The Weinberg Tunnel in Zurich, part of Swiss Federal Railways’ “Diameter Line Project”, was successfully broken through on 22nd November 2010. After boring a total of 4,382 m the convertible TBM resurfaced in the target shaft at the southern section of Zurich’s main train station.
From July to October 2008 the TBM was assembled on the main set-up area in the Brunnenhof shaft. From then until March 2010 it bored through the 4,105 m long hard rock section consisting of molasse rock. Between March 2010 and June 2010 the TBM was converted from hard rock mode to slurry shield mode.
In this set-up, it overcame the last 277 m to the target shaft. From a geological point of view, the transition from a tunnel face that is fully situated in molasse rock to a tunnel face that lies completely in soft ground below the ground water table was achieved on this section. Special support measures had been taken in advance along the soft ground section, i.e. a pipe umbrella support system had been built over a length of 120 m to 140 m in front of the target shaft.
The shield TBM with a bore diameter of 11.27 m was dismantled in January 2011, with the shield skin remaining in the ground in front of the target shaft.
The project that was commissioned by the Swiss Federal Railways SBB is being planned and supervised by the engineering consortium IG Zalo and carried out by the Joint Venture of Implenia Bau AG, Wayss & Freytag Ingenieurbau AG, Bilfinger Berger AG and PraderLosinger SA. Structural work after breakthrough will continue until mid 2012.