... ABSTRACT: In this paper a new solution for calculating the ground reaction curve at the tunnel crown around a circular tunnel, considering true triaxial stress state, is developed. The new solution is based on the unified strength failure criterion; thus it consists of a wide range...

... excavation of the top heading, large karst cavities with widths of up to ten metres were encountered. The karst cavities were found to be part of an approx. 500–m–long cave. Further huge karst cavities were encountered with an overburden of about 8 m above the tunnel crown. structural geology karst...