Albula Tunnel

A masterpiece of engineering was created between 1898 and 1903 with the first Albula Tunnel. The 5,864-metre-long tunnel at around 1,800 metres above sea level was the highest railway tunnel in the Alps. In just five years, it was driven through the mountain with impressive precision. More than 1,300 workers were involved in the construction, 16 of whom lost their lives in the process.

particular challenge was drilling through a 100-metre-long section of the Rauwacke fault zone. A massive influx of water meant that the tracks and tunnel floor were covered with the finest dolomite sand over a length of more than 500 metres. The machine drilling came to a standstill and the construction company commissioned had to give up. Under the leadership of RhB, it took around a year to overcome this fault zone.

The structure, which cost 7.3 million francs, was ceremonially opened on 1 July 1903. The Albula Tunnel has been a UNESCO World Heritage Site since 2008.

The Albula Tunnel is located on the Chur – Thusis – St. Moritz route and has been part of the UNESCO World Heritage Site since 2008. When planning the new tunnel, Rhaetian Railway worked closely with the cantonal and federal historic monuments and environmental authorities. All adaptations to the terrain and facilities were carefully coordinated.

The remote construction site was largely accessible by rail. To this end, separate construction stations were built for both tunnel portals. During the construction phase, larger areas were temporarily used. The excavated material was processed in Preda as a raw material for concrete and gravel. Lower-quality material was deposited and renatured in a suitable terrain chamber in the “Las Piazzettas” area near Preda.

A comprehensive environmental impact report accompanied the project. It documented the impact of the construction and operating phases on nature and the environment, and defined measures to protect people, animals, the landscape, air and water.

The construction of the new Albula Tunnel was geologically challenging. The penetration of the fault zone Raibler Rauwacke was particularly testing. This geologically unstable layer required a complex special process, as detailed below.

• The freezing of the fault zone: Over a period of nine months, the roughly 20-metre-thick Rauwacke was artificially frozen to -15 degrees Celsius over a length of 60 metres.

• Construction of a cavern: The freezing was carried out from here and the tunnel excavation continued under the protection of an ice shield.

• Stabilisation: After the breakthrough, the tunnel wall was secured with a 1.20-metre-thick concrete ring, including multi-layer, water-pressure-maintaining arch waterproofing.

The breakthrough into the cavern took place on 17 October 2017 from the Preda side. This was a significant milestone as it successfully broke through the most delicate zone.