Study on safe width of pillar in deep coal seam group mining

Based on the engineering background of Pingmei No. 8 coal Mine, this paper studies the reasonable width of coal pillar under the mining condition of deep very close coal seam group by means of theoretical calculation, numerical simulation and field experiment. The FLAC3D numerical model is established to simulate the evolution of the plastic zone, stress field and displacement field when the coal pillar width is 3-10m. The results show that when the width of the coal pillar is higher than 5m, the plastic zone of the surrounding rock can be effectively reduced and the deformation resistance of the coal pillar can be improved. When the width of the coal pillar is higher than 7m, the stress concentration degree of the coal body in the coal pillar gradually increases, and the deformation degree of the roadway gradually increases, and a large range of high stress concentration phenomenon will occur in the adjacent coal seam in the very close distance of 16.17. It is not conducive to roadway maintenance and gas control of 16.17 coal seam. The reasonable width of coal pillar is between 5~7m under the mining condition of deep and very close coal seam group. Through the field industrial experiment, the gas concentration on the solid coal side is higher than that on the coal pillar side, mainly because the amount of gas desorption in the coal body is larger than that on the coal pillar side. The gas emission on the coal pillar side and the gas emission in the roadway do not exceed the limit phenomenon, which effectively verifies the reliability of the coal pillar with a width of 5m, indicating that the coal pillar with a width of 5m meets the demand for safe production.