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由于保护层卸压开采,导致覆岩结构的运动,致使上覆煤层变形,产生卸压效应,改变被卸压煤层的透气特性,为卸压瓦斯抽采创造有利条件.采用RFPA2D-Flow数值模拟软件,分析了上覆煤岩层采动裂隙演化、卸压煤层采动应力及位移分布、瓦斯参数变化等规律,结果表明:1)下保护层开采引起的上覆煤岩层采动裂隙集中分布在采场两端部,并呈竖向偏采空区方向发育,离层裂隙发育至被卸压煤层上方;2)开切眼和停采线附近区域顶板裂隙明显发育,卸压开采导致上覆煤层产生膨胀变形,透气性明显增加;3)由于被卸压煤层和保护层之间关键层结构的力学效应,使被卸压煤层透气系数增加幅度不显著,导致抽采孔瓦斯压力降低速度放缓.无关键层结构时,采动影响区内抽采孔瓦斯压力降低较快.
As a result of the pressure relief mining of the protective layer, the movement of the overlying rock structure led to the deformation of the overlying coal seam, resulting in the pressure relief effect and changing the gas permeability characteristics of the pressure relief coal seam, creating favorable conditions for the relief gas drainage.Based on RFPA2D-Flow numerical simulation Software, the evolution of mining fissures in overlying coal seam, the mining stress and displacement distribution of coal seam, and the variation of gas parameters are analyzed. The results show that: 1) the mining fissures of overlying coal seam caused by the mining of protective layer are concentrated in The stopes at both ends of the stope are vertically oriented with the direction of goaf and the delamination cracks develop to the top of the coal seam undergoing pressure relief. 2) The cracks in the roof near the open cut and in the vicinity of the stope have been obviously developed, 3) Due to the mechanical effect of the key stratum structure between the pressure-relief coal seam and the protective layer, the increase of the permeability coefficient of the pressure-relieved coal seam is insignificant, resulting in the decrease of gas pressure in the suction hole When there is no key layer structure, the gas pressure in pumping holes in mining affected area will decrease rapidly.