Mechanism and application of pre-drainage of strip gas in coal roadway by cross-layer cave-making borehole
HE Jun
LIU Hongwei
LIU Xiaoping
LUO Ping
ZHENG Xu
WANG Fei
ZHOU Ke
Abstract：In order to solve the difficult problem of outburst elimination in coal roadway strip area of low permeability and high outburst coal seam,the mechanism and application of strip gas pre-drainage in coal roadway with large diameter boreholes were studied.Taking Sijiazhuang Coal Mine as an engineering example,discrete element and finite element simulation software were used to numerically ana-lyze the law of fracture development and gas migration around ordinary boreholes and large-diameter boreholes;Through field test,the ef-fect of pre-drainage of strip gas in coal roadway by large diameter boreholes is analyzed.The results show that when the diameter of the borehole is 60～400 mm,the number of fractures in the outburst coal seam increases exponentially with the increase of the aperture;When the aperture is less than 210 mm,the number of cracks increases rapidly;When the aperture is 210～400 mm,the growth of the number of cracks tends to be gentle.When the dip angle of the borehole(the angle with the horizontal direction)is 30°～90°,the number of frac-tures in the outburst coal seam increases exponentially with the increase of the dip angle,and the number of fractures reaches the maxim-um when the dip angle is 90°.Under the condition of ordinary borehole extraction,there are still a large number of strip areas with gas content greater than 8 m3/t on both sides of the return air roadway after 70 days of extraction,which cannot completely eliminate the out-burst;When the extraction is 120 d,the outburst can be basically eliminated on both sides of the air return roadway.Under the condition of adding two ordinary oreholes in each group at the pre-drainage of strip gas in coal roadway,the outburst elimination time is shortened to 100 days.After increasing the cross-layer large-diameter boreholes,the outburst elimination time is shortened to 70 days.It has been veri-fied by practice that the gas concentration and gas purity of large-diameter boreholes are much higher than those of ordinary boreholes in the first 2 months of extraction.The large-diameter borehole through the layer improves the gas drainage rate of the borehole,optimizes the outburst elimination effect of the outburst coal seam,and ensures the safe excavation of the coal roadway.
Keywords：outburst coal seambottom drainage roadwaylarge diameter drilling through the layergas pre-drainage
Publication Date：2025-08-31
Online Publishing Date：2025-09-12(First online date of this platform, not the publication date of the document)
Pages：12( 240-251 )