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基于颗粒流理论,以黄岛国家石油储备库地下洞库的花岗岩室内试验测试为背景,借助PFC2D(particle flow code)的黏结颗粒模型(bonded particle model,BPM)建立双轴压缩模型。以花岗岩室内试验的宏观力学参数和破坏形态为参照,通过“试错法”得出黏结颗粒模型相对应的细观物理力学性质参数。模拟试验的弹性模量、泊松比与室内试验值吻合较好,BPM模型由于选用圆形颗粒导致黏聚力和内摩擦角与室内试验值相比有一定偏差。模拟试验与室内试验的试件破坏形态均以单斜面剪切破坏为主。采用校准的细观物理力学性质参数,应用BPM模型再现花岗岩压缩试验全过程,深入分析微裂纹萌生演化及能量变化规律。研究表明,压缩过程中岩石试件内裂纹扩展主要经历平稳发展-急剧增加-平稳发展3个阶段;变形过程中,花岗岩试件边界能、应变能、黏结能、摩擦能及动能在各个阶段的变化很好地解释花岗岩受力破坏的细观力学机制。
Based on the particle flow theory, a biaxial compression model was established with the bonded particle model (BPM) of PFC2D in the laboratory test of granite in the underground reservoir of Huangdao National Petroleum Reserve. Based on the macroscopic mechanical parameters and failure modes of granite laboratory tests, the parameters of meso-physical-mechanical properties corresponding to the cohesive particle model are obtained by “trial and error method ”. The elastic modulus and Poisson’s ratio of the simulation experiment are in good agreement with the indoor experimental values. The BPM model has some deviations from the indoor experimental values due to the selection of round particles. The failure modes of the specimens in both the simulation and laboratory tests are dominated by the shear failure of the monoclinic. Using the calibrated parameters of meso-physical and mechanical properties, BPM model is used to reproduce the whole process of granite compression test. The microcrack initiation and evolution and energy variation are analyzed in depth. The results show that the crack propagation in the rock specimen mainly undergoes steady development during the compression process, which increases sharply and steadily. During the deformation process, the boundary energy, strain energy, cohesive energy, friction energy and kinetic energy of the granite specimen in all stages Variations explain well the meso-mechanics mechanism of granite failure.