Coupling effects of stress, seepage and damage during reconstruction and excavation of abandoned deep water-rich roadways

Abstract

A stress–seepage–damage coupling model considering the long-term creep of a deep rock mass was established to study the mechanism of evolution of stability of the surrounding rock during reconstruction and excavation of abandoned deep water-rich roadways in a mine. The research shows that the maximum compressive stress in a circular cavern is significantly lower than that in a horseshoe-shaped cavern. Stress is distributed more uniformly in the circular cavern, and appropriately enlarging the size of the reconstructed excavation site can improve the stability of the surrounding rock. As the creep duration for abandoned roadways increases from 1 to 9 years, the growth rates for vault settlement and horizontal clearance convergence remain constant and the roadway undergoes steady-state creep. With increasing burial depth of the abandoned roadway (200–400 m), a pressure arch is gradually formed in the roadway roof in the reconstruction and mining process. The surrounding rock forms a ‘self-bearing structure’ with arch mechanical characteristics and a load transfer mechanism to maintain its own stability, and the overall bearing capacity of the surrounding rock is greatly improved. However, once the burial depth exceeds 400 m, the effect of the pressure arch begins to diminish with further increases in burial depth. Furthermore, porewater pressure significantly weakens the surrounding rocks.