Turin-Lyon High Speed Railway, Lot 5A
Avrieux Shafts
The construction of the Lot 5A - Avrieux shafts (Puits d’Avrieux) project, part of the Lyon-Turin railway connection project (Tunnel Euralpin Lyon-Turin - TELT), involves preparatory works for the Modane safety site, located at the center of the 57.5 km base tunnel connecting the stations of Susa (Italy) and Saint-Jean-de-Maurienne (France). This project aims to creating a logistics hub at a depth of 500 meters, in preparation for the excavation of 18 kilometers of tunnel beneath the Ambin Massif towards Italy.
Works also include the excavation of four 500-meter-deep ventilation shafts in Avrieux, using the raise boring technique to ensure safety, efficiency, and cost control.
Webuild is carrying out this project in a consortium, where it has a 33% stake, in collaboration with its joint venture partners: VINCI Construction Grands Projets, Dodin Campenon Bernard, VINCI Construction France, and Bergteamet.
Technical Aspects: The Raise Boring Method
The raise boring method begins with drilling a 40 cm pilot hole from the surface, which emerges 500 meters below in the shaft’s base chamber. The drilled part is then replaced with a 5.2-meter-diameter reamer, which is rotated upwards to widen the shaft, allowing excavated materials to fall naturally to the bottom, where they are removed by loaders. This technique is faster and safer than traditional blasting methods.
The first three pilot holes have been drilled with high precision, with vertical deviations over the 500-meter depth well below the required 10 cm tolerance. The reaming of the first shaft was completed in March 2023.
Support work, including the installation of bolts and sprayed concrete, is carried out from top to bottom inside the shafts using a gantry/elevator system. The final stage consists of waterproofing and applying reinforced concrete lining using a slip-forming process, moving from the bottom to the top of the shaft.
At the same time, the excavation of a network of galleries is ongoing, including sections of the base tunnels and the construction of caverns. These excavations, carried out using conventional blasting methods, include tunnels, chambers, and seven caverns in Villarodin-Bourget/Modane, some reaching up to 22 meters in height and 23 meters in width.
The Tunnel Euralpin Lyon-Turin (TELT) Project
The Tunnel Euralpin Lyon-Turin (TELT) - a 57.5 km tunnel connecting Saint-Jean-de-Maurienne in France to Susa in Italy- is part of the program to develop European economic exchanges and improve passenger traffic. The project will enable a sustainable transition in freight transport by shifting long-distance transportation to rail. With one million fewer trucks on Alpine roads by 2030, the whole Tunnel Euralpin Lyon-Turin will allow a reduction of 3 million tons of CO₂ emissions per year and will represent a strategic link in the TEN-T Mediterranean Corridor, connecting East and West Europe.