Lyon-Turin #singleconstructionsite: progress June 2026

On 12 May, the first sections of the new TBM for the Mont Cenis base tunnel arrived at the CO5 construction site in Villarodin-Bourget/Modane.

Having set off from the Herrenknecht factory in Germany, they travelled over 500 km before reaching the Modane site. The various components of the tunnel boring machine, which arrive at the site in stages, are then moved underground, where they are assembled directly in the tunnel. This operation will take several months before the machine is ready to start excavation.

This is a gripper-type TBM which, in its final configuration, will be 334 metres long, weigh 3,200 tonnes and have a head 10.4 metres wide. It is designed to excavate 18 km of one of the two tubes of the Mont Cenis base tunnel, between the Villarodin/Bourget-Modane tunnel in France and the Clarea underground safety site in Italy.
During excavation, the TBM’s support equipment applies a sprayed concrete (spritz-beton) lining to the walls, together with anchor bolts and steel ribs. Behind the TBM, another 650-metres-long machine called the Würm (“worm”) advances, installing the tunnel’s permanent concrete lining.

At the same construction site, at the base of the access adit, excavation work has also begun on the tunnels for the safety site.
Five hundred metres further up, starting from the Avrieux platform, the final lining of the first two ventilation shafts of the base tunnel has been completed. Work is now continuing on the third and fourth shafts.
Continuing towards Saint-Jean-de-Maurienne, a few kilometres further on, the Viviana TBM – which is excavating the northern tube between Saint-Martin-la-Porte and La Praz – has not yet reached its operating speed due to the geological complexity of the massif.

In the same sector, starting from the access adits of Saint-Martin-la-Porte and La Praz, traditional excavation work is also continuing, both for the base tunnel and for the various logistics and interconnection tunnels, as well as for the La Praz safety site.
At the French entrance in Saint-Julien-Montdenis, whilst traditional excavation of the two tunnel tubes continues, the construction of the permanent lining in one of the two tunnels exceeded 1,000 metres in June.

On the Italian side, work is continuing at the Chiomonte construction site on the site yard and, in particular, on the construction of the new Berlin-type bulkheads required for the entrance to the Maddalena 2 tunnel, the first section of which will be built using traditional methods. The new yards will be able to accommodate the TBM, which has already been completed and tested at the factory.
Preparations are also underway at the sites for the management of excavated material: in Salbertrand, on-site assembly of the structures for the plant that will process the rock extracted from the tunnel equipment is beginning, whilst in Torrazza Piemonte, preparations are under way for the conveyor belt that will transport the materials to the disposal site; in Susa, the construction site yard to receive the spoil has been completed, and the relevant prefabricated sheds are currently being built at the factories.