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Raise borer machine for the Lyon-Turin ventilation shafts
Raise borer machine for the Lyon-Turin ventilation shafts

Avrieux, Villarodin-Bourget and Modane construction site

Construction of the ventilation shafts for the base tunnel and underground works

In this area, the ventilation shafts for the base tunnel are being built: four parallel vertical tunnels at an altitude of 1,300 metres. They are very important because they must reach the underground station of Modane (at the foot of the Villarodin/Bourget-Modane slope), 500 metres below, where they will contribute to ventilation and safety. Seven caverns, each up to 22 metres high and 23 metres wide, will also be dug during the work. They will be used for the assembly of the TBMs that will excavate towards Italy. In this area, the Modane underground safety site will also be excavated, as well as the 22 km of the base tunnel between the Villarodin/Bourget-Modane slope and the Italian border.

works in progress

Construction of the ventilation shafts

Work progress - May 2024

Key data

4 parallel shafts

500 metres of depth

5.2 meters of diameter

worker icon

300 people at work

Groups of companies at work

The contract for the construction of the Avrieux shafts, worth 220 million euros, has been awarded by TELT to the group of companies composed of VINCI Construction Grands Projets, DODIN CAMPENON BERNARD, CAMPENON BERNARD Centre Est, WeBuild, and MASTER DRILLING Europe.

The project management is entrusted to the group composed of Egis / Alpina.

Work techniques

The four parallel shafts with a diameter of 5.2 metres are excavated using Raise Boring Machines, a technology developed in the mining industry specifically for the mechanised excavation of vertical shafts of small diameter.

Once the-40 cm-diameter pilot holes are completed, bars are inserted into the holes. The heads of the vertical TBMs for digging the shafts will be mounted at the ends of the bars.

The excavated material, which falls by gravity in the chamber at the base of the shafts, is taken out through the existing slope.


Villarodin-Bourget / Modane slope

It is located on the right bank of the River Arc and is 4,036 metres long. It was excavated from 2002 to 2007 employing approximately 290 workers, using the traditional method. Once the base tunnel becomes operational, the slope will serve as a ventilation shaft, and as a maintenance and safety passage. This slope has enabled the testing of the transformation of inert excavation materials for concrete aggregate by constructing an experimental treatment plant in the construction site. The materials obtained were used in shotcrete or stocked for subsequent concrete tests.

News from the construction sites

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