Stability analysis of the support system for Sardasht long tunnel using convergence -confinement and Hoek-Brown criteria

Stability analysis of the support systems in tunnels is an important designing issue. Convergence-confinement method is used to estimate the applied load to the installed support system. The behavior of encountered jointed rockmass (which reduces the strength) could be studied, having established the degree of their convergence. Carranza-Torres and Fairhurst having used the latest version of Hoek-Brown correlation presented an analytical method to determine the relationship between factors describing the rockmass strength and mechanical reflections concerning the cylindrical underground spaces. In this article, using similar approach, the ground reaction curve was obtained for Sardasht long tunnel. Having compared the results with those prepared from a numerical method using FLAC 3D, it was clear that the above approach could be used for this tunnel where a safety factor of 3.14 was obtained for the stability of the segmented lining in the face of the applied loads.