Stability analysis of rock mass in underground caverns of pumped storage power station: experimental study and numerical simulation

Pumped storage caverns are often constructed in deep granite formations with complex tectonic stress conditions. Faults and random fractures widely distributed in rock masses seriously threaten the long-term safety of underground powerhouses. This paper investigates the rock mass stability of underground powerhouse caverns in pumped storage power stations via laboratory tests (uniaxial/compression, static/dynamic triaxial, AE tests) and orthogonal numerical simulations. Granite shows brittle/quasi-brittle failure under uniaxial compression; its strength increases linearly with confining pressure under static triaxial conditions, conforming to the Mohr-Coulomb criterion. High confining pressure makes rock ductile under dynamic loading, inhibits microcrack propagation and AE activities. Numerical simulations reveal rock mass mechanical parameters dominate cavern stability, with cohesion exerting the most significant effect on stress, displacement and plastic zone depth. The results provide theoretical and technical references for cavern stability evaluation and excavation support design.