近距离煤层群下行开采底板应力分布与瓦斯抽采技术研究

针对沙曲煤矿近距离突出危险煤层群开采的瓦斯防治难题，采用室内试验、数值模拟现场试验等研究手段对近距离煤层群下行开采底板应力分布特征与卸压范围及钻孔瓦斯抽采布置有进行分析。结果表明：煤层群各顶底板岩层物理、力学性质呈现不均匀分布，表现为岩层间横向性质相近，垂向岩性差异性较大的典型层状分布。其中，3号、4号、5号煤层间顶底板均为密度较大、内聚力较大、抗拉、抗压强度均较高的砂岩。4号煤层开采后采空区中部底板岩层一定范围内出现明显的垂直应力为0MPa的区域，底抽巷处在卸压区范围内，采空区中部下方底抽巷围岩垂直应力低于5MPa。底抽巷布置在距5号煤层14m处是合适的。工程实践表明，抽采半年后瓦斯压力由1.5MPa降至0.2MPa，平均抽采率维持在80%以上，采用底抽巷抽采瓦斯效果较佳。

Study on Stress Distribution of Floor and Gas Drainage Technology in Downward Mining of Close-Distance Coal Seam Group

Aiming at the difficult problem of gas prevention and control in the mining of close-range outburst dangerous coal seams in Shaqu Coal Mine, the stress distribution characteristics, pressure relief range and drilling gas drainage arrangement of the floor in the downward mining of close-range coal seams are analyzed by means of laboratory test and numerical simulation field test. The results show that: (1) The physical and mechanical properties of the roof and floor strata of coal seam group are uneven distribution, which shows that the horizontal properties of the strata are similar, and the vertical lithologic differences are large. Among them, the roof and floor of No. 3, No. 4 and No. 5 coal seams are sandstones with high density, cohesion, tensile and compressive strength. (2) After the No. 4 coal seam is mined, the obvious vertical stress of the middle floor strata in the goaf is 0MPa in a certain range, the high floor extraction roadway is within the pressure relief zone, and the vertical stress of the surrounding rock of the bottom extraction roadway in the middle and lower part of the goaf is less than 5 MPa. It is suitable to arrange the floor high extraction roadway at 14m away from No. 5 coal bed. (3) Engineering practice shows that After half a year of gas extraction, the gas pressure dropped from 1.5 MPa to 0.2 MPa, and the daily gas extraction rate maintained above 80%. The bottom drainage roadway has better gas extraction effect..