Data from: Experimental study on permeability characteristics for containing-gas raw coal under different stress conditions

The experimental study on permeability characteristics for raw coal under different stress state is implemented by applying the triaxial self-made "THM coupled with servo-controlled seepage apparatus for containing-gas coal", the result indicates: The flow rate of coal sample gradually decreases with the nonlinear loading of axial pressure and increases with the nonlinear unloading of axial stress and confining pressure. The flow rate, axial stress and confining pressure curves all satisfy the negative exponential function relation. When the sample reaches the peak intensity, the sample will be destroyed and the stress will drop rapidly, then the flow rate of the sample will increase rapidly. At this stage, the flow rate and axial strain show an oblique "v" pattern. The flow rate of coal sample increases nonlinear with the increase of gas pressure, the relation curve between flow rate and gas pressure satisfies power function relation. Under the condition of same confining pressure and gas pressure, the larger the axial stress is, the flow rate of coal sample will be smaller. Under the condition of same axial stress and gas pressure, as confining pressure decreases, the flow rate of coal sample will firstly decrease, but then increase. During the loading and unloading process post-peak, the flow rate of coal sample will decrease with the loading of confining pressure but increase with the unloading of confining pressure, and it will increase in wave shape with the increase of axial strain. The flow rate of each loading and unloading confining pressure is higher than that of the previous loading and unloading confining pressure. At the post-peak stage, the relation curve between the flow rate of coal sample and confining pressure satisfies the power function relation in the process of loading and unloading confining pressure.

本研究采用自主研制的含瓦斯煤THM（热-水-力）耦合伺服渗流三轴试验装置，开展不同应力状态下原煤渗透特性的试验研究。试验结果表明：煤样渗流速率随轴向压力的非线性加载逐渐降低，随轴向应力与围压的非线性卸载逐步升高；渗流速率、轴向应力与围压三者间的关系曲线均满足负指数函数关系。当煤样达到峰值强度时发生破坏，应力快速跌落，此时煤样渗流速率迅速增大，该阶段渗流速率与轴向应变呈现斜向"V"型分布特征。煤样渗流速率随瓦斯压力升高呈非线性增长，二者间的关系曲线满足幂函数关系。在围压与瓦斯压力相同的条件下，轴向应力越大，煤样渗流速率越小；在轴向应力与瓦斯压力相同的条件下，围压降低时，煤样渗流率先降低后升高。在峰后加卸载过程中，煤样渗流速率随围压加载逐渐降低，随围压卸载逐步升高，且随轴向应变增加呈波浪式增长；每一次围压加卸载后的渗流速率均高于前一次围压加卸载后的渗流速率。峰后阶段围压加卸载过程中，煤样渗流速率与围压的关系曲线满足幂函数关系。