突出危险煤渗透性变化的影响因素探讨

通过对突出危险煤渗透性试验研究,系统分析了不同围压、不同瓦斯压力和不同应力-应变状态条件下突出煤样的渗透特性,分别建立了突出危险煤的渗透性与围压、瓦斯压力和应力-应变等主要控制因素之间的定性和定量关系,探讨了不同载荷条件下突出危险煤渗透性的控制机制和变化规律。研究结果表明,载荷条件对突出危险煤的渗透性具有重要影响:(1)在固定瓦斯压力条件下,突出危险煤样的渗透率随围压的增大而减小,且服从指数函数变化规律。(2)在固定围压条件下,受Klinkenberg效应影响,渗透率与瓦斯压力之间大致呈"V"字型变化;Klikenberg效应发生在瓦斯压力p1MPa的范围内。(3)在三轴压缩下的应力-应变全过程中,不同载荷条件下突出危险煤样的渗透率-应变曲线变化趋势几乎一致,且都呈"V"字型走势;在微裂隙闭合和弹性变形阶段,煤样渗透率随应力增大而减小;进入屈服阶段后,渗透率达到最小值并在峰值强度到达之前完成反超过程;峰值强度之后渗透率持续增大直至试验结束;煤样渗透率反超后的变化要较反超前变化平缓。

Research on influencing factors of permeability change for outburst-prone coal

According to permeability test investigation of outburst-prone coal, permeability properties of outburst-prone coal specimens are analyzed systematically for different confining pressures, different gas pressures, and different stress-strain conditions. Quantitative and qualitative relations between outburst-prone coal permeability and confining pressure, gas pressure and stress-strain curve are established respectively. The controlling mechanism and changing law of outburst-prone coal permeability under variable loading conditions are discussed. The results show that the loading condition has an important impact on outburst-prone coal permeability, and the details are: (1) For fixed gas pressure condition, outburst-prone coal permeability decreases with increasing of confining pressure; and the decreasing rule obeys an exponential law. (2) For fixed confining pressure condition, the relation between permeability and gas pressure is showed a “V” curve approximately in shape affected by Klinkenberg effect, which happens in the gas pressure range of p < 1 MPa. (3) During the whole stress-strain process under triaxial compression, the change trends of outburst-prone coal permeability versus strain curve for different loading conditions are almost uniform, which are showed a “V” curve. At the stage of microfissure closing and elastic deformation, the coal specimen permeability decreases with the increasing of stress; after entering into the yield stage, the coal specimen permeability reaches the minimum and anti-exceeding is accomplished before reaching the peak strength. The permeability increases continuously until the end of test after reaching the peak strength. The outburst-prone coal permeability after anti-exceeding changes more mildly than before anti-exceeding.