Study on Pressure Released Gas Control Technology of Upper Protective Seam Mining

Taking No.726 coal mining face of Qingdong Mine as the upper portective seam,the paper discussed the gas sources of the upper portective seam and the gas sources were the mining seam gas and the gas emission from No.8 seam,the neighbor seam under the mining seam level.The calculation of the individual source prediction showed that the gas from No.8 seam was the main gas emission source of No.726 coal mining face.The protective seam mining in combination with the pressure released gas drainage was the main technical means of the mine gas control.The gas drainage with band steel mesh through bed boreholes in the roof gateway during the mining period of the mining seam,sectional sealing gas drainage in the roof gateway,through bed borehole gas drainage in the downward direction of the air returning gateway,in and along seam borehole gas drainage,pipeline buried in goaf gas drainage,and other gas control plan were provided.After using the comprehensive gas control measures,the average gas drainage flow was 15.96 m3/min in average,the gas drainage value of the coal mining face was 7.294 4 million m3,the gas drainage rate was over 75% and the gas content over the limit at the upper corner of the coal mining face was eliminated.