TunnelTalk Special Edition: Denmark Focus and Case Studies

Direct by Design

SPECIAL EDITION

FOCUS: DENMARK CASE STUDIES

SILVERTOWN TUNNEL, UNITED KINGDOM

BIG LIFT IN LONDON UK’s largest TBM is a Herrenknecht EPB Shield (Ø 11,870mm) that will bore two 1,120m road tunnels under the Thames through alluvium, London clay and Lambeth Group. The new twin-tube Silvertown Tunnel will help reduce chronic congestion at the Blackwall Tunnel and improve transport links, especially for cross-river bus journeys.

Together with three leading international construction companies Herrenknecht is pleased to support yet another project in London. herrenknecht.com/silvertown

Client: Transport for London Contractor: Riverlinx CJV (BAM Nuttall, Ferrovial Construction, SK Ecoplant)

TUNNELTALK SPECIAL EDITION DENMARK FOCUS AND CASE STUDIES FROM THE EDITOR’S DESK

Denmark a young but committed tunnelling nation

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enmark’s history of underground excavation is relatively young, but that history is daring and dedicated.

From the early days of the Copenhagen Metro, the capital city of Denmark has built in 25 years a network of 44 stations across four lines with 25 of these underground and connected with a total of some 32km of twin-tube TBM running tunnels.

In addition to the underground works, the Copenhagen Metro was one of the earliest to adopt driverless trains and to build a circle line as a foundation of the network.

The interconnectivity of Denmark with the European mainland and fellow European Union neighbours started with the legendary Storebælt TBM undersea fixed rail link in the 1990s. After surviving several construction and contractual difficulties, it is on the shoulders of the Storebælt project that more recent deep undersea TBM fixed links have been developed. Storebælt also provides a research study for the proposed Helsinki-Tallinn TBM bored subsea link in the same region between European Union nations Finland and Estonia.

On the Danish Faroe Islands in the North Atlantic, drill+blast technology is creating links of advanced engineering and construction to connect the islands of the archipelago. Taking a lead from the deep links under the fjords in neighbouring Norway, the headings are up to 189m below the seabed and include the world’s first undersea traffic roundabout.

For its current mega project, Denmark is drawing on its earlier Øresund fixed link with Sweden. Comprising a 2km long immersed tube from Copenhagen to a man-made island, the link transitions onto the 9.5km long bridge to the Swedish landfall at Malmö. In spearheading the road and rail fixed link with Germany across the Fehmarnbelt, Denmark has made significant progress on building the 18km long immersed tube project - the immersed tube winning out over an initial bridge option and consideration of a bored tunnel alternative across the strait.

CONTENTS 5 DENMARK LINK IN EUROPEAN CONNECTIVITY 9 UNDERGROUND ENGINEERING

CENTRAL TO COPENHAGEN METRO

Cityringen approved for construction First of four Seli EPBMs ready for Cityringen All TBM excavation complete for Cityringen 17 LINKING DENMARK WITH GERMANY

ACROSS THE FERMARNBELT

Tunnel beats bridge for Fehmarn fixed link TBM bored option rejected for Fehmarnbelt Road to political approval for Fehmarn sea link The road to start of construction

Direct by Design

Into the near future, the Danish Parliament has agreed an infrastructure plan to 2035 that includes €14.2 billion in new transport projects, eight of these comprising underground engineering projects. These include: • The 2km long Marselis Boulevard road tunnel at a cost of €365 million to provide a direct link between the E45 highway and the Aarhus harbour, the largest container port in Denmark; • A third Limfjord crossing estimated at €940 million and with the 20km long four lane highway including a 600m long immersed tunnel under the fjord; • A 1.4 km long extension of the Nordhavn road tunnel to improve access to Nordhavn and Lynetteholm in Copenhagen.

As part of developing its tunnelling experience, Denmark created the national Dansk Forening DFTU Tunnel & Underground Construction Society 1983 and in the same year became a Member Nation of the ITA (International Tunnelling and Underground Space Association). In 2013, Søren Degn Eskesen of Denmark was elected as the 14th President of the ITA to 2016. In 2022, Denmark hosted the 48th General Assembly of the ITA and the World Tunnel Congress in Copenhagen.

With a wealth of all types of tunnelling in the forecast and a short but intense history as a foundation, the industry of underground and undersea civil engineering in Denmark is secured. n

Shani Wallis, Executive Editor

27 STOREBÆLT CHALLENGES Screw conveyors take the pressure Storebælt calls on Project Moses for support Storebælt - the final chapters Chronology of the Storebælt TBM drives 42 DENMARK-SWEDEN ØRESUND FIXED LINK 43 RENEWED MOMENTUM FOR

HELSINKI-TALLINN FIXED LINK

Chinese onboard for TBM-bored Helsinki-Tallinn link Political considerations of the Helsinki-Tallinn plan 48 TUNNELLING ON THE FAROE ISLANDS Design of subsea road links Veteran TBM continues hydro works Copyright© TunnelTalk 2022. 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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318-17 adv. A4 civiele techniek_engels.indd 1

26-01-12 09:21

Denmark link in

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European connectivity

xpanding land-based transportation networks across the globe is driving the most marked increase in the demand for underground, undersea and tunnel engineering in history. Record breaking megaTBM drives, outstanding drill+blast excavations, and immersed tubes of extraordinary dimension are creating links between nations, across continents and under dividing straits, advancing a new era of global road and railway expansion.

route between Austria and Italy and the Lyon-Turin link between France and Italy.

In aspirations to physically link Scandinavia with the Mediterranean, as the longest of the nine core corridors of EU connectivity (Fig 1), Denmark holds a vital key. Its peninsular and archipelago provides the stepping-stones for the fixed link landfalls. Taking up its responsibility

Europe and the members of the European Union is leading the global surge for transportation interconnectivity, starting in the 1970s with advance of long road and rail links through the Alps and under the fjords in Norway to replace unreliable and expensive ferry services and into the 1990s with opening of the undersea Channel Tunnel link between France and the UK. Baseline mountain rail routes have since been developed in Switzerland and Spain and work continues now on the Brenner Baseline Fig 1. Core network corridors for transportation connectivity across the European continent with detail of the longest ScandinaviaMediterranean Corridor and details of the links via Denmark

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in this regard, Denmark has committed over the years capital, resources, and engineering endeavour to studying and creating the sea links, starting with the Storebælt road-rail bridge-tunnel fixed link between its mainland of Funen and the island of Jutland in the 1990s (page 27) and following on with the international roadrail, immersed tube-bridge fixed link across the Øresund Strait to Sweden (page 42).

Today it again steps up to the requirement and is taking the lion’s share responsibility for creating the international fixed link road-rail immersed tube sea connection with Germany (page 17), securing the funding for the budgeted DKK7.4 billion project (about €7 billion and US$8.2 billion) and creating the legal, political and management organisations to oversee its realisation.

The 19km long immersed tube will replace the ferry crossing bottleneck and support other sea crossings in the Baltic region including the proposed Helsinki-Tallin fixed link between Finland and Estonia (page 43) and a studied project for a metro rail link to connect the city centres of Copenhagen and Malmö in Sweden under the Øresund Strait (page 42). Such a project is supported by the metro network it has invested in over the past three decades for Copenhagen (page 9) and the experience it has gained through its design and construction of undersea infrastructure.

Not to be forgotten, the Faroe Islands of Denmark out in the North Atlantic, is also actively developing undersea infrastructure to link the islands and further develop its economic future (page 48).

Denmark contribution to the international tunnelling and underground space community

Although Denmark has a relatively young history in underground space and tunnelling, it took up the field of engineering and construction expertise with commitment.

Its operating and client organisations including the Government’s Ministry of Transportation, its Parliament and its state owners of public infrastructure, bought in the early expertise needed and support their domestic engineering and construction firms to develop their own expertise and experience.

While British firm Arup owes its foundation to Sir Ove Arup and his Danish heritage, leading civil engineering, construction and supply firms of Denmark today include Ramboll; Aarsleff; MT Højgaard founded in 2001 when construction companies Højgaard & Schultz and Monberg & Thorsen merged; Christiansen & Essenbæk; NOVENCO; Skamol Group and several others. Perhaps most notably in the underground engineering industry is COWI, a company founded in 1930 and today an international engineering firm of more than 7,300. Its major industry development came in the 1990s, when the firm was engaged to be responsible for the overall design coordination of the Copenhagen Metro. This work included the supervision of works on tunnels, stations, emergency shafts, and the mitigation procedure against potential damage to neighbouring buildings.

In the early 2000s, COWI strengthened its international presence and engineering base with acquisition of Jenny Engineering in the USA in 2013, Donaldson Associates in the UK in 2014, and the tunnelling assets of the ILF engineering firm in the USA in 2018, as well as opening offices in other parts of the world. Through its acquisitions and operations the company tendered for and became engaged in major civil engineering projects outside of Denmark while maintaining its leading position at home.

In developing its portfolio of tunnelling experience, Denmark has become a leading country in the field of underground infrastructure design and construction. In 1983 it created its national Dansk Forening DFTU Tunnel & Underground Construction Society and in the same year became a Member Nation of the International Tunnelling and Underground Space Association (ITA-AITES).

Denmark took its commitment to the ITA seriously and with dedication. It attended all the General Assemblies of the Association, no matter when in the world hosted, and assigned leading engineers to participate actively and reliably in the Working Groups of the Association.

In 2017, DFTU sponsored Søren Degn Eskesen, an engineer with COWI, as a candidate for the Executive Council of the Association. Eskesen was duly elected by a majority of the Member Nations at the General

Left: Søren Degn Eskesen, ITA President 2013-2016; Below: Denmark established the Dansk Forening DFTU Tunnel & Underground Construction Society in 1983 and became a Member Nation of the International Tunnelling and Underground Space Association in the same year

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Assembly and in 2010, Eskesen was again supported

by DFTU and was elected to the position of Vice President. In 2013, at the General Assembly hosted in Geneva, Switzerland, he was elected in a two-candidate vote, as the 14th President of the ITA for the three-year presidency to 2016.

Organized by the

Greek Tunnelling Society (GTS)

Through his tenure, President Eskesen encouraged delegates at WTCs (World Tunnel Congresses) to join the Association, either as individual or corporate members, and to become more actively involved in the operation and activities of the Association. In making it clear that the strategy for his presidency was to strengthen the Association, he oversaw the introduction of the ITA Young Members group for tunnelling professionals of 35 years and younger and introduced an initiative to examine the Association’s compliance with the Code of Ethics & Conduct as a registered member of the World Association of Non-Governmental Organizations. He also encouraged more active involvement of Member Nations in determining the direction of the ITA and its activities.

A further indication of the standing of Denmark in the international community was the selection of Denmark at the 2018 ITA General Assembly in Dubai, UAE, to host the World Tunnel Congress and 48th ITA General Assembly in 2021. Due to travel restrictions imposed by control of the Covid pandemic, the event staged at the Bella Convention Centre in Copenhagen was cancelled in 2021 and rescheduled to September 2022.

With a wealth of all types of tunnelling in the forecast, and through the work of its leading companies and via its association with the ITA, the international standing of Denmark in the industry of underground and undersea civil engineering is secure. n

TunnelTalk references •

European connectivity masterplans - April 2015

•

Brenner Base Tunnel – let the works begin! - April 2011

•

+60km of tunnelling completed for Iceland’s Kárahnjúkar power station - April 2008

•

Battling geothermal challenges in Iceland November 2014

•

Iceland advances coastal road links - May 2013

•

Jenny Engineering acquired by COWI - February 2013

•

COWI acquires Donaldson Associates of the UK October 2014

•

COWI purchases select ILF US tunnelling assets May 2018

•

ITA sets growth and development strategy at the first General Assembly for President Eskesen of Denmark - June 2014

•

Steep curve ahead to keep ITA relevant - May 2016

External links •

ITA – International Tunnelling and Underground Space Association

•

DFTU - Danish Society for Tunnels & Underground Works

•

2022 WTC World Tunnel Congress September 2022 Copenhagen, Denmark

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

Underground engineering central to Copenhagen Metro

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rom planning of the first line of the metro system for Copenhagen in the 1990s, underground engineering has been integral to the network. Of the current 44 stations across four lines, 25 are underground, and connected with 32km of twin-tube TBM running tunnels.

Development of the metro adopted advanced operating criteria. It is based on a driverless electric-powered light rail train system, picking up power from a third rail. It operates 24hr/day, 7days/ week with headways varying from two to four minutes and up to 24 minutes at nights. The trains run in both directions in one tube at nights to free up the parallel tube for maintenance operations. The trains are controlled by a fully automated computer system managed at two control and maintenance depots located south of Vestamager Station for Lines 1 and 2 and at Sydhavnen for Lines 3 and 4.

special in-tunnel safety and emergency purposes. A ride on the metro at the panoramic window at the front of the first car provides a perfect view of the civil engineering design of the running tunnels and junctions into the stations.

When the underground extension of Line 4 to Sudhaven opens in 2024, the Metro will be a 44-station network with 32km and 25 stations aligned underground

In concept, the underground stations have centre island platforms that are protected by platform edge doors and the underground spaces are open to the surface to allow natural day light to platform level. In the running tunnels there is a continuous sidewall walkway linking regular emergency cross passages and a lighting system that stays on at all times for 9

The panoramic window at the front of the driverless trains provide great viewing of the line ahead (right)

Planning for the start of the Metro system began in 1992 with the signing of two procurement contracts for the central 20.4km route of Lines 1 and 2. The two lines share the same underground infrastructure beneath the heart of the city and branch at an underground junction to underground stations on each before rising to the surface and elevated structures for later construction of extensions under new contracts to Vanløse to the west and Copenhagen Airport in the southeast.

Comet, a construction consortium comprising Astaldi (Italy), Bachy (France), SAE (France), Ilbau (Austria), NCC Rasmussen & Schiøtz Anlæg (Sweden) and Tarmac Construction (UK), was engaged for the civil works of the initial metro phase. Italian Ansaldo STS was awarded the M&E installations and rolling stock supply and a contract to manage the system for the first five years of its operation. The Comet consortium excavated 14.3km of twin tube underground alignment using two NFM TBMs from France together, with lengths of shorter NATM excavation for chambers and cross passages, and cut-and-cover for the nine underground stations. Construction started in October 1996 and

CASE STUDY: 2012-2018

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The parallel running tunnels run through stable limestone at about 30m depth. There are emergency cross passages every 600m so that no train is ever further than 300m from an exit. The outer diameter of 5.5m is lined to an inner diameter of 4.9m.

In 2003 and 2007, the extensions of Lines 1 and 2 to Vanløse on the west and southeast to Copenhagen Airport opened, adding six and five stations respectively to the network.

In 2008 work started on the Cityringen circle line, a route that runs entirely underground, has 17 stations and connections with Lines 1 and 2 at two interconnecting stations. Construction of is based largely on the same design and engineering parameters as the underground works of Lines 1 and 2 and the line opened successfully in 2019.

Copenhagen approves

onstruction of the entirely underground Cityringen circle line for the Copenhagen Metro moved ahead in December 2010 with award of a €1.7 million civil works contract to the Italian joint venture of Selini Construction with Tecnimont and Seli.

Divided into North and South excavation packages, the project included 15.5km of twin tube running tunnels; 17 box stations each a standard 62m long; five shafts; emergency cross passages and four crossovers, one of them in a cavern under the lake at Sortedams Sø to facilitate construction of the future Line 4 Nordhavn extension. Station design is for compatibility with the short three-car train system that operates on existing Lines 1 and 2, and have a relatively compact footprint of 20m wide x 60m long.

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while a dispute resolution process was required to resolve claims by the construction consortium for extra time and additional payments, the two lines were successfully completed and began public operation in October 2002.

Metroselskabet, the Danish client that commenced development work on Cityringen in 2006, also engaged a JV of civil engineering firms COWI, Arup and Systra to assist planning and preliminary civil works design. A separate contract for the trains and control system is awarded to Ansaldo, which already operates the existing parts of the Copenhagen Metro. During the development process the client was also re-constituted from the original owner, Ørestad Development Corporation, which has a wider infrastructure brief to the more metro focused Cityringen organisation.

Bids for the tunnel and station construction works were submitted in May 2010 with separate bids for the North and South tunnel and station works packages. Offers for all works combined were also welcomed. The North and South Contracts were divided at the Aksel Møllers

Junction for bifurcation of Cityringen to Line 4 extension to Nordhavn

Cityringen is followed closely by Line 4 which shares six stations and the twin tube alignment with the Cityringen and branches off for a 2.5km extension to Nordhaven with about 2km of twin tube running tunnels and an underground station at Nordhavn and an elevated station at Orientkaj. This extension was awarded to the Hochtief/Züblin JV in May 2014 for a contract price of €310 million. The JV used two Herrenknecht EPBMs to complete the twin drives. The project included construction of pedestrian tunnel to connect passengers conveniently to the urban S-trains at Nordhavn Station.

The extension opened in March 2020.

In early 2015, the Danish Parliament approved construction of the 4.5km Line 4 extension south to Sudhavn that runs entirely underground in twin tube running tunnels connecting five new cut-and-cover underground stations.

Construction was awarded to the Vinci-Hochtief joint venture under a €460 million design-build contract in February 2018. The JV used two CREG EPBMs to excavate 5.5m o.d. (4.9m i.d.) segmentally lined drives, completing both 4.5km long drives in late April and early May 2021 respectively. Excavation was completed in drives from

the central working site at Enghave Brygge, first south to Ny Ellebjerg and then north to Havneholmen. Work is currently in the M&E installation and rolling stock testing phases before scheduled opening in early 2024.

Designs on the future

While there have been several discussions and studies into new additions to the Metro network only one, a surface only 28km long light rail line, is in construction since 2019.

Others are yet to be adopted by the stakeholders of the operating organisations. One of the more exciting of plans is a proposal by the cities of Copenhagen and neighbouring Malmö in Sweden for a metro line under the Øresund Strait to provide additional capacity and faster connections than the exsiting Øresund tunnel/bridge road and rail fixed link (page 42). Supported by the European Union Regional Development Fund, ideas are based on a 22km long shuttle type service between two stations or a system integrated with transport networks on each side. The ideas envisage a travel time of 15-20 minutes between the two city centres.

Studies predict a construction period of six-and-a-half to seven years and at a cost of approximately DKK30 billion (about €4 billion) including a 50% risk contingency.

Cityringen metro line Have Station on the west and the Øster Søgade shaft on the east.

Two rival JVs tendered for the civil works before the SaliniTechnimont-Seli JV was selected. The rival groups were: MT Høgaard with Hochtief, Ed Züblin and E Pihl & Son, and Alpine Bau with FCC Construccion. Earlier in 2010, a prequalified JV of Bilgfinger Berger, Per Aarself and Vinci pulled out of the competition. Prequalification and shortlisting took place in 2009 and bid documentation was issued in October 2009. In early planning, back in 2008, it was anticipated that contract award might be possible by mid-2010. Although the process is half a year late, the overall completion of the scheme is unchanged for 2018.

The city’s geology comprises glacial moraine on top of limestone. Sand beds are also a feature of the alignment,

especially in the northwest of the city. As the JV partner responsible for the running tunnels, Seli has selected to use four EPBMs to excavate the 17km twin tube circle line. Supplied at a cost of €40 million, the four EPBMs and their auxiliary equipment will ensure safe excavation of the tunnels through soft soils beneath the urban environments.

The construction budget for the project is DKK21.3 billion (about US3.79 billion) in 2010 prices. While noting that the building costs are about DKK3 billion higher than expected, this is offset by lower financing costs to keep the overall financing for Cityringen within the initial set limits.

In a statement, Henning Christophersen, Chairman of the Board of Metroselskabet, said: “The price of the 11

The first of the four machines, with its long trailing backup, was fully assembled with elements of the second machine collecting in the adjacent fabrication bay. The cutterhead of the first machine was turned and its foam injection system activated for a test demonstration for the owner representatives from Copenhagen, Seli factory workers and staff, and representatives of machine design partner, Kawasaki of Japan. Through the licensing agreement, Kawasaki has designed and supplied the drive unit and screw conveyor components to fit with the Seli cutterhead, shield and backup design and fabrication.

The machine will be dismantled and containerised for shipping to Copenhagen.

All four machines, worth approximately €7 million each, are programmed to be built, shipped and launched during 2013.

The first Cityringen EPB machines will excavate the 8,900m north drive in two sections; Section 1 at 3,800m is between the Norrebroparken shaft to Platanvej Station, and Section 2 at 5,100m between the Norrebroparken shaft and the Oster Sogade shaft (Fig 1). Excavation is scheduled to begin in September 2013, with Seli, as Fig 1. Copenhagen’s Metro network with the Cityringen circling the city centre part of the construction JV, headed by Salini construction has risen, but we are satisfied that we can Construttori, building the 32km of twin tunnels and 17 finance the budget ourselves through savings on interest underground stations. expenses, which means that our owners will not have to find new funding for the project. The overall financial In making presentations during the open day, Remo situation is thus unchanged.”

Grandori, President of the 60-year old family-established Seli company, said that working in collaboration with the Henrik Plougmann Olsen, Chief Executive of Japanese engineers was a productive trans-national Metroselskabet, said: “I am very pleased with the outcome experience. The Seli-Kawasaki license was signed three of the negotiations. We are succeeding in dealing with years ago in April 2010, and a fifth collaborative EPBM the tenderers’ reservations and in reducing the price by was built in China for Seli’s Indian partner Coastal for its around DKK4 billion. It was a constructive negotiation metro contract in Bangalore. process involving tenders of the highest quality.”

Grandori told TunnelTalk that the machines for In announcing its tunnelling plan, Seli Chairman Remo Copenhagen are more robust than normal. “Each one has Grandori said: “Seli has extensive experience in dealing to complete longer than usual drives for metro projects. with complex hydro-geological issues and managing The machines will complete up to 8km each working projects in urban areas.” The company has worked on from a limit of three working shafts and either driving metro projects in Vancouver, Turin, Rome, New York, through the station zones or being dismantled, lifted and Athens, Sao Paolo and Caracas, all projects in urban relaunched as necessary to meet a tight construction areas which were successfully completed by the programme. Two machines will start at the Nørrebro company. The new line in Copenhagen is due to be Parken site, two more at the Ottobusses Vej site, with opened in 2018. subsequent relocation of TBMs to the Østersogade site.

