Numerical simulation of pillar width of stoping roadway under coal seam group condition

Under the cooperative mining condition of close coal seam group, mining disturbance caused by mining of overlying coal seam poses a serious threat to the stability of surrounding rock of mining roadway of underlying coal seam. Aiming at this problem, this paper takes coal seams 11号 and 13号 of Hui 'an Coal Mine as the engineering background, combined with elastoplastic theory and discrete element numerical simulation, puts forward the index of "influence coefficient of surrounding rock", and systematically analyzes the influence mechanism of overlying mining disturbance on the underlying roadway. By using FLAC^3D and UDEC software, the evolution characteristics of stress field and fracture field under different internal dislocation arrangement were simulated, and the disturbance boundary (F=−0.4) and instability critical (F=−0.6) criteria of surrounding rock were defined. The results show that when the internal fault distance is less than 20  m, the disturbance area of upper and lower coal seam roadway overlaps obviously, the fracture superposition is serious, and the stability of surrounding rock decreases significantly. When the internal fault distance is not less than 20  m, the disturbed area is decoupled, the roadway fissure area tends to be independent, and the structural integrity of surrounding rock is significantly enhanced. The critical deviation standard of roadway safety layout is studied, and the superposition mechanism of mining-excavation disturbance is revealed, which provides theoretical basis and technical support for optimal layout and support design of roadway in the underlying coal seam.