas of outstanding beauty in the UK. The contract is to be awarded in 2022 on a design-build basis and will progress construction through to 2026.

The new connection will run from Cilfor on the western edge of the Snowdonia National Park, under the Dwyryd Estuary, to Garth. Construction works will comprise a 4.4m i.d. segmentally lined cable tunnel, two shafts with permanent head houses, and removal of ten existing high voltage electricity cable pylons.

In 2020, the project received the key planning approval to construct the head houses. Further planning approval will be required as the design-build detailed design progresses. The project would also be dependent on the UK Government regulator confirming any necessary funding required outside of the £500 million already raised to mitigate the visual impact of power lines.

A slurry TBM is anticipated for the 4.4m i.d. drive beneath the estuary.

Geology along the route is expected to comprise mudstones, coarse-grained and fine-grained turbiditic sandstones, and quartzose siltstones. In areas of soft or poor

References •

Contract awarded for London Power Tunnels 2 – TunnelTalk, December 2019

Replacement required to repair UK aqueduct

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programme of works to replace more than 50km of water conveyance aqueduct, across six sections on the 109km Haweswater Aqueduct in northwest England, is being prepared by UK water company United Utilities. Procurement on the £750 million to £1 billion project will began in early 2021 with the publication of the contract notice. According to the company, contract award is expected to be in mid-2022 on a design-build-own-finance basis, with construction work expected to begin in 2023.

The planning application and environmental surveys are also expected to be published in early 2021. The online public consultation documents suggest that TBMs will be used for construction.

The route covers three counties from its northern end in Cumbria, through Lancashire, and to its southern end at the existing Woodgate Hill water treatment works in Bury, Greater Manchester. In a 2019 response to feedback from UK water industry regulator, Ofwat, United Utilities puts the total length of tunnelling at 51.5km.

Initial preparatory work is underway with Costain awarded the early contractor involvement contract in September 2019 to advise on preliminary design work, temporary land requirements for

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construction, and land and environmental surveys and investigations. The importance of preparatory investigations is being increasingly recognised within the UK, as United Utilities notes in its response to Ofwat concerning the proposed cost of ground investigations. According to the company, the consequences of poor preparatory work, such as inadequate initial investigations accompanied by an appropriate level of geotechnical baseline reporting, can lead to significant cost overruns.

The Haweswater Aqueduct programme of works also poses some atypical conditions for ground investigations in the UK with the average depth of more than 200 boreholes along 46km of the proposed route reaching 70m and a maximum depth of 240m on the Bowland section. There is a comparatively low amount of existing ground investigation information available along the project route.

After a series of market engagement events, United Utilities has opted to undertake one procurement exercise to engage a competitively-appointed provider (CAP) to design, build, finance and maintain the project. A second option, to run two parallel procurement exercises, one for the construction contracts and another for the funding of the CAP agreement, was rejected.

Built between 1933 and 1956,

Jonathan Rowland, TunnelTalk the existing 2.6m i.d. gravity-powered Haweswater Aqueduct supplies up to 570 litre/day of drinking water to Manchester and to communities in the Pennines, accounting for a third of the supply to the region. Recent investigations have indicated that the condition of the aqueduct is deteriorating and, although some more urgent repair work has already been undertaken, a longerterm solution is required to ensure the future viability of the pipeline. n

References •

Excavation complete in Delaware Aqueduct Bypass – TunnelTalk, August 2019

Route of the new 50km Haweswater aqueduct

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TBMs engaged in Asia Mumbai sewer TBM

Terratec News Releases

3.14m diameter EPBM for Mumbai sewer

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new 3.14m diameter EPBM for the Mumbai Sewer Disposal Project (MSDP) in India will be the 25th Terratec TBM to be delivered to the country in the last eight years. Previous machines have constructed more than 58km of key metro, sewer and hydroelectric projects in the country. The new EPBM will be deployed on the Stage-II Priority Works Project by contractor Michigan Engineers Ltd for the Municipal Corporation of Greater Mumbai (MCGM).

With 25 rings of 17in rear replaceable disc cutters and a high torque main drive that is still capable of rotating up to 5rpm,

Breakthrough on Pune Metro Line 1

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fficials from Maharashtra Metro Rail Corporation and staff from the Gulermak-TATA Projects JV celebrated the breakthrough of a second of two 6.61m o.d. Terratec EPBMs for the Pune Metro Rail project in Maharashtra, India. Breakthrough occurred at the underground Civil Court Station on the 16.56km long Line 1 Purple Line and marked completion of 1.6km long twin-tube tunnels. A third TBM is to be launched northwards towards Mandai Station in 2021.

The TBMs were launched at the end of 2019 on their second drives of the Breakthrough at Civil Court Station

the EPBM is designed to cope with varied geological conditions along the alignments consisting of mixed ground, basalt and breccia. It is also equipped with a fully active articulation system to accommodate a minimum curve radius of 250m. Due to size constraints and the installation of a full hyperbaric man lock, the main drive of the TBM is hydraulic.

The 4+1 universal rings of 200mm thick x 1m long reinforced concrete segments will be installed by the mechanical erector. Terratec rolling stock and battery locomotives will deal with muck removal and segment transport and machine supply. Machine operation will be assisted

by Terratec field service staff. n project near the College of Agriculture, and broke through at the northern end of a 155m scissor crossover, built by the NATM at the start of the Civil Court Station NATM excavation. The TBMs achieved a best monthly progress of 301m.

