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Excavation of the two tubes of the base tunnel between Saint-Martin-la-Porte and Modane
This construction site has two work platforms in Saint-Martin-la Porte and La Praz for the completion of the 23 km of the base tunnel towards Modane. The La Praz safety site, linkage branches every 333 metres between the tunnels, technical rooms, niches and tunnels for operation and safety will also be built. The territories of the municipalities of Saint-Martin-la-Porte, Saint-Michel-de-Maurienne, Orelle, Saint André, Villargondran and Saint-Julien-Mont-Denis will be affected by the works for this part of the tunnel.
On the Saint-Martin-la-Porte and La Praz platforms, the new group of companies proceeds with the construction site installation and the necessary activities to prepare the site for the excavations, which will begin with the traditional method on different fronts. The three TBMs for the excavation of this section were ordered at the end of 2022. Underground, in La Praz, the preliminary work for the bating of the existing slope is under way, necessary to the tunnel equipment activities.
23 km of base tunnel
3 TBMs
65 months of work
625 people at work
The contract, worth 1.43 billion euros, has been awarded by TELT to the group of companies composed of VINCI Construction Grands Projets (group head) / Dodin Campenon Bernard / VINCI Construction France TP Lyon / WeBuild.
The project management is entrusted to the group composed of Setec (group head), Systra, Italferr and Pini.
The tubes are excavated using the traditional method with the use of explosives: each ‘blast’ (each detonation performed in the tunnel) is planned and managed with professionals called ‘shot firers’ and in total safety. The excavated material is ground on site and reused to create the road surface in the tunnel. At the same time, the excavation of the niches that will reach the 7 km depth of the tunnel is under way.
In September 2019, the “Federica” TBM completed the mechanical excavation, started in 2016, of the first 9 km of the tunnel: an exploratory tunnel with the same diameter end axis of the new Mont Cenis base tunnel representing the first tunnel section through which the trains will travel. The excavation of a further 1.5 km of base tunnel continued using the traditional method, proceeding on two fronts with hydraulic breakers or explosives in order to cross the trickiest section of the mountain at the heart of the carboniferous front.
On 28 April the excavation of this section was completed with the fall of the last rock diaphragm. The consolidation with concrete of the excavated tunnel was completed in October 2022.
These works were assigned to the group of companies composed of Spie batignolles Génie Civil (group head), Eiffage Génie Civil, Ghella SpA, CMC di Ravenna and Cogeis SpA.
Three slopes were completed, that will serve as ventilation duct, maintenance and emergency exits when the tunnel will be operational. The first 2,400-m-long slope in Saint-Martin-la-Porte was completed in 2010 the second 1,800-m-long slope in Saint-Martin-la-Porte was completed in 2016 and the third 2,800-m-long slope in La Praz was completed in 2009.
Excavations reached a total of 35.5 km, of which 13 of base tunnel.
The companies of the UXT consortium, led by Itinera, signed the Sustainability and Security Pacts with TELT.
The contract worth EUR 1 billion was awarded to the binational group of companies composed by Itinera (agent), Spie Batignolles and Ghella.
Excavation has started for the ventilation shafts of the Mont Cenis base tunnel.
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