Energy Evolution Mechanisms and Hazard Prevention in Deep Granite Under Cyclic Loading-unloading

Based on in-situ stress measurements using the hollow inclusion method at depths of -835m to -1140m in Sanshandao Gold Mine and true triaxial cyclic loading-unloading experiments simulating burial depths of 500–2000 m, this study addresses surrounding rock stability in deep mining engineering. Field measurements revealed a horizontally dominated tectonic stress regime (σₕ/σ _v >1.5) with NW-SE-oriented maximum principal stress exhibiting linear increase with depth. True triaxial dynamic compression-shear testing analyzed granite deformation characteristics, while integrated monitoring of split-set bolt pull-out forces and roadway peak pressures enabled optimization of bolt parameters and installation techniques in high-stress environments. Results demonstrate rock failure governed by σ₃-direction dilation, with stress-strain curves showing concave profiles and hysteresis loops extending to 10 cycles; irreversible strains evolve exponentially along σ₁/σ₃ axes versus linearly in σ₂ direction; energy analysis confirms axial elastic energy accumulation coupled with circumferential dissipated energy increment, where damage-induced energy conversion dominates failure mechanisms according to the total energy equation. Crucially, increasing split-set bolt diameter significantly prolongs the elastic-plastic phase and enhances energy absorption capacity. This study conclusively demonstrates that cyclic-loading-induced micro-pore compaction and secondary crack propagation constitute primary damage mechanisms, with the energy dissipation framework providing theoretical foundations for dynamic disaster prevention, while the optimized bolt system integrating parameter refinement and expansion-based reinforcement presents an efficient solution for disaster mitigation in deep engineering rock masses.