不同应力路径下花岗片麻岩渗透特性的试验研究

 采用全自动三轴伺服仪，对花岗片麻岩开展渗流应力耦合试验，研究常规三轴压缩和轴压循环加卸载2种应力路径下，渗透率与渗压、围压、有效围压、体积应变及应力路径等因素的关系。结果表明：(1) 在2种不同应力路径下，岩石渗透率演化规律有差异性和一致性，同种路径下变形各阶段渗透率随有效围压增大而减小，但渗透率曲线的形态保持不变；(2) 渗压和围压对渗透率的影响，通过对岩石变形过程中内部微裂纹和孔隙变化产生作用，有效应力系数发生改变，有效围压效应随之改变；(3) 循环加卸载试验中，卸载渗透率均明显大于相应加载渗透率，体积应变转折前，加载渗透率减小，卸载后渗透率增加，形成比较完整的渗透率回滞环，体积应变转折后，加载渗透率增大，卸载渗透率降低不能够完全恢复；(4) 体积应变较轴向应变更清楚和灵敏反映渗透率变化规律，可把体积转折应变或其对应应力作为岩石渗透率变化的一项指标。试验研究旨在为岩石工程渗流–应力耦合稳定性分析提供参考。

Experimental study of permeability properties of granitic gneiss under different stress paths

Hydro-mechanical triaxial coupling tests were conducted on granitic gneiss with a servo-controlled triaxial equipment. The variations of permeability with seepage pressure，confining pressure，effective confining pressures，volumetric strain and stress paths were investigated based on the results of conventional triaxial compression and triaxial cyclic loading test. During the failure process of rock under two different stress paths，the permeability at each stage decreased with the increase of effective confining pressure. The influence of seepage pressure and confining pressure on permeability was described through the change of effective stress coefficient，effective confining pressure and internal micro cracks and pores in failure process. In triaxial cyclic loading test，the unloading permeability was significantly greater than the corresponding loading permeability. Before the turning point of volumetric strain，permeability decreased during loading and increased during unloading，forming a relatively complete permeability hysteresis loop. After the turning point of volumetric strain，unloading permeability can not be fully restored. The volumetric strain clearly and acutely reflected permeability variation. The turning volumetric strain or its corresponding stress can be regarded as an index of rock permeability change.