Study on the rational layout and control of gas drainage roadways in deep inclined coal seams

To determine the optimal positioning of the bottom drainage roadway in deep inclined high-gas coal seams, this study investigates mining-induced floor failure mechanisms. Based on the engineering conditions of the bottom drainage roadway in the East Third Mining Area of Dashuitou Coal Mine, a three-dimensional mechanical model of a deep non-uniform pressure roadway was established to investigate the formation mechanism of the excavation-induced plastic zone. Based on the semi-infinite solid theory, the inclined failure depth of the stope floor is calculated considering the distribution characteristics of maximum and minimum principal stresses. Combined with the slip-line field theory, the strike-direction failure depth of the floor is analyzed. A double-yield goaf numerical model is employed to accurately simulate post-mining floor failure behavior. From the perspective of the deviatoric stress second invariant, the distortion energy density distribution in both the floor strata and roadway surrounding rock during mining extraction is investigated. The results indicate that when the coefficient of horizontal pressure exceeds 1, the plastic zone radius expands predominantly along the roadway sidewalls, whereas when it is below 1, the plastic zone develops more significantly in the roof and floor regions. Theoretical calculations determine an optimal depth of 20 m for the bottom drainage roadway positioning. Numerical simulation results confirm the technical feasibility of this 20 m depth with staggered distances 45 m staggered displacement. A composite support system combining anchor cables with shotcrete was developed and successfully implemented in the field application.