低渗透岩石三轴压缩过程中的渗透性研究

 采用岩石全自动三轴伺服仪，对低渗透花岗岩进行考虑渗透水压作用的三轴渗流–应力耦合试验。基于试验结果，研究花岗岩在不同围压和渗压下的渗透特性，分析岩石应力、应变变化过程中渗透率随围压、渗压和体积应变的变化规律。试验结果表明：岩石的应力–应变关系具有典型的脆性特征，渗压相同围压不同时，岩石强度随围压增大而增加；围压相同渗压不同时，较低的渗压对低渗透岩石强度影响不明显。岩样体积应变经过压密和扩展2个阶段，最大体积压缩应变随着围压的增加而增加，而岩样渗透率最小值并未出现在最大压密处，而是出现在体积应变拐点前，约在最大压密体积应变的95%处，并给出渗透率与体积应变的关系式。

PERMEABILITY OF DENSE ROCK UNDER TRIAXIAL COMPRESSION

A series of coupled hydro-mechanical triaxial tests on granite specimens were carried out in order to investigate the permeability of dense rock under triaxial compression using servo-controlled triaxial testing equipment. The variations of the permeability with the confining pressure，the seepage pressure and the volumetric strain in the complete stress-strain process of the rock were obtained. The experimental results showed that the stress-strain relation exhibited the behavior of brittle failure. The strength of granite at failure increased with the increasing of confining pressure while the seepage pressure was kept constant. The low seepage pressure had little influence on the failure strength of rock. The granite specimens experienced a stage of compaction and a stage of expansion. The maximum volumetric compressive strain increased with the increase of confining pressure. The lowest permeability appeared before the inflection point of volumetric strain and the volumetric strain corresponding to the lowest permeability was found to be about 95% of the maximum volumetric compressive strain. A relationship between the permeability and the volumetric strain was presented.