水岩作用下花岗岩裂隙剪切力学特性演化规律

Evolution law of water-rock interaction on the shear behavior of granite fractures

为研究水岩作用对花岗岩裂隙剪切力学特性的影响,分别对干燥和不同浸水时长条件下的花岗岩裂隙试样进行了室内直剪试验。结果表明:峰值抗剪强度、剪切刚度随浸水时长的增长而减小;峰值剪位移随浸水时长的增长而增大;剪胀效应随浸水时长的增长而减弱;剪切损伤体积随浸水时长的增长而增大。采用三维蓝光扫描仪获得了裂隙面剪切前后的形貌特征,分析了剪切损伤体积随浸水时长的演化规律,提出了考虑浸水时长条件下的粗糙裂隙剪切体积模型。此外,还分别进行了干燥、浸水12个月两种工况下的花岗岩纳米压痕试验。相比干燥试样,浸泡12个月后试样的最大压入深度和塑性变形都明显增大,长时间浸水后花岗岩试样纳米硬度和Young’s模量明显降低,即裂隙凸起体更容易破坏。

To study the influence of water-rock interaction on the shear behavior of granite fractures, direct shear tests were conducted on Beishan granite fracture samples that were dry or immersed in water for different durations. The immersion affected the shear properties of granite fractures in terms of decreasing peak strength, shear stiffness and dilation, and increasing peak shear displacement. The three-dimensional morphologies of fracture surfaces before and after shear were recorded using a three-dimensional blue light scanner, and the volume changes of sheared-off asperities were calculated. With increased immersion duration, the volume of the sheared-off asperities increased significantly, and an empirical expression is proposed to describe this relation. Moreover, a nanoindentation test was conducted on the granite surfaces under dry and immersed for 12 months conditions. The maximum indentation depth and plastic deformation of the immersed granite samples were significantly larger than those of the dry samples. The nanohardness and Young’s modulus of the granite samples decreased significantly after the long-duration immersions, which indicated that the fracture asperities were damaged more easily after the immersions.