Assembly is underway in Zurich of the 11.24m diameter Herrenknecht TBM that is to drive the Weinberg tunnel from Central Station in the ‘Diameter Line’ project to increase capacity at Switzerland’s rail hub.
The Mixshield/shielded TBM (S-451) will be launched shortly from an assembly chamber and tunnel near Oerlikon station. It will drive a 4,863m tube to the receiving pit at Lowenstrasse station, which is being built below Central Station.
Geology along the alignment of the Weinberg tunnel comprises Upper Freshwater Molasse and moraine. Dewatering will be required locally at the Buchegg depression over which, for approximately 200m, cover is reduced as the route simultaneously passes from molasses into water-bearing strata.
Weinberg tunnel is being built by the Swiss rail authority, Schweizerische Bundesbahnen (SBB), as part of the ‘Diameter Line’ that will link Altstetten and Oerlikon stations via Central Station.
Underground works on Diameter Line involve construction of the Lowenstrasse Station, the Weinberg tunnel, and escape and rescue tunnels. Weinberg tunnel, which will be a single tube, double track rail link, has a pronounced bend and is almost ‘S’-shaped in plan. It is being built as part of Phase 3 of the scheme, which has four phases in total and is due for total completion around 2013-15.
SBB’s project designer and manager for Phase 3 is the ‘igzalo’ JV consisting of Basler & Hofmann, Pöyry Infra and SNZ.
All construction work is being undertaken by a JV of Implenia Bau, Wayss & Freytag, Bilfinger Berger and Prader Losinger, which won the two underground packages – Lowenstrasse and Weinberg tunnel – when they were tendered as separate contracts. The JV was awarded the contracts a year ago.
Local constraints in the launch area required the access shaft to be off-centre at the tunnel axis, which has resulted in more difficult assembly logistics. The JV contractor is having the TBM assembled in a chamber and also a NATM-driven tube, which will be 105m long to reach the portal before Oerlikon station.
However, there is not enough space for the full assembly of the backup and the shield is to be launched in two steps. Following an initial, short-mode advance of approximately 200m the backup will be completed. The TBM has a total thrust of 114,500kN, and cutterhead power and torque of 3,200kW and 23,700kNm, respectively. The NATM tube will be used for spoil removal.
A total of 14,000 concrete segments for the primary lining are being manufactured by Swiss firm Ceresola TLS. It won the segment contract in February and worked with the JV to design and build the plant – using a carousel owned by the consortium – within six months.
Production started last month and will use a heat backflow process to reduce the number of precision moulds needed. The JV needs nine rings per day, each 2m long, 300mm thick (600mm at floor areas), having a 10.9m o.d. The final, insitu lining will also be 300mm thick and unreinforced except at escape tunnel junctions.
TBM assembly underway for the Weinberg rail tunnel in Zurich
