Convergence-confinement is one of the most popular methods that is applied for analyzing the interaction of a circular opening in rock masses. It is assumed that circular tunnel excavated in a continuous, homogeneous, isotropic, initially elastic rock mass subjected to a hydrostatic stress p0.
Selecting appropriate failure criteria is very important in the analysis since it affects on plastic zone and on the resulted displacement and stress field around the opening. Some closed-form solutions have suggested for the ground reaction curve, although they are driven based on elastic-perfectly plastic or elastic-brittle-plastic models of rock mass behavior.
Brown et al. (1983) proposed a stepwise procedure based on Hoek-Brown criterion to solve stress and displacement around the circular opening for elastic-strain softening model of rock mass behavior. A similar stepwise procedure was extracted in this study for Mohr-Coulomb criterion. Finally a sensitive analysis was implemented for Mohr-Coulomb and Hoek-Brown criteria in respect to their parameters.
By comparison of the relative displacement caused by changing strength parameters in Hoek-Brown and Mohr-Coulomb criteria, it can be concluded that Mohr-Coulomb criterion is more sensitive in respect of variation of strength parameters of rock mass than Hoek-Brown.