Geotechnics, tunnelling and support of the second tube of the Tauern Tunnel and comparison with the first tube / Geotechnik, Vortrieb und Stützung der zweiten Röhre des Tauerntunnels und Vergleich mit der ersten Röhre

The construction of the Tauern Tunnel in the early 1970s was a milestone in the development of the New Austrian Tunnelling Method (NATM). The experience gained then formed the basis for the development of new technologies, which made tunnelling more efficient and safer and were applied consistently in the design and construction of the second tube. The present article describes the geological conditions, compares the geology with the original tunnel and then explains the starting points for the geomechanical design framework. The basic considerations for the planning of the tunnelling work are described, particularly for squeezing rock behaviour. Then there is a discussion of the geotechnical monitoring and implementation of the design during the excavation of the tunnel, with particular consideration of the problem of long-duration creep deformation and the difficulties in the project-specific determination of warning values. Finally, the conditions encountered along the new tube are summarised and compared with the design and geotechnical conditions of the first tube. This includes a description of the extremely complex and difficult tunnelling conditions in incompetent rock when passing through the approx. 300m long section in slope debris.