First of four Seli EPBMs ready for Copenhagen NOVEMBER 2012

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t an open day at the Aprilia factory about an hour south of Rome, Seli presented the first of four EPBMs it will use to excavate the Cityringen running tunnels. The four x 5.78m o.d. EPBMs will complete some 32km of twin tunnelling to link 17 underground stations and the depot of the circular metro line beneath the heart of the city’s ancient and medieval centre.

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The machines will work through complex geology under a high watertable, ranging from sound Copenhagen limestone with bands of flint, to till and glacial deposits of sand, gravel, silt and clay. The cutterheads are dressed with both discs and scrapers and the machines are tested to 9 bar working pressures to operate under the anticipated 4.5 bar pressures of the alignment as it runs between 7m and 42m deep. The 5.78m diameter machines have a maximum cutterhead thrust of 42,000kN, a cutterhead speed of 0-5 rev/min, a cutterhead drive power of 1,200kW, and are fitted with a vacuum segment erector.

Control of surface settlement and the protection of the historic urban fabric of the city centre is of the highest priority for the owner organisation Metroselskabet; the

Four EPBMs of Kawasaki/Seli design and manufactured by Seli at its factory south of Rome will excavate the Cityringen drives

owner’s design engineering JV of COWI, Arup, Systra; and CMT, the Italian Copenhagen Metro Team construction JV of Salini Construttori, Maire Tecnimont and Seli. “It is essential to maintain the ground water table,” explained Søren Degn Eskesen, Tunnel Design Engineer with COWI. “The alignment also passes above the existing Metro Lines 1 and 2 at Kongens Nytorv and under the famous Marmor Kirken in historic Copenhagen. The TBMs will be required to operate in full EPB mode at all times. The double articulation of the shields is required to negotiate tight radius curves on the alignment.”

“The key,” according to Grandori, “is effective conditioning of the material in the excavation chamber for controlled discharge through the screw conveyor and onto the transfer conveyor for haulage in muck trains of four, 20m3 skips.” During a tour of the machine and its operating cabin, Leonardo Pia, Technical Director of Production for Seli at Aprilia, explained that there are 10 foam or polymer conditioning agent injection points, eight into the excavation chamber and on the cutterhead, and another two into the screw conveyor. “Discharge through the screw conveyor is further controlled by the in-line discharge gate of the shorter rather than the longer screw conveyor with its external drive,” said Pia. “In addition, there are two belt weighers on the transfer conveyor, about five seconds travelling on the belt from the discharge gate, to provide rapid notification of any over excavation from the chamber.”

Safety elements include walkways along the backup to prevent anyone walking in the invert in the line

of the trains, and a shuttle conveyor to fill the muck skips of a stationary train, eliminating train shunting during skip filling.

The segments of the 300mm thick bolted and gasketed precast concrete segmental lining is being produced by the JV at a casting yard in Germany from where they will be transported by sea to Copenhagen.

Unlike the more usual method of tunnel infrastructure procurement, Seli, as a contractor and a TBM manufacturer, and as a member of the CMT construction JV, will operate the TBMs it has built for the project. “This was a main point of the JV’s prequalification proposal and its competitive bid against two other procurement finalists,” explained Guy Taylor, Civil Works Management Project Director for Metroselskabet. “Seli is one of few firms that undertakes both construction and TBM manufacture. It has designed and built these machines in collaboration with Kawasaki and now has to make them work. We wish the JV well in operating the machines without accident or incident.”

During his presentation at the open day, Yugo Nakagami, Director of the collaboration for Kawasaki said: “We are confident we have built TBMs of high reliability, durability and maintainability to manage and complete the tunnels in Copenhagen safely and within the programme.”

Claudio Lautizi, Director for JV lead partner Salini said that the TBM was built and ready on time and according to the contract. “The Seli team worked hard to meet the 13

Allé. Both machines had completed 3,398m since launch 17 months ago in August 2013 from the shaft at Nørrebroparken. The drives through Frederiksberg Allé to the shaft at Sønder Boulevard were completed in May and June 2015.

The eastern section of the alignment between Oster Søgade and Copenhagen Central will be the last to be completed.

In January 2015, a double breakthrough into Copenhagen Central Station marked the end of the first 1,360m drives for the second pair of four Kawasaki-Seli 5.78m EPBMs being used on the project by the Salini-ImpregiloMaire Tecnimont-Seli JV. Launched in July and August 2014, the two TBMs broke through the headwall at Copenhagen Central after launching from the Sønder Boulevard launch and reception shaft near the control and maintenance loop south of the main ring at Vasbygade (Fig 2). Both machines were then disassembled and transported to the launch shaft at Nørrebroparken in the north west of the city for their final clockwise 4.7km long drives to the shaft at Oster Søgade, and through the five stations in between.

All four machines procured for the project were manufactured at the Seli factory in Aprilla, Italy, under a license agreement that features a Kawasaki drive unit and screw conveyor Fig 2. Revised TBM plan of attack for the four TBMs advancing from fitted with a Seli cutterhead. They are designed three launch and reception shafts for the complex Copenhagen geology that deadline and it is an important day today to inaugurate sits under a high watertable and ranges from sound this first of the four project machines.”

Copenhagen limestone with bands of flint, to till and glacial deposits of sand, gravel, silt and clay. The Among the Seli management at the TBM inauguration cutterheads are dressed with both discs and scrapers day was Valerio Violo, Project Manager for Seli in and the machines are tested to 9 bar pressures.

Copenhagen, and Luca Giacomini, a Seli site manager Working pressures of up to 4.5 bar are anticipated as who has moved from his previous post as Site Manager the alignment runs between 7m and 42m deep. The for the Seli TBM drive for the Kishanganga hydro project 5.78m diameter machines have a maximum cutterhead high in the Himalayas in Kashmir to take up the Site thrust of 42,000kN, a cutterhead speed of 0-5 rev/min, Manager’s position for the EPBMs in Copenhagen. a cutterhead drive power of 1,200kW and are fitted with a vacuum segment erector.

In closing the ceremony, Grandori told TunnelTalk that “the target of the cooperation with Kawasaki is to develop Segments for the 1.4m wide rings of five segments and and manufacture a new line of EPB TBMs dedicated to a key, are manufactured by Mobil Baustoffe at a casting the most challenging projects in the technologically yard in neighbouring Germany. Segments are transported advanced markets with a special focus on Europe and to Copenhagen by cargo ship on a weekly schedule North America. We have the capacity to deliver seven and stored at a site in the north of the city, for onward machines from the factory here at Aprilia and another six transportation to the relevant TBM servicing shafts. or seven from the facility in China. Some 80% of the total TBM market annually is for EPB TBMs - that includes rock “We now have a very high level of confidence in the machines and slurry systems. As well as manufacturing machines and have achieved progress rates of up to 20 for our own contracts we can build machines for other rings or 28m/day, which are considerably better rates contractors. The TBM market will continue to grow than the average 10 rings/day of our programme,” said JV especially when other developing countries of the world Tunnel Manager, Simon Taylor. begin to drive demand.”

In the short term, the Seli team and works at Aprilia will be busy building the remaining three EPBMs for Copenhagen.

Breakthroughs in pairs

The first pair of TBMs holed through into Frederiksberg Allé Station, on the western side of the Cityringen alignment, in January and mid-March 2015. This followed nearly six months of arduous tunnelling along a tough 949m section between Frederiksberg and Frederiksberg 14

Not included in the current contract scope is excavation of the numerous pedestrian tunnels and escalators at the interchange stations at Frederiksberg and Kongens Nytorv and at the main rail stations at Copenhagen Central, Nørrebro and Østerport. “We are in the process of completing design and procuring this access tunnel work through a separate contractor,” explained Metroselskabet’s Cityringen Project Director, Guy Taylor. “This work requires interfacing with so many stakeholders and rail operators and we wanted to retain overall design control. A contractor is expected to be

appointed in time for delivery during the fitting out and M&E stages of the main Cityringen running tunnels.”

With Cityringen tunnelling in the east and south completed, more challenging mixed face geological conditions are expected to the north of the ring. Originally Cityringen was planned as two separate contracts, one for the more geologically challenging northern sections and a separate one for the easier southern drives. This might well have resulted in different machine selection for the northern alignment, said Taylor, but in the event letting the whole project as a single contract gave the winning contractor a greater degree of programme flexibility since drive sequence did not have to respect contract boundaries.

“During the bid evaluation it became clear that letting the contract as a single tunnelling package would make economic as well as logistical sense,” said Taylor.

All TBM excavation complete for Cityringen JANUARY 2017

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he last of the four 5.78m diameter EPBMs excavating the twin 15.5km long running tunnels of the Cityringen Line broke through in mid-February 2017. The milestone was celebrated by Seli Tunneling Denmark, part of the Salini-Impregilo Group and metro owner, developer and operator, Metroselskabet and in the presence of Danish Prime Minister, Ms Helle Thorning-Schmidt.

The four EPBMs completed the Cityringen loop in two halves. The twin tube drives of the north section were “the most difficult”, said Valerio Violo, Managing Director of Seli Tunneling Denmark SpA. The work included passing through 2km of soft ground comprising sand, sandy tills and glacial deposits. There were also “episodes” of CO and NH3 contaminants encountered and also some HCN. These required retro-fitting the machines to handle the unexpected conditions.

The contractor overcame the challenges via a combination of: • keeping settlement “very low”; • maintaining volume loss below the expected value;

•

working with train-based mucking out, due to the length and the radius curves of the tunnels; and, handling frequent hole-throughs at box stations.

•

In the longer, north section, the tools and cutters performed well in the hard limestone and flint, which is notable given the challenges posed by flint during previous Line 1 and Line 2 metro construction, according to Violo. During the drives the excavation diameter and the cutterhead tool configuration was adjusted for the soft ground, and articulation of the tail shield was modified to overcome challenges for advancing under certain conditions.

The TBMs were able to achieve best progress rates of up to 34m/day and 174m/week, said Violo. “Record monthly advance was 734m, working three shifts/day, six days/ week with Sundays reserved for maintenance. The drives saw very consistent and solid production.”

The lining is formed of five 300mm thick segments plus key in 1.4m long rings for 4.9m i.d. running tunnels. Twocomponent annular grout was employed with custommade rotary pumps which achieved “excellent results,” said Violo.

Also on the project, excavation for the 17 underground stations is complete, and excavation of the running tunnel cross passages is under way.

During the contract, Seli Tunneling Denmark was acquired by Salini-Impregilo, becoming a division within the major Italian group. The acquisition in 2015 followed the restructuring of Seli SpA. As part of the final TBM breakthrough celebrations, Metroselskabet confirmed that the new circle line serving the heart of the Danish capital should be complete and in service by early 2020. n

TunnelTalk References • • • • •

Three JVs bid Copenhagen metro packages - May 2010 Seli Copenhagen EPBM design - November 2012 Copenhagen advances Line 4 extensions - May 2014 Tough ground beckons for Cityringen - March 2015 All TBMs finished on Cityringen - March 2017

TBM breakthrough at Copenhagen Central Station (left) with Danish Prime Minister Ms Helle Thorning-Schmidt leading celebrations

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Linking Denmark with Germany across the Fehmarnbelt CASE STUDY: In September 2008, the Danish and German Ministers of Transport signed a treaty to establish a link across the Fehmarnbelt between the coastal towns of Rødbyhavn in Denmark and Puttgarden, Germany. It provides the missing link in an efficient transport corridor between Scandinavia and Europe. A study in 1996-1999 investigated a number of possible solutions, including bridge and tunnel (immersed and bored) options and of different configurations. Based on the study it was decided to construct a four-lane motorway and a double track railway. Deciding what sort of link to build and the journey towards bi-national Government approval and realisation of the infrastructure started with a feasibility and cost comparison of fixed link options to span such a wide strait of water and one of the busiest shipping corridors of the world.

Tunnel beats bridge for Fehmarn fixed link he numbers are in, and the tunnel has it by a nose.

A cable-stayed bridge across the Fehmarnbelt for a fixed connection between Denmark and Germany comes in at DKK38.5 billion (about US$7 billion or €5 billion) while the estimate for an immersed tube across the strait is slightly less at DKK37.9 billion. After agreeing the fixed link concept in September 2008, two teams within

the Danish owner organisation, Femern A/S, developed conceptual designs and cost estimates for a four-lane highway and a two-track railway connection across the sea on a cable-stayed bridge and in an immersed tube tunnel. Of these, the bridge had been considered the less expensive option and therefore the favoured plan.

Announcement of the cost estimates in November 2010 produced a surprise result with the immersed tube revealing a lower estimate than the bridge.

Fig 1. Route of the undersea road-rail fixed link across the Fehmarnbelt to connect Denmark and Germany

There are no shipping-channel obstructions with the immersed tube option - one of its principal advantages

CASE STUDY: MAY AND NOVEMBER 2010

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The result demonstrates the extensive work achieved by the tunnel team in exploring new concepts to reduce the cost of building, operating, and maintaining the proposed undersea link.

for either road or rail traffic. Compounded by the high shipping traffic in the strait, this would pose significant risks in the construction phase in both terms of cost overruns, delays and industrial accidents.

One of the most significant cost savings was elimination of an intermediate man-made island on the immersed tube link designed to accommodate a ventilation shaft and equipment installation. Projections of low traffic volumes in the initial years, together with significant and rapid advances in reducing toxic emissions by road vehicles, allowed the adoption of longitudinal ventilation in the two-lane traffic tubes. Instead of large ventilation buildings and an intermediate ventilation station island, fans will be installed in ceiling recesses at 400m intervals along the 18km link. This also optimises the design of the immersed tube’s cross section, eliminating the need for separate transverse or semi-transverse ventilation ducts. “The change also reduces the volume of concrete in the immersed tube elements by some 10%, which is a significant saving on a project of this scale,” said Steen Lykke, Project Director Tunnel for Femern A/S.

An immersed tunnel will also present considerable technical challenges. However, unlike a bridge, an immersed tunnel will have fewer technical operations pushing the limits of what has been achieved to date.

Essentially, the procedure will be the same as it was for construction of the Øresund fixed link’s immersed tunnel under the Drogden Channel between Denmark and Sweden (page 42), only many times longer and deeper.

The Fehmarnbelt tunnel will be about 18km long and up to 30-40m deep, while the Øresund tunnel is approximately 4km long and about 10m deep.

Since release of the cost comparisons in November 2010, Danish politicians have adopted the immersed tube tunnel as the preferred option. “The decision means that Femern A/S has reached an important milestone,” said Leo Larsen, CEO, Femern A/S. “As our conceptual designs are based on a thorough technical foundation, we can now focus on ensuring that the authorities approve the project, including from an environmental perspective.”

Making the case

Fewer risks, in both the construction and operational phases, than a cable-stayed bridge is how leaders of the project say they arrived at recommending the immersed tunnel.

A cable-stayed bridge across the Fehmarnbelt, with two free spans of 724m each, would be the largest spans ever Fig 3. Geological section of the Fehmarnbelt seabed

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Both a cable-stayed bridge and an immersed tunnel would impact the marine environment, but the preliminary conclusion is that a bridge would have slightly more significant permanent impact than an immersed tube.

In the interests of navigation safety, a tunnel poses fewer risks than a bridge. The Fehmarnbelt is a heavily trafficked stretch of water with 47,000 vessel transits per annum in 2006 data. In the coming years, traffic is expected to increase substantially to about 90,000 vessel transits in 2030.

Time and money factors

In financial terms, there is very little difference between the two projects. The construction estimate (in 2010 prices) for an immersed tube is about €5 billion and for a cable-stayed bridge about €5.1 billion.

The construction time for the tunnel is estimated at 6½ years and for the bridge 6 years. The cost of operation and maintenance is estimated at slightly higher for a tunnel than for a bridge. All told, the payback time for the

Fig 2. Comparisons of tunnel cross sections and their typical arrangements

two projects would be practically the same at about 30 years. In a press release of the announcement, Danish Minister for Transport Hans Chr Schmidt stated: “From an overall financial perspective, there is no difference between the bridge and the tunnel. The cost of the two solutions is the same, generally speaking, which confirms the project’s sound financial basis.”

In the year following the selection of the immersed tube over the bridge option, Femern A/S completed the Environmental Impact Statement to be considered by the authorities in Denmark and Germany in accordance with national regulations and will submit an application for construction approval to German authorities during the first six months of 2012. A construction bill will then be submitted to the Danish Parliament, the Folketinget, in 2013. Following approvals, construction of one of Europe’s largest infrastructure projects could be expected to commence in 2014 and open to traffic in 2020.

Towards that end, in April 2009, Femern A/S selected the consulting engineering joint venture of RambøllArup-TEC for the design phase of the selected immersed tube option. At more than 18km long, the size of the project will create major challenges for the design and its construction. As well as the longest and deepest of its type ever built, with foundation depths up to more than 40m beneath sea level, the immersed tube will be the world’s longest combined road and rail tunnel and the world’s longest under water road tunnel. The amount of material to be dredged for the trench is about 20 million m3 and about 3 million m3 of concrete will be needed to create the immersed tube elements.

Operational safety is also an important consideration for the project, not only on design, but also in the approval process and public acceptance of the tunnel solution.

In design, the emphasis has been on reducing the construction time and optimizing the required internal space while maintaining an adequate safety level and self-rescue ability for the road users and rail passengers.

Based on minimum functional requirements, such as the traffic envelope and the basic space requirements for installations, a wide range of options for the cross section have been studied and evaluated applying multi-criteria analysis to compare aspects such as cost, safety, construction time, constructability, operation and maintenance. A first evaluation has been based mainly on qualitative aspects and experience gained during the construction of similar projects including the Øresund fixed link, the Marmaray immersed tube railway crossing in Istanbul, and the Busan Geoje link in South Korea.

The generated cross sections can be divided into three arrangements;

• • •

Sections which combine rail and road in one level with the objective to concentrate material and functions.

Sections which combine rail and road in two levels to allow for a combined use of ventilation ducts and galleries for rail and road.

Separate tunnels for rail and road with the objective to allow for separate alignments and independent construction.

In addition to these arrangements three different structural concepts and/or construction methods have been considered (i) reinforced concrete constructed traditionally or by full section casting (ii) modified singular steel shell sections and (iii) steel concrete composite sections.

A quick assessment showed that the two-level arrangements did not have real potential to generate sufficient added value because the sections complicate construction and extend the production time since for this cross section full sectional casting is not an option. The tall cross section also requires deeper dredging, a deeper casting basin, and deeper and longer access channels to the casting basin areas. The combined use of centrally placed ventilation ducts and galleries did not compensate for the extra cost involved.

The option of having separate alignments for road and rail creates more flexibility with regard to design and construction but is more costly. Separate tunnels have the advantage that the rail tunnel alignment is not constrained with respect to the road alignment and visa-versa, but the impact on the landfalls might increase by having two different alignments. Another important drawback is related to safety as combined use of safety provisions in rail and road tubes is not possible.

The one level arrangement has been identified as having the best potential for final optimisation as the various arrangements of rail and road tubes allows for an effective use of the road tubes in case of an accident in the rail tube and vice-versa. It is expected also that the combination of rail and road in a one level cross section will result in synergy during construction, floating of the elements to site and immersion. The dredging depth is also minimised.

For the one level options, an arrangement with the rail tubes at the outside was favoured initially (Fig 2) but later abandoned due to space requirements for the necessary M&E installations. These installations are to be concentrated in special deeper elements every 1.8km. These special elements also provide space for the power transformers, pump rooms, parking lay-bys for maintenance staff, longitudinal ventilation fan niches in the roof, and other operational and maintenance facilities.

The intention has been to concentrate all diversions from the standard element cross section in these special units.

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Construction of the 80 x 200m long standard immersed tube elements will be a massive operation in which an element will be delivered to site for sinking every second week. To achieve this within the programmed time frame of about 2 ½ years, two production facilities will be required with four and five production lines respectively. The special elements are shorter than the standard elements but more complicated, so it is expected that these will be constructed in a casting basin using full section casting to prevent hydration cracking and assure sufficient quality.

Safety, rescue, ventilation

The biggest challenge to safety, rescue and ventilation is the tunnel’s length of about 18km under water. With little scope for egress or access points except at the portals, evacuation from one tube to another, combined with efficient management procedures for evacuation towards the portals, is paramount. The ventilation system must also be capable of transporting air or smoke over long distances and to overcome large pressure losses. Selfevacuation is to be through cross passage doors from the incident tube into an adjacent non-incident tube.

Early detection and early suppression of in-tunnel fires via remote controlled permanent systems provide a relatively safe environment from where the fire service can establish a bridgehead and commence operations.

The analyses to determine the parameters for the ventilation needs is made complicated by the fact that many of the calculation parameters are estimated on past experience or future expectations. The traffic volume, the vehicle emission factors, the NO2/NOx-conversion factor and the acceptable threshold values are all subject to significant global debate. This is further complicated by future transportation patterns and vehicle traction technologies that may differ significantly from that of today. Although projections for road traffic volumes indicate an increase

over the years, the overall traffic volume is relatively low when compared to a city centre road tunnel. The relatively low volume suggests that congestion will not be a regular occurrence, and this eases some of the requirements on the ventilation system under day-to-day conditions. Ventilation capacity requirements in the event of an in-tunnel fire is the topic of special study and evaluation.

Dredging

Required dredging will produce a trench some 40-50m wide x 12-15m deep and at a sea depth of up to -45m at the centre of the crossing. The soils to be dredged will vary from sands/silts to stiff and very hard clay-till with boulders (Fig 3). Conventional dredging equipment can dredge to a depth of some -25m. Dredging beyond -25m will likely be by grab dredgers and trailing suction hopper dredgers.

Re-use of as much as possible of the dredged materials in a beneficial way must be considered. While an obvious use for the dredged material will be the backfilling of the trench, it will only account for a part of the material.

Surplus material could be deposited in one or more marine disposal sites subject to environmental regulations.

Two work harbours will be constructed to provide a safe haven for marine construction equipment and to provide facilities for supply, stockpiling and load-out of materials and equipment. These work harbours could be converted into small marinas on completion of the works.

