The contract section KAT 1 of the Koralm Tunnel consti-
tutes the eastern part of the three tunnel sections and includes
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 are of geotechnical importance.
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BGG Consult attends to this project section with regard to the subjects geotechnics, hydrogeology and geology since the
feasibility evalua-
tion phase. Based on several subsoil exploration cam-
paigns, expert's reports were compiled for the route
selec-
tion procedure, the environ-
mental impact study, the permission procedure, and the tendering phase.
During construction, a super-
vision in the field of geotech-
nics and hydrogeology is conducted. This includes, among others,
the documen-
tation, monitoring and super-
vision of the bored pile works, the optimizations of the foundations and slope
securing measures, the oversight of the extended earth works and the moni-
toring of the slopes and bored pile walls by means
of geodetic measuring and inclinometers.
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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 consist of cover sediments. These materials are characterised by a low shear strength and a high
susceptibility to sliding. The miocene rock below is 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.
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