Effect of coal seam scouring zone on gas occurrence and gas emission control mechanism

In view of the abnormal gas emission in coal seam scouring zone in recent years,and the law of gas occurrence and emission is not clear,this paper starts from the formation pattern and spatial form of coal seam scouring zone,combined with the practice of gas occurrence and emission in different types of coal seam scouring zone encountered in the mining process of Hujiahe coal mine in Shaanxi Province and Xinjing Coal Mine in Shanxi Province,the influence mechanism of coal seam scouring on gas occurrence and emission in coal mines were summarized and analyzed.Studies have shown that when there are closed conditions at the top and bottom of the scouring belt,a certain scale of free sandstone gas can be formed,and the size of the inherited scouring zone and the post-production scouring zone is larger than that of the original scouring zone.The contemporaneous scouring belt and the post-production scouring belt will have an impact on the gas emission from coal seam mining,and the subsequent scouring belt is particularly serious.The contemporaneous scouring belt is beneficial to the occurrence of free gas in the banded scouring zone due to the uniform roof of the coal seam.Thus,the gas emission in the syngenetic scouring zone is obviously higher than that of the normal coal seams on both sides,but the influence of the scouring scale control is limited.The post-production scour scouring zone has a great influence on the mining process of coal mines in China,and the transition zone of coal seam scouring zone is a high incidence zone of coal and gas outburst.Due to the difference of lithological combination,the transition zone of the coal seam scouring zone causes shearing coal seam structure damage in the transition zone of the coal seam scouring zone,resulting in poor permeability of coal seam scouring zone and enhanced gas storage capacity.At this point,the pressure in front of the middle of the working face will increase the stress of coal seam,and the free gas of the higher pressure in the sand body of the scouring belt is rushed out.Therefore,it is easy to generate abnormal emission of coal and gasin the transition zone of the scouring zone.The distribution of geosyncline controlled by regional tectonics and the destruction of coal structure by tectonic movement in geological history provide geological basis for abnormal gas emission in scouring zone.In view of the hazards of coal seam scouring zone on coal mine gas emission,three-dimensional seismic method should be used to delineate coal seam scouring zone before coal mining,which can provide geological basis for coal mine gas prevention and control.