煤层冲刷带对瓦斯赋存影响效应及其涌出控制机理

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

针对近年来煤层冲刷带瓦斯异常涌出,但瓦斯赋存及涌出规律不清的问题,从煤层冲刷带的形成模式和空间形态出发,结合陕西胡家河煤矿和山西新景煤矿采掘过程中遇到的不同类型煤层冲刷带瓦斯赋存和涌出实践,总结分析了煤层冲刷带对煤矿瓦斯赋存和涌出的影响机理。研究表明,当冲刷带顶部和底部存在封闭条件时可形成一定规模游离砂岩气,继承性冲刷带和后生冲刷带规模要大于原生冲刷带。同生冲刷带和后生冲刷带会对煤层开采瓦斯涌出产生影响,其中以后生冲刷带尤为严重。同生冲刷带由于煤层具有统一顶板有利于带状冲刷带砂岩中游离瓦斯赋存,煤矿回采过程中瓦斯涌出量高于两侧正常煤层,但受冲刷规模控制影响有限。后生冲刷带对我国煤矿采掘条件影响较大,煤层冲刷带过渡区是煤与瓦斯突出高发地带。煤层冲刷带过渡区由于岩性组合差异,致使煤层冲刷带过渡区存在剪切力煤层结构破坏,导致煤层冲刷带透气性变差,瓦斯赋存能力增强。采掘至此,工作面中部前方来压,煤层应力增大,加之冲刷带砂体中较高压力的游离瓦斯涌出,从而易在后生冲刷带过渡区发生瓦斯异常涌出。区域构造控制下的地应力场分布和地质历史时期构造运动对煤体结构的破坏为冲刷带瓦斯异常涌出提供了地质基础。鉴于煤层冲刷带对煤矿瓦斯涌出的危害,煤矿采掘前应利用三维地震等方法做好超前探工作并圈定煤层冲刷带,为煤矿瓦斯防治提供地质依据。

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.