An extended micromechanical-based plastic damage model for understanding water effects on quasi-brittle rocks

Water effects on the mechanical properties of rocks have been extensively investigated through experiments and numerical models. However, few studies have established a comprehensive link between the microscopic mechanisms of water-related micro-crack and the constitutive behaviors of rocks. In this work, we shall propose an extended micromechanical-based plastic damage model for understanding weakening effect induced by the presence of water between micro-crack's surfaces on quasi-brittle rocks, based on the Mori-Tanaka homogenization and irreversible thermodynamics framework. Regarding the physical mechanism, water strengthens micro-crack propagation, which induces damage evolution during the pre- and post-stage, and weakens the elastic effective properties of rock matrix. After proposing a special calibration procedure for the determination of model parameters based on the laboratory compression tests, the proposed micromechanical-based model is verified by comparing the model predictions to the experimental results. The model effectively captures the mechanical behaviors of quasi-brittle rocks subjected to the weakening effects of water.