A renovation project of the Rhaetian Railway
The single-track, 677-meter-long spiral tunnel is located on the line between Thusis and Preda in the Swiss canton of Graubünden.
The project involves the renovation of the tunnel following the standard tunnel construction method of the Rhaetian Railway (RhB). The installation work was largely completed by autumn 2023. For the installation site, around 3,000 square meters of forest were cleared, and an even surface was created using excavated material from the nearby Albula Tunnel II to set up the installations.
From 2024 to 2027, the entire tunnel will be renovated. This first involves expanding the tunnel profile, followed by converting the track to the RhB slab system in the widened area. The interior finishing of the excavated section will follow in the subsequent year, including the creation of new tunnel drainage, the installation of base stones and tubbing elements, and the concreting of the bench.
The profile expansion and interior finishing will be carried out in one-third of the tunnel per construction year. This means that in 2024, the profile expansion will take place in the first third, in 2025 in the second, and in 2026 in the third section of the tunnel. The interior finishing will then follow, staggered by one year in each of the sections.
One of the major challenges of this project is that all renovation work must be carried out during night-time breaks while train traffic operates according to the timetable during the day. Only for the track conversion will there be a total closure of 14 days in the autumn of each year from 2024 to 2026.
Another challenge is the fact that the construction site is at an altitude of 1,645 meters, making the construction season extremely short. Work can begin in the spring, depending on avalanche conditions, around April and will be halted again with the onset of winter at the end of November.
