On December 21st, 2023, at the Herrenknecht factory in Germany, the delivery ceremony was held for the first Tunnel Boring Machine (TBM) that will traverse the border between France and Italy for the Mont Cenis base tunnel of the Lyon-Turin railway line. This TBM, with a diameter of 10.4 meters, weighing 3200 tons, and measuring 334 meters in length, marks the fourth of seven TBMs to be delivered. These machines are crucial for the project's completion, designed to excavate 18 kilometers of one of the two tubes of the Mont Cenis base tunnel, stretching between the Villarodin/Bourget-Modane access adit in France and the Clarea underground safety site in Italy.

The contract was awarded at the end of 2021 to the ELYOT group, comprising Eiffage Génie Civil (as the group head), Spie Batignolles Génie Civil, Ghella, and Cogeis.

This TBM is a gripper type, utilizing its two arms to directly clamp onto the tunnel walls, advancing as the equipped head, boasting 62 cutters, rotates and excavates the rock. The excavated material is conveyed back via a conveyor belt running through the TBM, transporting it to the outside[BH1] .

Simultaneously, as excavation progresses, equipment supporting the TBM applies shotcrete to the walls, securing them with bolts and ribs. Following the TBM is another machine called the Würm (worm), spanning 650 meters, responsible for completing the final concrete lining of the tunnel.

The choice of this TBM type is driven by several factors, including the geological characteristics of the excavation areas—relatively compact, uniform, and stable formations—the significant tunnel depth, with over 2,200 meters of overburden, and associated geotechnical phenomena such as detachments, convergence, and high natural temperatures at these depths.

The CO5 construction site for the Mont Cenis base tunnel traverses the underground border between Italy and France, starting from the Villarodin-Bourget-Modane access adit, passing through the Ambin massif, and reaching the underground safety site of Clarea. In addition to the 18 kilometers of tunnels excavated by twin TBMs (totaling 36 kilometers), 7.8 kilometers will also be dug using conventional methods. Besides these works, all interconnected and logistical tasks will be completed. Approximately 15 kilometers of tunnels will be constructed using conventional methods, including the underground safety area at Modane. The construction site, commencing after the completion of work on the four ventilation shafts of the tunnel under construction in Avrieux, will employ around 1,200 individuals.