The fifth of the seven TBMs to be used for excavation of the Lyon-Turin Rail Tunnel has been delivered to the French-Italian group of companies ELYOT, consisting of Eiffage Génie civil (group head), Spie batignolles génie civil, Ghella and Cogéis in a ceremony at the Herrenknecht factory in Germany.
The Client, TELT’s President, Daniel Bursaux, TELT General Director, Maurizio Bufalini, the European coordinator of the Mediterranean Corridor, Iveta Radičová and the French President of the Lyon-Turin Intergovernmental Committee, Josiane Beaud were present at the delivery.
Together with its twin TBM, delivered on the 21st December 2023, this TBM will excavate the longest, deepest and most complex section of the Mont Cenis base tunnel – the 18km stretch between the French and Italian border from the Villarodin/Bourget-Modane area to the Clarea underground safety site.
The ‘gripper’ TBM has a diameter of 10.4m, a weight of 3200 tonnes, a length of 334m and a capacity of 4,900kW. Designed specifically to meet the needs of the CO5 construction site, the TBM has several distinctive features, designed both to perform the initial lining of the tunnel and to deal with any geological difficulties along the alignment. It is equipped with a sliding rib and metallic rib erector, as well as rock drills for exploratory boring whilst progressing. Bolting machines allow self-drilling bolts to be applied for support whilst a shotcrete workshops on the machine will take care of additional support requirements.
Excavated material will be transported via a conveyor belt and both TBMs are equipped with a workshop to pre-classify excavated materials. Behind each TBM a further machine – called the Würm (worm) – advances. This is 650m long and carries out the execution of the final concrete lining placement in the tunnel.
The two TBMs will launch a few weeks apart, excavating each of the base tunnel tubes from France towards Italy. Five teams of 25 people each will be required to operate each machine in three shifts, 24 hours a day, 7 days a week.
The choice of this type of TBM was dictated by several factors: the type of geology in the excavation areas, which here consist of relatively compact, uniform and stable formations; the great depth of the tunnels to be built, with more than 2,200m of overburden; and the associated geotechnical phenomena, such as detachments, or ‘popping conditions’.
Also to be contended with are the ‘natural’ high temperatures present at these depths, highlighted during construction of the La Maddalena exploratory tunnel in Chiomonte, which significantly assisted establishing the specifications for these new TBMs.
The CO5 is the construction site on the Mont Cenis base tunnel that crosses the border between Italy and France underground. It starts from the Villarodin-Bourget-Modane access adit, passes through the Ambin massif and reaches the underground safety site at Clarea.
At the same time as the 18km of tunnels (for the two tubes) to be excavated by the twin TBMs (36km in total), 7.8km of tunnels will also be dug using the conventional method as well as all connection and logistics works. In total, around 15km of tunnels will therefore be constructed using the conventional method, including the underground safety area at Modane. The construction site will employ around 1,200 people.
The Mont Cenis base tunnel, currently under construction between France and Italy, is the central element of the cross-border section of the new Lyon-Turin railway line, whose construction is under the responsibility of TELT. It represents the heart of the Mediterranean Corridor of the new European TEN-T transport network.
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