复杂应力路径下大理岩三轴渗透试验研究

Triaxial permeability test of marble under complex stress path

在隧道施工过程中,围岩的应力条件非常复杂,研究复杂应力路径下围岩渗透性能的变化规律对在高水压地区修建隧道具有重要意义。以锦屏水电枢纽二级电站交通辅助洞大理岩为研究对象,进行了常规三轴渗透试验与控制轴向应变(简称应变ε)、围压先升后降的三轴渗透试验,探讨了轴压与围压之差的绝对值△σ(简称应力差)与渗透率的关系。试验结果表明:(1)常规渗透试验大理岩渗透率的变化过程有3个重要的特征点:渗透率最低点、渗透率峰值点以及渗透率稳定点;(2)大理岩的渗透率随着应力差的增大而减小,两者呈负指数关系;(3)对某一固定的应力差,升围压阶段测得的渗透率大于降围压阶段测得的渗透率;(4)对任何试验岩样总存在一阈值,当应力差小于该值时,应力差的改变对渗透率有显著影响;(5)应力差减小过程中岩样渗透率的"恢复能力"随着岩样轴向应变的增大而逐渐减弱。

The stress condition of surrounding rock is very complicate under different construction phases and it is important to study the permeability of rock under the complex stress path.In order to study the relation between stress and permeability of marble,triaxial permeability test under general and loading-unloading of confining pressure on the basis of constant axial strain,（which is called strainε in the following text） are carried out.Based on triaxial permeability test results,some conclusions can be drawn as follows.（1） In the general triaxial permeability test,the characteristics of permeability-strain curve of marble has three significant phases： the lowest permeability,the highest permeability and the stable permeability.（2） The permeability of marble decreases with the increase of △σ（the absolute value of axial stress minus confining stress）,following the law of exponential decay;（3） For the same value of ？σ,permeability of marble during the loading of confining stress phase is greater than it in the unloading of confining stress phase;（4） The variation of ？σ will influence the permeability of marble significantly when it decreases to a certain degree.（5） The permeability of marble will increase when ？σ decreases;and the recovery capability of permeability of marble will reduce with the increase of axial strain.