TunnelTalk references • • • •

Fehmarnbelt fixed link options - June 2009 Innovations for the Fehmarnbelt tunnel option - May 2010 Cost comparison for Fehmarnbelt options - November 2010 Deep geological data on Fehmarn link - May 2011

TBM bored option rejected for Fehmarnbelt CASE STUDY: DECEMBER 2011

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espite the environmental advantages and Denmark’s past experience of building the TBM bored tunnel under the Storebælt, technical investigation of a TBM option for the 18km long undersea crossing of the Fehmarnbelt did not shake preference for the immersed tube solution.

With an estimated cost of €6.8 billion, a TBM bored tunnel, based on two highway tubes and a twin-track railway tube (Fig 4), was more than 25% higher than the

2008 estimated €5.5 billion immersed tube option. It is also considered to carry more construction risk.

According to Femern A/S, the Danish client authority, the bored tunnel is a higher risk due to the combination of a large tunnel diameter, long drives, and difficult ground conditions. “A bored tunnel solution is believed to be pushing the boundaries of what is considered proven TBM excavation technology,” said Steen Lykke, Technical Director of Femern A/S. “The results of our TBM tunnel investigations do not change our preference for an immersed tube from the technical point of view. On the

Fig 4. Possible TBM bored tunnel configuration for the fixed link

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contrary, they have confirmed that an immersed tunnel has a number of advantages that apply to technical risks, construction time, construction costs, as well as operation and maintenance costs.”

Public hearings on the scoping report in 2010 returned recommendations that the bored tunnel should be

considered, and the technical investigation of the alternative is now included in the Consolidated Technical Report. The report also includes evaluation of the originally favoured cable-stayed or suspension bridge alternative. The 8km long twin TBM bored railway tunnel under the Storebælt was built in the 1990s (page 27).

Road to political approval for Fehmarn sea link CASE STUDY: FEBRUARY 2011

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s a key element in the unifying transportation connectivity of the European Union and one of Europe’s largest ever construction projects, realisation of the Fehmarnbelt fixed link is governed by a bi-national Treaty between the Kingdom of Denmark and the Federal Republic of Germany. The treaty was signed by the Ministers of Transport of the two countries in September 2008 and ratified by the Danish Parliament and the German Bundestag in March and June 2009 respectively. In assuming the sole responsibility for the financing, implementation and future operation of the fixed link, Denmark established the special purpose, 100% Danish state-owned organization Femern A/S. In April 2009, the organisation was appointed by the Danish Minister of Transport to move ahead with the project. With a majority in the Danish Parliament in favour of the project in 2011, Femern A/S began the regulatory approval in Germany by delivering a 10,000-page application to build the link to the Schleswig-Holstein authorities in October 2013. Schleswig-Holstein, as the northernmost state of Germany, is the landfall of the sea link on the German side and will be the state most affected by the project both in construction and in operation.

There was considerable concern in Schleswig-Holstein about the environmental impact of the project and the social and financial costs to the local environment in hosting the international road and rail infrastructure. As Germany considered these concerns, the Danish Parliament, the Folketing, passed the Construction Act for the fixed link and approved construction of its land works in Denmark in April 2015.

It would take another three and a half years of negotiation and study for German authorities to signal agreement to go forward with the project and on 6 February 2019 in the city of Kiel, the Schleswig-Holstein Ministry of Transport handed to Femern A/S its signed environmental approval for construction of the link. The long-awaited approval cleared the last major hurdle in preparations to building the link although German authorities anticipated and were met with an appeal against the approval in the Federal Administrative Court of Leipzig. For its part, Femern A/S and the company’s German advisors confirmed that they would assist the German approval process and kept valid also its contingency plan to allow construction to start in Denmark ahead of the Leipzig hearing outcome.

The German approval relates exclusively to the construction work on the German side. Activities on the Danish side are regulated by the Danish Construction Act passed by the Danish Parliament in April 2015.

As anticipated, formal legal objections were lodged in Germany in February 2019. Seven legal complaints were filed jointly by stakeholders including three ferry companies; two German environmental groups; two municipalities; and a local landowner. With the hearings by the Federal Administrative Court of Germany expected to take up to two years, Femern A/S reviewed and concluded that the timeline should not be impacted and that any extra costs as a consequence would be covered within the existing construction budget.

Through this time, Femern A/S as an organisation of about 160 employees working from its offices in Copenhagen, Rødbyhavn, Hamburg, Burg and Puttgarden, maintained the momentum of the project. It prequalified contractors, awarded contracts, managed early development work, defined the operating parameters to which the designbuild construction teams will construct and prepare the sea link for operation, and secured the necessary funding to see the estimated DKK52.6 billion, €5.5 billion, US$8 billion project (in 2008 prices) through to public service.

An early achievement of the organisation was the fouryear study into the selection of an immersed tunnel as the least risky of the sea crossing alternatives. A bridge lost to the immersed tube principally on its obstruction across the busy shipping corridor and the technical demands of the marine works for what would be the world’s longest, road-rail, double cable-stayed bridge and its landfalls (page 17). For the bored tunnel option, it was said that it would only provide a small environmental advantage during the construction phase and that this did not compensate for the major technical risks and heightened safety concerns for the crews on the long headings and the cost premium of about €1.3 billion.

As it is the immersed tube option is no easy undertaking. It will be the longest, largest cross section and the deepest road and rail immersed tube constructed in the world to date. Steps towards realisation of the link began in early 2013, with small preparatory works in the portal region in Denmark, including utility diversions, road and drainage works, archaeological studies, and the relocating of a lake on the tunnel alignment. Inland, the road and rail authorities also began improving networks for connecting to the undersea link.

Funding of the project

A large part of the capital to build the project is to be allocated by the Danish Government through its national transportation development budget. Further the Danish Government will provide State guarantees for the tranches of borrowed capital to be raised on the international capital investment markets.

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In addition, the project will receive significant contributions from the European Union. Initial EU contributions totalling €587 million covered about 20% of the early construction works and was applicable for up to 40% of the railway related costs that account for about one-third of the overall road-rail project. An extra €12 million allocation took EU funding to the highest possible subsidy rate of 30% for the preparatory construction works to 2020.

The project received also the highest possible 50% EU funding subsidy for the planning phase.

In June 2022, the EU Member States approved the European Commission’s proposal for funding allocations and the Fehmarnbelt project will receive a further €540 million (DKK4 billion) from its Connecting Europe Facility (CEF) for the budget period 2021-2027. The project is part of the EU’s strategic TEN-T trans-European transport network that aims to strengthen the internal EU market by removing bottlenecks and promoting more efficient cross-border transport corridors.

In 2014, Femern S/A adjusted the cost of the project for

inflation and increased its earlier estimated €5.5 billion cost to €6.2 billion in 2014 prices, the central immersed tube element contract increasing to €4.3 billion in 2014 prices. Landworks in Denmark for the combined road and rail scheme are excluded from the main figure and are handled separately in the project’s financial report.

Landworks for the German side of the project are also excluded from the Danish estimates as their procurement will be managed by the German Ministry of Transport.

The estimated cost of land works on the Danish side was revised to €1.3 billion in 2014 prices. The continuous financial analysis of the project includes traffic revenue estimates and various interest rate assumptions. Femern A/S said that while the interest rate has been less than 1%, it had set a higher rate of 3% for financial calculations.

It added that, depending on the level of reserves in the construction estimate, the financial analysis shows that the repayment period for the entire scheme is 32-37 years, set against an earlier estimate of 39 years. Within the overall DKK52.6 billion (US$8 billion) project budget, some DKK7.3 billion was said to be in its contingency reserves.

The road to start of construction CASE STUDY: MAY 2011

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n backing construction of the fixed link with Germany, Danish Members of Parliament backed the solution proposed by Femern A/S, to build an immersed tube of 18km long and comprising a four-lane motorway (two lanes in each direction) and a double track electrified railway. Further agreed was that all features of the infrastructure would be built in a single cross section rather than in separate parallel tubes, with the two rail track sections together to one side and the two road decks together to the other (Fig 5). The single cross section for all structures calls for elements of 42.2m wide x 8.9m high. All the necessary M&E equipment rooms of the link would be housed in the basement compartment of 10 special elements of greater height to be installed at 1.8km intervals along the crossing (Fig 6). These will also house the neches for the longitudinal ventilation fans.

While increasing the fabrication demands, providing the four traffic compartments in the single cross section, had significant safety and installation advantages.

The gradient from the surface into the immersed tube lanes is more gentle, the trench depth is considerable shallower than for a double deck configuration and the

compartments together on the same level allows for more direct evacuation of people from an incident tube into the safety of a parallel compartment through emergency doors at regular intervals along the dividing walls.

In preparing for the construction by selected designbuild contractors, Femern S/A divided the works into four large construction packages (Fig 7). For the immersed tube elements and their casting and installation, the 18km long route was divided into two halves – the North and the South tunnel packages. The two groups would have three fabrication casting bays each at the one element casting site at Rødbyha on the Danish side of the project and would float out and sink their elements from each coast towards installing the final connecting element in the middle of the element strings. Dredging of the seabed trench and of the casting yard harbour on the Danish side are the works of the third main package while further dredging and reclamation works for the two marine portal structures at both landfalls are the elements of the fourth major construction package.

Additional separate contracts will complete the earthworks and landward approaches to the immersed tube interface in Denmark and Germany. Another large separate contract will provide for the M&E installations of the completed civil works.

Left: Fig 5. All compartments of the immersed tube are to be cast in one 42.5m wide cross section with emergency doors in the dividing walls linking them as a major safety feature; Right: Fig 6. Cross-section of the ten special M&E installation units

Reaching this stage of the works began in May 2013 when five consortia prequalified to compete for the main large design-build contract packages. Together with confirmed subcontractors and design engineers, the prequalified groups the four packages were as follows: North and South Tunnel packages: •

Fehmarn Belt Contractors: Hochtief Solutions (lead), Ed Züblin, Boskalis International, and Van Oord Dredging and Marine Contractors. Subcontractors: MT Hojgaard, Volker Construction International, and Strukton. Consultants: Capita Symonds and Grontmij.

•

Femern Link Contractors: Vinci Construction Grand Projects (lead), Per Aarsleff, E Pihl & Son, CFE, Soletanche Bachy International, BAM civiel, BAM International, Wayss & Freytag and Max Bogl.

Consultant: COWI

•

Joint Venture of Salini (lead), Impregilo, Samsung C&T and Johann Bunte. Subcontractors: Danish firms CG Jensen and Barslund, and a Dutch consortium of Mammoet, Arcadis, Seatools and Ratio. Consultants are together in a JV called Fehmarnbelt Consultants, comprising EKJ, Mott MacDonald and GEO

•

Joint Venture of OHL (lead), Daewoo Engineering and Construction, and Daelim Industrial. Consultant: Aecom Immersia: FCC (lead), NV Besix and Jan De Nul

Fig 7. Procurement of the fixed link infrastructure was divided into four major construction contracts

While the environmental and political approval processes held some uncertainty for the project, Femern A/S approached its realisation responsibilities with confidence and determination. It pushed ahead with the operating design of the fixed link and began the process of inviting construction companies to bid for the construction packages in early 2011. This started with release of the geotechnical data compiled by site investigation contractor Fugro and data from offshore geophysical tests commissioned by the project’s design engineering joint venture Ramboll-Arup.

About 15.5 million m of dredging at up to 43m below sea level is needed to form the trench for the 18km link.

Into this, 89 precast concrete elements – 79 standard elements of 217m long and weighing about 73,500 tonnes each, and 10 special ventilation and M&E elements of shorter length and greater height – will carry the road and rail link across the strait.

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The marine site investigation studies comprised drilling two bore holes of up to 100m deep at 50 test locations across the strait. The studies confirmed that there are no geological or geotechnical obstacles to constructing an immersed fixed link in the area. The geology along the alignment comprises moraine clay, chalk and a complex plastic, or fat, clay which has required extra study by consulting firm Per Aarsleff. The moraine and fat clay beds were found to be more glacially disturbed than expected.

Given their greater construction challenge, a large 30m x 60m test area was set up 1km off the German coast to gain more data and experience about working with the deposits.

The Ground Investigation Report released by Femern A/S states that the Palaeogene deposits are all high plasticity clays. The clay content is typically 70%-80% with a typical plasticity index of 50%-140%. There are also fissures in the clay related to slicken sides.

Within a year of releasing the geological data, Femern A/S opened the invitations to prequalify for the construction works. At that time, the anticipation was that the procurement phase of the project would run through 2012-2013 to enable construction to commence in 2014 and the project to open in 2021. As was to be expected, these optimistic forecasts have met with time delays and the costs have also increased through the procurement phase. Nonetheless the project is today pushing ahead full steam and major construction works are in progress on both coasts and the seabed dredging operation is well underway.

•

The same contractors and in different combinations also prequalified to bid for the landfall works and the dredging and reclamation contracts: Portals and ramps packages: •

Fehmarn Belt Contractors;

•

Femern Link Contractors: Under leader Per Aarsleff and with consultant COWI;

•

Salini/Impregilo/Samsung/Bunte JV;

•

OHL, Daewoo and Daelim JV.

Dredging and reclamation packages: •

Fehmarn Belt Contractors: Under leaders Boskalis and Van Oord;

•

Femern Link Contractors: Dredging International (Lead) with sub-contractors: Great Lakes Dredge & Dock Co;

•

Jan De Nul: bidding alone.

In December 2013 a request for qualifications was also called for the single large M&E contract, the scope of which includes ventilation and cooling systems, power and back-up power systems, drainage, cables and pipework, emergency doors, fixed fire detection and prevention systems, air quality monitoring, emergency call points, lighting, and control and communications systems.

Tendering for separate contracts for the electric power supply installation and for the highway toll plazas was also underway. A separate advanced works contract was already progressing to improve road access to the main construction site of the project on the Danish side.

Bid evaluations

In evaluation, the technical proposals were weighted at 50% and the financial bids at 50%. Further competitive dialogue was permitted in the evaluation process, but the preliminary financial bids when submitted in December 2014 all came in much higher than expected. With 23

Works are developing rapidly at the Rødbyhavn site in Denmark (left); Smaller scale works are also progressing at Puttgarden in Germany

bids at about 20% over budget, Chief Executive Claus Baunkjaer said the bids needed to be negotiated down “significantly”, noting that “our form of tender allows for reducing prices” and that “several suggestions have been put forward to help cut bid costs without impacting functionality or safety.”

Ongoing negotiations over the budget-busting bids delayed hopes of getting main construction started by late 2015 and the legal process to hear objections to approval of the project in Germany was also still in progress.

After months of negotiation and dialogue, the bidding process culminated in early 2016 with provisional award of the main construction contracts with the North and South Tunnel packages and the Protals and Ramps package going to the same selected group Femern Link Contractors JV (FLC) comprising Vinci (France), Per Aarsleff (Denmark), Wayss & Freitag (Germany), Max Bogl Stiftung & Co (Germany), CFE (Belgium), Solétance-Bachy International (France), BAM (Netherlands), and BAM International (Netherlands) with named sub-contractor Dredging International (Belgium) and with COWI (Denmark) as the group’s lead design consultant.

The provisional contractor group for the Tunnel Dredging and Land Reclamation contract was announced as the Femern Belt Contractors JV (FBC) comprising Boskalis International (Netherlands) and Van Oord Dredging and Marine Contractors (Netherlands), with Sweco (Denmark) as design consultant.

FLC has the task of constructing the tunnel elements and sinking them into position as well as constructing the portal buildings on both sides of the crossing. FLC is also building a Tunnel Town in Rødbyhavn that will house most of the tunnel workers.

In March 2016, with the procurement process for the civils packages almost complete, and faced with the unexpected delay in Germany, Danish politicians gave Femern A/S the green light to award the main construction contracts on a conditional basis. “Conditional means that final and binding contracts will be signed with the successful contractors, but construction work will be postponed until the German construction permit is in place,” said Femern A/S. “The provincial contracts signed in May 2016 will be valid until the end of 2019 with the option to renegotiate and/or extend at that time.”

Following conditional award of the construction contracts, Femern A/S prequalified a list of consultants to provide services in two framework packages for the design and construction phase. Consultancy services since 2009 had been provided by the Rambøll-Arup-TEC JV. The two framework packages replaced that existing single consultancy service contract and divided the scope into: • •

Client Consulting Services, to provide conventional consultancy services including dealing with potential contractor claims, and Technical In-House Consulting Services, to provide personnel as required to the client’s technical division and provide ad hoc quality assurance services.

The new consultancy contracts were expected to be signed in the first quarter of 2017. “There are no significant changes in the services,” said Jens Villemoes, Press Manager for Femern A/S. “Nor does the consultancy tender affect staff levels within the client organisation as it is re-tender of an existing technical adviser contract.”

An advantage of the two-contract system for the client is to have one technical adviser providing quality assurance on the other, said Villemoes.

FBC is undertaking the dredging work at sea and construction of the two work harbours on the Danish and German sides, as well as creating new reclaimed land areas using the dredged materials. FBC will also perform the preparatory work for the tunnel portals on the Danish and German sides.

Following the tendering process, the Rambøll-Arup-TEC JV, with sub-consultants WTM Engineers and Schønherr, secured the Client Consultancy Services contract and the Technical Support Services contract was awarded to ÅF-Hansen & Henneberg supported by sub-consultants ÅF Infrastructure, Atkins Denmark and Obermeyer Planen + Beraten.

In May 2016, after a delay when the Danish Review Board for Public Procurement received a complaint over the tender process from two of the unsuccessful bidding contractors, Femern A/S signed four conditional designbuild contracts with the selected two groups to a total value of DKK30 billion (€4 billion/US$4.47 billion).

With a revised start of construction date in 2017, the completion date for the project was also pushed forward to 2026. This schedule slipped again in late 2017 and was pushed forward by another almost two years as a contingency to deal with expected prolonged legal resistance in Germany. Femern A/S had hoped to gain

environmental approval in Germany for the sea link by late 2017 and to start construction by mid-2018. However, despite positive progress in talks with German authorities, the project was now on track for a start in 2020 and an opening of services in 2028. This was helped when Femern A/S was granted permission from the Danish Government for the main contractors to start some of the main works in Denmark in 2019.

Work on the drydock harbour at Rødbyhavn began in Autumn 2019 and construction of the immersed tube element casting factory and necessary near-shore dredging and reclamation works were also started.

The casting factory is being constructed in stages with the first of six production lines expected to be operational for casting to begin in 2022. Once fully operational, the factory will be capable of casting a 217m long standard element every two weeks for some three and a half years. The elements will be cast in segments of approximately 24m in the factory. Nine segments comprise one standard element and the whole process to create one element will take about nine weeks. Quality control in the casting factory must comply with the desired design life of at least 120 years.

Follow-on main construction activities would include all offshore dredging for the immersed tube trench, all concrete casting, the float-out and placement of the elements, and all construction work at the portal ramps near Puttgarden in German. An expedited permit was granted to allow some preparatory works at Puttgarden in Germany while the court case proceeded.

Further good news came in late 2020, when Femern A/S activated the main construction contracts with FLC effect from 1 January 2021 allowing construction of the immersed tube casting factory and the tunnel portal and ramp structures at Rødbyhavn on the Danish side to ramp up to full capacity. Work on the factory began in the Summer of 2021 and is expected to be completed by the end of 2022.

On the German side, work began on preparing the smallscale construction site on Fehmarn Island in the Spring of 2021. A small-scale work harbour and a portal building will also be established there. This work will begin in 2022.

Latest progress reports

In June 2022, the roof for the first of the three production halls for the element casting factory was completed.

Contractor FLC expects the casting factory to be ready to go into element fabrication by the end of 2022 and for the immersion of the tunnel elements to begin in 2023. Work,

also by FLC, to build the tunnel portals on the Danish and German sides will start in 2022. The portals will have a grid in the roof at ground level to provide a smooth transition between natural and in-tunnel light.

In May 2022 an important milestone for the project was celebrated when dredging of the seabed trench for the immersed tube elements passed the 50% mark. The Dutch consortium FBC is using some of the world’s largest dredgers and barges to remove up to 19 million m3 from the seabed. Most of the material will be reused east and west of Rødbyhavn and on Fehmarn Island on the German side to create new reclaimed nature and recreational areas. Dredging works got underway in July 2021 and are expected to be completed in 2024.

In May 2022 Femern A/S signed a contract with the Femern Service Contractors (FSC) consortium for the installation of advanced electro-mechanical equipment and services. FSC comprises contractors: • Sociedad Ibérica de Construcciones Eléctricas (SICE) (Spain) • SICE Tecnología y Sistemas (Spain) • Cobra Instalaciones y Servicios (Spain) • Moncobra (Spain) and supporting entities: • •

Cobra Instalaciones y Servicios Internacional (Spain) SICE subsidiaries in USA, Sweden, New Zealand and Australia

Work on the M&E installations will begin as soon as the first elements are in position.

Following a thorough testing and commissioning period, the revised target opening date of the toll highway and international freight and passenger railway connection is now set for 2029. Once opened it will take 10 minutes to drive the 18km of the undersea link between Germany and Denmark and 7 minutes on a 200km/hr passenger train. These journeys currently take an hour by ferry. n

TunnelTalk references • • • • •

Deep data on Fehmarn Link - May 2011 Civil tenders submitted for Fehmarn Link - April 2014 Fehmarn link approved but initial bids “too high” - April 2015 Germany approves Fehmarnbelt fixed link - February 2019 Objections filed as Fehmarn prepares for construction - June 2019

Images: Femern A/S

Left: Construction of the first of three element casting halls, each housing two production lanes, was completed in June 2022 Right: By May 2022, a fleet of dredging vessels had some 50% of the immersed tunnel trench on the seabed complete

Storebælt challenges

At 18km long, the Storebælt road and rail fixed link comprises two bridges and a twin bored tunnel, the road and rail decks on the 6.6km west bridge from Knudshoved to the island of Sprogø and the road going over the 6.8km suspension bridge and the rail going under the east channel in the 8km long twin tube TBM tunnel to Halsskov

CASE STUDY: After the Channel Tunnel between the UK and France (construction 1988-1994), and the Seikan Tunnel linking the islands of Honshu and Hokkaido in Japan (construction 1971-1988), the Storebælt rail link in Denmark (construction 1988-1997) was one of the most demanding subsea bored tunnel projects of the era. The project employed the latest in TBM technology with the experiences taking these technologies to their limits. A set of confounding calamities taxed the contractual relationships between the parties almost to the point of collapse. Only through professional dedication and collective determination did the effort survive to completion, contributing a great deal to the advancement of TBM technology and to the development of contracts to anticipate, manage and share all risks associated with undersea and underground excavations. It is on the experiences of the Storebælt enterprise that many of the undersea and subaqueous bored tunnel projects of recent times have been a success and on which those to come, including the planned TBM drives for the proposed Helsinki-Tallin undersea link (page 43), will profit by. The reporting of the project through the construction years was made possible with the assistance of the Storebælt Public Relations team and with access to the senior managers of the project parties and their frank, up-front and honest interviews.

