Research On Gas Pre-drainage Test By Boreholes In 6-2 Seam In Gubei Mine

The coal mining environment is extremely complicated in our country and underground mining is the majority,in which gas hazard is the primary disaster resulting in mining accident.In the past,explosive accidents induced by gas occur for plenty of times,causing a number of casualties and loss of property.With regard to gas control,surface and undermine hole extraction are the common measurement widely adopted and this technique has obtained great achievement in gas management.This paper is aimed at 6-2 coal seam in Gubei mine.Besides,the original gas pressure of 6-2 coal seam is 2.1Mpa and its gas content is 4.51 m3/t.Furthermore,the seam belongs to outburst one because of its low gas content but high gas pressure.To prevent from dynamic disaster,pre-drainage by drilling test is conducted in 8-6-2 mining zone.Firstly,the effective drainage radius of cross-drilling in 6-2 seam is investigated by gas pressure drop method.Secondly,the effective drainage radius of down-drilling is investigated by gas content method.Thirdly,several groups of drainage subpressure tests are designed by gas content method,which comes to the conclusion that a higher drainage subpressure improves gas drainage effect.Additionally,the sealing craft of boreholes is inspected by monitoring gas concentration of several drainage boreholes.Ultimately,on the basis of theoretic analysis and experimental results,some valuable guidance are put forward about the layout of drilling and drainage system.