Abstract:
In view of the stability of grouped concentrated roadway in close coal seam mining in a mine in Northwest China, a numerical calculation model for the stability of grouped concentrated roadway in close coal seam mining is established, and the evolution laws of roof displacement, roof stress, surrounding rock stress, bolt (cable) prestress field and fracture field after close coal seam mining are analyzed. The results show that: (1) after close coal seam mining, the roof on both sides of the roadway pillar breaks and collapses. The farther away from the roadway pillar, the greater the roof subsidence; (2) With the close coal seam mining, the concentrated stress of the protective coal pillar between the main roadways gradually disappears, the stress concentration of 10MPa appears in the protective coal pillar of the main roadways on both sides of the working face, the range of the stress reduction area is greatly increased, and the stress is transferred to the protective coal pillar of the main roadways in the left and right working faces; (3) With the mining of coal seam, the compressive stress of roadway surrounding rock in the superposition field of in-situ stress field and bolt (cable) prestress field, which affects the minimum principal stress, gradually increases, and a closed and continuous compressive stress zone is formed around the roadway, its range increases, the minimum principal stress value decreases gradually, and the mining of lower coal increases the stress of roadway bolt (cable) of upper coal; (5) The mining of the lower coal increases the depth of the shear failure zone of the protective coal pillar of the main roadway on both sides of the upper coal, and the maximum failure depth increases by 14 m. The main roadway of the lower coal only has a shear failure zone with a depth of 2 m on both sides, while the protective coal pillar of the main roadway on both sides of the upper coal has a shear failure of 10 m.