Screw conveyors take the pressure FACTORY VISIT REPORT: APRIL 1990

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1.2m diameter x 20m long double screw conveyor weighing 160 tonne lies at the heart of the four identical 8.5m o.d. custom-made shield TBMs that will excavate the 8km long rail tunnels under the Storebælt strait in Denmark. MT Group, awarded in November 1988 the £239 million contract to build the twin-tube rail tunnel for the government-established client, placed the order for all four machines, with the same manufacturer. The MT Group comprises Monberg & Thorsen of Denmark, Campenon Bernard and Sogea of France, Dyckerhoff & Widmann of West Germany and Kiewit Construction of USA. James Howden of Glasgow, Scotland, was awarded at the last moment one of the largest orders ever placed with a single TBM manufacturer. Worth more than £45 million,

the closest contenders for the order were the Kawasaki/ Fives Cail-Babcock JV and the Mitsubishi/Marubeni JV. According to Howden, its acquisition of Wirth of West Germany just prior to the award gave it the increased capacity and the wider engineering base needed to design the complex mixed-ground TBMs and handle such a large order.

“We always intended to place the order for the four machines with the same manufacturer,” said Olav Nielsen, Project Manager for the MT Group. “It was considered more convenient to have the same type of machine from the same manufacturer on all the drives.

Training and maintenance would be easier and quicker; operators could be interchanged as could TBM parts; it reduces the necessary spare parts inventory and, finally, simplifies the administration. Howden won the order because it had the necessary hard rock expertise 27

through Wirth and the soft ground technology from Mitsui. It also had the best price.”

Open and closed operation

The ground through which the TBMs must work comprises two basic strata. The upper glacial till is a soft sandy clay matrix which contains large granite boulders of up to 1m in dimension. These have been identified in a seashore count and predicted in core drillings and found in trial holes. The lower, relatively soft, marl strata are fissured, and water content is subject to the full hydrostatic head of the 80m deep Great Belt channel above.

About a quarter of the tunnel, or 2km from each portal, is in the upper glacial till, with the middle half, or about 4km, in the marl. Minimum cover at the deepest point is about 15m.

To cope with such conditions, the TBMs are based on the earth pressure balance concept and are designed to withstand hydrostatic pressures of up to 12 bar. They will also work in the faster open mode where pressurised conditions are not necessary. They are expected to start in the open mode through the relatively impermeable clay and glacial tills and convert to the closed mode through the fissured marl. Picks or spade teeth will excavate the marl and soft till, and disc cutters will attack the granite boulders.

Although based on the Japanese EPB concept, the TBMs have a distinct European character. They are more robust than some Japanese machines. The shield is built of at least 50mm thick steel and all components and electronic circuits are designed specially to be reliable and robust rather than to be excessively sophisticated.

The detailed design also reflects ideas of not only the contractor but also of the client, which, through the contract, is sharing a large portion of the risk. The COWIConsult/Mott MacDonald JV, the client’s Danish/British consultant, has also been required to review the design of the machines.

The design is further influenced by recent experience on the Channel Tunnel project, where several fullface TBMs are driving undersea tunnels through similar ground conditions. Sogea of France, a partner in the MT Group, is also a partner in Trans-Manche Link, which is using EPB machines on the French side of the Channel Tunnel. James Howden has four TBMs working on the British side of the project, including the undersea service tunnel TBM.

German contribution

Further European influence comes from Wirth, which is responsible for the design and assembly of the cutterhead, the main bearing, the drive train and hydraulic system, and the segment magazine, feeder and erector.

These were assembled in West Germany and shipped to Scotland for full assembly and factory testing of the machines prior to dispatch to Denmark.

“Engineering the screw conveyor has been our biggest challenge,” said Gordon Ince, Director of the Howden design office in Basildon, near London. “It must not only cope with the possible 8 bar hydrostatic head but also the added earth pressure intensification load applied by the forward thrust to a maximum of 10 bar. In accordance with the EPB concept, the screw must not only transport material out of the excavation chamber but also reduce the prevailing ground pressure to zero for discharge at atmospheric pressure into the muck wagons.”

Screw conveyor discharge

To achieve this, the 1.2m diameter screw conveyor is divided into two lengths. The primary 12.5m long screw extends through the bulkhead and into the excavation chamber and will transport muck from the chamber both in the open and closed modes. It has been engineered to last the full length of the approximate 4km long drive for each TBM, since to replace such a large component would be difficult, although possible.

In the open mode the screw extends into the excavation chamber and lies in a retractable trough. Excavated material is channelled on to the screw via retractable hopper bars. The muck, once transported from the face, is discharged from the encased screw conveyor on to the single continuous belt conveyor which will carry it back to the waiting muck trains.

In the closed mode, the screw trough and hopper bars are retracted, the discharge opening is closed and the system extended to include the second 7m long conveyor and activate the depressurising EPB capability. The principal means of reducing the possible 10 bar total operating earth pressure is a plug zone created between the two sections of the screw conveyor.

The plug is established by creating a zone of tightly packed muck to hold back the water content of the material. It is maintained by varying the rotating speed of the first and second conveyors. This also controls the rate of muck extraction. In the open mode the first screw

Fig 1. Four 8.5m o.d. EPBMs supplied by James Howden of Scotland will excavate the 8km long twin-tube tunnel

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rotates at between zero and 22 rev/min and in the closed mode each screw rotates at between zero and 15 rev/ min. Extraction is controlled by changing the volume of the plug by moving the second screw backwards and forwards across its 2m maximum length of travel.

The second stage of pressure containment is a casing rotator. By rotating the casing in the same direction as the screw, an additional plug zone is created. Varying the speed of the casing provides fine control of the packing density of the plug.

At the end of the second screw, material enters the discharge chamber via a double guillotine gate.

Depending on the consistency of the material, the width of the opening can be varied to control the extrusion rate.

Muck is finally discharged on to the belt conveyor through a second guillotine discharge gate.

The consistency of the material is vital to the success of the EPB system. If too dry, the material clogs in the flights of the conveyor, increasing the torque and the power needed to move the material along. If too wet, an effective pressure dissipating plug of material cannot be sustained. To control this there are several double-valve controlled injection ports in the bulkhead through which water or additives, such as thickening agents, can be injected to improve the consistency of the material to make it more or less fluid.

The shields can also convert to the slurry type with the charge and discharge slurry pipes installed as a contingency measure, although this is not expected to be required.

Screw combination

The front portion of the primary screw is of the ribbon type, while the last 4.5m portion, and all the second 7m long conveyor, is of the central shaft auger type.

This combination is designed to offer better loading properties while still holding back hydrostatic pressure.

The volumetric capacity of both types is the same.

The rotating cutterhead has eight arms, fitted at all times with 188 picks and 64 disc cutters. Intermediate spacer bars, instead of hydraulically operated mechanical doors, reduce the openings between the arms and prevent the passage into the excavation chamber of any lumps or boulders greater than 600mm in dimension. These spacer bars are designed to be removed when in the marl, where boulders are not expected. Should a boulder enter the excavation chamber, the ribbon conveyor will accept blocks of up to 600mm in dimension, but such lumps will not pass through the central shaft conveyor. If they remain at such a size, they must be removed since there is no

Rear view of the shield with the secondary screw conveyor being fitted into the erector bridge

stone crusher in the machine. There is instead a boulder trap into which solid lumps or boulders of up to 600mm dimension will fall. A horizontal watertight door will close off the conveyor housing and the contents of the stone trap will be manually emptied at atmospheric pressure.

Going under pressure

Man entry into the excavation chamber will be necessary for inspection, maintenance and tool changes. Discs and picks can both be replaced from behind the cutter arms. A double lock situated within the shield will allow man entry to 3 bar pressure. If man entry is required in pressures above, certified saturation divers will be required. The divers will be pressurised on the surface in a life support capsule which will then be transported down the tunnel and attached to the in-situ lock to allow entry. The divers will then transfer back to the capsule and be transported to the surface once again for the long decompression.

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38m along the top of the 200m long trailing backup lifts the conveyor belt and tips the muck on to a smaller transverse conveyor which then fills the stationary train of six 15m3 capacity Mühlhäuser rota dump muck wagons.

The conveyor has a capacity of 750m3/hr at a rated belt speed of 2m/sec and will fill a train in about ten minutes.

The same system is being used on the Howden Channel Tunnel TBMs. Maximum speed of the belt is 3m/sec.

The man entry lock, supplied by Drass of Italy, serves also as the materials lock

Consolidation capability

Should it be necessary for any reason, a drill fitted within the shield is capable of drilling ground treatment injection holes ahead of the face to consolidate a 16m diameter zone up to 11m ahead of the cutterhead. There is also a separate probe drill fitted further back, capable of drilling up to 70m long probe holes. If the material becomes sticky, there are high-pressure water jets in the excavation chamber to prevent caking. It is also possible to inject additives into the chamber or cutterhead area and along the screw conveyor tract either to increase the fluid content of the muck or thicken its consistency.

Once through the screw conveyor system, the muck is discharged on to a single belt conveyor which runs the full length of the muck train. A carriage travelling The shield complete with cutterhead, bulkhead, erector, erector bridge and screw conveyors, weighing about 980 tonne total, was shipped as one single piece

The tunnel is lined to 7.7m i.d. with gasketed precast concrete segments bolted with curved bolts. All seven segments, including the key, are lifted off the flat car by a vacuum-lift crane on to the overhead segment feeder.

The segments, which weigh up to 7.1 tonne, are lifted off the magazine by the mechanical hydraulic pin of the Wirth­designed twin-headed segment erector. Attached to a single chassis, each erector has an operating range of ±200°. At the customer’s request, the erector must apply a 40 tonne metre torque to compress the neoprene gaskets and force the cross joints closed prior to bolting.

The circle joint is forced closed by the 36 thrust rams of the shield. There is also a ring reformer to support the ring during back grouting if necessary.

Four rows of wire brushes, designed and supplied by Mitsui from Japan, form the vital tail seal. The individual 200mm long sections are bolted to the circumference of the tail skin and during operation the brushes, with their interlaced mesh membranes, are positively fed with a special fibrous grease. There are no integrated rubber lips in the seal. There is an emergency Phoenix inflatable seal in front of the wire brushes. This is kept flat by a vacuum pump when not in use. In the event of a power loss, all gates would automatically close, compressed air would be automatically applied in the pressurised sections of the shield and the emergency Phoenix tail seal would inflate.

Each of the four TBMs have five principal bearings. There is the main 5.6m diameter cutterhead drive bearing, two 1.6m diameter bearings in the screw conveyor systems, and a 4.6m diameter bearing in each of the two segment erectors. There are also the bearings in the disc cutters.

Bearing the load under difficult conditions

All four main cutterhead bearings, including one spare, and all the screw conveyor bearings, including three spares, are supplied by RKS, the French specialist slew bearing manufacturer within the large Swedish SKF group. The main drive bearings weigh 23 tonne each and are triple-row roller bearings with an integral gear on the inner ring. The three 1.6m diameter bearings in the screw conveyor systems have an external gear on the outer ring.

Rote Erde has designed and supplied the 4.6m diameter bearings for the segment erectors.

The bearings for the disc cutters have also come under specific redesign by Wirth. To work in these particular soft ground pressurised conditions the discs have been designed to reduce bearing friction. The disc bearings are sealed for life and are precharged with grease lubrication. Because the discs are assembled in free air, the zone inside the cutter is not pressurised.

In order to maintain the integrity of the seal, a piston through the central shaft transmits external pressure through the sealing zone to equalise and balance any pressures seen by the seals. With this device the 30

pressure inside the grease labyrinth of the cutter is at all times equal to the prevailing earth pressure around the cutterhead. The cross-section of the disc cutter ring is of a triangular shape that will stabilise the disc in the difficult geology.

The 12m long, non-articulated shields are steered solely by the 2.22m stroke thrust rams. These are grouped in independent sets of three and can be slightly skewed to counteract roll and correct line and level. Each TBM has an installed thrust capacity of 9,660 tonne. During operation, normal thrust load will vary depending on ground conditions using up to 50% of the installed capacity. Steering is not expected to be a problem as there are few curves, the tightest having a gentle radius of about 3,000m.

While there is manual override on all controls, most excavation operations are automatic and computer controlled by the French Conception d’Automates de Pilotage (CAP) system. All the necessary dial and pressure gauges are displayed on the console in the operator’s cabin situated about 15m from the bulkhead.

The shields are expected to work 24hr/day, 7 days/wk with manufacturer specified maintenance shifts. They are designed to achieve a penetration rate of 80mm/ min in the open mode and 50mm/min in the closed EPB mode and build a full ring in 18min. One 1.65m long cycle is expected to be completed in one hour.

The first two machines were dispatched from Howden’s Renfrew factory during February and March 1990 and are being assembled at the eastern portals of the tunnel on the island of Zealand. The second two machines

References •

Channel Tunnel in hindsight - February 1993

•

TBMs considered for Fehmarn sea link - December 2011

•

Equipping TBMs for tough conditions - November 2019

•

Tokyo Bay highway engages eight mega TBMs - August 1994

•

Links across the waters - January 2010

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TBM highway under the Bosphorus - September 2015

•

Storebælt calls on Project Moses for support - April 1993

•

Storebælt - the final chapters - May 1995

will be shipped in May 1990 and will be launched on the mid-channel island of Sprogø to advance towards an undersea junction with the first two TBMs meeting towards the end of 1991. As there are no facilities on Sprogø, electricity will be supplied by a sea cable from the mainland, salt water will be used in the cooling systems and all men and materials will have to be ferried from the mainland.

Winning the manufacture of these machines is a credit to the enterprise and engineering skills of Howden with Wirth and Mitsui. The detailed design of the machines is a combination of input from various sectors. The result of all these efforts will be judged in the actual performance of the machines. It appears, however, that all possible eventualities have been covered. This is perhaps best illustrated by the client’s demand that there be four TBMs employed to drive two 8km long tunnels. “We want to be sure that the tunnels will be completed in the 15-month tunnel driving schedule,” said Knut Poulsen, Project Director for Storebælt.

Storebælt calls on Project Moses for support SITE VISIT REPORT: APRIL 1993

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fter a catalogue of calamity, 1993 looks set to be the year when the East Channel rail tunnel section of the road and rail Storebælt link in Denmark is led out of its troubles. Mechanical problems with the four EPB TBMs, difficult ground conditions, and management troubles have had a compounding effect on a project which is now running about two years behind its original schedule and more than DKK2 billion (£200 million) over the original DKK3 billion (£300 million) budget estimate.

Having been launched between August 1990 and March 1991, the four TBMs excavating the total 6km of 7.7m o.d. bored tunnel should have finished towards the end of 1992. Instead, by then only about 20%, or 3km, had been completed.

The technical challenges of boring a tunnel under the Storebælt through boulder-infested glacial till and heavily fractured underlying marl were recognised from the start.

Granite boulders of up to 3m diameter, relics of the Ice Age, were to be expected in the till, while in the fractured marl fissure flows of up to 500 Iitres/min of water into the TBM excavation chambers had to be expected. These fissure flows could also be under the direct influence of the full hydrostatic head of the Storebælt above. At the deepest point (about 80m below sea level) this would exert up to 8 bar pressure on the TBMs.

“Despite many technical problems, the choice of the EPB technology for these conditions is certainly correct in my opinion,” said Alastair Biggart, formerly Tunnelling Director of the project’s COWI-Mott MacDonald consulting group and now Project Director of the East Channel tunnel for Storebælt, the client. “It is the high requirement for manentry interventions, due to excessive cutterhead wear, and the behaviour of the till when excavated that have been underestimated.”

The EPBMs excavating the four downhill headings from Halsskov and Sprogø were expected to work in the non-pressurised open mode in the overlying clayey till, comprising 35-40% sand, 35-40% silt and 10-15% clay, and revert to the closed pressurised mode when in the underlying fissured marl. However, while the till will stand unsupported in the short term, it has the tendency to ravel upwards with time. This is the most accepted likely cause of the devastating flood of the two Sprogø headings in October 1991. The leading of the two TBMs, Jutlandia, was at about 358m and was about 250m out under the sea, under about 10m of cover and 6m of water and was in a man-entry maintenance period in free air. Water was seeping through and the maintenance subcontractor, unfamiliar with tunnelling work, trailed the cables of a submersible pump through the man-entry lock to pump out collecting water. When water began pouring in the maintenance crew evacuated rapidly. There was no time to remove the pump and other equipment to allow 31

Extensive rebuilding work was required to repair excessive wear of two of the four TBMs excavating the twin tube rail tunnel

closure of the air lock door. The screw conveyor is also retracted, leaving the closed mode ports of the screw conveyor open. Inundation of up to 4m3/sec of water flooded the heading in about three hours, spilling over at the portal into the parallel TBM drive, flooding that TBM and heading too. A well-placed dumping of a barge-load of clay within hours of the incident stemmed the flow substantially to allow recovery to begin.

The lack of fines in the till has also caused over excavation and collapses of the face during TBM advance. In addition, lenses of water-charged glacial sand create a sudden surge into the excavation chamber when encountered.

Closed mode operation has been required to control such situations and avoid back runs of material into the working area through the screw conveyor.

Excessive wear in the highly abrasive till is currently requiring man-entry into the cutterhead at about 120m intervals. This is about ten times more frequent than on the Channel Tunnel, a project with which Storebælt has been compared since its inception. “Although at Storebælt the marl will be less abrasive than the till, we do expect a greater need for man-entry during the remainder of the drives than previously anticipated,” said Biggart, who like many comes to Storebælt from the Channel Tunnel project where he was Operations Director for the contracting group Trans-Manche Link from 1982 to 1987.

Originally, man-entry under the highest anticipated pressures was expected to be rare and would require the most advanced in deep sea diving know-how. Under more frequent man-entry, this was unacceptable from the time, cost and safety points of view. Methods of assisting the TBMs under the most extreme of conditions were required if the bored tunnels were to succeed.

One plan was to apply compressed air to the full tunnel length of each heading with a bulkhead and lock at or near the portals. Another was to establish safe havens of grout injected consolidated ground ahead of the TBMs in which necessary maintenance could be safely carried out at reasonable pressures. Both have been rejected on grounds of cost and logistics and have been superseded by one of the most ambitious dewatering schemes ever attempted.

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Project Moses

Under what is known as Project Moses, a series of 36 wells on the sea bottom supported by six power supply barges is extracting up to 120m3/hr of ground water per well to lower the pore water pressure in the ground and reduce TBM working pressures to about 3 bar or less at tunnel axis. The objective is four-fold: •

to improve the stability of the tills and increase their inherent self-supporting strength - a debatable point among many;

•

allow safe man-entry into the excavation chamber when necessary;

•

assist safe hand excavation of the 29 undersea cross passages which are about 250m apart and have a 4.4m i.d.;

•

reduce the risk of TBM seal failures when working under maximum potential pressures in the closed EPB mode.

As Biggart explained: “It reduces the technological demands of the project significantly.”

Dewatering underwater is not a new idea. An early application, although much smaller than that being undertaken at Storebælt, was carried out by Edmund Nuttall on the Weymouth outfall tunnel in the UK in 1978. The plausibility of dewatering on Storebælt was supported by the fact that on one occasion compressed air in the working chamber of the TBMs was found escaping through land-based dewatering wells, causing a water level rise of up to 4m in certain wells. Early trial wells also revealed a broad horizontal sphere of dewatering influence of up to 3.5km radius from each well. The relic water extracted from trial wells indicates very little vertical recharge from the sea above through the upper layers of clayey till. “The aim is not to dewater the ground or lower the water table to below the tunnel invert but rather to reduce the pore pressure to a sustainable 3 bar pressure,” said Stuart Warren, engineer in charge of Project Moses for COWI-Mott MacDonald.

Site investigation of two geological anomalies in the Channel, including melt valleys filled with sand, presented the opportunity for Storebælt as the client, with COWIMott MacDonald and specialist consultant, the Danish Geotechnical Institute (DGI), to install the first five trial

From left: Fig 1. Project Moses comprises 36 x 360mm diameter wells extending up to 100m through the tills and marl to the limestone bedrock to lower the pore water pressure in the seabed soils; Fig 2. A typical undersea dewatering well

wells in September 1992. From these, the feasibility of the scheme was confirmed, the full installation was designed, and the technical details of the seabed well heads was refined. Under a variation order to its existing contract, MT Group, the contractor, took over installation and operation of the £17 million dewatering scheme in December 1992.

Under a subcontract, United Drilling Contractors, the contracting division of DGI, used three jack-up drilling rigs to install the 36 wells. A steel casing 5m into the marl prevents compressed air from the advancing TBMs escaping via the wells and moving along the critical marl/ till interface.

The wells are located about 125m apart and lie alternately either side of the tunnel route. To avoid TBM interference, the wells are about two tunnel diameters from the main tunnel walls (a 35m tunnel corridor) creating a 70m wide dewatering corridor. Nine additional piezometer wells continually monitor the pore water pressure in the ground ahead of the TBMs with data relayed via radio telemetry systems on the barges to monitoring stations onshore.

Water is discharged from well heads on the seabed and it has taken 8-10 weeks of pumping to draw down the water table and establish a sustainable 3 bar pore pressure at tunnel axis. Wells will be turned off progressively as adjacent cross passages are completed. Under the new schedule agreed as part of the settlement between MT Group and Storebælt in May 1992, all main tunnel excavation and the last of the cross passages is expected to be completed by mid-1994.