The EPBMs feature robust mixed-face dome-style cutterheads designed to work effectively at pressures of up to 4 bar and in the compact basalt that was expected on these contracts. As the TBMs progress, 1,400mm wide by 275mm thick pre-cast concrete segment rings are being installed, each ring consisting of five segments and a key. n

Refurbished EPBM for Delhi Metro Phase 4

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refurbished 6.5m diameter Terratec EPBM has been delivered to a joint venture of the Hindustan Construction Company and Vensar Constructions Company, for the Line 8 Magenta Line of the Delhi Metro. After a successful site acceptance test, the EPBM started to install the first ring of segmental lining for the 1.4km twin bores from Vikaspuri Park shaft

to the Vikaspuri ramp near Keshopur.

The Terratec EPBM has a traditional soil configuration, equipped with a spoke-type cutterhead with a 57% opening ratio. Cutting tools are exchangeable for 17in disc cutters to allow excavation through diaphragm end walls and the ability to cope with any unexpected obstacles such as old wells or foundations. The geology is composed of

Microtunnelling in Ahmedabad

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ontractor ITD Cementation selected Terratec micro TBM systems (MTBM) to complete about 6.5km of trunk-line sewer in the city of Ahmedabad, India. This is the first use of the microtunnelling technique in the city and will avoid the disruption of alternative open trench installation of the a new trunk sewer in the western part of the city.

The machine is supplied to install 1.4m diameter DN1400mm concrete pipes with the option of a later size increase to install DN1600 1.6m diameter pipes. The scope of the Terratec equipment supply includes the MTBM shields, main jacking stations, intermediate jacking stations, slurry transport and pipe lubrication systems, digital guidance systems and operator control cabins.

Terratec also provided ITD Cementation with an on-site service package which includes the assistance of key engineers and MTBM operators.

The project began in the Vadaj area and will take about two years to complete with breakthrough of the first of many pipejack drives in early December 2020. n Breakthrough at the end of the first drive

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silty sand, fine sand, sandy silt and clayey silt.

The reinforced concrete segmental lining is of the universal design comprising five segments and a key in each 1.4m x 6.3m o.d. (5.8m i.d.) ring. Along with the TBM drives, at an average depth of 15m, the contract includes a 365m long ramp and a 220m long station box. Work is expected to take 36 months. n

Early breakthrough on Bangkok Orange Line

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n early breakthrough has been celebrated on one of three underground civil works contracts for the first 23km-long east section phase of the Orange Line Metro project in Bangkok for the Mass Rapid Transit Authority of Thailand (MRTA).

A Terratec 6.39m diameter EPBM made the breakthrough on the westbound tunnel of Contract E3 for contractor Italian-Thai Development (ITD) a month ahead of schedule, giving hope for an early breakthrough on the upcoming eastbound drive. n Breakthrough on Contract E3

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Mumbai Metro structures, methods and progress With 17 TBMs of different types and open-cut and NATM for 26 underground stations and associated structures, construction of the 33.5km underground alignment of the Mumbai Metro Line 3 had reached more than 80% by early March 2020. Started in early 2017, S K Gupta, Director (Projects) for the client MMRC, Mumbai Metro Rail Corporation, reported that “all the TBMs have performed well” and that the station and rail tunnel works “are on track to complete all excavations by June 2020”. The dense and historic urban environment of Mumbai, on the narrow north-south peninsular, demanded underground alignment for the full 33.5km of the Line 3 alignment with a transition ramp to the one surface station at Aarey and to the surface depot in the north. Line 3 is the first underground metro line for Mumbai, all other public rail services in the city are either at grade or elevated.

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exposed NATM faces are sealed with steelfibre reinforced shotcrete and grout injection is used to control local excessive water ingress,” said Gupta.

All the running tunnels on the project are designed with a 5.8m i.d. and are lined with precast concrete segmental linings reinforced with rebar cages. Most linings have straight bolted or dowelled circumferential joints while the lining design on Package 1 has knuckle joints on the circular segment-to-segment ring joints and are bolted on the longitudinal joints. The segments for all the contracts are produced at a concrete casting works in Wadala, about 10km from central Mumbai.

Each contractor has managed the fabrication of its own segment production.

Muck haulage behind all TBM drives is by rail-bound muck cars with service trains carrying in the segments for each ring of advance. Jet grouting has assisted the break-out and break-in of TBMs in zones of softer, mixed face or highly fractured or jointed rock conditions.

Ahead of selecting and ordering their TBMs, the appointed contractors of each package carried out additional site investigation. “This resulted in contractors ordering different types of shielded TBMs to cope with conditions,” said Gupta. “These include slurry, EPB and dual and multi-mode machines and all have performed well.”

The supplier of most TBMs to the project, supplying seven of the 17 machines, is Terratec, delivering five new dual mode rock TBMs and two used rock EPBMs. The 6.6m i.d. TBMs achieved consistent progress rate averages of near or above 300m/month with bests of 102m/week and up to 20m/day.

On Package 3 from Mumbai Central to Worli, the Dogus/Soma JV is using two NFM/ Robbins rock slurry TBMs, one new and one refurbished. The first TBM completed its 2,073m drive from Science Museum to Worli in 16 months, after launching in September 2018, being pulled through Acharya Atrey Chowk, and achieving final breakthrough in February 2020. The second 1,645m drives for the two TBMs, from Science Museum to

TunnelTalk reporting

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s well as bringing metro services to the tip of the peninsula at Cuffe Parade, the new Government funded Mumbai Metro Line 3, at an investment of about INR25,000 crore or US$3.3 billion in 2011 approval values, links with the main railway and long-distance bus stations in the city and also to the main domestic and international CSIA airport terminals. In several areas, securing the land space for the open cut stations, shafts, and for providing working sites has required the acquisition of private properties, and the relocation of businesses and residents before works could start.

