轴向应力循环加卸载作用下含瓦斯煤渗透性研究

 针对构造煤渗透率对轴向应力循环加卸载的响应特征，利用自行研制的含瓦斯煤热–流–固耦合三轴渗流试验装置，进行试验研究，并结合试验结果进行渗透率动态模型分析，结果表明：含瓦斯构造煤的渗透率与应变的关系呈斜“V”字型走势，峰值强度后，煤样渗透率增加趋势明显，且增速大于初始压缩阶段渗透率的降速；煤样渗透率与轴向应力在加卸载过程中符合负指数函数分布，渗透率在加载过程中减小，卸载过程中有所恢复，渗透率与有效应力未形成封闭曲线，循环加卸载使煤样中孔隙进一步压缩，渗透率损失量增大，同时渗透率对于有效应力的敏感度降低；通过引入加载过程渗透率敏感性损失因子及卸载过程中渗透率损耗因子，建立循环加卸载过程中渗透率与有效应力的动态演化模型，试验数据与理论计算数据对比验证了模型的适用性。

Permeability of coal samples containing methane under cyclic loading-unloading of axial stresses

In order to investigate the response of tectonic coal to cyclic loading-unloading of axial stresses，experimental study and analysis of dynamic model of permeability were carried out with experiment facility developed in-house for triaxial seepage test considering the fluid-solid-heat coupling in gas filled coal. The results show that the relation between the permeability of gas filled coal and the strain presents a trend of inclined letter ‘V’. The permeability of tectonic coal samples increases obviously after peak strength and the growth rate is greater than the reduction rate of permeability in the initial stage of compression. The permeability of coal samples and the axial stress presented a relation of negative exponential function during unloading. The permeability decreases under loading and recoveres a bit under unloading. The permeability and the effective stress does not form a closed curve. The reduction of permeability increases and the sensitivity of permeability to the effective stress decreases because that pores of coal sample are more compressed under cyclic loading- unloading. A factor in reduction of permeability sensitivity when loading and another factor in reduction of permeability when unloading were introduced，and then the dynamic evolution model of permeability and effective stress under cyclic loading-unloading was established. The comparison of experimental data with theoretical results verified the applicability of this model.