Deep meeting

Traffic in the international shipping lanes of up to 20,000 ships/year and more than 50,000 single ferry trips/year eliminates the possibility of setting wells in the deepest section of the tunnel alignment. Lack of till cover in this 1.5-2km stretch would probably cancel the effects of dewatering anyway. It is hoped, therefore, that this section can be completed without the need for man-entry.

Chemical grout injection, lateral brine ground freezing, and horizontal dewatering, all from within the main tunnels, will be used either singularly or in combination to assist excavation of the cross passages in this area.

Under current plans, the TBMs will junction face-to-face on one side or the other of this zone. The shields will be

stripped of all components and the segmental lining will be erected inside the skins to complete the link.

After extensive mechanical repair to each of the TBMs, all four were back working again by the end of January 1993. Since then, tunnelling has progressed better than at any time in the past, erecting at best 5 x 1.65m rings of lining in an 8hr shift. Each 400mm thick ring of the bolted precast concrete lining comprises six segments and a key. To ensure the required 100-year design life of the segments, a low water/cement ratio of 0.35 was specified for the concrete. The concrete mix, developed

by MT Group, produced average compressive strengths of 70MPa, well above the 50MPa specification. To retard corrosion, all reinforcement has a minimum 35mm concrete cover and the reinforcement cages are covered with a fusion-bonded epoxy coating of between 150 and 450 microns thickness. To provide a watertight lining, the segments are fitted with EDPM rubber gaskets supplied

by Tunnel Accessories of the UK. These have been tested to 16 bar pressures and are compressed during ring build and held in position by curved bolts on both the radial and circumferential joints.

A fully automated casting yard on Halsskov produced all 62,000 concrete tunnel segments between January 1990 and April 1992. With tunnel boring at a standstill for much of that time, storage of the segments became a problem.

Today, there are stockpiles of segments on all available open spaces and the factory is now producing the precast elements for walkways and other finishing elements.

Each TBM is fitted with two guidance systems. The CAP (Conception D’Automates De Pilotage) system maintains correct alignment by using the TBM orientation to automatically compute the necessary ram extensions.

CAP also controls and monitors many of the TBM functions for rapid fault diagnosis and warning of potential mechanical problems.

A Dywidag system continuously surveys the TBM position and orientation using automatic theodolite measuring of both angles and distances to four reflecting prisms set in the TBM. By comparing the TBM position with the required alignment, the sequence of rings is identified to either maintain or return to correct alignment. A wriggle software package developed by COWI-Mott MacDonald 33

provides a final check of completed rings and overall alignment. As the rings leave the tail shield, the annulus is filled immediately with a cement/bentonite/water grout injected at about 2 bar pressure above ambient. Proof grouting takes place about 50 rings back.

Spoil problems

That boulders have not caused a problem proves that the cutterheads (a Wirth design contribution) are working well and that the stiff till matrix holds them well enough for effective break-up by the cutters. Also, the ribbon section of the primary screw conveyor allows the passage of stones or boulders of up to 600mm in dimension to the stone trap where they are removed at atmospheric pressure.

A criticism of the cutterheads is that they do not mix the excavated material well. The clayey till tends to cake inside the excavator chamber. The extended screw conveyor tends then to drill itself a hole in the compacted dry clay without extracting any material. “Substantial amounts of water must be introduced to create a material that will feed into the screw,” said Ove Lauritsen, Deputy Project Manager for MT Group. This causes a mess in the working area as wet material spills off the conveyor belt on its way to the muck cars. “Polymer additives injected into the excavation chamber with the water helps bind the water into the material and create a more homogeneous mix,” said Lauritsen. The possibility of recycling excavated muck back into the chamber to improve boring conditions when in the marl is also being investigated.

Besides those on the screw conveyor bearings, the main bearing seals, the Japanese-type wire brush tail seals, and the segment sealing gaskets, are all standing up well to working pressures encountered so far. Project Moses will help ensure their adequate performance through the remainder of the job.

Hindsight

According to Gotfredsen, good quality assurance systems, approved by Storebælt, were established by Howden, but as manufacture began to run behind schedule, adherence to the system began to slip. At the time, MT Group headed by the Danish company Monberg & Thorsen, did not have the necessary knowledge and experience in managing a bored tunnel project. Toward the end, Storebælt had more people supervising TBM manufacture at Howden than did MT Group. In their defence, Howden claims that there was a great deal of modification and change requested by both the client and the customer to their accepted design.

Initially, four TBMs were considered excessive for 16km of tunnel and MT Group tried to avoid the logistics and expense of working from Sprogø island. The client’s insistence on four TBMs, however, has been prophetic and, ironically, it is now the Sprogø TBMs which are expected to complete most of the tunnel excavation. By mid-February 1993, the two Sprogø TBMs had completed 617 and 739 rings respectively since being launched in December 1990 and March 1991. This is compared with 377 and 589 rings completed by the two other TBMs since their launch in August and December 1990 from Halsskov on the mainland.

After the many troubles that have plagued the project, the moral of the story according to Hans-Henrik Gotfredsen, Managing Director of Storebælt, is: “Don’t build bored tunnels - at least not under the sea in the glacial tills of Denmark.” Gotfredsen admits that from the beginning he favoured a steel immersed tube, much like the link under the San Francisco Bay for the BART mass transit system.

This recommendation lost against strong support for a bored tunnel from the national railway authority and from certain politicians. According to Gotfredsen there was high optimism among the tunnelling industry given the start of the Channel Tunnel project. There was also the aspiration of the state railway authority to introduce bored tunnel technology to promote new rail tunnel projects; environmentally, the bored tunnel raised fewer demands; and when tenders came in for all three options, the bored tunnel bid was DKK400 million cheaper than either the steel or concrete immersed tube options. The actual cost of an immersed tube could also have escalated considerably, especially as this would have been probably the most ambitious use of the immersed tube technique to date.

“The practical problem with a TBM-bored tunnel,” according to Peter Lundhus, former Project Director of the tunnel for Storebælt and now Technical Director of the Øresund Denmark to Sweden fixed link, “is that so much capital and so much of the progress is in the hands of so few. Management is denied the flexibility of taking action to speed progress if problems occur. Everything depends on the actions of the 10 to 20 people operating the TBM at the time.”

“With a bored tunnel more or less forced upon us, we as the client decided to establish as tight a control on the construction as possible,” said Gotfredsen.

While the Project Moses dewatering plan will assist excavation of the cross passages, no chances are being taken. The 10m to 16m long x 4.4m i.d. cross passages will be driven from one heading starting with a 1.8m diameter cast iron segmental lining and then reamed to full section which will also be lined with cast iron segments. A team of well experienced Irish hand tunnellers from the

In efforts to maintain control, Storebælt took a direct interest in the design of the tunnelling machines and retained construction supervision. The COWI-Mott 34

MacDonald consulting group took over construction supervision in March 1992. Prior to that it was engaged as advisors to the client when the EPB tunnelling concept was specified and four TBMs were insisted upon.

Storebælt liked the Kawasaki TBMs but wanted them to be manufactured in Japan instead of Europe. Kawasaki said this couldn’t be achieved within the time allowed and pulled out. Mitsubishi agreed to manufacture in Japan but was now in the race by themselves and the price was creeping higher. When Howden appeared with Wirth, it reintroduced competition for the order. MT Group preferred the Howden offer not only on price but also because manufacture would be closer geographically and language would be less of a barrier.

However, with many contractual and mechanical problems now behind them, all involved on the tunnel section of the project are cautiously optimistic about the advantages Project Moses will bring during 1993. “We hope to maintain a consistent advance of about six rings/8hr shift and have the main tunnels completed during the first half of 1994,” said Lauritsen. “To make up time, we have also started concurrent excavation of the cross passages with main tunnel driving and will allow mechanical and electrical installations to begin before full completion of the civil contract, where possible.”

UK company Anglo Globe has been subcontracted to complete the cross passages, each one taking between six and eight weeks to complete. A system of horizontal dewatering has also been installed, while a heavy steel safety door mounted on circular beams in the main tunnel section can be triggered automatically and shut tight against water inundation. The last of the cross passages is scheduled to be completed by mid to late 1994.

Finance matters

As the totally independent yet State accountable organisation set up to build, own and operate the fixed link, Storebælt is responsible for all its financial and daily management. “That the politicians wanted to be directly involved in the project, unlike the British and French Governments in the Channel Tunnel project, gave us the benefit of Government guarantees on borrowed money,” said Gotfredsen. “With State guarantees, we can raise loans at interest rates of up to 4% lower than Eurotunnel which is raising money without Government guarantees.

Financing costs for the total DKK26.5 billion borrowing of our bridge-tunnel project at 8% interest is about DKK14 billion. This could have been as high as DKK21 billion without the Government guarantees.”

The cost of the link is to be shared 50/50 between the road and rail facilities. When opened, Storebælt as operator will own both the road and rail services. The State railway will then take over operation and ownership of the rail link after 30 years when it pays off its half of the cost. Originally the rail link was to open about two years earlier to give it a head start on the road which

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would have to wait for completion of the East Bridge. As it happens, the road link is expected to open by early 1998 with the rail link opening two instead of five years earlier in early 1996 instead of 1993. The road link is also now seen as the ‘fat cow’. Road tolls equivalent to ferry fares are forecast to pay back the road half of the cost in about 15 years from opening. The cost of the full link at road opening in January 1998 will be about DKK37 billion (£3.7 billion). This is about 20% higher than the original DKK21.5 billion estimate in 1988 prices.

In the meantime, the road and rail West Bridge between Funen and Sprogø is advancing well ahead of schedule and is expected to be completed early in June 1993 but will have nowhere to go until the East Channel links are completed. Much hangs on the success of Project Moses for the completion of the much troubled tunnel section.

When completed, albeit late, at a higher cost and after many trials and tribulations, the bored tunnels will provide a top-quality structure with low maintenance requirements over its long structural life.

Storebælt - the final chapters SITE VISIT REPORT: MAY 1995

O

n 15 October 1994, Prince Joachim, the second son of the royal family of Denmark, became the first person to walk officially through the completed southern tunnel of the twin tube rail link under the eastern channel of the Storebælt Strait. As the Prince emerged from the air lock of the second of the two TBMs which stood facing each other across a 0.3m section of hand-excavated tunnel, a great cheer went up from the crowd - a cheer that not only signified celebration of this breakthrough, but also echoed an almost audible sigh of relief from the international tunnelling community an enormous milestone for this troubled project, and a credit to all those who have engineered solutions to extraordinarily difficult problems and have stuck with the job through the most devastating of calamities.

When the DKK3,100 million contract for the 8km long twin-tube bored tunnel under the eastern channel of the Storebælt was awarded by Storebælt A/S to the MT Group in November 1988, tunnel excavation was programmed to be completed between January 1990 and September 1991. To meet the programme, MT Group mobilised four 8.75m diameter EPB TBMs from James Howden of Scotland in association with its acquisition of TBM manufacturer Wirth of Germany. These would work from the four portals - two from the Halsskov landfall on Zealand and two from Sprogø Island in the middle of the Storebælt. Each was programmed to excavate about 4km, advancing towards a mid-tunnel junction on the Sprogø side of the nadir, or deepest part of the channel.

Prince Joachim emerges from the second TBMs air lock after being the first person to walk through the completed link in the southern tunnel of the twin tube link

However, a catalogue of disasters and problems befell this extremely challenging project (page 36).

First, the TBMs arrived up to 10 months behind schedule and were late being commissioned. Problems continued when impurities were found in the hydraulic systems of the new TBMs and went on to include the disastrous 35

Chronology of the Storebælt TBM drives June 1988: Tenders for immersed tube tunnels of

steel and concrete as well as a bored tunnel option are submitted.

November 1988: A DKK2,800 million contract for

a bored tunnel (lower than its lowest immersed tube option of DKK3,200 million) is awarded to MT Group comprising Monberg & Thorsen (Denmark); Campenon Bernard (France), Dyckerhoff & Widmann (Germany), Kiewit Construction (USA) and SOGEA (France).

Four EPB TBMs ordered from James Howden of Scotland with newly acquired Wirth of Germany. Main tunnel excavation is scheduled from January 1990 to September 1992.

May to August 1900: TBMs arrive after delays for late

modifications and the first starts boring from Halsskov towards Sprogø.

September 1990: Impurities found in hydraulic system

of first TBM launched and systems of all TBMs are stripped and cleaned.

2 March 1991: All four TBMs now working.

28 March 1991: After 218m, fine particles penetrate the

seals and damage the front screw conveyor bearing of one of the TBMs. The full 80 tonne weight of the 12.5m long front screw is held by the single bearing at the back end. When full of muck the screw floats centrally in the casing. Otherwise, it lays heavily on the casing invert adding extra load to the bearing. Bearings on all four machines are replaced with bearings of more robust design and with a positive grease feed to the seals.

28 October 1991: Divers succeed in securing TBM

Jutlandia against further inundation. Water in the portal zone is arrested at some 14m below sea level.

Had inflow continued it could have overtopped the dewatering wells and jeopardised the island's madeground in which the tunnel portals are established. It takes until November to pump out the shorter parallel TBM heading first and until 27 November to pump out the longer TBM Jutlandia drive.

Early 1992: Low penetration of up to 7 hours for each

1.65m stroke (instead of the more normal 30-40min) and at maximum 14,700kN torque indicates critical need for cutter and pick changes on the two Halsskov TBMs, but the ground is too unstable to risk extended manentry maintenance shifts, particularly after the flood experience off Sprogø, and the TBMs are kept going in search of better ground. It becomes evident that the TBMs will need auxiliary support in more technically demanding conditions than expected.

January 1992: MT Group starts constructing a 365m long

18.5m and 168m into their drives) for modification and replacement of the front screw conveyor bearings.

Relationship between MT Group and Howden break down and Howden leaves site.

x 70m wide clay peninsula over the Halsskov headings.

First man-entry reveals excessive wear not only of the cutting tools but also of the cutterhead body. A clay blanket is built up to a peninsula from which a zone of vertical ground consolidation by jet grouting is carried out just ahead of the TBMs. When in the zone, shotcrete supported chambers are excavated in front of TBM cutterhead from within which rebuild work is carried out in free air. A 2m diameter x 21m deep shaft allows access and materials supply to the chamber from the peninsula.

September 1991: The two TBMs resume boring from Sprogø

February 1992: Spirit of the contract between MT

7 May 1991: All TBMs stopped (the other three at 264m,

14 October 1991: The Sprogø island flood. The leading

TBM, Jutlandia, has advanced about 358m and is about 250m out under the sea, under about 10m of cover and 6m of water and has now been stopped for about 70 hours for face inspection and tool changes in free air. Water is seeping through and the maintenance subcontractor, unfamiliar with tunnelling work, trails the cables of a submersible pump through the man-entry lock to pump out collecting water. Early morning and the heading is evacuated rapidly as water begins to pour in. No time to remove the pump and other equipment to allow closure of the lock door. The screw conveyor is also retracted, leaving the closed mode ports of the screw conveyor open. Inundation of up to 4m3/s of water, described as just like pulling a plug, indicates an obvious direct link with the sea above. The heading flooded in three hours. Water spills over at the portal into the parallel TBM drive and floods this heading too. A wellplaced dumping of a barge-load of clay within hours of the incident stems the flow substantially.

The total cost of retrieving the situation after the flood was about DKK200 million of which MT Group's insurance 36

paid the largest part. Storebælt's insurance paid for its equipment and damage to the permanent works.

Sole insurer for the project is Danish company Hafnia which has reinsured about 95% of the cover worldwide mainly with the help of British broker Sedgwick after its involvement with the Channel Tunnel project.

Group and Storebælt becoming extremely contractual and claims orientated. In March, the client extends the advisory role of the COWIconsult-Mott MacDonald consulting engineering JV to include construction supervision. This was in the hands of Storebælt hitherto.

March 1992: A jammed guillotine gate at the screw discharge point prevents one of the Halsskov TBMs moving into the consolidated zone. Vertical nitrogen ground freezing from the peninsula is required to repair the gate.

May 1992: Contract now at stalemate. To avoid contractor

leaving the job or being dismissed by the client, the contract is renegotiated. All claims settled at DKK300 million with a further DKK650 million as progress related payments. The settlement is binding until the finish of the construction works now rescheduled to mid-1994. Under the new arrangement the contractor accepts a greater share of the contractual risk and agrees to work with the client and its consulting engineer in developing measures to assist the EPB TBM technique. Project cost for East Tunnel now more than DKK5 billion and the new tunnel commission date extended to late 1995/early 1996.

June 1992: Both Sprogø TBMs resume work after the flood.

September 1992: Project Moses trials begin and show

positive early results. Flood is also partly blamed on the confidence of working ahead of the face but at the outer edge of the field of influence in free air and in ground unknowingly benefitting from the island's dewatering system.

November 1992: First TBM resumes boring from Halsskov after extensive rebuild of worn cutterhead.

December 1992: MT Group and Howden settle their

differences out of court with £5 million of withheld fees paid by MT Group to Howden, significantly less than £10 million claimed by Howden. Howden will provide MT Group with technical advice and assistance as required under a new service agreement.

End January 1993: All four TBMs now boring. Project

Moses is being implemented with the last of 36 wells expected to be in by the end of April 1993. Excavation of the first mined cross passage has started. Casting of all 62,000 tunnel lining segments was completed in April 1992. 1993 begins with morale on the project higher than has been for many a long dark month.

16 February 1993: Latest progress report: • • • •

Sprogø TBMs have advanced 1,220m and 1,020m Halsskov TBMs are at 972m and 622m Project best: five rings (8.25m) in an 8hr shift and 11 rings (18.15m) in a 24h day achieved by TBM Dania from Halsskov in January 1993.

All man-entry is now under 2-3 bar compressed air pressure.

June 1994: The TBM fire.

September 1994: Horizontal ground freezing needed to permit safe man-entry to replace worn cutters on one of the Halsskov TBMs.

October 1994: Junction of the two TBM drives for the southern tube of the link and Prince Joachim of the Danish royal family is the first to pass through the completed tunnel on 15 October 1994.

Mid-February 1995: Reconstruction of the damaged

area of the TBM fire heading begins and is completed by early March 1995.

7 April 1995: TBM Fionia from Sprogø, progressing

towards the fire damaged TBM Dania from Halsskov builds its last ring of segments at about 0.5m from the Dania TBM heading. This is almost five years after the first TBM built the first ring of segments in August 1990.

inundation and flooding of the two tunnel headings from Sprogø Island in October 1991. Failure of the main bearing seals of the large screw conveyors of the EPBMs, when less than 200m into each of the drives, then caused five to six months delay on each machine. Add to this the nine months required to rebuild the cutterheads of the Halsskov TBMs after suffering incredible wear caused by the highly abrasive glacial till material and the inability to enter the cutterhead chamber to execute timely cutter changes, due to the high compressed air pressures required to accomplish safe man-entry.

Other mechanical problems required time consuming and expensive support methods to allow safe repair.

These included the vertical nitrogen ground freezing to repair a jammed screw conveyor discharge gate on the TBM 1 from Halsskov in March 1992 and the horizontal ground freezing needed to allow safe man-entry to replace worn cutters on the Halsskov TBM 2 later in 1994.

All of these events conspired against progress of the project, leading to tremendous strain in the contractual relationship between the contractor and the client and break down of communications between the contractor and the machine supplier.

The fire

Despite extremely desperate times, these problems were overcome and culminated in October 1994 with the breakthrough of the southern tube. But celebrations at the breakthrough were subdued, for not 25m away in the parallel northern tube, tunnelling to complete the last 58m of that tunnel was in a critical situation.

In June 1994, when only 1% of tunnel excavation was left to complete, and when few could believe that anything more could plague this ill-starred project, a devastating fire broke out on the Dania TBM 2 heading from Halsskov. Fortunately, no-one was killed or seriously injured in the fire, which is believed to have been caused by the ignition of oil vapour escaping from a broken hydraulic hose on the TBM. The fire blazed for several hours, causing considerable damage to the TBM and, more seriously, nearly destroying the top segments of the leading six rings of the tunnel’s 400mm thick precast segmental lining. In some places only 160mm of the crown segments remained as the barrier between the free air tunnel environment and the enormous ground and water pressures of up to nearly 5 bar acting on the outside of the tunnel. Had the fire burnt a few hours more the last few millimeters of the lining would have also spalled away and inundation would have followed inevitably. Such an inundation would have flooded the Damaged segmental lining above the zone of the intense TBM fire with more than half the segment thickness spalled away

Summer 1995: After establishing ground freezing, hand

excavation of the final 0.3m of ground between the two face-to-face northern tunnel TBMs begins.

Expectations for opening the finished sea crossing: Rail bridge/tunnel expected to open by end 1996 or early 1997 Road bridge expected to open a year later in 1998.

37

entire Halsskov tunnel and through the completed hand excavated cross passages into the parallel bore.

need six minutes to evacuate the heading and retreat into the safety of the bulkhead airlock.

Retrieving this situation, when the end of all tunnel excavation was so tantalisingly close, has been a difficult test, not only technically but also for the morale of all involved on the project. To mitigate the immediate risk of flooding and to protect workers during the repair phase, a carpet of plastic material was laid over a 25m x 25m area of the seabed directly above the damaged tunnel. Next a substantial bulkhead immediately behind the TBM back-up trailing gantries was erected as quickly as possible to isolate the damaged area from the rest of the tunnel system. The bulkhead was a concrete plug of about 5m thick which was equipped with a man and materials airlock. The bulkhead was about 200m from the tunnel face, about 2km from the Halsskov portal and just west of cross passage number seven which was being completed when the fire occurred and has since been finished.

Reconstruction of the damaged area began in midFebruary 1995 and was completed by early March. At that time, the Fionia TBM from Sprogø, which faced the damaged and stranded Dania TBM from Halsskov at a distance of 58m, started boring again to complete the last 35 rings of the northern tunnel. Fionia was stopped in July 1994 to prevent any possible adverse influence on the extremely vulnerable section of fire-damaged lining in the Dania heading.

While the situation in the tunnel was being stabilised, the engineering teams from COWl-Mott MacDonald, the tunnel design and construction supervision JV; MT Group, the construction contractor; and Storebælt A/S, the client, finalised a reparation plan. During most of this period, the damaged area was under constant observation by CCTV. Air pressure was applied once the bulkhead was in place and was gradually increased to about 0.75 bar pressure.