The geology in the Mumbai is largely hard basalt and softer tuff and breccia with hard basalt rock at up to 125MPa in compressive strength to the south and softer breccia and tuff to the north. For the most part the hard rock excavations in rock Classes I and II are dry with groundwater ingress experienced in the fractured and jointed rock of Classes III, IV and V. Groundwater ingress, some at high volume and under hydrostatic pressures of up to 5 bar, is also experienced in mixed face conditions and through upper sedimentary overburden and in softer tuff and breccia deposits.

“In planing the project, the main underground works were grouped into seven packages of between INR21-30 billion ($315-445 million) in value and between 4-6km of twin running tunnels in each package along with two or three stations and other associated works,” said Director (Projects) S K Gupta.

Of the 26 underground stations, 19 are cut-and-cover boxes of normally up to 250m long x 22m-30m deep, and seven, in the particularly congested areas at Hutatma Chowk, Kalbadevi, Girgaon, Grant Road, Santacruz, Sitladevi and Marol Naka, are a combination of cut-and-cover and mined NATM excavation. The stations at Cuffe Parade and BKC are up to 450m long to include crossovers. The cut-and-cover station boxes and access shafts on the line are supported by secant piles with rock and soil anchors and struts providing extra support as core excavation has progressed.

Excavation has advanced using controlled drill+blast, breakers and excavators.

For three of the mined stations, at Kalbadevi, Girgaon, Grant Road, Shitladevi and Santacruz, the TBM segmentally lined running tunnels were excavated through the station zones ahead of later breakout for station platform enlargements. Mined station excavation is also by controlled drill+blast, breakers and excavators, with rockbolts and steel fibre shotcrete for immediate support and for sealing all exposed faces against water ingress and deformation. “All

Fig 1. Mumbai Metro Line 3 and its contract packages the Mahalaxmi Metro open-cut station box and on to Mumbai Central, are on the critical path of the TBM excavation programme and began their drives in mid-2020.

Three Herrenknecht TBMs, one new and two refurbished EPBMs, are completing the 10.43km of tunnelling for Package 4 from Worli to Dharavi for the ITD-TATA-CEC JV. The three TBMs are completing the tunnels in four twin drives of from 600m from the Naya Negar open-cut launch site to Dharavi, to 2,490m, the longest drives on the project, between Naya Nagar and Dadar.

On Package 7, the L&T-SUCG JV operated three STEC EPBMs, two refurbished and one new, to complete the

From left: Twin breakthrough of 40 TBM breakthroughs on the project; Secant pile and support of open cut access shaft excavation

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7km of twin tunnelling from Marol Naka to Seepz. The three machines completed their tasks in three drives passing through MIDC and Seepz Stations to the transition ramp to the surface station at Aarey and the surface depot. The last TBM completed its drive in December 2019 with Package 7 being the first to complete all its TBM tunnelling.

Through the hard basalt rock on Package 1 from Cuffe Parade to Hutatma Chowk, the L&T-STEC JV selected two XRE Crossover TBMs from Robbins. The machines are completing the tunnels in three drives, starting at the Cuffe Parade Station box and breaking into and relaunching from the Vidhan Bhavan and Churchgate Metro Station boxes. The two machines started their third and final drives in January 2020 to

complete the 649m drives by mid-2020.

As excavation works approach their ends, attention for the project is turning to finishing works and M&E installations.

All NATM stations, crossover caverns and cross passages are to be finished with a waterproofing membrane and reinforced cast concrete. For the Sahar crossover cavern, an in-situ steel fibre reinforced cast concrete final lining is planned. M&E contracts have been awarded and are currently in design for approval by MMRC the Matro owner Corporation. Also ordered from Alstom are the 31 metro trainsets of 248 cars for the new line services, to be manufactured and supplied from the Alsthom factory in SriCity, Andhra Pradesh.

“The schedule remains under

continuous review and there have been some delays and challenges imposed by the coronavirus pandemic and with the construction of the open-cut stations and structures very close to buildings,” reported Projects Director Gupta. “However, we keep our target dates for opening Phases 1 and 2 of this important addition to metro services in Mumbai in sight.” n

References • • • •

TBM drives under old town Mumbai – TunnelTalk, August 2019 Twin Crossover TBMs prepare for Mumbai Metro drives – TunnelTalk, July 2018 Mixed ground TBM ready for Mumbai Metro – TunnelTalk, September 2017 TBM orders for Mumbai Metro Line 3 – TunnelTalk, February 2017

Crossover TBM for Mumbai hard rock drives

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wo 6.65m diameter Crossover TBMs completing the 2.8km twin running tunnels for Package 1 for the Mumbai Metro Line 3 project are working through challenging mixed ground conditions of basalt rock with transition zones of shale, tuff, and breccia. The hybrid-type rock/ soft ground single shield machines have completed the first two of their three drives, taking about 90 production days to complete the 499m and 482m drives from Vidhan Bhavan Station to Churchgate Station.

Package 1 was awarded to the Larsen & Toubro and the Shanghai Tunnel Engineering Company (L&T-STEC) JV and the first TBM started boring from Cuffe Parade in August 2018 and the second in November 2018.

They broke through into Vidhan Bhavan Station in April and Churchgate Station in October 2019 respectively.

The two TBMs are working beneath a cover of 15m-20m with sensitive structures on the surface, including the Mittal Towers and the historic Bhikha Behram Well. All have been instrumented to monitor vibrations, movements, and potential settlement.

