Reasonable coal pillar width of protective layer during high-gas coal seams mining

The high gas coal seam group of Shendong Baode coal mine was taken as the engineering background, and the stability of coal pillar retained in the protective layer coal seam 8# and its influence on pressure relief effect of protected layer were studied. The results show that the larger the coal pillar width, the smaller the plastic zone ratio, vertical stress and horizontal deformation of coal pillar are, and the higher the stability of coal pillar is. The vertical stress at different depths of the floor rock in unloading blind zone below coal pillar is irregularly related to the width of coal pillar. The areas of coal pillar floor at different depths are divided into three regions according to the different depths of the coal pillar floor: the negative correlation zone (depth between 0 m and 15 m), the transition zone (depth between 15 m and 30 m), and the positive correlation zone (depth more than 30 m). The width of coal pillar has almost no influence on the range of complete pressure relief zone and the degree of pressure relief. The expansion deformation of coal seam 11# is 0.7% and the minimum vertical stress is only 0.57 MPa after complete pressure relief; the width of blank zone in coal seam 11# is 55 m. The field test results are basically consistent with the numerical simulation results. Considering the stability of coal pillar, the pressure relief effect of protected seam and the recovery rate of resources, it is suggested that the width of coal pillar in coal seam 8# should be optimized to 25-30 m. © 2020, Editorial Board of Journal of CUMT. All right reserved.