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鉴于试验砂岩内摩擦角较大及峰后脆性强的特点,选用颗粒流程序PFC~(2D)中的cluster单元进行模拟,在常规三轴压缩试验校正的基础上得到一组能够真实反映砂岩宏观力学行为的细观参数,模拟了砂岩两种卸围压路径,结果表明其峰值强度随初始轴向应力的增大而不断增大,其规律与试验相同。选取了两种卸围压路径微裂纹数目随应力-应变的演化趋势进行分析,结果表明卸围压对试样造成的损伤较加轴压大,同时初始轴向应力增大一定程度上增加了试样承受破坏的能力。通过对不同应力路径裂纹两侧位移场的分析可知卸围压会造成颗粒在横向产生位移不连续,导致试样破坏。
In view of the large internal friction angle and the brittleness after the peak in the test sandstone, the cluster element in the particle flow program PFC 2D was used to simulate. Based on the conventional triaxial compression test calibration, The results show that the peak strength increases with the increase of initial axial stress. The law and test are the same. The results show that the damage caused by unloading confining pressure on the specimen is larger than the axial compression, and the initial axial stress increases to a certain extent The ability of the specimen to withstand damage. By analyzing the displacement fields on both sides of the crack with different stress paths, it can be seen that the unloading confining pressure will cause the particles to move discontinuously in the transverse direction, resulting in the destruction of the specimen.