New Albula Tunnel: RhB and its lifeline
Since the start of the twentieth century, it has connected Preda on the northern side of the Albula Pass with Spinas in Val Bever to the south: the Albula Tunnel is the lifeline of the Albula Line. An examination of the state of the over 100-year-old tunnel in 2006 revealed that it, understandably, could no longer meet current safety standards. And that is how, in March 2015, major construction work began to make the new Albula Tunnel.
Overhaul or new build?
More than 100 years later, however, the impressive Albula Tunnel was beginning to show its age: ice, water, frost and the pressure of the mountain above it had taken their toll. An examination of all tunnels by RhB experts in 2006 showed that the substance of the Albula Tunnel was in poor condition at many places and that the tunnel, after 100 years of operation, had to be refurbished and brought into line with modern safety standards. But how? Repair the old tunnel or build a new one? A group of experts consisting of engineers, geologists, environmental specialists and representatives from the UNESCO World Heritage organisation worked on a plan to repair this important transit connection for four years. After a detailed examination of the two options, RhB decided in 2010 to build a new narrow-gauge tunnel. The clinching arguments were the relatively minor difference in cost, the lack of relevant disruption to timetabling during the construction phase on the Chur, St. Moritz and Tirano lines, and the considerably improved safety offered by a rebuild. So, the ground-breaking ceremony for the new Albula Tunnel costing 345 million Swiss francs took place on 25 June 2014. The new project, also to be just short of six kilometres, is scheduled to be opened in 2021. Construction site tours and an Infoarena provide all the latest information and an insight into the building of the tunnel.
A mountain is frozen
Today, building a tunnel does not require the sheer manpower it did over 110 years ago: there will be around 90 tunnel workers involved. But there are still challenges. Raibler cellular limestone, a very soft stone, requires creative solutions. During the building of the first tunnel, construction work came to a halt for nine months because large amounts of water dissolved the rock into fine dolomite sand preventing further tunnelling. Nowadays this danger can be held in check: the soft rock formation can be strengthened using injection grouting. Wherever there are incredible amounts of water, the mountain – whether you believe it or not – will be frozen. This takes place with freezing pipes and cooling units, built in beforehand, which freeze the water and thus strengthen and seal the entire mountain area. Nevertheless, this stretch of the tunnel, around 130 metres long, will not be blasted like the rest of the Albula Tunnel, but will be excavated with mechanical picks.
The old transport route becomes a new safety tunnel
And what is going to happen to the old Albula Tunnel? It is being retained. As soon as the Albula Tunnel is taken into operation in 2021, the old tunnel will no longer be needed as a transport route and will then be transformed into a safety tunnel. The new safety concept for the Albula Tunnel is based on the principle of self-rescue: in an emergency, passengers can quickly leave the scene of an accident by one of the twelve transverse accesses to the safety tunnel.
Construction work in the UNESCO World Heritage area
The Albula Tunnel has been part of UNESCO World Heritage since 2008. To make sure that stays this way, RhB cooperated closely, throughout the planning of the new tunnel, with the cantonal and Swiss federal authorities in charge of listed buildings. A master plan contains guidelines for dealing with the historic building and new structure. The railway sets great store by sustainable building: the site was prepared largely from the railway itself, which required the construction of temporary stations at both ends of the tunnel. A large part of the resulting rubble is to be reused: as hardcore in the subsequent concreting and formwork. RhB is also paying particular attention to protecting flora and fauna: one of the many protective measures is the resettlement of the local adders so they are not disturbed by the construction work in their habitat.