Assessment Of Tunnel Construction Possibilities In Deep High Squeezing Permo-Carboniferous Ground
The base tunnels crossing the Karavanke mountain range, located at the border between Austria and Slovenia, have a rich history in finding a proper tunnel construction methodology. Both, railway tunnel, constructed in 1906, and road tunnel, constructed in 1991, faced the most difficult conditions in extremely weak Permo-carboniferous rocks with overburden between 500 m and 1100 m. Such rock types represent extreme conditions for tunnelling, resulting in large convergences, over breaks and high squeezing ground potential. The calculation results of ground loads on the designed support system and displacements are analysed with a 3D numerical geomechanical model adopted for highly faulted ground surrounding deep underground structures. Based on the results of these numeric analyses several important measures that are crucial when facing such extreme conditions are pointed out.