£855M contract awarded to drive final section of tunnel on Turin to Lyon rail line

A consortium led by Itinera and including Spie Batignolles and Ghella has been awarded the €1bn (£855M) contract for the excavation of the Mont Cenis base tunnel in Italy.

The twin bore Mont Cenis Base Tunnel, also known as the Mont d'Ambin Base Tunnel, is the largest engineering work on the 65km Lyon-Turin (Telt) high speed rail project between Susa in Piedmont, Italy and Saint-Jean-de-Maurienne in Savoy, France.

Telt will support the main high-speed rail link between Italy and France, carrying both passenger and freight trains. It will be a key part of the Trans-European Transport Network’s Mediterranean Corridor that will connect southwestern Europe with Central and Eastern European countries. The Mont-Cenis base tunnel comprises 57.5km of the line and will be the longest rail tunnel in the world when complete.

Telt general director Maurizio Bufalini confirmed start of excavation work in Italy was a key milestone in the progress of the base tunnel.

With excavation work on the French side of the tunnel first breaking ground in May 2022, work on the Italian section is now being carried out in the Susa valley in Piedmont. It will commence from the active construction site in the Maddalena di Chiomonte area. Over the coming months, contractors will build the section of the tunnel up to the Susa entrance, in addition to accessory technical tunnels. The work is planned for 91 months for a total excavation distance of 28.5km.

In addition to the twin bores of the base tunnel, the Maddalena 2 tunnel through which the tunnel boring machines will descend will also be constructed, as well as cross passages between the two bores.

In addition, the project includes the construction of the Clarea safety site and the cut and cover tunnel at the eastern entrance to Susa. For the excavation from the Clarea safety site to Susa, the use of two dual mode TBMs is planned. These can change their mode of progress according to the type of soil they face and are equipped with a head with rotating cutters that can excavate hard rock or “soft” ground consisting of sand or gravel.

For work in this more friable soil, the TBM is set up to support the tunnel face by exerting an active counterpressure that allows it to advance safely. This approach will cover a section of approximately 1.5km in the Cenischia valley undercrossing. During the work, 2.3M.m³ of materials will be extracted, up to 60% of which will be reused in construction sites of the international section.

Ahead of award of the contract to the Itinera led consortium, evaluations of the tender were made on financial criteria and technical criteria. For the latter, the quality of the proposed solutions was assessed in terms of criteria including construction time and environmental sustainability. In particular, the contract required companies to guarantee the supply of energy from renewable sources.

The deal with the consortium for the base tunnel completes the awarding of all works for the excavation of the entire tunnel, which is co-financed by Europe, France and Italy.

Telt president Daniel Bursaux said that this completion meant that the “central link in the Mediterranean Corridor” of the Trans European Transport Network network was closer to becoming a reality. He described the move as: “One more step towards decarbonising transport in a better-connected Europe.”

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