ABSTRACT
In the middle section of the tunnel, the parallel faulting accompanied the excavation for long distances, whereby the fault bundles, which were located close outside the tunnel cross-section, induced strong
ABSTRACT: In the western part of Austria for an Expressway a road tunnel with two tubes each 5,8 km are under construction. The “Strenger-Tunnel” named tunnel crosses east-west striking and south dipping quartzphyllonites and quartzitic schists with an overburden up to 800 m. The geological condition shows a number of fault zones, parallel to the axis. On a length of appr. 2.500 m heavily squeezing rock mass behaviour were encountered. Due to the high overburden investigation bore holes were not possible on the whole length of the tunnel during design and tendering process. An adaptable contract and experienced tunneling personal on owners side (designer, supervision and geologist), and also experienced personal on contractors side were chosen to manage the expected geotechnical difficulties. Large deformations up to 80 cm were to be mastered with continuous adjustment of rock bolt lengths and numbers, as well as with the installation of yielding steel elements in slots of shotcrete lining.