As expected, significant amounts of groundwater at up to 300 litres/min have been encountered between Cuffe Parade and Vidhan Bhavan. Water pressures of up to 2 bar were foreseen. The expected geology and the presence of ground water required the use of a TBM with the ability to excavate effectively in continuously changing conditions.

Optimised for abrasive rock geology using a robust cutterhead mounted with disc cutters and a reinforced screw conveyor at the centerline, the hybrid XRE Crossover Design of the Crossover XRE machines

machines can operate in open, closed and semi-closed mode using features designed to advance in soft ground with water inflows.

Dual ratio gearboxes adjust cutterhead speed and torque to the geological conditions encountered and the screw conveyors and their bulkhead gates and discharge gates control muck extraction from the excavation chamber. Conditioning with foam and polymers and probe drills for pre-excavation grouting assist TBM operations.

The cutterhead design is optimised for hard rock with six peripheral bidirectional muck buckets. In extreme soft and running ground conditions, the opening ratio of the cutterhead can be increased by removing part of the face plates and installing soft ground cutting tools. The roll angle of the TBM is maintained by alternating the direction of cutterhead rotation at each TBM stroke. This allows for a simpler thrust system, eliminating the need for a skew ring.

A screw conveyor in the centre of the XRE Crossover TBM offers several advantages over both traditional hard rock and EPBM designs. Full mucking of the cutterhead chamber in rock mode via six loading plates that continuously scoop and deposit excavated material from the invert into the screw conveyor inlet allows for minimal wear by keeping the amount of rocks inside the chamber to the minimum. The centre screw also offers the ability to work in pressurised modes to control ground water, with the cutterhead chamber full of material and using the screw conveyor as a plug to maintain pressure at the excavation face. This is vital for avoiding ground settlement at the surface.

Extra wear protection was added to the

JP Bayart, Jim Clark, and John McNally, The Robbins Company screw conveyor and the conveyor includes a replaceable casing liner, replaceable flight plates, and extra access doors in the casing for maintenance and replacement of the wear plates.

A major advantage of the centre screw and peripheral muck buckets is a substantial reduction in wear to cutter tools compared to an EPBM boring in rock. An average of almost 600m3 of rock cut/cutter is an impressive statistic when assessing basic cutter costs. From an operational point of view, 17 linear meters of boring/cutter reduced the frequency of interventions to an average 54m of boring.

The TBMs are equipped with a foam plant feeding six injection nozzles on the cutterhead and one at the inlet of the screw conveyor. Foam controls dust in the excavation chamber in rock mode, reduces friction and wear in soft ground mode when the cutterhead chamber is full of material, and reduces the permeability of the ground to reduce ground water inflow.

A probe drill installed on the erector ring for ground mapping ahead of the excavation.

Drilling is through 12 ports around the TBM shield at a 7˚ angle from the TBM axis and through six ports straight forward through the cutterhead. Probe holes can be used in an umbrella pattern for pre-excavation grouting to consolidate and seal the ground in front of the cutterhead to permit higher boring rates.

Several lubrication ports are installed radially along the TBM shield to inject of bentonite to reduce friction in sticky conditions or squeezing ground.

While the term hybrid machine has been used in the industry for some time, there is now a generation of machines that are truly hybrid, which can change from rock mode to soft ground mode almost instantly. n

References • • • •

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XRE TBM conquers toughest drive in Turkey – TunnelTalk, February 2019 Crossover TBM powers through in Akron, USA – TunnelTalk, September 2018 Mexico City XRE TBM finishes on a high note – TunnelTalk, July 2017 Crossover TBMs bridge the gap for Robbins – TunnelTalk, March 2015

www.TunnelTalk.com

Mumbai Metro NATM station Amalendu Gope, Ayesa India and Sandeep Singh Nirmal, RITES

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NATM mined stations in highly congested areas

Fig 1. Platform level plan of Kalbadevi Station and its excavation sequence excavation for subsequent breakout and enlargement of the station platform cavern and adit excavated to platform level.

The next phase in the sequence, to excavate the station platform tunnel and removal of the TBM lining segments to platform level, was the most challenging task. The sequence had to ensure stability of the rock in the crown and around the TBM tunnel as gradual enlargement progressed, excavating in the longitudinal direction (perpendicular to the existing TBM tunnel) and installing the primary support of rockbolts and shotcrete according to the rock Class (Fig 2).

Excavation then progresses longitudinally to excavate the crown and platform tunnel and remove the TBM segmental lining to platform level and above a temporary invert backfill. The process is completed with drill+blast excavation and primary support of the bench and removal of the temporary backfill and invert segments of the segmental lining along the full 211.45m length of the station platform.

After excavation and installation of

primary support for both platform tunnels, excavation of the central concourse cavern will begin, following a top-heading and bench sequence. Longitudinal excavation of the platform tunnels and the central concourse will progress from both TBM tunnels via Adit 2 and from the cut-andcover access shafts at both ends towards midpoint junctions.

Station structures will be finished with a waterproofing membrane and a final in-situ concrete permanent lining to 9.5m wide x 8m high i.d. for the platform tunnels, to 6m wide x 6.5m high i.d. for the adits and to 9.5m wide x 7.6m high for the central concourse cavern. The twoaccess cut-and-cover shafts at either end of the station will become the ingress and egress structures and will also provide space for electrical, mechanical and ventilation systems. n

ASIA

he design approach for creating the Kalbadevi Station, located in the heart of the densely inhabited heritage district of Mumbai, focuses primarily on minimising disturbances to the surroundings. The station is part of Package 2 of the Mumbai Metro Line 3 and is being constructed as a mined station using NATM with temporary cut-and-cover access boxes at both ends.

