Tunnelling for German High Speed Railway Lines — A General Report

Several high speed and extension railway lines are under construction or in planning progress in Germany (table 1). In the course of the planning of these new railway lines a great proximity to existing transport routes was desired for reasons of environmental protection. As a consequence highways must be undercrossed several time with partly very little covering heights. The undercrossing of built-up areas was accomplished by massive additional measures from within and outside the tunnel in order to stabilize the ground - especially the tunnel face - to minimize deformations and to guarantee the stability and the serviceability of the tunnel itself as well as of building structures above the tunnel. The in general double-tracked tunnels are constructed mostly in an universal driving with sequential excavation of crown/bench/invert in shotcrete tunnelling method. Alternative driving techniques such as universal drivings with a preliminary pilot tunnel or side wall drifts under application of a groundwater relaxation hurrying on ahead, drivings with air-compressed stabilization of the face and shield drivings are presented and discussed on the basis of performed drivings and feasibility studies. A special tunnelling technique that has been applied in Berlin will be described. A short survey on some results of the geotechnical and geodetic monitoring and the effect of optimised tunnelling techniques will be given. Prior construction large investigation programmes have been carried out; efforts to determine the ground risk and to evaluate the remaining risks will be pointed out