基于颗粒离散元模型的花岗岩压缩试验模拟研究

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。

Simulation research on granite compression test based on particle discrete element model

Biaxial compression tests for granite in the underground caverns of Huangdao State Oil Reserves were virtually simulated using the bonded particle model (BPM) in particle flow code (PFC2D). The mesomechanical parameters corresponding to the macromechanical parameters of indoor compression tests were obtained through trial and error method. The simulated elastic modulus and Poisson's ratio show good agreement with the corresponding values of indoor compression tests. Due to the circle particle in BPM, cohesion and internal friction angle have some certain deviation compared with those of indoor compression tests. The simulated failure pattern of specimens is shear failure along single inclined plane, which agrees with the failure pattern of indoor compression tests. With the calibrated mesomechanical parameters, the microcrack development and energy dissipation of granite were further studied. The results show that there are three main stages during the microcrack development, i.e. stable development stage, rapid increase stage and stable development stage. The changing of boundary energy, strain energy, bond energy, frictional energy and kinetic energy has given an excellent explanation of the mesoscopic mechanics.