Frozen junctions

The reparation plan entailed reconstructing the damaged area of the tunnel lining using surplus stock of cast iron rings from the Channel Tunnel project. The Channel Tunnel rings have been built inside the existing precast concrete rings, reducing the internal diameter at this point from 7.7m to 7.2m over a distance of about 36m or 22 Storebælt rings. This however does not adversely affect the operation of the trains.

Crews of up to 12 persons at a time worked in the compressed air zone ahead of the concrete bulkhead. In case of emergency, it was calculated that workers would

On 7 April 1995, Fionia placed the last segment in the bored tunnel programme. This comes almost five years after the first segment was placed in August 1990 but is not the end of excavation. Now begins the final phase to excavate by hand the last 0.5m still existing between the two TBMs. Originally, all four TBMs were programmed to meet within the better quality, underlying marl on the Sprogø side of the nadir where a junction could take place at normal atmospheric pressure. However, the highly abrasive and technically demanding nature of the overlying glacial till, particularly on the Halsskov side, resulted in much slower progress than anticipated. In the event, it was the two Sprogø machines that completed the passage under the nadir and progressed toward a junction on the Halsskov side of the channel (Fig 1).

Very slow progress by the Halsskov machines then forced a junction for both tunnels in the till, rather than the better quality marl. This in turn demanded the use of extensive ground freezing above the TBMs to create a safe environment for hand excavation of the junction.

It took four months to create this umbrella of frozen ground above the first two TBMs, Jutlandia and Selandia, to junction in the southern tunnel. The two TBMs were

Fig 1: Plan and geological section of the Eastern Channel railway tunnel crossing with location and date of major events

38

stopped in May 1994 and hand excavation of the final 0.3m began in September 1994. The same process was then repeated for the junction between the Fionia and Dania TBMs in the northern tunnel. After stopping these two TBMs on 7 April 1995, the final breakthrough was expected to be accomplished toward the end of the Summer in August/September 1995.

In the meantime, the components of the two southern tunnel TBMs, inside the sacrificial skins, have been cut up and removed and a cast iron lining has been erected, providing a completely finished tunnel bore in which track laying and other mechanical and electrical installation work now continues. Excavation of the last two of the 29 crosspassages between the bored tunnels is also under way.

According to a status report distributed by the Storebælt Public Relations Department, a team which has kept the media fully informed of all events during the bedevilled development of the project, the rail component of the Storebælt link, comprising the road/rail bridge across the Western Channel from Knudshoved on Funen to Sprogø, and the twin tube rail tunnel under the eastern channel from Sprogø to Halsskov on Zealand is expected to be open for traffic by the end of 1996 or early 1997. The road facility, with traffic passing over the eastern channel on one of the world’s longest single span and most impressive high-level bridges, is expected to open a year later in 1998.

The current budget for the entire Storebælt link, the two bridges and the tunnel, is DKK21.6 billion in January 1988 prices (approximately US$3.5 billion). This includes all costs relating to the delays incurred on the tunnel project.

A settlement with the contractor in May 1994 resolved all claim situations, resulting primarily from the flood at Sprogø in 1991, increasing the original DKK3.1 billion contract to DKK4.9 billion. This however did not affect the overall cost of the project as there were sufficient reserves in the original budget. Since this settlement was binding to the end of the contract, the final cost of the tunnel for Storebælt A/S remains unchanged despite the damaging fire in the Dania TBM heading in June 1994 and its consequences. MT Group can only look to its insurers for damages caused by the fire. For Storebælt, the fire impacts significantly on its financial situation causing yet a further extension of the debt servicing period on borrowed money. Danish State Railways, as the sole user of the rail tunnel facility, will actually shoulder this increased cost.

Last segment in the northern tunnel tube was erected by the final TBM on 7 April 1995

close accordance with schedules and are within their original budget prices. Whereas the road and rail is carried on the western channel bridge, the rail had to be separated from the road bridge over the eastern channel because the very long 1.624km free-standing span of the bridge could not carry the weight of both.

Storebælt challenges

While almost every conceivable calamity that could befall a subsea tunnelling job has occurred on Storebælt including inundation, the greatest risk of all - it must be remembered that this tunnel was recognised from the start as being one of the most challenging of this century and one that would require the most advanced tunnelling technology available. Despite the succession of disasters, and in some cases directly because of them, the job has undoubtedly advanced the leading edge of tunnelling technology and its support systems.

Geology and TBM selection

The design of the EPBMs specified for use in the complex geology beneath the Storebælt was of the most demanding to date. These had to work in two distinct layers of material - 40% in the upper glacial till which contains boulders up to 3m in size, 40% in the underlying chalk marl which is highly fissured, and 20% in mixed faces of both. The water content of the material is influenced by the full hydrostatic pressure of the sea above with the tunnel alignment being under about 1 to 5 bar pressure in the till and between 5 and 8 bar in the marl. The sand, silts and gravels of the till also have a high quartzite content and are extremely abrasive. Irregular pockets or

The project is financed by loans raised both in Denmark and overseas at competitive interest rates. The all-in borrowing cost on the Storebælt debt of DKK27.6 billion was 7.2%, including exchange rate adjustments. Such interest rates are made Fig 2. Simplified section of the four 8.75m diameter EPBMs used on the possible by the Danish Government which subsea rail project with their 20m x 1.2m diameter screw conveyors is underwriting all loans raised for the project. These loans will be paid back from revenue accrued by the collection of a toll charged for using the road link and the fees paid by the Danish State Railways to Storebælt A/S for use of the rail link. Debt for the road link is expected to be repaid by 2012, and on the rail link by 2026.

Thankfully work on the two bridges, despite taxing logistical and technological demands of their own, has progressed well. Both bridges have progressed in

39

The rail tunnel will provide a top quality, highly durable low maintenance structure though its 100-year design life

lenses of sand, under the full hydrostatic head of the sea above, with tialso added to the difficulties of working in the till. The marl is a more favourable tunnelling medium generally but the heavily fissured areas, particularly under the nadir, exposed the TBMs to the maximum 80m hydrostatic head of the Storebælt.

To cope with these conditions, • the EPBMs had to be capable of working in both the open and closed modes; • the cutterheads had to incorporate both disc cutters and drag pick teeth; • the main bearing seal was designed to resist water pressures of up to 15 bar; • the bulkhead and other closed mode components had to withstand water and soil pressures of up to 8 bar with an adequate safety margin; and • the tail seal system was designed to withstand not less than 12 bar pressures.

The four TBMs manufactured by James Howden and Wirth and equipped with their 20m long x 1.2m diameter double screw conveyors and four rows of grease fed wire brush tail seals with an emergency rubber lip seal fitted forward of these, complied with all of these specifications.

Project Moses

The TBMs were built according to specification but the high abrasivity and technically-demanding nature of the overlying glacial till in particular, was seriously underestimated.

Rapid wear of the cutterhead tools demanded much more frequent entry into the excavation chamber on all four TBMs for inspections and tool replacement than originally anticipated. However, man-entry was not always possible when required because of the high pressures required to execute safe entry. The high water and soil pressures were also placing high demands on the sealing systems of the TBMs. Early in the tunnel boring programme, it became evident that the pressures acting on the TBM systems had to be reduced in some way. This led to the implementation of Project Moses, the largest sea bed dewatering scheme ever carried out in connection with a sub-aqueous tunnelling project.

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Project Moses cost about DKK180 million and involved installing 43 dewatering wells of between 35m and 115m deep into the marl under the sea bed. These wells were fitted with dewatering pumps which were operated from six barges anchored in the sea channel, each barge supporting six or eight pumps. At its peak Project Moses comprised 37 wells working simultaneously, extracting 3,100m3 of water/hr from the ground of the sea bed. Over the area of influence, the system achieved the objective of reducing the ground water pressure at tunnel axis to less than 3 bar, thus reducing the demands on the pressurewithstanding components of the TBMs and allowing man-entry into the excavation chambers under more reasonable compressed air pressures in areas where this would otherwise have been impossible.

Unfortunately, Project Moses could not be installed in the busy shipping lanes of the nadir, and would have been ineffective in this zone in any case. However, the marl in this area proved less fissured than anticipated and the area was passed without serious incident.

Cross passages

Excavation by hand of the 29 sub-sea cross passages could be considered the most hazardous operation on the project due to the possible risk of inundation from the sea, particularly in the till sections. A team of experienced hand excavation tunnellers from Ireland was employed on these 17m long x 4.5m diameter connections which are lined with rings of bolted and gasketed SGI iron segments.

In the till, excavation started with a 1.8m diameter SGI lined pilot tunnel which was subsequently broken out in a sequence of small controlled steps to full 4.5m diameter.

While Project Moses assisted cross passage excavation substantially, further local ground treatment measures were installed to ensure safety. A lateral system of vacuum dewatering was installed around the cross passage area from the main tunnel bores and grout injection from the main tunnels consolidated any ground loosened by the passage of the TBMs and reduced water flow through bands of sands and gravels. For cross passages in the nadir, outside the influence of Project Moses, horizontal dewatering was used for their excavation. Work was

carried out under the protection of an emergency door which could be closed rapidly in case of threatened inundation. All but two of the cross passages were complete by mid-April 1995 and excavation, at the time of writing, had taken place without major incident.

confirmed yet again the inherent risks associated with tunnelling, be it a short length micro tunnel or a major subsea excavation project, and has emphasised the essential need to appreciate and manage these risks from the start.

Precast concrete segmental lining

It also revealed how unforgiving tunnelling is as a civil engineering discipline. A mistake made at the beginning of a tunnelling job must be carried through to the bitter end.

There are few opportunities for a u-turn other than complete abandonment of the job or substantial modification of the system once installed, which is often extremely difficult and requires enormous time, effort and money.

The lining is a one-pass system and must meet a specified 100 year durability in a potentially corrosive environment. To meet this, the reinforcement cages are protected with fusion-bonded epoxy coating applied by preheating the cages to 200-240°C and dipping them into a pit of epoxy powder fluidized by injected air.

But other questions arise. For example: • Could soil investigation have been more accurate and, if so, what different or better methods could have been used?

• What technical improvements could be included to ensure that TBMs can cope better with such difficult geological conditions in future?

• How can auxiliary methods be used efficiently and to best effect to assist the chosen tunnelling system?

• Why exactly did the flood and the fire occur and what must be done to ensure that anything similar does not happen again?

• Why did the concrete segments spall so badly in the event of the fire?

The 1.65m wide x 400mm thick rings of six gasketed precast concrete segments bolted in minimally-sized bolt pockets with curved rather than straight bolts are reinforced with 80kg/m3 of fully welded steel reinforcement cages.

Being a one-pass system, the quality of the ring build had to be within very tight tolerances. Following a long learning curve, this has been attained, but a final pass through the tunnels will be required to carry out back grouting and other water-tightening measures once the dewatering system of Project Moses has been switched off and the natural hydrostatic pressures return to normal.

Lessons to be learned

After all the trials and tribulations, the tunnelling industry must ask: What can be learned from the Storebælt tunnel project experience? If nothing else, Storebælt has

The root causes of the troubles endured by the Storebælt project may never be fully understood and blame certainly cannot be placed at the door of any

41

one party. Discussions about reasons why Storebælt proved to be such a troubled project would have to include: • • • •

Cross examination of all parties, and investigating the run up to various contract awards; The relationships between the client and its consulting engineer and contractor; The relationship between the parties of the contracting joint venture and its management of the contract; The relationship between the contractor, the client and

•

the consulting engineer with the TBM manufacturer; and A review of the specialist tunnel workers noting in particular their appreciation of the job and their previous tunnelling experience.

The Storebælt experience however, must not pass into history without the tunnelling industry taking stock of the messages it carries and without taking steps to redeem the reputation of TBM bored tunnelling as a feasible option to other civil engineering alternatives for providing major transportation infrastructure. n

Denmark-Sweden Øresund fixed link CASE STUDY: APRIL 1993

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erhaps predictably, there are no bored tunnels on the Øresund fixed link between Denmark and Sweden.

The road and rail link will comprise an immersed tube from the Danish coast to a manmade island and a combined low level and cable stayed bridge over the shipping lanes to Sweden.

When Sweden and Denmark ratified the March 1991 treaty in June and August 1991 respectively, the type of link to be built was specified in detail. “This avoids any exotic schemes coming forward from interested construction groups,” said Peter Lundhus, Technical Director of the Danish-Swedish client company Øresundskonsortiet. “We know exactly what type of structures are to be built. Any changes would require a change in the law.”

The Øresund road and rail link with Kastrup Airport in Copenhagen in the foreground, the immersed tube to the main-made island, and the bridge connecting to Malmö, Sweden, at the top

The 16km coast-to-coast link comprises a four-lane motorway and a two-track railway between Copenhagen and Malmö. A further 9km of road and 18km of rail is to be built in Denmark as part of the crossing, with further extensive land works in Sweden. Both land works may involve tunnelling. The state-owned national clients are Svedab in Sweden and Øresundsforbindelsen (a sister company of Storebælt) in Denmark, each holding a 50/50 share of Øresundskonsortiet, the client for the coast to coast link.

In Denmark, the plan includes a new road and rail link to Kastrup Airport on the coast. It is the proximity of the airport which demands the need for a tunnel off the Danish coast. An artificial peninsula will be constructed adjacent to the airport in which the immersed tube ramp will be established. The tunnel will be a combined road and rail concrete immersed tube much like the Eastern Harbour Crossing immersed tube in Hong Kong. At 2km long, it will be one of the longest immersed tubes built to date. It will rise on an artificial island built in the channel where road and rail will pass onto 9.5km of low level bridge and a cable stayed bridge of some 50m clearance above sea level.

Although ground conditions are more favourable under Øresund than Storebælt, a 16km long coast to coast bored tunnel option was rejected as it would be rail only and a road and rail scheme was wanted.

Credit: Photo by Koosha Paridel

Of the total DKK17-18 billion cost, the coast to coast section is estimated at DKK12 billion. All necessary working capital will be raised on the international money markets with the help of two State Government guarantees. The road link will be paid for by tolls gathered at plazas built on the Swedish side only. The cost of the rail link will be paid equally by the Danish and Swedish State railways at a total of DKK150 million/year each.

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The link is currently planned to be in operation by the year 1999. Towards that end, tenders have been received from interested consulting engineering companies and award of a conceptual design contract is expected

by June 1993. Work is then likely to start early in 1994 when four or five design and construct contracts worth between DKK1-3 billion are awarded.

“The West Bridge for Storebælt is a design-build contract offered as an alternative by the winning contractor,” said Lundhus. “We feel we can benefit from the same approach by maximising the expertise and experience of a consultant/contractor combination.” n

CASE STUDY: From the earliest notions of a fixed link for the 100km distance between Helsinki in Finland and the capital city Tallinn of Estonia, the project has engaged civil engineers. In 2014, a pre-feasibility study was commissioned for the project as part of the TEN-T connectivity networks for the European Union, with a target for completion by 2030–2035. Bored and immersed tube tunnels and bridge options and in combinations, were considered as well as rail only, or rail and road, and rail passenger or cargo services only, or both, were studied. As a result, the railway option with two bored rock tunnels was recommended for further planning. Development from there took an interesting turn when private enterprise The Helsinki-Tallin undersea rail fixed link is integral to the European TEN-T interconnectivity masterplan across the Baltic became actively involved.

Renewed momentum for Helsinki-Tallinn fixed link FEBRUARY 2018

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spirations for a fixed link between the capital city of Finland, Helsinki, and the capital city of Estonian, Tallinn, across the Baltic Sea would create the longest undersea fixed link to date at approximately 100km long. In the Summer of 2016, after some years of study, business entrepreneur Peter Vesterbacka, Finnish founder of mobile gaming company Rovio Entertainment Vesterbacka, began funding and promoting the FinEst Bay Area Helsinki-Tallinn Tunnel consortium. The initiative is based on a public-private partnership concessionaire model and is an independent option to the projects being developed by the Governments of Finland and Estonia.

A feasibility study by FinEst Link, suggests that its planned link could be constructed over 15 years and at a cost of €16 billion. Within the model the private sector would finance construction and a European Union grant would be needed to cover 40% of the costs. A subsidy to run state rail services from Finland and Estonia would amount to an estimated €280 million/year for 40 years and revenues from tunnel usage fees would cover operational and maintenance costs.

Members in the FinEst Group include consulting design groups Pöyry and Fira and the FinEst Bay Area Development corporation. Also in the team is AINS Civil Engineering of Finland, adding know-how in underground

Fig 1. Major elements of the FinEst fixed link vision

43

structures, construction management and the use of digital tools and platforms in construction.

speed trains providing a commuter journey from Tallinn Airport to Helsinki-Vantaa Airport in 20-25 minutes.

Central to the 100km long undersea link, the project includes a wide range of infrastructure engineering to create a proposed man-made island off the coast of Finland and four new stations at the Tallinn airport; on the artificial Island; at OtaKeila and at the Helsinki-Vantaa Airport (Fig 1). The FinEst project will be designed for high-

The vision is to create a new metropolitan hub of two million people at the heart of the Baltic Sea area, connecting the leading technology and business hubs of Finland and Estonia. As well as creating an international connection, the new districts around the stations would support economic growth with services and housing construction.

Chinese onboard for TBM-bored Helsinki-Tallinn link AUGUST 2019

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evelopment of the private initiative project picked up pace in 2019 when the China Rail International Group (CRIG) signed a memorandum of understanding for construction of the link with project developer the FinEst Bay Development consortium, together with TouchStone Capital Partners providing funding and Turkish contractor GAMA Holding.

“Engineering and technical design has been started

by Pöyry and AINS,” said Valtonen. “The work will now be accelerated with the addition of CRIG to the team.”

Construction of the 100km route will be by TBMs of 17.4m diameter, said Valtonen. “This is not an easy task, but it is achievable based on the geology between Finland and Estonia. The bedrock is granite and ideal.”

The longest drive will be about 25-30km between Development of the proposed 100km long rail link two artificial islands of the project also entered the environmental (Fig 1). At the deepest point, the impact assessments (EIA) stage with Fig 2. Route options for the tunnels will be up to 250m below sea engineering companies ÅF Pöyry and FinEst bored tunnel connection level (Fig 3).

AINS progressing civil engineering design work for the proposed twin TBM rail tunnels and the two artificial islands.

“The project is already looking at The EIA process in Finland began some potential TBM suppliers including a time ago and had completed the public couple of Chinese manufacturers,” comment phase by August 2019. said Valtonen. The expectation was for TBMs to start excavation in 2021, to take about 2.5 years and hit the On the Estonian side, the EIA process was ambitious projected opening of the link awaiting key decisions by the Estonian in late 2024.

Government in order to proceed. “We are responding to requests for further information,” said Kustaa Valtonen, a The two artificial islands are primarily cofounder and co-owner of FinEst Bay needed for ventilation and emergency Area Development. “Hopefully, when exits. Excavated rock will be used they have received this information, to create the islands, reducing the they will make their decisions quickly impact along the rest of the route. The and we can proceed.” larger of the two islands, off the coast of Finland, will include commercial and residential spaces.

Completion of the EIA process will determine which route will be developed. Three options are under A project budget of €15 billion investigation on the Finnish side and estimated excavation at about €12.5 four on the Estonian side (Fig 2). billion. A third of the funding will be Fig 3. Longitudinal geological section of the Helsinki-Tallinn rail link

44

provided by TouchStone Capital Partners, which has many Chinese state-owned enterprises as investors.

Neither CRIG nor its parent company, China Rail Group (CREC), are investing in the project, said Vantonen, and Chinese ownership of the project will be limited to less than 50%. Additional investors are being sought in Europe. “We would like to bring in local Finnish and

Nordic funding partners, as well as from Europe, just to keep a good balance of funding.”

It is estimated that project investment alone will result in a 1.1%/year increase in Finnish GDP and a 2.5%/year increase in Estonian GDP in the short term. The longterm economic benefits are expected to be much higher.

Political considerations of the Helsinki-Tallinn plan JULY 2020

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evelopment of a rail link under the Baltic Sea to link Finland with Estonia and mainland Europe hit a political snag when local politicians in Finland published a 2020 long term regional plan to 2050. The Uusimaa Regional Council decided to support only one alignment for the link passing through the centre of Helsinki. The decision is taken before environmental impact assessments and geological investigations in both Finland and Estonia have been completed.

“There is not enough information yet to make a decision about alignments,” said Peter Vestebacka, a cofounder of the project’s developer FinEst Bay Area Development.

Privately-owned FinEst Bay Area Development is currently the only organisation developing the fixed sea link, after the two-year government-backed FinEst Link project produced its final feasibility report in 2018.

The environmental impact assessments (EISs) include different possible alignments on the Finnish side and on the Estonian side (Fig 2).

In another unusual turn, the long-term plan would result in development of two underground rail links between Helsinki and the airport. “The two would be on top of each other,” said Vestebacka.

“The decision by the city regional council also complicates work on the Estonian side,” said fellow cofounder Kustaa Valtonen. “If you fix the route on the Finnish side, it has implications on the Estonian side, as you cannot freely mix and match potential alignments.”

Work on the project continued in the meantime. The EIA is well underway in Finland, although the Covid-19 pandemic during 2020 slowed the process. In Estonia, preparatory work to begin the EIA was taking place.

“Legislation in Estonia has been going through some

changes,” said Valtonen. “Our understanding is that it 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 China-based CRIG, China Rail International Group, a subsidiary of China Railway Engineering Company, CREC. The project design includes twin TBM-bored 100km long rail tunnels for dedicated passenger and freight trains, as well as two artificial islands off the coasts of Finland and Estonia.

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 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 a 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 stateowned 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.

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.”