The geology for the area is mostly Class-II and I basalt with high compressive strength and few fractures. The approach adopted includes removal of the earlier TBM drive segmental linings followed by widening of the platform tunnels and construction of three 6.7m adits to connect the platform tunnels to the central concourse cavern using drill+blast excavation (Fig 1).

Approximately 1,200 segments in a total 304 x 1.4m wide rings of segmental lining have to be demolished to create the 211m long station platform tunnels.

Two 27.5m deep cut-and-cover shafts were constructed to base slab level using secant piles to support the excavation. The identified location of the shafts required some buildings to be demolished and the residents and businesses relocated.

Other challenges include stringent surface settlement allowances, drill+blast vibration limitations and controlled influence to the existing groundwater regime.

Within the 5.8m i.d. downline running tunnel, segments were marked for breakout of the three proposed concourse connection adits. Holes were drilled into the breakout segments to release any built-up water pressure behind the lining.

Temporary u-channels and rockbolts supported the lining rings before removal of the breakout segments and against the anticipated increased stresses of adit excavation. The segments to be removed were cut out with circular core drills around the perimeter.

A small 2.8m x 3m transition zone breakout from the running tunnel will give way to the larger 6.7m x 7.5m adit

References • •

Delhi Metro emerging – TunnelTalk, March 2002 See also NATM Focus starting p37 and Concrete Linings Focus starting p42

Fig 2. Transition zones for platform enlargement excavations; Adit breakout into a running tunnel

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Chinese TBM for Mumbai coastal highway drives

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12.9m diameter slurry TBM supplied

by Chinese manufacturer CRCHI has started work on the first stage of the coastal highway for Mumbai in India.

The highway will include about 3km of TBM and cut-and-cover excavation between Naruman Point and Bandra Worli (Fig 1). In total, the first stage will run almost 10km of a planned 29km route to connect Marine Drive in the south and Kandivali in the north. Despite the Covid-19 lockdown, developer Brihan Mumbai Principal Corporation (BMC) managed to complete 17% of work on this section by December 2020. While work is delayed, it is expected to be completed by July 2023.

The underground alignment will consist of twin TBM drives of 1.9km long with three traffic lanes in each. The southbound tube will include 660m of cut-and-cover at both ends, and the northbound drive has 410m of cut-and-cover at the Nariman Point end

and 660m of cut-and-cover at the Banra Worli end. Ten cross passages will link the twin underground roadways.

The tunnels will run at depths of about 70m through complex geological conditions that include basalt, breccia and shales, with maximum compressive strengths of up to 200MPa. The engaged contractor L&T Larson & Toubro, procured the CRCHI TBM for the project.

At 80m long and weighing 2,300 tonne, the CRCHI slurry TBM is equipped with a mixed cutterhead, with eight spokes and panels, as well as a large-diameter slurry feed port and several slurry flushing lines to increase the flow rate of the slurry to the cutterhead. Additional features include: • 20in disc cutters; • A dual-chamber indirect slurry control system; • A dual-circuit automatic pressure system; and

Jonathan Rowland, TunnelTalk • A high torque, retractable main drive.

The twin tubes of the Mumbai road project will have a finished precast segmentally lined diameter of 11m, with a prefabricated, man-entry technical conduit in the invert. The cut-and-cover sections have a cross section of 11m wide x 6.5m high. Ventilation in the operating highway will be provided by a Saccardo system.

In addition to the difficult geological conditions, the bored alignments run under several historic and high-rise buildings, requiring careful operation of the TBM. During excavation, surface monitoring will be undertaken with feedback provided to ensure appropriate operating parameters and mitigation measures. n

References •

Hard rock TBM for Mumbai water transfer – TunnelTalk, December 2019

ASIA

Fig 1. Underground highway route between Naruman Point and Bandra Worli (left); The TBM arrived in Mumbai in April 2020 and will operate 25m below ground level at Girguam and 75m below ground at Malabar Hill

Metro excavation to roll on in Kuala Lumpur

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s all excavation for the 13.5km central underground section of the 52km Putrajaya Line 2 of the KVMRT, Klang Valley Mass Rapid Transit, in Kuala Lumpur came to an end, the Government of Malaysia announced approval to proceed with the MRT Circle Line 3. Suspended by the previous Pakatan Harapan administration, the new Malaysian Government of Prime Minister Mahiaddin Yasin included Line 3 in its 2021 capital investment budget.

The Circle Line at about 40km with about Scope of the Klang Valley MRT and its underground sections

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half aligned underground, will integrate Lines 1 and 2 and other public transit rail services in Klang Valley. Line 3 has an early estimate of US$11 billion. At the end of 2018, the MMCGamuda JV, which completed construction of Line 1 and is currently completing construction of Line 2, submitted a proposal to construct Line 3 in phases, the first phase costing about $5 billion.

Line 1, with seven open-cut underground stations and 9.5km of twin running tunnels opened for service in July 2017. The 52km Putrajaya Line 2 is progressing towards phased opening of the 17.5km elevated alignment first. Phase 2, which includes 10 underground stations and 11.5km of twin tube running tunnels, is scheduled to open in January 2023. The twin running tunnels were completed between March 2018 and November 2020 using 12 TBMs on 16 drives. MMC-Gamuda completed the total 23km running tunnels in 31 months.

