Hydro-mechanical coupling of granite with micro-defects: Insights into underground energy storage

In order to revel the hydro-mechanical coupling characteristics of granite at various pore pressures and confining pressures. The spatial micro-pore structure before and after the failure of granite is extracted by high-precision CT scanning system. The results show that the UCS of the damaged granite decreases with the increase of pore pressure under certain confining pressure. The sensitivity of UCS of granite to the change of pore pressure is lower than that of confining pressure. In the rock compaction stage, the permeability decreases slightly, while it increases slowly in the elastic and plastic stages. From the perspective of microscopic fracture structure, the number of roar channels increased by 134 times, the total length increased by nearly 100 times, the average equivalent radius was expanded to 1.64 times, and the permeability increased by 443 times before and after rock failure. The permeability characteristics of granite are most affected by pore-throat structure.