Experimental Research Of Gas Drainage In Extremely Short-distance Overlying Adjacent Seam

In order to actively respond to gas management dilemma at the working face caused by national ban on the “U+L” type ventilation mode,Experimental study on gas drainage of changing Y type ventilation to “U+L” type ventilation were conducted in 42207 working face of Xingwu coal mine,When the ventilation mode of the working face is changed,the air discharge capacity of the working face were decreased greatly,the paper based on the actual situation of 42207 working face exists extremely short-distance overlying adjacent seam 4up seam which fall with the mining,experiment of gas drainage in extremely short-distance overlying adjacent seam were conducted,exploring the effective method of gas drainage of extremely short-distance overlying adjacent seam.This paper analyzed the stress distribution of coal seam in front of the working face after caving 20 m.40m.60 m.80m and 100 m with the help of COMSOL Multiphysics software,defining the excavation height is the sum of the mining height of working face and the height of caving zone,Simulation results show that there is an advance pressure relief effect on the coal and rock mass in front of working face,and the width of advanced pressure relief area in extremely short-distance overlying adjacent coal seam is 15 m.Through the testing experiment of the width of advanced pressure relief area,verifying that there is an advance pressure relief effect on the coal and rock mass in front of working face,the testing width of advanced pressure relief area is 18.26 m,which is basically consistent with the simulation result and verified the simulation is reasonable,furthermore,the causes of the differences between the two are analyzed,It provides the theoretical support and the field basis.The long directional horizontal drilling hole in 42207 working face can conduct advance pressure relief gas extraction before the extremely short-distance overlying adjacent seam falls into the working face,gas drainage result shows that the average extraction concentration is 12% and 36%,the average extraction purity was 0.46m3/min and 0.74 m3/min,maximum single hole gas drainage concentration is 63.03%,maximum single hole gas drainage pure quantity reached 1.86 m3/min gas drainage effect is remarkable.According to the test result,the extremely short-distance overlying adjacent seam gas drainage holes can be used to extract advanced pressure relief gas in the extremely short-distance overlying adjacent seam and solve the problem of upper corner and return air gas concentration exceeding limit,and reduce the ventilation pressure and gas emission in goaf at the same time,and guarantee the working face is in production safely,and provide a reliable basis for gas control of the backup working face.