Gas Control Technology of Coal Mining in Upper Protective Seam of Contiguous Outburst Seams Group

In combination with the mining conditions of the upper protective seam in Qingdong Mine,the FLAC3D software was applied to the simulation of the floor pressure releasing law in the upper protective seam mining.The study results showed that the pressure released gas emission rate of the protected seam was 30.0%~36.5%.After the upper protective seam mined,the in-situ ground stress of the protected seam would be reduced from 10.5～10.8 MPa to 1.0～1.5 MPa.The initial pressure released location in the protected seam would be 40~50 m to the coal mining face.According to the study results,stereo gas control technology with roof rock roadway in coal layer,bedding drainage,a roof high level gas drainage gateway,tubing buried at the up corner,downward borehole through strata with fracturing in the air retuning gateway in the upper protective seam was set up.The engineering application showed that the pressure released gas would account for 86.8% of the total gas emission of the coal mining face,the gas emission rate of the protected seam was 30.4% and the initial pressure releasing location of the protected seam was the location that the coal mining face advanced at 40 m.