In April 2021, the Governments of Finland and Estonia signed the memorandum of understanding for development of the project. This followed a memorandum of understanding signed by the transport ministries of Finland and Estonia to co-operate on the FinEst Link project in January 2016. The 2021 MoU is in force until 2030 and is expected to provide a better environment for requesting funds from the EU for the project. n

TunnelTalk references •

European connectivity masterplans - April 2015

•

Links across the waters - January 2010 45

Fig 1. Route of Eysturoy subsea link; Fig 2. Location of the Eysturoy and Sandoy subsea links

Rock pillar creates roundabout for undersea route

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Design of subsea links

s part of the Kingdom of Denmark, the Faroe Islands has for several decades been investing in road tunnels to improve connectivity on and between the archipelago of 18 islands. Most recently, the Eysturoy tunnel, as one of four subsea links, is of particular design. The 11.2km long route includes an underground roundabout and bifucation to portals on different islands to connect the Faroese capital, Torshavn, with both sides of the Skala fjord (Fig 1). In accessing both sides of the fjord, the project faced the unusual challenge of creating an underground cavern for the roundabout. A rock column was left in situ to support the cavern, with vehicles circling around the pillar.

The construction contract was awarded to NCC of Sweden in late 2016 together with a second subsea route to the south of Torshavn and running from Gamlaraett on Streymoy to Tradardulur on Sandoy (Fig 2). The client,

P/F Eystur-og Sandoyartunlar (ESTunlar), is a special purpose company set up by the Faroese Ministry of Industry to own, build, and operate both the Eysturoy and Sandoy toll roads. Geotek ehf is the engineering geology consultant for the client. The Eysturoy link advanced ahead of the 10.5km Sandoy route and achieved final breakthrough in June 2019 despite some challenging conditions.

Geology along the Eysturoy route, with its deepest point at 189m below the seabed, is primarily basalt.

The southern end is at Hvitnes and the portals at the y-shaped northern end are at Strendur and Rokin (Fig 2).

The single-tube, two-lane, bi-directional tunnel is 10.5m wide at road level and has a cross-section of 82m2.

“Construction on the Eysturoy project began in early 2017,” said NCC Project Manager, Alf Helge Tollefsen.

Completed roundabout cavern and its support pillar; Drill+blast excavation of the 82m2 road tunnel cross section

for Faroe Islands “Excavation was undertaken from opposite ends using two Atlas Copco XE3 jumbos with wire mesh and shotcrete support and rock bolting as required.” Weekly advance rates reached a peak of almost 190m in a single week in April 2018.

“One of the main challenges,” said Tollefsen, “was that much more pre-excavation grouting was needed than expected. This included one small part of particularly bad rock quality.” Approximately 7,500 tonne of grout was used on Eysturoy, “considerably more than was typical for two earlier road tunnels on the Islands.”

Construction of the roundabout with the profiled rock pillar in the cavern was a further, and unusual, challenge.

“The rock quality was quite good but the roundabout was systematically grouted,” said Tollefsen. Standard excavation was performed “but with focus on smaller

sections, with immediate bolting and shotcreting.

These elements together were quite complex.”

While working on the remaining tasks at Eysturoy, the NCC team is also managing construction of the Sandoy project with the lowest point at 157m below the seabed.

Work started on the straight 10.5km undersea alignment at the start of 2019. Following completion of the main excavations at Eysturoy in June, the two NCC Atlas Copco jumbos were quickly moved across the islands to begin the drill+blast operations at Sandoy.

The Faroese Parliament approved the projects in 2014, aiming to improve transport infrastructure to the immediate north and south of the capital. Local company, Jardfeingi, completed geological investigations, Norconsult performed the tunnel design, and Sintef acted as technical advisor. NCC previously built the

Eysturoy subsea breakthrough celebrations

4.9km long Vaga and 6.2km long Nordoya subsea road links on the islands, completing them in 2002 and 2006, respectively. Other sea connections on the archipelago of 18 islands rely on bridges and ferries. Road tunnel construction on the islands began in the 1960s and there are plans for about 30km of additional land and subsea road connections. n

TunnelTalk References •

Links across the waters - January 2010

External Reference •

List of road tunnels on the Faroe Islands

Veteran TBM continues work on Faroe Islands CASE STUDY: NOVEMBER 2010

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urchased originally in 1984, a Robbins 3.35m diameter TBM, as the first and only TBM to ever operate on the Faroes Islands, was several hundred meters into a new drive for the Eidi II hydroelectric plant on the island of Eysturoy in late 2010.

Bought new in 1984 by the Danish and Faroese contractors MT Hojgaard and J&K Petersen, the TBM was excavating a new 8.4km collector tunnel having already excavated about 25km of tunnel for the initial Eidi hydro scheme development.

The latest drive is part of a new green energy initiative by the SEV utility agency for the Faroes. Hydroelectricity is ideal for the collection of 18 windswept islands in the North Atlantic that is home to nearly 48,000 people.

Situated between Iceland and Norway, the mountainous islands receive an average of 250 days of rainfall

TunnelTalk references •

Marathon TBM finishes at Pinglu - December 2010

•

Workhorse TBM holes through for Bi-County - May 2013

•

Demonstrating the value of refurbished TBMs - October 2015

•

Rebuilt TBMs - are they as good as new? - May 2018

annually, creating significant runoff that can be channeled in collector tunnels to turn the generating turbines of small hydropower plants. Started with a launch ceremony in mid-September 2010, the new tunnel will collect water from 25 streams to increase the annual capacity of the Eidi plant from about 43 GWh to about 60 GWh. Prior to startup for its latest job, the SEV-owned machine underwent some refurbishment to the gearboxes, main bearing, lube system, and hydraulic hoses. “Prior to beginning this project, we contacted Robbins for an assessment,” said Anders Nedergaard-Hansen, Head of the Power Production Department for SEV. “We got an immediate response, and two technical engineers were sent to inspect the machine. They concluded it was in good condition following the upgrades.” Robbins also provided key spare components including for the cutterhead, grippers, hydraulic and lube systems, and Robbins Field Service personnel were on site assisting the TBM operations for the project duration.

By October 2010, the machine had excavated several hundred meters of tunnel in basalt rock with no problems.

“We are looking into using the machine for additional projects in the next five to ten years. The TBM was well-built by Robbins, and we have done a good job maintaining it,” said Nedergaard-Hansen. Tunnelling at Eidi II is expected to be complete in March 2013, and the newly expanded plant commissioned later that year. n

New 8.4km drive for 25 year old Robbins TBM on the Faroe Islands adds to the 25km it had already excavated for the Eidi hydropower scheme

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LPG nt Depa were 100psi soon , throu e the civil cons first mine at Wistow, needed to the proje Electricity Generating as the work began Undergrou Site investig team for rtmen let in late propan most importa geology is perhap e or tructi first of liquefy ct’s publi gh which the the 30psi coal production Board at nearby immediately ation succes • Cont on to nd Ltd s 1993, nt conside majority t from it began with power stations. million contrac c fundi racto and later and cons contain signs “One butane, thus acts was ing it.ofThe contrliquefy s depend ration. of ng tunnelling of the a £2 Its truction majo presen engineer rs and their spine modificatioof the most impo is granted. roads continuing r excav natural geolog s to a great extent two for each t to sink four access ce of substan In the interim the started. aquifer desig swork is essenti s: See to connect the remaining ation conveyors in the spine shafts, along the n claus cavern, was rtant of on By the following n-build al. alignm the tial “Unlike almost four mines. gases, more ical properties. Petrole Thyssen/Pigot roads will transport es we several end of ng constructi other awarded tunnelli contract pages both coal from the ent 5th all introd to the Janu jobs, t Consortium. easily stored um of water surface arywe welcom mines work was form, are boreholes as they come on The south drift tunnel total 230-won conditions document base uced into Nine service in liquefie seeping into 1996 corridor line and muck from , the e the sight for each is being driven the d will s temper liquefied by either eek progr in week , is a corridor d the of behind contr cavern were with the 5.8m and cased tunnelling machines lowerinofg their stipulation on ICE ature or the unde continu being equiv up to 90m of theand prayactor amm diameter Robbins e!” e and 117works drilled

by Boldon would in their deadit by compre three times wide, the ed Paterso TBM end headings. implement rgrou art confess with an average that the be boun surface, conventional alent to excav Drilling using ssion. 75% of about 100m/wk. ation n.

The Anderson Strathclyde of site selectio complete. Thend On the sectio d to acce the alignm appro oil well type an acce a familiar it is usual to store n was n lies provi The conveyor in stratum for north tunnel, some Of the pt and drilling rig. ent depth ximately The £4.5 leration them in The the South Tunnel about in findingding refrigerated the 70m parallel, is being it caverns was JLE the million a many . incorporates progr for tanks whose waterand that is sufficie shown Projectnt excavated using tunnelling pressure was awarde 57 x 16mm steel methods vessels. Cheape rather cons to be practamme minimcontrolling a Titan 134 roadheader the cost team contract rope cords across to contain than tructi d in on is supethe LPG asinflow the full so great estim while as making about half them under five tenders to Fairclough, the width of the 30mm contractor r still is to icable ising settle ground move available rvisin but reaso appo lowest of the rate of progress to make thick belt. The Anderson . Geostore, pressure store sseepag not nable,” said ates were acce ment inted the cost g Proje used on ment, nearl at Strathclyde Cable or econs about 50m/wk. Coal underground in larger comp French compa a licencee technicalof pumpin ct Mana Mike Smith pted JLE. water leted capacit y all have and cannot be extracted Belt conveyor in of the ulting from the cavern facilities. ny Geosto ger for y Inthesome cannotg until the cross have the designed To comp North Tunnel is a been Liquefiedand prepa engineers prohibi origin ck, which Constructi , JLE’s cases adit connecting and supervi al detai steel rope reinforced gases red tive. allow the Robbins TBM doubles thisled has pressurbeen successfully ensate predicted may the two conveyor be jeopa on. sed the contr groutin belt spine roads and of several require extensi project desig stored under g operati with two steel ropes e in leached On a proje the bore hole connecting settlement for areas of construction act docu LPG the speedthe ns our ve rdised by programm “We high, ons ment of 57mm in roadheader and alteratio cavities in ct of water where for many years the mine above is chalkexcavation caverns diameter supporting there have ground may still this size salt deposit the , including one ation. n of contr ol. The events that are e to meth grout inject completed. regime a lightweight 1in-thick spine roads in northernfor but finding and around s the France,Selby provethe been ion groun prove too engineer. ods come belt. The steel ropes within constru is the consult in for a purpos The Wistow mine suitableOne the caverns n its contr acceleratio unforeseen complexity, of the Associated geolog e-built underg came online in April d treatm n claus are spliced together At by of water gallerie ing no into y most adve ction grouting actual months contracts constru its final e has to form an endless easy task, ent round in October and water usefulness 14.5km ction length, methods their own. Two include the s above, when rsecurtains difficulties. facility as Paterso of a new rope at each side. will the conveyor permeation betwee were effective over the South NATM was the used on River be the n explained: on the is 1994 LPG jetty n caverns collapse being negothe recovery “The geolog longest Humbe ofr, its unrelated, of Killingh on the olme, grout kind .

JLE progr and excav At in y stren operation neither pipeline tiated ing, to must be include water gallery in Europe. ammes ation work enough to connect the gthen Airport grouting nor s which will .” concis compe allow extensi stabilise Express but facility to expect urren tent also of a and comp loose water ed to be Sett t, Heath the Conoco Rail ve excavaan imme lem and Becaus course the Linketunne bearing ent con tion anddiate refinery the lgeologi row necess more limited Grounary. the effect ensation grout groun and the proje require trol cal Jubile d site respo TBM vs movement d, ing for ct. Asproperties of the suppor s ment, the arensible e proje roadhea so importa A Titan der been one intercept of predicted mitigating ct team induc E205 roadhe more econom react nt, a geotech its contr t bay Since the introduction volum ground of the most ed by excav been establision, ader excava the JLE nical ic theactors has volun movement e losses and of the hed, equippe ting the 9m piezom projec TBM, the critical conce ation has Waterloo to stop tarily instru progress rates in s as they wide x 5m d with t team. The to measur cted and Lond eters NATM the South Tunnel benea rns for the Compen high top headin occur.

Line, integrity th some worke ground have on Bridg and of the oldes running as it g, with visible e to review at imporwater Compens sation gro does 1km of bandssafety of tant and t, histor ation uting the is the work NATM of marl and ically most a comp grouting subjected prestigious, work had flint for JLE s. Abou presen areas of to the is princ t int at that managemelex exercise London, chalkion time and been completed thelimitat NATM ipally tolerances most stringent work a tunne decision-m nt and co-op in multi-level damage restarted although revise the delay lling projec ever before d in imposed had a provided aking base erative all-pa Assessme t in the city. damaging due course, on d rty nts of all predicted instrument by extensive on information effect on Compens build 1mm settle the the ings geotechnic ation grou analysis. ation and 12.4km ment contowithin the ting array al computer-b “The undergrou Harris, aim,” s unde ased nd route ur along a Direc explained r the West tor of defines the princ minster David a ipal geote the company area insta on comp GCG as lled from ensation chnical advis five temp er to grouting, orary grou “is to keep JLE ting shaft the s

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to be well - if it is being achieved Mott MacDonald beginning, all appears question remains The ED: MA Authorityof the after collapse it not back then?

Manager: control Water PUBLISH under • Construction in now why was Severn Trent at Heathrow of an in-depth unnel sites. The REPORT works G H Hill & Sons • Client: that is the subject t: Eurot d portal Taylor Woodrow er: station excavation &Safety Designers: being answer to • Clien from the UK Health of the intende tunnels is about lting Engine and its The tunnelling now ) 1994.

Contractor: Co investigation by • Consu introduced ractor m &faultless. ed of which is kept October million vicinity m depth of the Link (TML • Design-build looks Mowle • Cont as che project ms were a £15.1 (HSE), the report John taken and wet fissur for the out ctor: carried and Executive (6.5 maximuCore samples were ) months yet. lling syste through the Balfour Beatty start hat started Trans-Manma(p56 • Contra eight firms men and machinery appear for several at the build 10.5km ton the tunnen to tunnel ners:160m.ls) sortiu ation by the The application of t to the unlikely to r chalk andtunnel Con the is still being collected for examin el Desig t. of view, at Carsing Japa headings. contrac is impressive ctTunn the uppe evidence Tunne store causing ard likely contrac in resources of d, point de ect Material aquedu project of legal ical long ortium result remains highly avoid the was identifie geolog for the tunnel au d’Étu that the technical Tunnel to conn e conditions rsea and landw ly available mile) and the possibility is meticulous. severe • Cons proceedings as a (Bure instabilityto detailadjuste tendering d slightly to indicated rom a run into attention BETU the from the site not readi the early hire has d tion their unde Channel Calais in Franc excava nt to be on the scale of France: tion ofonal The borings driven mostly through for the parties involved. made clear to alignme to of e systems were to McD While an event undersea s for in Derbys and comple nd the struts ing be ared used or have and Mott actor ies, UK: two years behind in Engla not be the need for props, whalings Therefore, it was h would difficultthe affected area. the 8kmwould Grit series with underly ct, as comp ing in ThesEuropean contr could avoiding Dover as and tunnels water an all-party-organised end l up lt proje the Frenc through be as much maytunne to was r rescue shaft Fullface TBMs shallow angles 60m diameter Strait cross pt and journalists attending amount of a difficu may the Ashove datee and dipping at running the ls. NATM Seikan s attem briefing in late June scheme, the large passing ment to series was not these planned of ary technical en lty for ly tunne e 1970 nes, main and equip n access marin mpor ard chos of site visit original of core excavation becaus ls mudsto tunnel. The ar fashio with the nes ease d by as much.UK landw great difficu about the causes the conte example. The ng tunne and the lack d pre-grouting. lengths of longcontract,inawarde spectacultorlongalong 1996, that questions l, had red conditions costing twice ng x 21.2m rail runni for strata of mudstones, expected, would m e tunne Japan 7.6m i.d. tunnelli then usedty tothe do the specifie interbedded contrac and the costs thereof in isolated UK nts are: fractu ed 164k sandsto to time. two The servic n) collapse and the except 2 veme face al contain es m, that of Authori st, at centr achie siltston , one sectio was was Water eter x comprising The journalists however of drill+bla specifically Marl stratu , chosen diam excavation notable It ded with geophysical survey two tunnels high (252m Severn Trent not be answered.

4.8m i.d.

The use interbed on the Chalk h was also weak by ber. calls for A Two other of the large 55m the Frenc tedcham and a x 15.4m of the thorough briefing Mowlem, wide4.8km, connec shortversa. d in the rmeable, rapid over time to confirm of vice were treated to a circumstances, the bids. In view a visit vation cross shaft on John ationand was aligne rally an impe (Fig 1). r out at the same design le for access the other due to progress and to from • Exca access ing undersea carried er pipeline for excav 3.6km and project's current ls unde excluded expected also is gene . During the of the highly suitabzones with thetunne again tunnel at 66m deep principal work three 3kmx 1.6m diamet which problems various sections a shieldof the borings site investigation, used 140m ute to ous rock red 1.6km the . land rail r en-ro underground into to specify extensive aspects how main long ing rsea and a ings. isAll ader a shorter side as homogene although fractu be anticipated more Knowing exactly enginee was decided gault clay stage, following the 500mconsult . Roadhe explore in to There also three undetunnel head on-going works. faulting, it nal site. and soft in The tion method best option, borings to for its takes the sump tunnelling, inflows were el termi of the of workmanship ream end. Castle Hillester. ard a large the stratum t to two downstwas nel Tunnwas supplementary the current quality based excava Manch sea level differs from what long landwtransported to considered it Hill & Sons of high waterthe Chalk Marl to be moved UK Chan eH ground adjacen were is: supervision scheme was below need the the wher G the also is construction never ion d detail One portal out ation for ly booms equipment would t muck was m of the shaft Following a maximum 115m ed. Tunnelling the collapse may include ial ment hmen were made. its original all Site investig pumped l Coal Board to was going on before portals this 1979 of specand some m3 the seab accomplis line e to Nationa distance from of surface and in the botto water and tunnels ing in through Worthy les along was explained in million out during servic ll some icalthe beneath with are going to work available. flameproofed be known, but it downhi an area boreho logist interval s, ssary large 4.5 carried slurried and 75m suited nece now being progressed as the tunnels the possibility of nce. of deep site when long UK readily sal in a 1km dista highly • The lly at sinkingside, standards detail how the work ng1mthe inthe planned with three y was t tried and for dispo ct, genera systems es strata, nued original. of runni holes the remarkabl the UK the aquedu pond abou were well ed Coal Measur encountered. is different from the al shallow particularly These conti efrom settling n of NATM on of ation of addition geology changed grouting ls. trains, which allow on ss uct schem excav tunneAqued with several methane being r also specified the catio ls What had al advances lling time acce allowed oir andsame undersea • Appli initially for rapid and tunne Reserv d tunne l ologic stable ground The Enginee Giant shaft rescue most extensive bers Fig 1.g Carsin /week e tunne area gton while at the high spee used the techn ensure sealed,to tunnel and to cross obvious, lex cham hallin um 428m breaking ncing servic regime to of the d To start, the most st a maxim a maximum 8h the comp rground mars record through which the adva t excavation of ground expensive, modification This forme side of unde to be almo conditions d amount and clearly most of the is the 60m the UK 7 days/week with week) building are Cliff. station and concurren ber, which had of the two advance the expecte scope of works espe with ly stages: shift/ original deal the day, l ing Shak ce to three to ental the at (24h/ tunnel; over cham before arriva is done in cofferdam built in ipal work TBMs used e maintenan concrete segm The excavation driving the water. This diameter x 30m deep m. airport the princ of the six downtime ure Similarly, advance of complete e servic and radial Area (CTA of the site non-bolted l of o.d. 8,036 k on grouting in are built; machines. ages and press the marin Central Terminal totally launch a fully ted. the rings tunnel muck km each 22km of 179m/wee rsea tunne and 3) to almost been comple grouting as cross pass had to share Terminals 1, 2 and 18.77 of the complete lined unde ll average was l south. the lining has ncing of the remove the extent 17.36km ducts also grouting after the adva l encompass and Only by tunnel, best overa e running tunne rn slurry and relieving tion times with ings. s l to porta disturbed ground. marin collapse and the side, mode) pressurised the UK from porta ecutive drive transporta ng tunnel head which French of this huge excavation Tunnel work ce (EPB runni Four consfirms that bid the job, Mowlem On the standing at the edge upper Channel Work marine l cross mining ure balan appreciated. "The Of the eight hand lowest tender. was 53km long could its scale be and earth press many latera ducts of the the second and • The water-bearing ground relief hed the won with l section 20m through soft ber 1981 1.2m the four outer accomplis and pressure and stabilized by in Septem four years. tunnels.

Geologica rescue shaft and inx 30m supported is deep ted started central bored gravels ages on comple and diameter only one to pass main access shaft, 60m to be piles which interlock d the Trace of of thethe original 19m diameter Fig 1. designe techniques e the three diameter Secant ed on different stages plan was linking portals Alan Powderham, surveying superimpos to ensur shafts Mowlem the four all of which were under access The fromtunnels, 1.06m centres," explained Foundations and advanced ms employed heading tunnels platform aders outer l • The of the andmain syste lyde roadhe concourse drive the Managing Director collapsed Strathc fact rsea tunne guidance onworks the of Mott MacDonald nor Steel sea. In Anders six unde excavation using when uct e Geotechnical Division m and Grosve under the that the C in representative on h servic in Markha gton Aqued lly meet at Portal Carsin mounted the Frenc and the lead designer's Team convened on ing started did actua the UK and and D in s of the 10.5kmm shields. Tunnell and at Portals B on ofsectionwas within 350m the so-called Solutions cross juncti and 1982, the collapse to engineer ings ry udinal following April. head Februa Longit l in e immediately Fig 2. tunne on level. finally at A way forward. "The stage, in the marin 60mm March, and at an early a safe and economic ns, line and ents of created is supported by 900mm It was decided ed ground conditio establishmUK side which a London Clay below in plan predict • The piles which step chalk cliffs m3 on the hensive ing view of the diameter contiguous the lagoons tion, the white el head te a compre million a further 20m below, foot of ice Tunn to formula the method of excava With from, and continue some 3.75 and tightly at the capping beam at UK Serv site for ent lining. incorporating re for the Secant piles. "A substantial concrete collar disposal what is an small t and perman the main a rigid in manufactu roof suppor Employer, ground surface forms site. both of muck TBM in ent of the ries in Report 79 working together.

