间距对上保护层开采保护效果影响的相似模拟实验研究

摘要

为研究上保护层开采保护效果随层间距的变化规律,以南桐矿区作为实验背景,保持保护层倾向工作面开挖长度、煤层埋深、倾角、岩层物理力学性质相同,将层间多层岩层处理为复合岩层,分别进行近距离、远距离和超远距离上保护层开采相似模拟实验.综合分析被保护层卸压规律及基于被保护层垂直于层面的膨胀变形保护准则所得保护范围可知:上保护层开采被保护层卸压曲线呈"凸形",且"凸形"中心线偏向下山方向.随层间距增加,"凸形"底部被保护层小于原岩应力的卸压范围与"凸形"顶部卸压曲线顶部较大卸压的范围均呈减小趋势;两者中心位置均向下山方向转移,且后者转移度大于前者;被保护层卸压曲线中卸压范围的卸压程度及应力集中范围的应力集中程度均呈减弱趋势;以垂直层面的膨胀变形量3‰确定的上下边界膨胀变形保护角均小于《防治煤与瓦斯突出规定》中相应条件的卸压角,因此以该方法确定的保护范围相对《防治煤与瓦斯突出规定》偏于安全,且随层间距增加保护范围长度呈加速减小趋势.%To study the change laws of the protection effect in the upper protective layer mining with the inter coal seam dis -tance , the Nantong Mining District was taken as the test background , and with keeping the excavation length of the protective layer oriented to the working face , the buried depth of coal seam , the dip angle and the physical-mechanical properties of rock formation as the same , the multi-layer rock formation between the layers was treated as the composite rock formation , then the similar simulation tests of upper protective layer mining un-der the short distance , long distance and ultra-long dis-tance were carried out respectively .Through comprehen-sively analyzing the pressure relief laws of the protected layer and the protection range obtained by the swelling deformation protection criterion with the protected layer being perpendicular to the layer , it showed that the pres-sure relief curve of the protected layer in the upper protective layer mining presented the convex shape , and the center line of the convex shape preferred to the dip direction .With the increase of the inter coal seam dis-tance, both the pressure relief range at the bottom of convex shape when the protected layer was less than the in situ stress and the range at the top of convex shape with a larger pressure relief presented the decreasing trend , the center positions of both transferred to the dip direction , and the transfer degree of the latter was larger than the former .Both the pressure relief degree of the pressure relief range in the pressure relief curve of the protected layer and the stress concentration degree of the stress concentration range presented the decreasing trend .Both the swelling deforma-tion protection angles of the upper and lower boundary determined by the swelling deformation of 3‰of the per-pendicular layer were smaller than the pressure relief angle of the corresponding conditions in the Provisions on Prevention and Control of Coal and Gas Outbursts .So the protection range determined by this method preferred to be safer compared with the Provisions on Prevention and Control of Coal and Gas Outbursts , and the length of pro-tection range presented the acceleratingly decreasing trend with the increase of inter coal seam distance .