Dual-mode TBM for rail drives in Sicily

Direct by Design

Dual-mode TBM begins rail drives in Sicily

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9.98m diameter dual-mode TBM designed and manufactured in China by CREG has started excavation of the 6.7km twin tube section of the Cefalù to Castelbuono railway project in Sicily. The project, awarded to Toto Costruzioni Generali by Italian rail company Rete Ferroviaria Italiana, is another link in the European Union TEN-T connectivity masterplan to improve passenger and freight rail services between Scandinavia in the North to Sicily and Malta in the South via the Fehmarn Belt immersed tube link between Denmark and Germany and the Brenner Base Tunnel under the Alps between Austria and Italy.

TunnelTalk reporting May 2022 Toto and CREG tunnelling crews at the launch ceremony in early March The TBM is named Margherita after the Toto General Manager’s daughter

The new 6.7km twin tube TBM tunnel is the largest of three tunnels on the new 12.3km double-track rail line between the coastal towns of Cefalù and Castelbuono on the Messina to Palermo rail route (Fig 1). The new double track contract awarded to Toto Costruzioni Generali for €374 million runs almost entirely underground and follows a different route to the existing single track rail line that hugs the coast

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At 9.98m diameter, the cutterhead is designed for closed EPB mode and open mode rock excavation

line. Together with the twin TBM tunnel, the contract includes the 4.3km long Sant’Ambrogio single-tube, double-track tunnel, excavation of which started in June 2019 and is now about 80% complete. Construction of the viaducts connecting the Cefalù and Sant’Ambrogio portal is also underway. Open-face excavation of the smaller 135m Malpertugio tunnel near Castelbuono Station is a double-track, single tube excavation progressing in an easterly direction towards Messina. Construction of the underground station of Cefalù and the surface station at Castelbuono is also part of the Toto contract.

Geological conditions on the Cefalù alignment and beneath a cover of 300m maximum, range from marine sediments to silty sandstone, sandy gravel, clay, clay limestone, sandstone, siltstone and harder quartz sandstone. To meet the challenge, Toto purchased the dual-mode

The EPB screw conveyor and the open mode belt conveyor remain in place at all times for quick and efficient switching between modes

EPB/rock TBM from CREG to operate at maximum 5 bar pressure in EPB mode and cut rock of 30-120PMa UCS strength rock in open mode. According to the geological survey, approximately 850m of the alignment will be in marine sandy gravel in EPB mode with the remaining 5,850m through siltstone and sandstone rock.

A fault zone of fractured sandstone is also identified.

The alignment includes a 400m radius curve and passes beneath many historical and cultural monuments of the ancient city of Cefalù.

With an excavation diameter of 9.98m, the dual-mode TBM is designed and manufactured entirely in China at the CREG factory in Zhengzhou. Once delivered to Sicily in September 2021 the CREG team of Chinese engineers, engaged by Toto to provide on-site services, managed assembly and commissioning of the TBM in

Assembled TBM at the Ogliastrillo portal and ready to start on its first 6.7km long drive

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strict accordance with the regulations of the project and the demands of the client. “In spite of epidemic restrictions, the team completed assembly efficiently and successfully, for which the client and project owner gave them high praise and recognition,” said Claudio Madanici for CREG in Italy.

The TBM is the first dual-mode machine exported by CREG overseas and the second large-diameter TBM exported to Italy. It follows the CREG 10.03m diameter EPBM manufactured in China for main contractor Cepav Due for excavation of the twin tube Lonato rail tunnel on the new Milan to Verona high speed rail line. For Cefalù, the TBM is designed specifically to meet its dual-mode operation.

Chinese engineers from CREG engaged by Toto will provide on-site technical services through the TBM drives

Table 1. CREG TBM technical data Bore diameter

9.98m

TBM type

Dual EPB closed and single shield open mode

Drive power

3,850kW

Cutterhead torque

21,560kNm maximum

Total installed power

5,653kW

EPB operating pressure

Designed for up to 5 bar operating groundwater pressure

Screw conveyor

17.35m long x 400kW installed power

Segment erector

Vacuum erector

To achieve efficient mode switching in the tunnel, CREG has designed the bulkhead of the main drive to allow the machine’s belt conveyor to work directly with the cutterhead structure and bypass the screw conveyor which will remain in place but inoperative during open mode operation. Mode switching relies on a gate on the bulkhead that permits the retractable screw in the permanently fitted screw conveyor to extend into the invert of the excavation chamber and a telescopic bulkhead in the center of the main drive designed to permit the main machine belt conveyor to extend into the excavation chamber in open mode. This effectively improves the efficiency of mode switching and saves on the construction period. The transition from EPB to open mode is anticipated twice on the alignment and additional switches will be achieved efficiently if, and when, necessary.

The dual-mode TBM was designed and manufactured entirely in China at the CREG factory in Zhengzhou

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The cutterhead for closed EPB mode is designed with an open ratio of 20% and is equipped at all times with six central twin disc cutters, 55 single disc cutters, 46 scrapers, 224 front bucket lips and one copy cutter. In open mode, scrapers are reduced to 20 units and 32 back bucket lips are added for loading muck to the belt conveyor in both clockwise and anticlockwise cutterhead rotation.

With an installed power of 5,652kW and a maximum cutterhead torque of 21,560kNm, excavation is anticipated to progress at an average penetration rate of 100mm/min.

