倾斜厚煤层覆岩瓦斯高渗区应力场-渗流场联动演化采高效应

Mining height effect of stress field-seepage field linkage evolution in gas high permeability zone of overlying strata in inclined thick coal seam

倾斜煤层开采后覆岩应力场分布特征与水平、近水平煤层存在着较多的不同点,其上覆岩层瓦斯高渗区域及其裂隙演化规律也有所差异,同时受煤层采高的影响较为明显。为掌握倾斜厚煤层覆岩瓦斯高渗区应力场-渗流场联动演化规律,基于数值模拟方法,以新疆昌吉硫磺沟煤矿的主采工作面为原型,研究倾斜厚煤层采动覆岩裂隙演化规律的采高效应,揭示不同采高条件下覆岩裂隙高渗区的时空演化规律。结果表明:倾斜煤层的覆岩应力场总体上呈采空区下端应力高、上端应力低的非对称“蝶形”分布,采空区下端瓦斯高渗区以横向延展为主,采空区上端瓦斯高渗区以纵向扩大为主;此外,煤层开采引起的瓦斯渗流场变化和应力破坏形成更多瓦斯运移通道的耦合作用是采动瓦斯渗压改变的原因,而瓦斯高渗区为阻断瓦斯并且控制瓦斯贯通的重点区域。因此,将瓦斯抽采系统布置于瓦斯高渗区内可从最大程度上降低整个采动裂隙场的瓦斯浓度,有效地控制生产期间瓦斯浓度异常的风险。

There are many differences between the overall pressure characteristics of the mine after the mining of the inclined coal seam and the horizontal and near-horizontal coal seams.The high permeability area of the overlying strata and the evolution law of the cracks are also different,and the influence of the mining height of the coal seam is more obvious.A numerical simulation was performed to explore the evolution law of stress field-seepage field linkage in the high permeability zone of overlying strata in inclined thick coal seam.Taking the main mining face of the Liuhuanggou coal mine in Changji,Xinjiang as the research object,the mining height effect of the fracture evolution law of overlying strata in inclined thick coal seam was studied,and the temporal and spatial evolution law of the high permeability zone of overlying strata under different mining heights was revealed.The results show that the overburden stress field of inclined coal seam generally presents an asymmetric“butterfly”distribution with high stress at the lower end of goaf and low stress at the upper end.With the increase of coal seam mining height,the peak stress increases,and the influence range of mining pressure relief area also increases.The gas high permeability area at the lower end of the goaf is mainly extended horizontally,and the one at the upper end of the goaf is mainly expanded vertically.In addition,the coupling effect of gas seepage field change and stress failure caused by coal seam mining to form more gas migration channels is the reason for the change of mining gas seepage pressure,and the high gas permeability area is the key area to block gas and control gas penetration.Therefore,to arrange the gas extraction system in the gas high permeability area could reduce the gas concentration of the whole mining fracture field to the greatest extent,and effectively control the risk of abnormal gas concentration during production.