Eight of the machines used oh Phase 2 are Herrenknecht variable density TBMs, developed specifically to work through the unpredictable karstic limestone of the Kuala Lumpur region. The TBMs are designed to convert efficiently between EPB and slurry mode and to vary the density of the bentonite slurry to prevent loss through the porous and karstic geology. The other four machines are EPBMs working through the more predictable deposits of the Kenny Hill formation.

TunnelTalk reporting

On the Putrajaya Line, the Gamuda TBM tunnelling team also developed and deployed an autonomous TBM operating system that provided automatic management of excavation variables in faster reaction times than possible by human TBM operators. The systems improved overall productivity, safety and quality of tunnel construction.

With Line 3 now in planning, discussions include the preferred delivery model. Repeat of the project delivery partner model (PDP) as used for the Line 1 is suggested as expediting construction work and ensuring a timely completion. A turnkey model, as applied under a restructure of the Line 2 contract in late 2018 to reduce cost, is another option. The Gamuda and MMC partnership, that has worked on both Line 1 and Line 2, has the advantage of continuity for moving seamlessly to construction of Line 3. It has an established expertise in the construction teams, the continuing operation of the Tunnelling Academy to train workers for the underground works, and extensive inventories of necessary equipment, including TBMs and segmental lining facilities. n

References • •

KVMRT to repeat Line 1 success for Line 2 – TunnelTalk, April 2016 Metro TBM excavation for Line 3 Kuala Lumpur complete – TunnelTalk, March 2018

www.TunnelTalk.com

Underground river at the bottom of the karst cave

Giant karst cave encounter in China Qing Weichen, Senior Engineer, China Railway Eryuan Engineering Group

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www.TunnelTalk.com

adopting a traditional solution of a scaffolding platform to protect the cave roof, and to build the railway structure inside, would be difficult and dangerous. For this reason, the solution was to completely backfill the cave with recycled drill+blast excavation spoil.

In response to the structural problem of creating a high-speed railway crossing in a giant karst cave, the solution was to construct a tunnel through the backfill body and then erect a large-span bridge inside the tunnel (Figs 2 and 3). High-pressure grouting was used to stabilize the backfill and surrounding rock and support excavation of the 432m2 super-large tunnel section in five top-down benches. To compensate for the potential of uneven settlement and deformation in the foundation, the design imitated the spine of an animal, dividing the tunnel structure into 5m long segments set with deformation joints between adjacent segments.

The large-span bridge inside the tunnel was built in a 38m+108m+38m three-span continuous beam as the bearing structure to meet the limits of high-speed rail track deformation of not greater than 15mm.

An automatic monitoring system was installed and a compensation grouting system was established to control any differential settlement of the foundation.

To meet the project deadline, a series of fast construction measures were developed.

First, five adits were excavated on the vertical and at 20m between them, to complete the huge 1.08 million m3 backfill quantity of the 120m high void (Fig 4). The backfill was divided into five layers and completed layer by layer from the bottom-up, taking eight months to complete.

A special side-wall formwork was created to cast side wall concrete, and a Bailey beam truss trolley was developed to cast the arch lining and bridge structure in the tunnel. This parallel construction saved three months on the construction period.

Fig 1. Karst cave and river system To protect the environment, a threedimensional groundwater drainage system was built to maintain the original groundwater system. Before backfilling, a 450m length of the underground river was redirected to the outside edges of the cave. A layer of large rocks was placed in a 3m area around the outer walls of the cave at 20m above the original underground river level to create a three-dimensional seepage layer to channel fissure water around and back into the underground river system.

Since the opening of the new line in late 2019, the structure across the giant karst cave has performed successfully.

The measured maximum settlement of the bridging tunnel at its invert is 7mm, which meets the high-speed rail structural safety requirements, and the water volume of the downstream underground river is stable, meeting the production and domestic water demands of the local villages and the hydropower plant.

In the 2020 series of the ITA Tunnelling and Underground Space Awards, the Yujingshan Mountain crossing of the giant karst cave and the management treatment of the underground river as designed by the China Railway Eryuan Engineering Group and built by the No 5 Engineering Group Co, was the winner of the Overcoming the Challenge category. n

ASIA

assage through the Yujingshan Mountain in the middle of the Chengdu-Guiyang high-speed railway in Yunnan Province required a 6.3km tunnel heading into one of the most intensive karst development regions in China. The region is also the home of the Miao and Yi ethnic minorities and is a sensitive ecological environment in which heavy construction work is difficult.

With a design speed of 250km/hr, the railway will connect the city of Chengdu, the capital of Sichuan Province, and Guiyang, the capital of Guizhou Province, and cut current rail travel time from 14 to three hours.

In July 2016, at about 2km from the portal and 60m below ground, a giant karst cave of 95m long x 230m wide x 50m-120m high was discovered (Fig 1). The deposits at the bottom of the cave are 30m-90m thick, with a scree slope of 30-40 degrees. At the lower side of the slope emerges a large underground river of 5m-15m wide that runs for 18km and has a flow of 70m3/sec in the rainy season.

The solution to continue through such a giant and complicated karst cave was to suspend a bridge structure near the roof of the cave, with a distance of 40m from the cave bottom and running 110m perpendicular to the water surface of the underground river. The conditions presented four major construction challenges.

The first was construction safety.

Tensile joints and fissures in the rock mass provided for poor stability around the tunnel, with frequent rock falls from the cave roof, some with a maximum diameter of 15m.

These directly threatened the safety of the construction workers and equipment.

The second challenge was selecting a reliable structure to meet the strict track settlement control requirements of a highspeed railway. The tunnel is 40m above the bottom of the karst cave and has an overhanging length of 90m.

