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采动裂隙是瓦斯运移的通道,搞清瓦斯运移规律是瓦斯治理的前提。在考虑岩石动态破坏过程和含瓦斯煤岩渗流-应力-损伤耦合的基础上,结合平煤五矿实际地质条件和开采工艺,建立了数值计算模型,应用RFPA-Gas程序模拟了近距离上保护层采动顶底板岩层变形破坏、裂隙演化规律与瓦斯运移规律。模拟结果较好地再现了保护层开采过程中煤岩层应力变化、顶底板损伤及裂隙演化过程,得到了上覆岩层移动的“上三带”(冒落带、裂隙带和弯曲下沉带)和底板变形的“下两带”(底板变形破坏带和弹塑性变形带)。得到了被保护层瓦斯流量分布、瓦斯压力分布和透气系数的变化规律,卸压煤层瓦斯透气性增大了2500倍,得到了煤壁下方压缩区和膨胀区之间的张剪瓦斯渗流通道,并将保护层底板压缩区和膨胀区的瓦斯渗流特征提炼出来:压缩区对应的是渗流减速减量区、膨胀区由卸压膨胀陡变区和卸压膨胀平稳区组成,分别对应着渗流急剧增速增量区和渗流平稳增量区。指出卸压膨胀陡变区是瓦斯突出危险区,为近距离保护层开采瓦斯治理指明了方向。实践表明,瓦斯治理效果显著。
Mining fissure is the channel of gas migration. It is the precondition of gas management to find out the law of gas migration. Based on the dynamic failure process of rock and the seepage-stress-damage coupling of gas-bearing coal and the actual geologic conditions and mining technology of Pingdingshan Minmetals, a numerical model is established and the RFPA-Gas program is used to simulate the close-range protection Deformation and failure of top and bottom floor rock strata, evolution of fissures and gas migration laws. The simulation results can well reproduce the changes of coal rock stress, roof and floor damage and fissure evolution during the mining process of the protective layer, and obtain the “upper three zones” (caving zone, fracture zone and bending subsidence) Belt) and floor deformation “under the two bands ” (floor deformation damage zone and elastoplastic deformation zone). The variation of gas flow distribution, gas pressure distribution and gas permeability coefficient of the protected layer was obtained. The gas permeability of pressure relief coal seam increased 2500 times, and the gas and gas flow paths between the compression zone and the expansion zone under the coal wall were obtained. And the gas seepage features in the compression zone and expansion zone of the protective floor are extracted: the compression zone corresponds to the seepage deceleration deceleration zone, and the expansion zone consists of the steep pressure relief expansion zone and the relief smooth expansion zone, corresponding to the sharp increase of the seepage flow Incremental area and seepage increment steadily. It is pointed out that the pressure-relief expansion steep zone is a gas outburst danger zone, which indicates the direction for gas treatment in mining the protective layer at short distance. Practice shows that gas treatment effect is remarkable.