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Saint-Julien-Montdenis and Villargondran construction site

Excavation of the 3 km base tunnel between Saint-Julien-Montdenis and Saint-Martin-la-Porte 

Excavation of the tunnel section between the French entrance portal in Saint-Julien-Montdenis and Saint-Martin-la-Porte. Work is also planned on the Villard-Clément platform between the artificial tunnel to the west (the cut-and-cover tunnel, already constructed) and the natural entrance of the tunnel into the mountain to the east. In addition, there will be communication branches every 333 metres between the two tunnels, technical rooms and niches for operation and safety.


Base tunnel excavation

Work progress - May 2024

The excavation of the base tunnel, started in December 2022 in Saint-Julien-Montdenis, continues towards Saint-Martin-la-Porte. The acoustic hangar, the conveyor belt and all the installations necessary for the smooth operation of the construction site were also built on this platform: offices, concrete plant, access tracks, etc.

Key data

3 km of base tunnel

70 months of work

worker icon

300 people at work

2026 end of the excavation work

Engineering and construction companies

In July 2021, TELT awarded the contract to the group of companies composed of IMPLENIA Suisse (group head) / IMPLENIA France / NGE / ITINERA / RIZZANI de ECCHER. The project management is entrusted to the group composed of Egis (group head) / Ingérop / Alpina / Geodata. The value of the works is € 228 million.


Excavation in this section is carried out using the traditional method, i.e. with explosive or a jackhammer. These techniques are used in the most complex mountain sections, where it is not possible to use the TBM. Explosive excavation involves drilling holes in the rock face that are filled with explosives and then blasted. Once freed of debris, the face is consolidated with ribs and shotcrete. In some cases the calotte can be reinforced with steel bars. If the rock is less resistant and explosives cannot be used, a jackhammer is employed, consolidating the excavation with ribs and concrete.


Cut-and-cover tunnel

In Saint-Julien-de-Montdenis, in the Villard Clément area, the cut-and-cover tunnel, the artificial tunnel that will be the French entrance to the base tunnel, was completed in November 2021.
Works to build the concrete ‘box’ under the A43 motorway and the RD1006 road started in 2019 and were completed in 32 months, as planned. The works were carried out by the group of companies led by Bouygues Travaux Public Regions France.

Consolidation of the embankments of the Arc river in the Villargondran area

Consolidation works were carried out on the embankments of the Arc river to protect the Saint-Jean-de-Maurienne basin from floods, as well as to prepare the platform where the others railway and technical structures of the Lyon-Turin cross-border section will be located.

The land was raised by approximately 6 metres, using as backfill 25,000 tons of excavated material from the cut-and-cover tunnel and Saint-Martin-la-Porte construction site.

The work, which started at the end of 2018 for a value of approximately € 6.8 million, was carried out by a group of companies composed of Vinci Construction Terrassement (group head), Cofex GTM Travaux spéciaux, and TP Manno.

Telt - Suivi de Chantier

News from the construction sites

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