Numerical and experimental study on reasonable bottom location of high level boreholes in Xiegou Mine
LIU Zhenming;NIAN Jun;LYU Xiaobo;LI Runzhi;Xishan Coal Electricity Group Co.,Ltd.;CCTEG Shenyang Research Institute;
In order to improve the efficiency of the gas extraction of high level boreholes at the No. 18205 working face in Xiegou Coal Mine,the evolution of permeability of gob roof strata was analyzed by means of FLAC~(3D) simulation and field test,based on which,the bottom location of high level borehole was determined. The results show that during the first 120 m of working face moving forward,the range of longitudinal depressurized zone of gob roof strata increases with the advance of working face,after that,the change in the range of longitudinal depressurized zone becomes smaller and smaller and it starts moving away from the working face. The efficiency of gas extraction is pronounced when the bottom location of high level borehole is 16 ~ 18 m from the coal seam roof. Specifically,in the case of the above distance being 17 m,the gas concentration in the upper corner is about 0.6% and the gas concentration of the return current is about 0.42%.