Pressure relief law of double upper protective layer superposition mining
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Abstract:
To obtain the law of stress redistribution of coal seam under the action of overlapping mining in multi seam working face, taking Pingmei No.8 Coal Mine No.1 mining area as the prototype, the process of overlapping mining in group D and group E coal seams was simulated using FLAC3D software. The results show that the stress concentration occurs in the corresponding range of the coal pillar at the boundary of the mining area only when the coal seam in group D is mined. The maximum stress value of the coal pillar reaches 19 MPa, and the influence range is 80 m below it. The maximum stress value of the coal pillar in the section between working faces reaches 39 MPa. The pressure relief affects J group, and the stress relief value of J Group coal seam is about 1 MPa. When the D group and E group coal seams are overlapped, and when the E group working face is located under the coal pillar of the D group coal seam section, and the D group working face is located above the coal pillar of the E group working face section, the stress concentration of the coal pillar of the D group coal seam section is weakened, and the stress value of the coal pillar of the D group coal seam section is unloaded from 39 MPa to the range of 7.5 MPa to 10 MPa. At the same time, when the coal seam of group I is located in the independent protection range of group E, the vertical stress relief value is 2 MPa to 3 MPa. When the coal seam of group I is located in the joint protection range of group E, the vertical stress relief value is from 4 MPa to 6.5 MPa.
