TUNNELLING RISK REDUCTION BY THE MEANS OF A PILOT TUNNEL DRIVING IN THE HIGHWAY PROJECT VISNOVE IN THE WEST CARPATHIANS, SLOVAKIA

摘要

The highway tunnel Visnove will be the longest one in the West Carpathians, Slovakia. A risk prediction for the tunneling was preliminary assessed on the basis of the first stage of engineering geological investigation. The geology in the line of the tunnel seemed to be rather simple, however, experience gained by the pilot tunnel driving indicate rather another physical state of the rock mass and of the ground water condition as originally anticipated - huge overbreaks and concentrated groundwater inflow took place.