South tangent Karlsruhe, building 40

Sand and gravel in alternating beds, loosely deposited. The groundwater is to be found some 9 m below the upper edge of the track, roughly at the level of the base of the tunnel that was to be built. On account of the fact there was dense traffic along the German Railways' line including IC trains, it had to be ensured that the two-track main line was kept open during normal hours of operation at as high a speed as possible. In order to make sure that train services would be unimpeded, the pipe-jacking method was selected. First of all, steel pipes with a diameter of 2.50 m were thrust into the railway embankment from three starting shafts using a tunnelling machine. These pipes accommodate the rails for the subsequent thrusting of the tunnel blocks. A cantilever retaining wall was selected for the abutment for the jacks, which was supported against an 8 m high earth wall. The tunnel blocks were concreted on a platform and with the aid of 20 jacks, which were distributed over 5 application points, thrust into the railway sub grade. The total force of the jacks amounted to 120 MN. Through grouting bentonite between the structure and the surrounding soil, the frictional resistance during thrusting can be considerably reduced. The structure was completed using watertight concrete. On account of the high mechanical stresses caused by the thrusting process, the entire base zone was provided with a 4 mm thick steel plate, the ceiling zone with a surface seal made of plastic.

Country: Germany
Region: Baden-Württemberg
Tunnel utilization: Traffic
Type of utilization: Road tunnel
Client: Stadt Karlsruhe
Main construction method: Open?
Type of excavation: Pipe-jacking?
Lining: Concrete formwork?
No. of tubes: 2?
Tunnel total length: 122.04 m
Cross-section: 29 T
Contract Volume: approx. 27 mill. DM
Construction start/end: 1985-1987 (24 months)
Opening: 1987