瓦斯压力对卸荷原煤力学及渗透特性的影响

运用自主研制的含瓦斯煤热流固耦合三轴伺服渗流试验装置，以原煤煤样作为研究对象，在不同瓦斯压力条件下对含瓦斯煤进行了固定轴向应力的卸围压瓦斯渗流试验，研究卸围压过程中瓦斯压力对煤体的力学及渗透特性的影响。研究结果表明：开始卸围压后，煤体出现明显的扩容现象，径向发生明显膨胀应变，煤体中的渗流通道张开，煤体中瓦斯的渗流速率随之加快；随着瓦斯压力的升高，解除单位围压后煤样产生的变形变大，渗流速率升高的速率也随之增大；瓦斯压力越高，煤样从开始卸围压起至破坏的时间越短，即煤体强度越低；在卸围压初始阶段，煤样变形模量变化不大，在进入屈服阶段和失稳破坏阶段后，煤样的变形模量减小的速率开始明显加快。从煤样开始卸围压至破坏之前，煤样的变形模量下降了3.71%~7.45%；煤样的泊松比逐渐增大，围压与泊松比的对应具有较为明显的幂函数关系。

Influence of gas pressure on mechanical and seepage characteristics of coal under unloading condition

Based on domestic developed triaxial servo controlled seepage equipment for thermal hydrological mechanical coupling of coal containing methane，the experimental study of unloading confining pressure of coal was performed on coal samples under different gas pressure.The results show that the characteristic of distinct dilatancy is displayed in the process of unloading confining pressure，therefore seepage channels in coal body are extended and seepage velocity increases.The deformation of coal containing methane per unit decreased confining pressure and seepage velocity increases with the increase in gas pressure in the same stress paths.The compressive strength decreases gradually with the increase of gas pressure.In the initial stage of unloading confining pressure，deformation modulus of coal containing methane changes little.After the yielding occurs，it decreases obviously.The deformation modulus decreases 3.71%-7.45% in the process of unloading confining pressure.Meanwhile，the Poisson’s ratio turns to increase and a function can be used to describe the relationship between confining pressure and Poisson’s ratio.