Time‐Dependent Failure of Rock: Insights From Grain‐Scale Stress Corrosion Simulation

ABSTRACT This research investigates the time‐dependent damage deformation of granular rock using a grain‐scale stress corrosion (GSC) modeling approach. Stress corrosion, originating from damage within the grains and along the grain boundaries, is considered the main mechanism causing weakening and time‐dependent damage of granular rock. To account for the microstructure geometry of rock, the parallel‐bond stress corrosion (PSC) model is extended to a grain‐based model (GBM) within the Particle Flow Code (PFC). Accordingly, the modeling parameters are calibrated against data from uniaxial compression and fatigue tests on Lac du Bonnet granite. The numerical modeling results show that the long‐term strength and failure time of granular rock increase prominently with the increase of confining pressure and the decrease of the driving‐stress ratio. The number of microcracks along the grain boundaries is far more than that within the granule interior. Grain crushing, which is traced by granule interior microcracking, appears in specimens with high confining pressures. It is found from the simulation results that the damage in the failed specimens caused by long‐term loading, both inside the grains and along the grain boundaries, is less than that caused by short‐term loading. The results also show that stress corrosion within the granule interior significantly influences the time‐dependent behavior of granular rock under high driving‐stress ratios, whereas stress corrosion along the grain boundary becomes dominant under low driving‐stress ratios.