Spherical cavity expansion in porous rock considering plasticity and damage

Abstract

AbstractIn rock engineering, damage evolution upon loading imposes significant impacts on the stiffness of rock mass and its deformation characteristics. In order to investigate the influence of both damage and plasticity on cavity expansion, a plastic damage solution is derived for undrained spherical cavity expansion in rock medium. For the consideration of plasticity‐damage, Modified Cam‐Clay (MCC) model is selected as the plasticity driver, a damage evolution criterion is adopted and coupled with MCC. The coupled damage MCC model is validated against experimental data in the literature. The proposed cavity expansion solution with the consideration of plasticity damage is verified through a classic solution in literature. The role of damage in undrained spherical cavity expansion is investigated by studying the spatial variations of effective stress, pore pressure and damage for cases with different stress ratios. Distribution of cavity expansion induced plastic and damage zones for cases with different stress ratios are also reproduced and discussed. Cavity expansion results show that, the damage zone should be considered for engineering application as the plastic zone is affected due to the damage evolution. In addition, the stability (e.g., radial stress) of rock mass is overestimated in classical solution without the consideration of damage zone.