The Albula Tunnel II
The Albula Tunnel Line is regarded as one of the most spectacular rail routes through the Alps. The Rhaetian Railway climbs up the Albula Valley 1,820 meters towards St.Moritz from Thusis via the Landwasser Viaduct and through helical tunnels. As a glowing example from the pioneering days of the railway line, the line has been recognised among UNESCO’s heritage sites since July 2008.
An inspection of the Albula Tunnel revealed that it required reconstruction. Serious damage to the natural stone vault, drainage system and insufficient rock ballast fill reserves were noticed due to the end of service life of the tunnel track. Furthermore, the clearance area no longer complies with modern requirements regarding rail operations and passenger safety.
Reconstruction of the tunnel is currently taking place meaning that the new Albula Tunnel II will replace the old 5,864m long Albula Tunnel I. Albula Tunnel I will become a Security Gallery connected with the new Albula Tunnel II by 12 cross passages. On both sides of the tunnel are stations which will be extended and renewed.
The tunnel is placed mainly in hard rock (granite and schists). Excavated materials are then prepared and used as concrete aggregates and the less suitable material is deposited on a specific disposal site near Preda Station.
The crucial geological section of the project is the ca. 110m long so-called Raibler-Rauwacke with loose, silty rock and groundwater, which represents the “Pièce de résistance.” About 110 years ago the tunnel advance of the Albula Tunnel I was extremely complicated and delayed while cutting through the Raibler-Rauwacke. In the current projects, the weakest section of the Raibler-Rauwacke had to be passed under protection of frozen soil.
The Raibler-Rauwacke was a huge challenge that took more than two years to prepare and to cross. After the cavern had been finished, investigations from site tests made clear that the ground material of the Raibler-Rauwacke was very inhomogeneous and partly not injectable. It then became clear that the only promising method would be a combination of injections and freezing the loose ground and 6 atmospheres of water pressure. The drilling work was very challenging because of the ground conditions and the high-water pressure. Thanks to different injection equipment, the work succeeded to seal the permeable zones of the ‘swimming’ Raibler-Rauwacke which was the main requirement for the success of the ground freezing. The freezing was done in the foreseen time and no leak in the frost body had to be registered.
Over the coming years, work to complete the tunnel will include:
- Finish the tunnel lining and uninstallation of the tunnel contractor.
- Installation of the slab track in the new tunnel.
- Installation of the catenary conductor rail in the new tunnel.
- Construction of the new facilities at Preda and Spinas stations.
- Assembly of railway and electrical engineering equipment in the new tunnel and in two new stations.
- Finish the project-specific landfill near Preda.
- Commissioning the new Albula Tunnel I into a Security Gallery.
- Construction and installation of two new ventilation stations in the Security Gallery to provide the gallery with excess pressure in case of emergency.
- Commissioning the new Security Gallery in 2024.
- Finish the project in 2025.
Peter Wenger, Senior Project Manager at Amberg Engineering told RAIL CONSTRUCTION NEWS MAGAZINE: “The Albula Tunnel line is a very important track in the network of the Rhaetian Railway. Accordingly, the renewal of the tunnel is vital for the Rhaetian Railway. The new tunnel offers greater safety, which benefits the Rhaetian Railway and its customers.
“A major tunnel project usually takes around 20 years therefore, not a lot of major tunnel projects can be realised in an engineer’s life time. The Albula Tunnel project is my last one and I will probably not see the end as I retire in June this year.”
Set to open for operation in 2022, construction work started in July 2014 with the main tunnel work starting in August 2015. In 2023-2024, the Safety Gallery is set to be completed meaning that by that time; the whole system can be put in to operation.
PREDA, 2OKT18 – Gruppenbild mit der Mannschaft, welche den Durchstich geschafft hat, kurz nach dem Durchstich des neuen Albulatunnels der Rhaetischen Bahn am 2. Oktober 2018 zwischen Preda (Albulatal) und Spinas (Engadin) in Graubuenden.
Impression of the tunnel breakthrough of the new Albula Tunnel of the Rhaetian Railway in Preda, Switzerland, October 2, 2018.
swiss-image.ch/Photo Andy Mettler
