Numerical Simulation of the Stress Corrosion Rupture Zone for Deep Tunnels

Abstract

Stress corrosion is a geological phenomenon that damages the long-term stability of underground projects. A comprehensive approach for stress corrosion prediction of underground projects combining creep experiment, particle flow code (PFC)and Finite element method (FEM) is proposed. Calibration of the numerical model was undertaken according to the data obtained from laboratory tests. Based on the numerical model, biaxial and triaxial stress corrosion compression tests were conducted to investigate the stress corrosion mechanism of Jinping marble. Through numerical tests, the stress corrosion process was visually observed. According to the development history of microcracks, the stress corrosion rupture process of surrounding rocks can be divided into 4 stages, i.e., rapid growth, slow growth, rapid growth and instant leap. The process was controlled by driving stress ratio and confining stress. On or near the tunnel wall, most stress corrosion microcracks are induced by tensile stress and the direction is parallel to the direction of the maximum principle stress. Near the yield zone of tunnel, the ratio of shear microcracks becomes larger with increasing confining stress. And the amount of microcracks is larger at the rupture stage than that on the tunnel wall, which makes the stress corrosion rupture process look like a ductile failure process. There is a linear relationship between the logarithm of stress corrosion lifetime and driving stress ratio if the confining stress keeps constant. Stress corrosion lifetime will increase when pc becomes higher or driving stress ratio becomes lower. Based on the laboratory and numerical tests, the stress corrosion rupture depth of the tunnel section was predicted using FEM, which can optimize the length of bolts.