The Method of Determining Reasonable Sealing Length of Gas Extraction Borehole

In order to determine the reasonable sealing length of bedding extraction borehole in No.12 coal mine,and to improve the extraction effect,the relationship between the sealing length and "three zones" of stress is analyzed in this paper.The distribution characteristics of roadway stress "three zones" are determined by numerical simulation and field measurement method.The range of pressure released zone is from the coal wall to the inside 0～4 m;the range of stress concentration belt is from coal wall to the inside 4～10 m;and the range of original stress belt is from coal wall to the inside 10 m deep,which determines a reasonable sealing length of 10 m.Through on-site test inspection,it is verified that the sealing length of 10 m is reasonable.