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Opening of the Ceneri Base Tunnel

The New Rail Link through the Alps (NRLA) is possibly the project of the century in the Swiss Alpine region. Never before have such long tunnel sections been built in the Alps under such a massive rock cover.

01.09.2020 | swisstopo

Geological profile at the Ceneri
Geological profile of the NRLA at the Ceneri (© swisstopo)

The 15.4-kilometer-long Ceneri Base Tunnel connects the Camorino traffic junction in the Sopraceneri with the Greater Lugano region in the Sottoceneri and makes it possible for the journey between Sopraceneri and Sottoceneri to take only half the time. Together with the Gotthard Base Tunnel, it forms the eastern branch of the NRLA in Switzerland.

Detailed geological knowledge about the composition of the subsurface is an essential prerequisite for the planning and construction of such large installations. The first exploratory drilling was carried out between 1991 and 1994 as part of the preliminary studies and served to obtain basic lithological and rock mechanical data along the tunnel corridor between Sant'Antonino and Lugano. After the Federal Council had approved the definitive tunnel system as «two single-track tunnels» in 1999, supplementary exploratory borehole data were obtained along the final route.

Work in the Ceneri Base Tunnel
Work in the Ceneri Base Tunnel, Cavern Saré west (© AlpTransit Gotthard AG)

The tunnel system consists of two single-track tunnels and traverses the bedrock of the southern Alps between Vigana and Vezia. The two tunnel tubes are connected by 48 cross passages. About 2 km before reaching the south portal of Vezia, the underground branch-off structure Sarè was excavated, from which two 150-m-long tunnels start. These are foundations for the construction of a future extension of the tunnel towards the south.

Thanks to the excavation work in the Ceneri Base Tunnel, the geological field and map information from the ground surface could be completed with the data from depth. Also impressive are the outstanding engineering achievements in the planning and implementation of the structures by means of geotechnical and safety measures throughout the entire construction project. The published report provides a summary of these unique findings from the tunnel drives.