Working three shifts/24hr day, seven days/week, an average daily advance of 16m is estimated with peaks of more than 20m/day. At these rates, excavation and segmental lining of the twin tunnels is expected to be completed by November 2024. With more than 350 workers employed on the site, the TBM will be managed by about 100 workers.

Mucking out behind the TBM is by continuous conveyor in both closed EPB and open modes. As the TBM advances, its vacuum segment erector will install a precast concrete segmental lining of six segments and a key in each 2.2m wide x 400mm thick ring. Segments are being fabricated in the on-site casting factory and are reinforced with 110-140kg/m3 of steel rebar cages and are fitted with a sealing gasket. Segments and supplies to the TBM will be via MSV, wheel-bound multiservice vehicles.

Following a launch ceremony at the main working site at the west portal at Ogliastrillo, the TBM launched on 3 March 2022 in the closed EPB mode and will progress the first 850m before needing to covert for the first time to open mode. At the end of the first 6.7km drive, the TBM will be dismantled and returned to the west portal at Ogliastrillo for its second 6.7km drive.

The Cefalù project marks a return to large diameter TBM excavation technology for Toto. In 2011, it deployed one

of the world’s largest EPB TBMs at 15.62m diameter to excavate the 2.5km long twin tube Sparvo tunnel on the new highway between Florence and Bologna. Toto promoted mechanised TBM excavation for the Sparvo project as an alternative to the project design for traditional open face excavation.

When opened, the new Cefalù to OgliastrilloCastelbuono section for the upgraded Massina-Palermo railway will not only complete another important section of the Trans-European TEN-T masterplan, it will provide an improved 90km direct link between the Punta Raisi Airport to the west of Palermo, and the tourist destination of Cefalù. Upgrade of the line from Palermo to Punta Raisi is already in operation and included significant underground works. Within the scope of that project, the ring railway around Palermo was mostly underground and included the first TBM on the rail upgrade projects in Sicily. As well as providing a faster, safer and more efficient connection between the Cefalù and Punta Raisi Airport, the new line will also remove the existing surface rail barrier on one of the most famous stretches of the Sicilian coast and remove numerous level crossings on the local road system.

Another major rail project for Sicily is the upgrading of the lines from Messina to the east coast city of Catania and across the island to Palermo. In mid-2021, Italian consortium of Webuild and Pizzarotti secured a €640 million contract for the Fiumefreddo-Taormina/ Letojanni Functional Lot 1 section of the project. It added to the previous €1 billion contract with WeBuild for the Lot 2 Taormina-Giampilieri portion of the railway.

Both Lots include underground stations and lengths of underground trackway.

At the March 2022 inauguration of the CREG TBM at Cefalù, the Site Supervision team for the project client Italferr said: “This contract has had many ups and downs

VIDEO: Watch detailed assembly of the TBM and production of the segmental lining in the on-site segment casting yard 6

EXPERIENCE, PASSION AND INNOVATION. UNDERGROUND AND ABOVE.

Margherita More than 60 years of experience in the construction business have led Toto Costruzioni Generali to develop unique competencies in tunnelling, heavy prefabrication and viaduct construction.

We have worked with the largest, award-winning TBMs, providing state-of-the-art solutions to meet our clients’ goals and inventing new ones to solve every issue.

A wealth of experience that drives us today on a new journey underground in Sicily.

WWW.TOTOSPA.IT

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Segments for the 2.2m wide x 400mm thick precast lining rings are being produced at the on-site casting factory

since the handing over of the site and has managed to progress thanks to the great determination of all the parties involved. After months of hard work assembling the TBM, its symbolic launching is a huge satisfaction for us, after so many years spent working mainly on underground projects, to get back on the line with a new TBM, with the same enthusiasm we had the first time round. This is the second railway project TBM to be launched in Sicily and looking to the future, yet more TBMs are envisaged for the main lots of the Messina-Catania-Palermo rail line in the coming years.”

“We took on the commitment to carry out this crucial project for Sicily and the country, and we are here to bear witness to the dedication of our technicians and workers in bringing it to completion,” said Alfonso Toto, General Manager of Toto CG. “All of the project’s stakeholders, from the client to the regional government and the contractor, have worked tirelessly over the years to identify the best technical and design solutions and to ensure respect for the rules, safety and the environment and contain execution times without sacrificing the quality of the work.”

For CREG, Madanici said: “The Cefalù TBM is a significant order in the CREG portfolio. It is the tenth large diameter TBM we have sold to international projects and adds to the many advances the company is making in the design of TBMs. This order is a testament to the confidence clients have in the technical engineering of GREG TBMs, the quality assurance of CREG TBM manufacturing in China and the trust placed in the CREG site technical team engaged by the client to see the TBM through to a successful final breakthrough.” n

TunnelTalk references • • • • •

European connectivity masterplans TunnelTalk, April 2015 Lonato rail link TBM set for assembly in Italy TunnelTalk, June 2020 A1 Sparvo highway tunnel TunnelTalk, July 2013 Mega TBM success at Caltanissetta in Sicily TunnelTalk, November 2017 Undersea drive begins for CREG slurry TBM TunnelTalk, April 2019

Main image: Working portal of the 4.3km long single tube, double track Sant’Ambrogio tunnel with the coastal highway route above; Inset: Installation of the waterproofing membrane and final in-situ concrete lining in the Sant’Ambrogio tunnel