The western section of the Sieberg Tunnel is situated within a clayey cover layer and in superficially weathered oligocene clay marl. In deeper zones, confined slope water has been explored. An inactive slide mass was assumed. After excavating to a depth of a few meters, a wide-stretching earth slide occurred. With the help of a geomechanical model, the methods for the tunnel construction were changed significantly on the one hand, and permanent groundwater lowering methods by means of gravel pile galleries and single wells were implemented on the other hand. While the deformations completely subsided at the cut-and-cover tunnel section after remodelling the original terrain geometry, ongoing displacements were recorded at the open cut section despite comprehensive protection measures. Only after the implementation of permanent dewatering measures and a large-scale profiling of the terrain with shallow drainages, the movements could be kept in check.
展开▼
