Beating Squeeze at the Strenger Tunnel

This article describes the construction of twin tubes of the Strenger Road Tunnel in the alpine region of western Austria using the New Austrian Tunneling Method (NATM). Highly squeezing ground in fault zones required innovative solutions. Safe excavation was ensured by using deformable rock bolt plates, installing yielding steel elements within shotcrete slots, and increasing the rock bolt pattern. In critical areas rock bolts were increased in length and in number; 30 bolts ranging between 8 and 12 meters were installed per meter of heading. This reduced shotcrete damages and rock bolt failures.