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为探究微裂纹优势方位与各向异性的关系,研究了岩石单轴压缩实验过程中的微裂纹萌生与扩展机制和各向异性参数的演化过程。利用最大周向应力理论和提出的剪切滑动导致局部拉应力假设,建立了单轴压缩条件下的微裂纹萌生和扩展理论,并根据该理论对岩石的各向异性参数进行理论分析。为进一步验证理论的有效性,选取大理灰岩和花岗斑岩进行单轴压缩实验,得到弹性模量和泊松比的变化趋势图,实验结果与理论分析一致。最后针对原生微裂纹和次生微裂纹的优势方位问题和微裂纹按优势方位排列对实际工程的影响进行了探讨。研究表明:在单轴压缩条件下,岩石微裂纹的优势方位与最大主应力平行,并导致岩石的各向异性,且泊松比对微裂纹定向排列的敏感度高于弹性模量。
In order to explore the relationship between the azimuth and anisotropy of microcracks, the mechanism of microcrack initiation and propagation and the evolution of anisotropy parameters in uniaxial compression experiment were studied. Based on the theory of maximum circumferential stress and the assumption of local tensile stress caused by shear sliding, the theory of microcrack initiation and propagation under uniaxial compression was established and the anisotropy parameters of rock were theoretically analyzed. In order to further verify the validity of the theory, the uniaxial compression experiments of Dali limestone and granite porphyry were selected to get the change trend of elastic modulus and Poisson’s ratio. The experimental results are consistent with the theoretical analysis. Finally, in view of the advantages of the primary and secondary microcracks and the effect of micro-cracks on the actual project according to the arrangement of the dominant azimuths, The results show that under uniaxial compression, the dominant azimuth of rock microcracks is parallel to the maximum principal stress and leads to the anisotropy of rock, and the Poisson’s ratio is more sensitive to the orientation of micro-cracks than the elastic modulus.