Coal seam stress evolution and its application under the influence of large spacing coal pillar and mining superposition

Abstract

The Ⅵ-22080 working face of Pingmei No.8 mine was selected as the research object. Through FLAC3D numerical simulation method, the stress evolution characteristics of the working face were analyzed, and the working face was divided into regions. The results show that the stress distribution of working face has a great difference under the joint influence of large spacing coal pillar of group Ⅳ coal seam and the coal seam mining of group Ⅴ coal seam. Stress concentration phenomenon is distributed in the whole haulage roadway, especially in the range of 150 m to 500 m from the outer entrance of the roadway. The maximum vertical stress of the roadway is 27.5 MPa, increased by 8 MPa. There is a pressure relief zone near the air-return roadway of the working face and the maximum pressure relief degree is 10 MPa. With the increase of stress, the fracture rate and permeability of coal decrease by 29 % and 64% respectively. In the high stress superimposed area, the gas pressure gradient increases, the permeability of coal body decreases, and the outburst risk increases. On the contrary, the permeability of coal seam in the pressure relief zone increases, and the outburst risk is smaller. According to the difference of outburst risk in different areas of working face, the working face can be divided into general outburst risk area, medium outburst risk area and severe outburst risk area.

Keywords

• stress concentration
• coal pillar
• permeability
• numerical simulation
• gas control