Koralm, Graz - Klagenfurt Railway Line,
Koralm Tunnel, KAT 1 Contract Section
Client: Austrian Railways Infrastructure AG
Development Period: 1996 to 2019
The contract section KAT 1 of the Koralm Tunnel constituted the eastern part of the three tunnel sections and included an open land route with a length of 3.2 km and four bridges, a 300 m long tunnel section, built with the cut-and-cover method, and a tunnel section (length 2.0 km) using the mining technique.
Besides the tunnel advance and the foundation of the bridges, the extensive earth moving measures in the open land section as well as the securing measures for the building pits by means of bored piles or anchored shotcrete in the cut-and-cover section were of geotechnical importance.
BGG Consult attended to this project section with regard to the subjects geotechnics, hydrogeology and geology since the feasibility evaluation phase. Based on several subsoil exploration campaigns, expert's reports were compiled for the route selection procedure, the environmental impact study, the permission procedure, and the tendering phase.
During construction, a supervision in the field of geotechnics and hydrogeology was conducted. This included, among others, the documentation, monitoring and supervision of the bored pile works, the optimizations of the foundations and slope securing measures, the oversight of the extended earth works and the monitoring of the slopes and bored pile walls by means of geodetic measurement and inclinometers.
Building Pit Securing Measures Cut-and-Cover Section Koralm Tunnel:
The building pit for the tunnel section, built with the cut-and-cover method, features depths up to 20 m. To a great extent, the slopes to be secured consisted of cover sediments. These materials are characterised by a low shear strength and a high susceptibility to sliding. The miocene rock below was also classified as instable, due to fine-grained, cohesive intermediate layers, slickensides and the confined ground water.
In order to avoid very high slope cuts and to minimize the geotechnical risks, the slopes in the area of the deeper cuts have been secured by anchored bored pile walls (partly anchored in multiple levels) or shotcrete walls.