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通过开展单裂隙花岗岩不同围压加、卸载和不同水力梯度作用下的渗透试验,研究应力历史对裂隙渗透性能演化的影响。试验结果表明:在围压加载过程中,渗流流量与渗透压差大致呈线性关系;在渗透压差相同的条件下,围压越小,流量越大,随着围压上升,裂隙渗流流量持续减小,但随着围压的进一步增大,流量的减小有减缓的趋势。在围压相同以及渗透压差相同的条件下,单裂隙花岗岩在卸载条件下的渗流特性与加载条件下相比,其渗流流量明显降低,且卸载过程中渗流流量与渗透压差开始偏离线性关系。从试验前、后裂隙面粗糙度系数值的对比可以看出,由于法向应力挤压以及渗流流体的冲蚀作用,试验后裂隙面粗糙度系数明显降低。卸载的过程中,裂隙渗透性能的恢复具有明显的滞后效应,表明在法向应力和流体冲蚀的共同作用下,裂隙产生了不可恢复的非弹性变形。
The effect of stress history on the evolution of fracture permeability was studied by carrying out infiltration tests under different confining pressure of single fissured granite under different confining pressure, unloading and different hydraulic gradient. The results show that the seepage flow rate and the osmotic pressure difference are approximately linear in the process of confining pressure. Under the same osmotic pressure difference, the smaller the confining pressure is, the larger the flow rate is. As the confining pressure increases, the seepage flow rate of fractures continues Decreases, but with the further increase of confining pressure, the decrease of the flow rate tends to slow down. Under the condition of the same confining pressure and the same osmotic pressure difference, the seepage flow rate of single-fractured granite under unloading condition is obviously lower than that under loading condition, and the seepage flow rate and the osmotic pressure difference begin to deviate from the linear relationship . It can be seen from the comparison of the roughness coefficient values of the fracture surface before and after the test that the roughness coefficient of the fracture surface obviously decreases due to the normal stress extrusion and the erosion effect of seepage fluid. During the unloading process, the recovery of fracture permeability has a significant hysteresis effect, which indicates that the fractures produce non-recoverable inelastic deformation under the combined effect of normal stress and fluid erosion.