A Swiss tunnelling experience

摘要

The Steg-Raron contract forms the southern section of the 35km Loetschberg tunnel, part of the AlpTransit project, in Switzerland. In total the Loetschberg project consists of 81.5km of tunnels, to form the twin bores that will carry the railway. The US$410M Steg-Raron civil works contract (excluding trackbed) is notable for being the only portion of the main Loetschberg tunnels to be constructed using TBMs (Figure 1). At the northern end of the project, there is one other IBM section - the 9.6km Kandertal exploration/service tunnel. The four main partners of the MaTrans joint venture for the Steg-Raron contract are Marti Tunnelbau AG of Switzerland (the lead partner), Balfour Beatty of the UK, Porr Tunnelbau GmbH of Austria and the Walter Group of Germany. The Steg and Raron sections were initially awarded as separate contracts but, after MaTrans won both, it was decided to combine them into one contract. The first of these was awarded in November 1999 and runs for 6 years. While the bulk of the Steg-Raron section is driven using two TBMs - with drive lengths of 10km and 8.9km - there is also a 4.6km length of running tunnel, 8.4m i.d., constructed using drill and blast. In addition, there are also 30 cross passages, located at intervals of 333m, a turn-out tunnel and two operations chambers.