Howden the agreem linking all the piles confined ent casting facto ns of CIRIA ct Practices’ of high ideas were recommendatio segm "Originally, recovery ed Contra thousandsents were large • The where l approach ling - Improv on excavating a based segm genera tries ‘Tunnel ry the . instinctively lining coun facto d and ents. tunnel x 65m," said Powderham The UK were followe the contract docum tial box of about 65m precision at high rats. in were to a poten incorporated s of the tunnel produced Grain had for per day Isle of Although sectiontent rock, the need segments 755 on the ed near in compe of 1,152 required 4,42, be driven t was expect output roof suppor ced the . immediate and produ within 3.5 years on of the segments lation now goingand lengths 42 instal units • The thousands of and other g, track many ical cablin of electr

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CASE STUDY:

Application of a TBM for developm in North Yorkshire ent of one of the was the first use twin spine roads of a TBM on a demonstrated to link five coal mining project the significant mines in the UK. The 5.8m advantages of Robbins went on CASE Robbins diameter the technique STUDY: TBM to supply TBMs to over traditional Excavation mine operations roadheadan non-circular TBM of the first er estima the world over. Most excavatio for excavating ted half n and ever purpo recently Robbins also rectangular cross the cost of se built LPG has developed provided a sections. greate new r securi creating the same storage caver storage capac ty for these ns in CAS E the vital infrast ity STUUK in the 1980s DY: JUNE 1983 ructure facilitie in tanksturbu on the were built JLE, lentsurfac SITE VISIT at s.

London times.e. Underthe REPORT: MAR groun Excavatio including Undergr d storag e ound n CH 1984 the Big Jubilee and Lond Ben cloc progressed Line Exten under on Bridg k towe or alon services r and the sion proje gside to area e mainline railw Hou ct, lived some limits of s of sout of the ay statio ses of Parliame the h most impo through exci ns; and nt; crea excavatio Underground and east Lond ting as rtant land passed ted new well as on, system. n work under metro marks the mos s Controllin which until of the then had the River Tham stations unde t critical collapse on the conc g excavatio challeng r the Wate city, rema es four labyrinth n and urrent es toge times of unlined rloo settlemen ined outside Heathrow to bring he Selby coal ther with SITE VIS closed-circuit tunnels, driven the tech t and man mine complex Express metro managin ITS AND and loading in nica Yorkshire was aging beneath the in chalk some 190m Rail Link g termina designed by the the ABR the impa l construction ls flatland budget project tankers at • Client: UK National for rail and bank of the IDGED UK National Coal ct of the Immingham. and the in Coal Board road River Humbe on the south FROM Board (NCB) statio as the first to connect five M&E insta October 1994 • Client: • Consultant: National TWO JLE separate mine sites mined underg r, will be used Calor Gas were amo n llations.

Coal Board - at Geol petroleum Wistow, Stilling Fleet, SUP Ltd round liquefie ogy PLEMEN ng gas (LPG) • Contractor • Consu Riccall, Whitemoor d

SITE VISIT REPORT:

CASE

1994 Rail Link in October the Heathrow Express prosecution excavations on world. The criminal of the NATM station and across the works and Collapse industry in the UK on to recover the CASE STUDY: made during ns sfor the tunnelling later, after working decisions how of high impact ramificatio the shielddesign-build engineer four years had its eaders in and ated t experience the roadhcontractor thattrial of the was a salien than anticip insult to injury. aqueduct t predicted added more water the project, last. The and Carsington complete for the projec or drill+b a bidding harder rock 10.5km long mining nts ctors The when : ided hand amou . Contra right turn to , prov wrong CASE STUDY sly1998 to keep large as. They were eaders and go seriou ects. Its ressed air Christm ices in before can serv proj their roadh design JUNE 1996 under comp rail hillside ture give up toinst aga SITE VISIT REPORT: public be on theinfrastrucfour arks advanced drives ned to would e mega shield, was of the chm futur three out d as benkept its roadheader and ope ing of forced pleted lems, stan and fund face, which el, com nted prob remaining l. nization nnel Tunn , orga docume under contro The Cha e planning its well of water well as STUDY: vativ 1983 CASE el for the inno successes, as .

RT: MARCH tion akes role mod VISIT REPO construc similar mist SITE ing d the project in outstand rs will avoi • Client: BAA that occurred on mind, othe for the owner: job in the collapse always focus the which 9 • Consulting Engineer hatever jinxed the October 1994 will

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common diameter. of that An orde Ther size r TBMs, we ever built. e were not placed for two new hard too man While sour visited with Herr on the y enknecht rock gripper AlpTrans the two Herrenkn cing supply machines TBMs was for the signed it During echt rock of two new WCSO a lease Lötschberg the contract TBMs work 2004. project Mike Rob site visit, agreeme Time is in the the critic nt with Herr Switzerland ing fact that the Nan ison, Resident first point and cy Construc of contact TBMs in Herrenknecht al factor for this enknecht in and in assoCreek and was with tion Man May nine mon West could com contract ciati the othe Cree on ths was mit to with EDT Area CSO proje ager for both k proje r building and the ct and for cts compone manufacturer a significant Hatch the two edge on s.

Mott Mac with Delo management with JJ&G, the botto nts in mid-May After taking n of offer run Ham the Donald from a s from deliv , for WCS pton AssociateNancy single end of m of the 312f we plan to laun ery of the water recla site offic O. July, whic t (95m) TBM e location Both proje s and deep Rockch the first TBM h will be construct mation cent cts at ahead er dale Shaf at SITE VISI T “We are, of our base flows fromion of the pum (WRC). At one the R.M. Clay are t by REPO RT: ton p station end of line prog the the Nan DEC EMB shaft sinkiin fact, ahead cons the is ram. truct cy Cree of ER 1987 k proje underway to WRC path elem ng and site mobschedule at the WCS ion of the new accept ct. the mom new under from each ent and we are ilization, but ent with MassAna O project will , dedicated At the other Seattle’s ground street for mini treatmen end, begin. answer to the TBM TBM to rema looking for 60-7 ng is the criticthe buses only At the the seco is sinking the Parall WRC site, t plant for s urban was week with round-the-cloc in on schedule 0ft (18- 21m) al “Ideally, a an uphi nd WCSO TBMClayton acce under the el 1.3 mile (2km) long traffic congestion.

Obayash /day ss closed ll k on . We streets of full pressua the, wee be better reception gradient to the will excavate shaft from whic i/ to 50% of the centra tunnels, up to 45ft rized day for main three 8hr shift will operate in the water kend tunne 23,000ft the buses l h ling shield tenance s/day, 6 is a mainbearins.g Part Station,” Shaft will shaft. The first 215ft (65m) present 4 off the streetdistrict, will take up (7km of would days on said groun the deep tena ) each mile/hr comm / John agre s and tech MacD nce cont d south mac Atkinson, to its 148f advance 20,5 TBM, launched North Aven in mile/hr in Pione nt with ract with ofeme “but therenician ononald er Herr hine on 00ft Projec peak period uter traffic flows increase the ue t (45m) each, mac t Manag with Herr one er many sky are deep deep Clea (6.2km) in at the Rockdale s. to about full-tfor hine We tie backs scrape ime Herr enknecht an uphi 12 rs alongenknecht r Creek exca with these also “Two TBM . We will .ancho Tunneling the tunne ring have reception ll gradient thea cutte enknecht we need vated and began in pay they willl route easy acces majority of shaft. the WCS s are a minimum anda tofixed r contract Atkinson/Dil November deal s to thesupp theAsse tunne 1986 when face.ly Also, all theascuttecost/yd 3 of chose two mbly l isofin dry, by the O tunnels com requirement lowest of lingham JV won rock ther need openthe firstcompetent consent pleted to get exca eight comp the contra the Guy F hold the upper faced machines said Ken and TBM at ground, s.” decr below the ct with eting bids Rockdale we with breas the Johnston ee deadline the facility in vation of part of the $61.6 million at $44.2 WCSO ting plates oper Shaf the more face in softer of 7 Nov , the contract. tot, the gripp usual 30-to- Engineer’s Estim million, well wet condit ember ation Of the variou “As well City’s Project ate. Instea er sect a job of this 36 month ions.”

2007,” ion s d Man as machi const of scale, goin the ne ruction was “techn Seattle Metro g down TBM drive ager for the tight 17 month ically super proposals, the one with only , the client period for s, the cont program is also Seattl from ior and most by early inches , imposed to have ract e-based makin economical.” Robbins 1990. to spar e (right) reliable mach To meet this, the system in servic a g delivery Robbins Atkinson easy and e ines, one The machi and delive quick. needed for each nes are quite two red quick tube, desig open-faced ly. different ned, built the backh shields. To provid from the more familia The geolo e oe paddl gy e-type excav optimum face acces r tripod of clay with the is mostly over-consoli inter-r ator is moun s, dated sands built two other eacting hydraulic of Pioneer water table rising ted on a , silt and cylinders. close to the Square Statio machines Washi Robbi water table to this surface south ngton DC n (Fig 1). North is Metro in 1974 design, one used ns has of the Statio Caracas Metro over conso well below the tunne on the and the other n, the lidated mater in 1978. l elevation used on the and the dry ials can be very hard.

The 21ft (6.4m) a thrust capac diameter, 140 tonne , 600hp shield ity of 2,400 tonne via the 20 thrusts have 62 rams

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Most of the tunnel and BM tunneling and fine to medium grained, station excavation lies in favorable, is taking the Twin mined station excavation St Peter Sandstone well-rounded and uniformly graded Cities first light line beneath , a deposit that rail transit extends some 150ft (45m) beneath the Excavation runs up the Minneapolis/St Paul Airport. limestone. Groundwa to 70ft (21m) beneath sandstone, about terminals and taxiways 2m below invert level, ter lies deep in the the runways, relatively impervious and a thin layer of the area's expansive of the airport, making use of Glenwood Shale cap of Platteville water table in the creates a perched provide a natural open bedding planes layer of solid support. Limestone to Limestone and in of the Platteville the overlying alluvial and glacial top soils.

Top of rail at the During a site visit center of Lindbergh in July 2002, the Station is about 37ft (11.3m) beneath the first 7,400ft long o.d. (2.25km x 6.5m) limestone cap, which x 21ft segmentally lined thick, and creates is about 30ft (9m) finished and the running tunnel was a flat ceiling to the Herrenknecht EPBM station excavation CASE STUD (152m) into the parallel . was Y: An exten Client for theSeattl drive. The Obayashi/ some 500ft undergrou JV had also started Johnson e bega ndn works at thesive light rail Bros excavating the 14-6ft Metropolitan Airports in the late airport is the netwo of the 525ft long deep topheading the SeattlCommissio rk in 1980s with n (MAC) and x 60ft e downtown team for the design-bid the design excavation 12m) Lindbergh Station. wide x 40ft deep (160m x18m bus -build of x mmodate contract istunne Corporation acco ls. Today led by HNTB the with specialist both metro subconsul tunnels bus servic MacDonald for tants Hatch The running tunnels trainsMott tunnelinges and of the LRT pass and electr mark ; the directly beneath undergrou and ventilation advanced across CNAbegin Consulting ic the airport and are the central alluvial nd exten ning of tracked valley beneath the sions of the several a moving exclusion t, includ taxiways (Fig 1 top Transiby LRT zone ing the deep as thesystem right) TBM for Sound station on Beacon Hill the exten undergrou sion south for the U-Link nd to Tukwila; and North TBM drives -Link exten Link servic sions; and es that share the through Eastspace with the famo highw us Moun run unde t Baker Ridge ay traffic r the street tunnel and s of Bellev SEM tunne ue in the l. For Sound Line’s new the Seattl Transit LRT, e bus tunne it all starte ls. d with

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bus tunnel

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, complex planning option ated city ensive complic the least exp . stor y of provide geology ect is a Chalk USA to LRT proj and it is expected in the place e Austin is highly abrasive NATM as City favorabl The alluvial material of cutterhead tools tion of the Dall and in the complete changes applica stor y of d with tunnels four mandatory hydrostatic pressures that at least two another combine greatly running oulders, high treacherous The contract specifies ts and dor, TBM will be needed. , conditions will allow materials were the men corri and the on the s in areas where abrasive alluvial concerns LRT and arrange d LRT station ghout TBM tunnelers man entry inspection compressed air pressures of less funding oun conditions awaiting ent throu neighborhood gn of the under cost San Diego in the undergr desi safe intervention developmental and outfall project in y and for an probability of t dela ted,” said South Bay ocean ning and Y 199 2 bated than 3 bar. to this was the high through the environmted the plan in significan investiga s-based OR T: MA n on its much-deh 1992 mid-1990s. Added on and man entry, lted plica REP constructi were assisted resu com air IT Dalla Marc during actio an the ntly chance for as among the options T for seismic activity the shaft.

SITE VIS began seeing real system in earlycivil contracts The first possible ranking this project driven in the conseque as various of Huitt-Zollars, ultant to DAR about 3,000ft from port facility’s design life, allas cons is in Reach 2 at erns of the ic trans on the first two tunnels to be ident us ties however, m conc publ Pres subaqueo facili rs, ral er syste LRT. SA tunnel in Canada most difficult light rail ndbreaking of the 3.5 mile long T) Bob Zollag firm and gene ile start the St Clair railway and geological section through complex 1990s, along with in Denmark. with grou of the 20-m d Transit (DAR n contract built in Figs 1 and 2. Plan consultin project. t railway project Rapi essway, outfall, which passes d .8 millio er truction and the Storebael s Area the Expr four-lane to an studied in South Bay undersea of the Pacific Ocean the start for cons 67-mile Dalla work on its $86and its associate , a beneath the floor cut facilities plan tion is that machine driven ent the alluvial materials 1989 the 11ft i.d.

R eventual Chicago started und station while across townn complica increased from dOBE in a deep long, implem . to ) miles to ipal 3.5 deposits (CDM) esse er (P/CM At nearly millio ntown RT: deprOCT undergro ing tunnels The princ1950s, is to be manag complex mix of alluvialages. The Healy of DresseraMcKee of is to be from dow Campthrough on its $18.8 passes Nut VISI T REPO Cityplace the runn 6 by tunnel onwealth River over built onestuary running the late eSITE 1985-8 way and ed work Trinity River. for the of twin tube Tijuana Comm was the ion free start by the d plant sect s of thesecon rado washed down l city of way. us distinction, at the mouth treatment eight-lan mile (6.5km) , the 3.5 mile helps of Colo bridge over the capita grew, asands st High of thee seabed onsewag ed ry 4 s the dubio of theof being the region compositi primaand n’s first As clays to granular Northwe ess ukee, for the nd theoston tts, share succ Bosto Hensel-P to build the LRT , establish silts and and y in 1952.

1968. After s from fine ationed by the and Milwa cobbles Massachuse Chica authority it has been outlet ranges in Quinc future go Island in sizeable rpor just beyo charg Island contract d Transit at Deer in which with and ntly cities ork, by inco through short the to do built gravels deep shaft alluvial rge along planning sign loosewas een (EPA) waterfront betw Discha s Area Rapirated LRT netw rating process, d. From a 200ft the is discharged plant Agency large d USificain 1986 has are anticipate maximum. place, g those frust the waste T, the Dalla boulders of an ence the tunnel integ lems long tation large ing, discharge mile the shoreline, tal Protection At City amon ision screen For DAR manage an the expec onefrom d by theing and often duling prob nmen ent is influ otiations thanback es. oon in Diego cause r.

1 mile Formation Enviro to ion prov Neg about more the aftern the Sanout little federal on. expensive get and sche gn issues, have ed the developm waterIncoursthe of the harbo ofset ages in 1983 the pollut its lead a day passinthrough about T agre e into once to LRT stati Bud arduous, ay. ve designed und pass thingDAR the waste to Jim about 230ft beenplace ded.below d sewag and is and desi carry of an some takes a long, at this point. seabed and dissol Expressw ly treate undergro tide willthe rs andicient this ill-foun planning ys, but according 158ftg below to dilute e and with e DART: of the helmed. at up insuff thetoebbin plac ofund l ability develope proves that overw that to arriv with complex stationr’s natura es2). r side dela ent for of City been 1 and at beach nce er eithe (Figs time agem since the rgro level harbo light enie better on ther own sea n one and , Man unde The has long toge Waste solution on nsive h towers,biologdically Company n of 7-11 conv high costof Construction n the LRT greeer system in finis based the a comprehe to prick the andoutfal thlan to both waste caused l. To date, group ms, CDM on studies nt re ural nal chai the architect been give the Sou and investigati Director ilation of the start date.” siteproble efflue outfalls ing the designer ual or pressu Intensive internatio return, led Parsons authorities Martin, excited to have construction project istanceby Know and vent toward anteindivid d 1996 long-d prepared sea tunne of the takes be report ovings public case, an avid ribu under far astly can ent land 14 long geologica y to get by the schedule parent Oftenlditcont r civil work “We are that, as treatm large, otheslow-m indicate larges are about t currenreaches on.Boston’s of wou ienceh,ofwith are read In Science only there water . s, g , milli ation for and four the the action Engineerin 1980s store consc oper nsible last t $40 through the are taking on whic into abou will pass in ated tunnel ide, and into the worldw agency respo them cost tunnels much scaled lia. are said to lie estim predicted, operation of the stati Foundation y force rolling y, Austra in Reaches 1 and 3 running a ents, will r sued the Statelace rvation was anLawsect ion. geology. in which and uction in Sydne Conse me. The and its material lved on tion s,Agenc quite different requirem beach jogge Cityp gravelly constr treatment be Proteccost rgro tal und me,The station m sandy and plan the sche services. now invo has all nmen mustfrom sewer Water Act es in porous granular faciliti nal sche CBD unde of the seaflow and origi Cityplace und sections proposals for m) starter syste n Cleanated le Enviro redualcing c pressure Feder 7-mial al CDM thethe Island with to be in withFeder er the hydrostati bar ntow in aa er the Feder 7 (32k 1972 elev n, sued A Deer full of ged the the dow Und turn on an Island Bosto anticipated undergro ion of earli mile ing State. ay In char n partnot enforc 2 and 4 are ) in the at about by r to Deer ion ontheExpr under the 20 taking place Reaches dary for DART was nded by suing sect s (11km an order expected. the harbo siltyry material $218 millio (EPA) secon down vers osal for edessw d discharge underpermeable respo t 7 mile was estimated me was impos esse run this May , when EPA to ever prop prima and 1986 carriet,d less depr how Authority out to competen After Island l. the ns more In 1989and the in was finding rces original rground for abou miles and sche of ) n Nut tunne Resou ent and the estio t Court (CBD nsive The rged 8-10 pressure. suggestio median Thes Water moderate (7.6km) long a suggDistric more e theMassa ran unde ness district such an expe to be found. will be discha chusettse 5 mile m to rectify of water where Departm abovthe busi using a progra way median. High the effluent limits in about 110ft 1 and lly there structure which central n. Approval for natives had ally at-grade r treatment, the harboconditions implement of reachesnatura3, dilute e on the to State d gravelly of the ocean can or excavation A) had tanti per alter million. by thelatermen porous, or at grad (MWRted thebeyon t. 1999. $1.1 billio than Insea e the TBM plenum, runs subs (Fig 1). balanc and chea at $828.7 into ical entry on by noalign ruling to LRT lines freezing. In no man were rejec ning waste ecolog situati denied now being built and is priced can thebe the court along the withThe assistance of ground to requirewill by theremai of the a There grade the reaclyhed. comp residents -of-ways scheme was chamber, r side Coordinated expected and biodewithout is Deer work ise to rground. ness Island facility to lose. rail right of the s eithe prom safe man entry essway formed scale busi be unde sedhold no time existing The the face. gallons/ reaches 2 and 4, in boxe , a com propo the newly d left n, Expr has to central of the to helpthan ay 1989 deadline d air 1,200 million leted, the t divisio ion cost 37 a short nsultants compresse system e. From the tral Expressw ral part comp mmodate emen In June truct such degree sub-coged When of consits ity of more mgmanag ial an integ be acco lace the nativ ated and progra ts enga a peak capac wouldits own Engin (HNTB) and estimeers North Cen r commerc ey At Cityp ptable alter ng. Bein an have ultan ndoff Kaiser the cutti ed was majo with ws Berge truction uction engag by&cons en highway multistor a boxes, es Tamm is no acce route follo Cityplace, a MWRA e consmme/constr thesrds ng two the progra Needl designed their as its project, and through district, n, were 1988 comprisi built. Both have Howa millio Aprilartment 19 passes development st in Dep program. of $189 yet to be which Geote essway ential Highway which is plans. by the and resid second of in the Expr T LRT ated ay the rpor DAR rs, inco towe Expressw ct on the h Central and intense major impa of Nort ent, ction artm nstru way Dep d reco State High “Propose Texas by the

DY: The

starts with

SITE VISIT REPORT : SEPTEM BER 2002

Mitsubishi behind the Pacific Ocean shaft and site tested with the 200ft deep access being lowered into

CASE STU

Unde Sea rmttini leng LRT system

STUDY: Excavatio n of the first Minneap out of the ordinary olis/St Paul LRT for the time. It required line to the Twin Cities airport was management of early application a project the tricky transition of a specified dual between open EPB-open mode make, and was and closed mode TBM, with one of the rare occasions of an a decision for use of a Herrenkn the contractor underground cavern echt TBM in the to with a flat crown.

USA market, requiring electrical systems It was also the first professional adaptatio to comply with USA power supplies n of the mechani and safety specifica cal and tions.

ground outfall in difficult Driving a sub-sea

ce LRTexecution Citypla Dallas planning and

chan Autho was one programm .

USA. This r project r Resources the TARP Milwaukee setts Wate Boston Harbo Harbor. After , including Massachu t Lakes, the of Boston ing on since of the Grea e pollution many follow Michigan up sever USA with go into Lake ups in the from Chica tion clean back-up fully assembled st CSO pollu EPBM and its Boretec and large and before

CASE S TUDY

paid one

Bosto ar, flowin s when ted water Y: For years d to a ten-ye the 19080 1997 st : MAY nted pollu atically in CASE STUD A) contribute REPORT preve VISIT of the earlie ged dram SITE e that rity (MWR

UK FOC US

nians had

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UK FOCUS C ASE STUDY

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