Fracturing rocks using expandable materials for steeply inclined thin vein mining

This study proposes an expansive splitting method using expandable materials for steeply inclined thin vein mining to reduce blasting-induced disturbance to the surrounding rock mass. The failure evolution and energy conversion are investigated in five-hole (variable spacing) and six-hole (different boundary force) configurations via theoretical, experimental, and numerical methods. In five-hole cases without boundary forces, decreasing hole spacing concentrates stresses, force chains, and strain energy towards the rock center, while reducing them at the periphery results in localized central fracturing and larger peripheral fragments. In six-hole configurations with boundary forces, the stress distribution, strain energy evolution, and crack propagation parallel to the force direction are minimally affected. However, crack progression and stress/strain energy accumulation perpendicular to the force direction are significantly restricted. Increasing the boundary force transforms the rock damage pattern from a tic-tac-toe to a parallel configuration. The fracturing mechanism of expandable materials provides a theoretical basis for non-blasting mining of steeply inclined thin veins.