基于开采高度对工作面覆岩裂隙演化影响的钻孔瓦斯抽采研究

Research on borehole gas extraction based on the influence of mining height on the evolution of overburden fracture in working face

采动覆岩裂隙演化规律对层间瓦斯运移起主导作用,研究覆岩裂隙发育分布规律对于提高瓦斯抽采效率至关重要。以甘肃省魏家地矿西2107综采工作面为工程背景,采用UDEC模拟软件建立不同采高的数值模型,利用分形几何理论分析了工作面覆岩近场裂隙演化与不同开采高度的关系,确定了钻孔瓦斯抽采最优工作面高度,并通过理论经验公式、覆岩裂隙窥视情况与现场瓦斯抽采结果对其验证。结果表明:采动裂隙总数随着采高增大而增大,但不同阶段增大的幅度皆不相同,覆岩裂隙不断向覆岩四周呈“伞状”发育;不同开采高度的工作面覆岩近场裂隙均经历产生、扩张贯通、压实稳定的3个阶段,且采高越大,压实区范围越小,适当增加采高,有助于提高覆岩瓦斯抽采效果;当采高选择4 m时,顶板裂隙在位于10 m与40 m位置处的裂隙发育密度与范围均明显大于其他区域,该区域与布置高、低巷双位一体的协同抽采巷最佳位置相一致。

The evolution of fractures in mining overburden plays a pivotal role in interlayer gas migration.Therefore,a comprehensive study of crack development and distribution improve the efficiency of gas extraction.This study the west 2107 fully mechanized mining face in Weijia Mine of Gansu Province as the engineering background,Specifically,this study established numerical models of different mining heights by using the UDEC simulation software,and analyzed the relationship between the evolution of near-field fractures in the overburden of the working face and different mining based on fractal geometry theory.The optimal working face height for gas extraction was determined and validated through theoretical empirical formulas,field observations of overburden fractures,and gas extraction results.The results show that the total number of mining fractures increases with the increase of mining height,but the amplitude of increase is different at different stages,and the overburden fractures continue to develop in an"umbrella"shape around the overburden.The near-field fractures of the overburden rock at different mining heights have undergone three stages:generation,expansion and penetration,and compaction stability.Increasing mining height,smaller compaction zones.When the mining height is 4 m,the development density and range of roof fractures at 10 m and 40 m are significantly higher than those in other areas,which is consistent with the optimal position of the collaborative extraction roadway with high and low roadways.