Study on main control factors of pressure relief of deep and long distance coal seam group and optimization method of initial mining

In order to select a reasonable protective layer for the first mining of deep and long-distance coal seams，the simulation research on the main control factors of pressure relief in coal seam group mining is carried out，the coupling relationship of main control factors for effective pressure relief is established，the optimization method for the first mining protective layer of deep and long-distance coal seam group is proposed and the engineering application research is carried out based on the existing regulations and standards for the selection of protective layer，the pressure relief protection effect of the first mining layer on the adjacent layer is investigated，the effect of outburst prevention measures in the area of pressure relief gas drainage in the protection area is tested,and the rationality of the optimization method for the first mining protective layer of deep and long-distance coal seams is evaluated. The results show that：without considering the thick and hard strata between coal seams，the key factors that influence the pressure relief effect of the overlying adjacent layer were the mining height of the protective layer and the distance between the coal seams，and The key control factor of the influence of the mining of the upper protective layer on the pressure relief effect of the underlying adjacent layer was the seam spacing. Only the mining mode of lower protective layer could be selected for deep and long-distance coal seam group，the layer spacing must be within the maximum vertical distance of protective layer required by the detailed rules for prevention and control of coal and gas outburst，and reached the minimum theoretical layer spacing without damaging the upper protected layer，the mining height of the protective layer should meet the requirements of the minimum thickness of the protective layer. No.11-2 Coal Seam should be selected as the first mining protective layer for No.13-1，No.11-2 and No.8 coal seams in the remote coal seam group of Zhujixi mine，which mining could form effective pressure relief protection for No.13-1 coal seam overlying，and cannot form effective pressure relief protection for 8 coal seam underlying，and the regional outburst prevention measures can be effectively realized by using the surface well combined with the underground drilling for pressure relief gas drainage in the No.13-1 coal seam within the effective pressure relief protection range. Optimization method of first mining protective layer of deep and long distance coal seam group based on key controlling factors was reasonable，and the technology of outburst prevention by the combination of up and down extraction in deep and long distance coal seam group was reliable.