Application of High Efficient Gas Drainage Technology with Double Casing Pipe to Mining Seam

In order to solve the technical difficult problems of the low drainage gas flow,low gas content,easy borehole collapsing and difficult borehole sealing in the gas drainage borehole of the mining seam,the paper analyzed the shortages of the available gas drainage technology.According to the actual condition of the transportation gateway in F15-13330 coal mining face of No.8 Mine of Pingdingshan Tianan Coal Company Ltd.,a high efficient gas drainage technology with double casing pipe was provided in the mining seam.The paper studied on the function principle of the gas drainage with the double casing pipe and the rational length of the double casing pipe and others.The site application results showed that in the borehole gas drainage in the mining seam with the seam Protodyakonov coefficient f≥0.25,the high efficient gas drainage technology with the double casing pipe applied could effectively prevent the borehole collapsing and jammed and improve the sealing quality of the borehole.The average initial volume fraction of the gas drainage with sigle borehole was up to 89%,the pure gas flow value was improved by 80% and the gas drainage flow value only reduced by 12% after drainaged 31 days.The gas volume fraction of drainage pipe in test face kept over 18%,the gas drainage rate in coal seam of the mining face reached to 45%.