Analysis on Protected Effect of Mining in Far Distance to Upper Protected Seam of Qidong Coal Mine

In order to protect the safety mining in No.9 seam with outburst in potential in Qidong Coal Mine,according to the deposits of the mine seam group and the outburst danger conditions,a coal mining in a far distance to the upper protective seam and strata in combination with the gas pressure releasing and gas drainage with boreholes through the floor of the protected No.9 seam were conducted as the gas control measures.The results showed that after the above measures conducted,the gas pressure in No.9 seam was reduced from 3.3 MPa to 0.2 MPa,the gas content was reduced from 11.2 m3 /t to 3.2 ～ 6.5 m3 /t,the swelling deformation of the seam reached to 1.7% and the permeability coefficient of the seam was increased by 1 484 times.All above could reach the targets to the regional coal and gas outburst prevention and control for No.9 seam.