Balancing technical precision with adaptation to the terrain, this section of the tunnel illustrates the expertise deployed to cross the Alps.

This section of the tunnel, located between the French portal at Saint-Julien-Montdenis and Saint-Martin-la-Porte, also includes works at the Villard-Clément platform. Eleven cross passages are planned every 333 metres between the two tubes, along with technical rooms and operational and safety recesses.

In this section, excavation is carried out using the conventional method, with blasting or hydraulic breakers—techniques suited to the most complex mountainous areas—together with systematic ground support using steel arches and shotcrete.

Construction site photos

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Completion of excavation works

Companies involved in the works

   

Project management
     

In July 2021, TELT awarded a €228 million contract to a consortium composed of Implenia (lead contractor), Implenia France, NGE, Itinera and Rizzani de Eccher. Project management is carried out by a consortium led by Egis, together with Ingérop, Alpina and Geodata.

Completed works

The Saint-Julien-Montdenis covered trench, the future entrance portal of the Mont Cenis base tunnel, was completed in November 2021 after 32 months of works carried out beneath the A43 motorway and the RD1006 road.

In parallel, reinforcement works were carried out on the Arc River embankments in Villargondran in order to protect the Saint-Jean-de-Maurienne basin from flood risks and to prepare the platform for future construction sites. These developments notably made it possible to raise the ground level by nearly 6 metres through the reuse of 25,000 tonnes of excavated material.

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Saint-Julien-Montdenis

French prime Minister Gabriel Attal visits the construction site!

A ministerial delegation was also present during the visit of the base tunnel works in Saint-Julien-Montdenis.

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