Progress on the northern drive of the Mont Cenis base tunnel has slowed as excavation has reached a geologically complex section.
TBM Viviana, a 10.4m-diameter Herrenknecht machine, was launched in September last year to build the 9km tunnel that runs parallel to the one completed in 2019.
TELT, the French-Italian public company managing construction of the Mont Cenis base tunnel project, said the slower pace of excavation had been anticipated as the section between Saint-Martin-la-Porte and La Praz was one of the most geologically complex along the route.
“For this reason, the first tunnel had been classified as a study and exploratory tunnel,” TELT says.
“The experience gained with the Federica TBM, which had previously excavated this section and encountered similar difficulties at various points, has given us an understanding of how the TBM behaves in geological conditions of this kind. Federica subsequently completed the excavation on schedule and within budget.”
The organisation added: “The TELT teams, companies involved and experts were working to implement all the necessary measures to ensure the safe passage through this specific, locally critical section, and to enable a gradual resumption of tunnelling operations.”
The 9km northern tunnel is being delivered by CO 6/7, the Italian-French consortium comprising Vinci Construction, Webuild, Dodin Campenon Bernard and Campenon Bernard Centre Est.
The 57.5km twin-tube Mont Cenis base tunnel – 12.5km in Italy and 45km in France – will be one of the longest rail tunnels in the world and is the core of the new Lyon-Turin railway line. As of July this year, 49km of tunnelling had been completed.
