Study on Pre-Drainage Seam Gas Technology with Borehole Drilled Along Seam in Outburst Mine

No.111706 coal mining face in No.17 seam of Xin'an Mine was selected as a trial zone of the gas pre-drainage technology with the boreholes drilled alon g the mining seam.The rational parameter values of the gas pre-drainage technology for No. 17 seam were studied.The results showed that with the borehole cross layo ut method,the gas pre-drainage value could be improved by 40% and the gas pre-drainage value with the 94 mm large diameter boreholes would be 34% higher than th e gas pre-drainage value with the 65 mm diameter boreholes.The borehole gas drainage concentration within the borehole drilling site would be one time higher than th e borehole gas drainage concentration in the gateway,the borehole sealing depth should not be less than 5 m.The paper proposed that two directional gas drainage bor eholes should be drilled to cover the whole coal mining face and the borehole depth in the gateway driving face should be controlled within 100 m.