Belchen Tunnel Rehabilitation: Excavation with Switzerland’s biggest TBM Diameter

Altogether 500 million Swiss francs will be invested for redeveloping the 3.2 km long Belchen Tunnel.  The scheme began in 2015. A JV comprising the companies Marti Tunnelbau, Marti Basel und Marti Solothurn is charged with building the new tube on the Swiss A2 motorway between Hägendorn in the Canton of Solothurn and Eptingen in the Canton of Basle-Land on behalf of the Swiss Federal Roads Office (FEDRO/ASTRA). Once completed in 2022, the new tunnel will enable the two directionally-separate, two-lane tubes of the original Belchen Tunnel dating back to 1970 to be refurbished without restricting traffic. Currently the four available lanes cope with a traffic volume of no less than 55 000 vehicles per day.

Excavation scheduled to be finished in May 2017

Following extensive preliminary work, the largest TBM ever used in Switzerland began operating in early February 2016 in order to build the new tube at a distance of 40 to 116 m parallel to the existing tunnel system. The cutter head diameter of the single-shield TBM S-947 made by Herrenknecht amounts to 13.97 m. The TBM is 75 m long and weighs around 2000 t. During the excavation, which is scheduled to be completed in May 2017 , around 470 000 m³ of rock is to be removed.

Once the new tube is in service, the two existing, over 50 year old tunnel bores will be renovated one after the other as from 2023. During this period, traffic will pass through the third, new tube. Nonetheless, the new tunnel does not represent any expansion of capacity – once the refurbishing work has been completed traffic will still only have two tubes with a total of four lanes at its disposal.

G. B.


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