隐伏逆断层带的瓦斯涌出规律及控制因素研究

Law of methane emission and its controlling factors in the blind reverse fault zone

针对林华煤矿20916工作面隐伏逆断层揭露实例,基于隐伏断层带断裂力学性质、断层两盘岩性和断层规模,分析了该工作面推进期间瓦斯涌出量随掘进和回采长度的变化规律,对隐伏断层带构造应力场进行数值模拟研究,揭示了瓦斯涌出异常的控制因素。结果表明:1)林华煤矿20916工作面隐伏断层为不渗透压扭性逆断层,断层内构造煤发育良好,断层两盘岩层致密,不利于瓦斯逸散运移;2)不渗透压扭性逆断层应力场有利于瓦斯赋存,应力集中区存在瓦斯富集现象,且应力集中范围与瓦斯积存范围表现一致,煤层区域性瓦斯赋存明显受断层控制;3)工作面局部瓦斯异常涌出由煤层末端构造控制,在沿巷道、回采推进正前方距离断层20 m左右范围内的控制影响明显,瓦斯涌出量峰值出现的位置正是在断层两盘的拖曳褶曲段。

Taking the disclosure of the blind reverse fault in the working face of No. 20916 at Linhua coal mine as an example, the variation regularity of the amount of methane emission with respect to the length of driving and retreating was analyzed as the working face advanced based on fracture mechanics in the blind fault zone, petrophysical properties of two fault walls and the scale of the fault. Tectonic stress field in the blind fault zone was investigated through numerical simulation, which revealed the controlling factors causing the abnormality of methane emission. The results showed that： 1） The blind fault in the working face of No.20916 at Linhua coal mine is a nonpermeable reverse fault of compress-shear feature, in which tectonic coal was well-developed, and rock strata of two fault walls were tight, resulting in the difficulty in gas emission and migration; 2） The stress field of this type of fault is conductive to gas occurrence, methane accumulation can result in the zone of stress concentration, the scale of stress concentration is consistent with that of gas accumulation, and gas storage in the regional area of the coal seam is significantly controlled by the fault; 3） The abnormality of gas emission in the working face is controlled by the structure of the end of the coal seam, and the control role played the structure is significant in the range of 20 m ahead of driving and retreating working face, the gas emission peak position is at fault two disc drag fold section.