Thirdly, the engineering is extremely difficult and would take time. With just three years remaining before the programmed opening of the railway, how to work out a solution as soon as possible and execute it efficiently to ensure the timely opening of the line was the challenge.

Environment protection was the fourth challenge. Water resources in the project location are scarce. The underground river in the cave is the main water source for downstream villages and the only water source for a downstream hydropower station.

All the stakeholders formed a team to solve the construction challenges through scientific and technological research and comparisons of different solutions.

With a clear height of 120m, and the unstable deposits at the bottom of the cave,

References •

Karst cavern encountered on TBM drive in France – TunnelTalk, March 2018

Fig 2 and 3. A bridge structure within a tunnel in complete backfill of the giant void carries the railway across the karst cave; Fig 4. Five adits were created to complete the bottom-up backfilling of the cave

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Breakthrough after tough drive in China

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n January 2020, a Robbins 5.97m diameter main beam TBM cleared its final hurdle when it broke through in Guangxi Province, China. The TBM had completed the first of two tunnels, an 11.9km long conduit for Lot1 of the North Line Water Irrigation Project.

The TBM encountered challenges from karst cavities to fault zones and water inflows. Workers on project for contractor Guangdong No 2 Hydropower Bureau, and the owner, Construction Management Bureau for the Letan Water Reservoir, had much to celebrate after completion of what Breakthrough celebrations

is regarded as the most complex and longest drive on the North Line project. Boring with the Robbins main beam TBM and supported by a continuous conveyor muck haulage system began in Summer 2015.

“There was no precedent in this Province for using a main beam TBM to excavate tunnels longer than 10km,” said Yongjiu Jin, Deputy Manager of contractor Guangdong.

“We did not have relevant local experience to use for reference.” Despite a number of difficult geological obstacles in the limestone rock, the TBM was still able to achieve advance rates of up to 40m/day in good ground.

Much of the geology consisted of lightly weathered limestone in rock Classes II to III. Sections in Classes IV to V required the heaviest amount of ground support, ranging from rock bolts to ring beams and mesh.

“Robbins personnel provided valued technical support, from equipment installation and commissioning to tunnel completion, and were on-hand throughout the project offering on

Desiree Willis, Robbins site assistance,” Yongjiu added.

While the completion of the first tunnel, thought to be the longest single-heading construction on record for water tunnels in Guangxi, is a milestone, there is more to do. The Robbins machine will be inspected and relaunched to bore a second 4.2km drive. The ground conditions are predicted to be equally challenging, but the tunneling operation will be guided by ground prediction methodology.

Tunnel reflection tomography (TRT), consisting of ground prediction using seismic waves, is being used to detect changing conditions ahead of the TBM. The method can predict the distribution and scale of joints and fissures, enabling the crew to plan ahead.

Located near Laibin City, the North Line project provides much needed drought relief through a network totaling 29.4km. n

References •

Recording setting TBMs on Yellow River drive - TunnelTalk, January 2001

ASIA

Mega slurry TBM ready for Shanghai river crossing

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15m mega slurry TBM manufactured

by CRCHI of China is ready for construction of the twin tube Genshan East Road highway crossing under the Qiantang River in the city of Hangzhou near Shanghai. The TBM will excavate 3km of the total 4.7km long project that includes about 2.3km at up to 44m beneath the river bed and a further 4.6km in tunnel for surface road connections either side. The twin tube tunnel will have three lanes in each tube and be designed for 80km/hr traffic speeds.

The project is to be built by the China Railway 14th Bureau. As is common practice for mega TBM projects in China, a different manufacturer will supply a TBM of similar dimension for the parallel TBM drive. The project is a total investment value of CYN 4.6 billion (about USD$675 million).

The 15m diameter mega CRCHI TBM has an installed power of about 9,755kW, a rated torque of 42,784 Nm, and the Double mechanical erectors on one traveller for installing segments and precast box culvert elements

maximum excavation speed of 50mm/min.

The twin TBM drives are mainly through soft soils, including silty soil, mucky soil and cohesive soil. Construction difficulties will include: • Maintaining stability of the mega 15m diameter face; • Advancing through soft soil where poor bearing capacity and poor permeability will cause the TBM to sink, and the segments to float; • Operating a large capacity slurry treatment plant; • High reliability for TBM seals including the main bearing and main drive seals and tailskin seals; • High wear resistance for the cutterhead, cutters, and slurry pipelines; and • Constant monitoring of harmful gases which will require a high-powered ventilation system on the TBM. The machine has been designed by

CRCHI News Release the CRCHI research and development department to have: • A soft soil cutterhead to feature cutter changes in free air; • Frequency conversion motors for the main drive; and • A retractable cutterhead.

The rubber seals of the cutterhead main bearing will be automatically pressurized with a high precision gas system. The pressure on the rubber lip seals can be automatically set to balance the slurry pressure in the excavation chamber so as to protect them from collapse due to high pressure in the excavation chamber. The high precision balance control ensures seal performance and reliability of the main drive seal and results in more precise control of the pressure in the excavation chamber to support the ground and avoid collapse of the tunnel face.

It is also fitted with two erectors to allow simultaneous installation of the invert box culvert precast element while erecting the segments of the segmental lining rings.

The two erectors use the same traveler with the segment erector at the front and the box culvert erector at the back. Both are mechanical erectors with the segment erector lifting and installing the 10 segments/ring with seven standard segments, two neighbouring segments and a key in each ring.

