中远距离煤层群叠加开采双重卸压效应数值分析

Numerical analysis on double relief effect under superposed mining of coal seam group with medium-distance

煤层群开采双重卸压效应的应力分布及卸压范围是制约煤与瓦斯瓦斯高效共采效果的关键因素,为了掌握中远距离煤层群开采双重卸压效应,以朱家店煤矿为例,采用数值模拟研究了对该矿4#、6#煤层叠加开采顶底板应力、位移及塑性区分布与演化特征。结果表明:开采4#煤层时,煤壁应力集中系数为2.0,底板塑性破坏深度及卸压深度分别为20m和62m,顶、底板位移量分别为60mm和30mm;叠加开采6#煤层时,采空区侧煤壁应力集中系数降低为1.7,底板塑性破坏深度及卸压深度分别增加至21m和68m,顶、底板位移量相对减小,顶板垂直应力较小,局部区域应力趋于0,同时,6#煤层顶板竖向位移由上向下转变,且其顶板采动破坏带与4#煤层底板破坏带相沟通,裂隙较发育。最后,经过现场瓦斯抽采工程实践,很好地验证了研究所得的双重卸压强度及范围。

Stress distribution and pressure relief area of double relief effect in coal seams ＇ mining are the key factors which constrain the effective co-production of coal and gas. In order to understand the double relief effect of the mining of coal seam group with middle-distance, this author takes Zhujiadian Coal Mine as an example, its distribution and evolution characteristics of stress, displacement and plastic zone in roof and floor rock under superposed mining of 4# and 6# coal seam were studied by numerical simulation. The results show that stress concentration factor nearby the coal wall is 2. 0, the plastic failure depth and pressure relief depth of the floor strata are 20m and 62m respectively, and the displacements of the top and bottom plates are 60mm and 30ram respectively as 4# coal seam mining; during 6# coal seam superposed mining, the stress concentration factor of the coal wall near the goaf is reduced to 1.7, the depth of plastic failure and pressure relief depth of the floor increases to 21m and 68m respectively, the displacement of roof and floor is relatively reduced, the vertical stress of roof is small and tends to 0 in some local area. Furthermore, the vertical displacement of the 6~ coal seam roof changes from upwards to downwards, and its roof mining-induced failure zone of the coal seam is connected with the floor failure zone of the 4# coal seam, and the fracture is more developed. Finally, the double relief intensity and range are well verified by gas drainage engineering.