EFFECT OF IN-SITU STRESS RATIO AND ROCK PROPERTY ON THE FAILURE INITIATION LOCATION AND MODE OF FAILURE

This study investigates the failure behavior of rock mass surrounding the circular tunnel under high internal pressure by numerical analysis. Three factors consisting of the rock properties (cohesion and tensile strength), the in-situ stress ratio, k, and depth of cavern are varied to investigate their influence on the failure behavior in the rock mass in terms of the failure mode and failure initiation point. The Mohr-Coulomb criteria and tensile criteria are used to evaluate the failure initiation point in the rock mass under shear failure and tensile mode, respectively. To assist identifying the failure mode and failure initiation point, a boundary line in the relationship between cohesion and tensile strength of rock mass is developed. The results indicate that the in-situ stress ratio has a strong influence on the position of crack initiation while the initial failure mode of rock depends on the rock mass properties, especially the relationship between cohesion and tensile strength.