Energy evolution mechanisms and hazard prevention in deep granite under cyclic loading: a case study from Sanshandao...

This study investigates the stability of deep granite roadways under cyclic loading and unloading, focusing on the energy evolution of surrounding rock in the Sanshandao Gold Mine. In-situ stress measurements between - 835 m and - 1140 m reveal a horizontally dominated tectonic stress field, with both maximum and minimum horizontal stresses increasing approximately linearly with depth. On this basis, true triaxial cyclic loading-unloading tests were carried out on granite specimens to simulate burial depths of 500-2000 m. The results show that irreversible principal strains in the σ₁ and σ₃ directions increase approximately exponentially with cycle number, whereas the σ₂ direction exhibits an almost linear trend. With repeated cycling, axial elastic energy continues to accumulate while circumferential dissipated energy grows and then stabilises, indicating a damage-induced energy conversion mechanism in which a large part of the input energy is consumed by plastic deformation, frictional sliding and crack development rather than being released catastrophically. Using these insights, an energy-based support design framework was developed and applied to the - 1050 m haulage roadway at Sanshandao, where an optimised split-set support system with enhanced energy-absorption capacity significantly improved roadway stability. The proposed energy dissipation framework and associated support strategy provide a practical basis for mitigating dynamic hazards in deep hard-rock mining.