塑性流动下砂岩渗透率演化试验研究

Experimental Study on Permeability Evolution of Sandstone under Plastic Flow

为了研究剪切屈服后煤层顶板岩体在开采过程中渗透率的演化规律,进行了不同轴向应变下的围压循环加卸载渗透试验。当达到峰后轴向应力的90%时开始循环加卸载围压,分析剪切屈服后砂岩渗透率随围压、轴向应变的变化规律。结果表明:(1)随着围压、轴向应变的增大,砂岩的渗透率均呈现降低趋势;(2)随循环次数的增多,围压对渗透率的影响越来越小,渗透率恢复率升高;(3)随着轴向应变的增大,砂岩产生的塑性变形越大,由此围压对渗透率的影响减小,渗透率恢复到初始值的能力降低。最终得到剪切屈服后围压和渗透率的理论关系式,为预测巷道开挖过程中的涌水量提供一定的参考。

In order to study the evolution of permeability of coal roof rock mass during the mining process after shear yielding, the confining pressure cyclic loading and unloading permeability tests under different axial strains were carried out. When it reaches 90% of the axial stress after the peak,the confining pressure is cyclically loaded and unloaded, and the sandstone permeability changes with the confining pressure and axial strain after shear yielding are analyzed. The results show that:(1)With the increase of confining pressure and axial strain, the permeability of sandstone shows a decreasing trend;(2)With the increase of the number of cycles, the influence of confining pressure on the permeability becomes smaller and smaller, and the permeability recovery rate Increase;(3)With the increase of axial strain, the greater the plastic deformation of sandstone, the impact of confining pressure on permeability decreases, and the ability of permeability to return to the initial value decreases. Finally, the theoretical relationship between confining pressure and permeability after shear yielding is obtained, which provides a certain reference for predicting the water influx during the roadway excavation process.