Numerical simulation of permeability evolution during progressive failure of Aue granite at the grain scale level

A micromechanical numerical model is proposed to simulate the hydro-mechanical coupled behaviors of Aue granite at the grain size level. The hydro-mechanical coupled behaviors of simulated granite samples under triaxial compression tests show similar observations related to stress, strain, and permeability evolutions found in laboratory tests. The proposed modeling strategy gives more in-depth insight into the damage pattern along grain boundaries under triaxial compression. It reveals the importance of tensile microcracks for enhanced permeability (Percolation) and can duplicate all hydro-mechanical phases observed in the lab except the macroscopic fracture evolution at the end of the post-failure region. The model reveals the development of highly inhomogeneous pore water pressure distribution and flow paths in a sample under triaxial compression and steady-state flow conditions. Linear correlations between volumetric strain and permeability are observed from both numerical and experimental results.