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地下工程开挖造成围岩破坏,其破坏方式可归纳分析为两类:张拉型破坏和压剪型破坏,这两种破坏导致的裂隙面的细观形态并不相同,这种不同的细观形态导致张拉和压剪型裂隙的渗透率表现出不同的演化规律。为此,对花岗岩进行了不同围压下三轴压缩试验,产生张拉和压剪型裂隙,进行含裂隙岩样在静水压力加载条件下渗透系数试验。试验表明,相比于含压剪裂隙试样,含张拉裂隙试样的渗透率对静水压力更敏感。进而,分别对不同围压条件下的三轴压缩试验获得的张拉和压剪裂隙面进行扫描电镜试验,获得张拉和压剪裂隙面的细观形态,花岗岩单轴压缩试验所产生的裂隙面表现为典型的张拉型裂隙,破裂面比较光滑;随着围压的不断增大,破裂面的细观形态发生明显的变化,从破裂面上可以明显地观察到逐渐增多的压剪型裂隙,破裂面比较粗糙。在静水压力的作用下,张拉裂隙较快闭合;而压剪裂隙的锯齿能够一定程度上阻止裂隙的闭合。张拉和压剪裂隙面的不同细观结构决定了含张拉和压剪裂隙岩样的不同渗透率演化规律。研究结果对于地下工程分析中确定围岩的渗透率具有一定的意义。
Surrounding rock damage caused by excavation of underground engineering can be summarized into two types of failure modes: tension-type failure and compression-shear failure. The mesoscopic morphology of the fracture surface caused by these two kinds of damage is not the same. View of morphology leads to different evolutionary laws of the permeability of tensioned and pressure-shear fractures. For this reason, the granite was subjected to triaxial compression tests under different confining pressure to produce tensile and compression-shear fractures, and the permeability coefficients of fractured rock samples under hydrostatic pressure were tested. Experiments show that the permeability of specimens containing tension-fractured joints is more sensitive to hydrostatic pressure than those of specimens containing pressure-shear fractures. Furthermore, the tensile and compression shear fracture surfaces obtained under the triaxial compression tests under different confining pressures were examined by SEM, and the mesoscopic morphology of the tensile and compression shear fracture surfaces were obtained. The fractures produced by the uniaxial compression tests of granite The surface shows a typical tension-type fracture, and the fracture surface is relatively smooth. As the confining pressure increases, the mesoscopic morphology of the fracture surface changes obviously, and gradually increasing pressure-shear type can be observed from the fracture surface Cracks, rupture surface is relatively rough. Under the effect of hydrostatic pressure, the tension fracture is closed more quickly; while the serration of the compression shear cracks can prevent the fracture closure to a certain extent. The different mesostructures of the tension and compression shear fracture surfaces determine the evolution of different permeability of the fractured rock samples with tension and compression. The research results have certain significance for determining the permeability of surrounding rock in the analysis of underground engineering.