The double erector will eliminate a second pass to install the box culvert after excavation of the drive and will save time on the drive programme. Breakthrough at the end of the 3.2km long drive is expected in March 2022. n

References •

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Tracking the world’s mega-TBMs – TunnelTalk, Discussion Forum

www.TunnelTalk.com

Shanghai completes complex highway drive

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inal breakthrough of the bored STEC, Shanghai Tunnel Beiheng Expressway drive in Engineering Co Shanghai marked the conclusion of more than three years of work. The parameters were adjusted as necessary Beiheng Expressway is one of the three ahead of excavating and building the main east-west highways of Shanghai, next ring. These procedures proved with a total length of 19.1km and a successful with a ground loss rate of combination of at grade, underground only 2%. and elevated sections.

Even more challenging was the Lot II of the project, owned by the TBM crossing under operating metro SMI Road Group, designed by the lines with 6.6m diameter double tracks.

Shanghai Municipal Engineering Design Minimum clearance under the Line 11 Institute and the Shanghai Tunnel transit tunnel was 7.06m. It was the Engineering & Rail Transit Design and Compact TBM for navigating tight S curves on 15m o.d. double desk highway drive first time that a 15m diameter TBM has Research Institute, and constructed by crossed under a metro line.

STEC, the Shanghai Tunnel Engineering front shield, middle shield and tail shield It was decided that the speed of the Co, is the most important and difficult part gradually decreased by 3cm respectively. of the Beiheng Expressway project. With In addition, four over cutters were included trains would be limited and the TBM would a full length of 7.8km, all underground, the on the cutterhead design to overcut progress without any stops. After 70 hours, main element of Lot II is the bored tunnel the ground on the inner side of each the TBM completed the 44m distance with consisting of two drives of 2.76km and curve. The machine was equipped with a a progress rate of 7 rings/day. Deformation 3.66km long either side of an intermediate 10-point annular grouting system to ensure of the metro tunnel was under the specified level of maximum allowed settlement of access and ventilation shaft. adequate simultaneous segmental lining 20mm, and the operation of rail transit was The bored tunnel was designed as a 15m back grouting. not influenced. o.d. and 13.7m i.d. double-deck six-lane Two types of universal segmental lining The TBM also succeeded in passing highway. A new 15.56m diameter Mixshield were designed: one with a taper of 4cm, for under Metro Line 7. At this point and after TBM, the largest of its kind ever used in straight sections of the alignments and where Shanghai, was procured from Herrenknecht the curve radius was more than 1,000m, and advancing 4.8km of the total 6.42km long for the project. The whole tunnel alignment the other of 8cm erected in sections where drive, the TBM suffered serious wear of the tailskin, which made this under passing more runs along a densely residential and the radius curve was less than 600m. risky. The TBM finished this underpass in commercial corridor and the route passes a During excavation, horizontal large number of structures which made the displacement of the 2m wide segment 71 hours, crossing a distance of 38m and limiting deformation of the Line 7 metro project incredibly challenging. rings was monitored continuously. From the Additional challenges included the monitored data, the attitude and tendency tunnel to 8mm.

The whole process of the Beiheng curved alignment that presented several of the oncoming rings was predicted. tight S curves of as little as 500m radius This was then used to select the curve Expressway construction was based on and the highly sensitive environmental shape and calculate advancing quantities. full lifecycle construction management. conditions. On its drive the 15.56m In the first sharp curved section, with a The project was the first in Shanghai diameter x 120m long x 3,000 tonne TBM turning radius of 500m, the TBM made a to use fair-faced concrete in its interior passed under 89 buildings and structures, successful S curve turn within 13 days at structure. The technique is based on including three live metro lines, four flood an advance rate of 5.9 rings or 11.8m/day single castings, without any additional finishing, and using the natural surface of retaining walls of the Suzhou River, and a working 24 hours a day. number of urban utilities.

Along the alignment, 30 buildings were the in-situ cast concrete as the final finish.

Some 80% of the alignment is curved under passed and 59 were side passed. It is a breakthrough for the design of interior and 50% of this is through curves of 500m Among these were the nearly 100-year- structures and construction technology of to 600m radius. Attention was needed to old Zhaofeng Villa buildings. While passing long, large diameter tunnels in China. During avoid staggered segmental lining rings, under the old buildings, the TBM was while the project, efforts to lower noise, vibration tailskin wear by the segments, failure of the negotiating a 500m radius sharp curve under and dust emission were also adopted. n tail seal due to uneven tail skin clearance, and shallow cover and in unfavourable ground. the scraping of the inner lining by the TBM During the passing, every ring erected was References • Mega-TBMs for China double-deck link – backup gantries. monitored by an independent company to TunnelTalk, May 2014 During TBM selection, the first concern check the settlement of buildings and of the • Tracking the world’s mega-TBMs – was whether the front sections of the TBM ground within the area of influence, and the TunnelTalk, March 2019 shield should be articulated. Ultimately, a fixed tailskin structure was chosen. The shield design was governed by the load Video: A complex railway station under parts of the Great Wall of China case of 36m overburden plus additional are part of preparations to host the 2022 Winter Olympic Games in Beijing six-storey building overload. The radial shield deformation at the articulation section would be more than 10cm, and no strengthening measures could be taken because of the articulation design. Leakage of the articulation seal would therefore be inevitable. After evaluation of three different shield design concepts STEC and Herrenknecht concluded that a shield with a fixed tailskin was the safest solution.

The TBM shield and the gantries were designed to be compact and conical to increase the flexibility of the TBM and decrease the friction between the TBM and the ground. For the 15.56m diameter machine, the diameters of the

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