The purpose of this study was to investigate the microscopic mechanism of rock load relief rupture may be unveiled. The PFC2D meso-structure parameters are calibrated based on a set of results from uniaxial compression test on indoor rocklike materials, and then the particle flow software is used to simulate biaxial compression and load relief tests. Study shows that, in the numerical simulation test of biaxial compression, only a main shear rupture zone forms after the rocklike material is damaged. Local shear rupture zone seems weak; while in the numerical simulation test of load relief, there are multiple shear rupture zones produced after it gets destroyed. The biaxial compression shear rupture zone appears wider than the unload shear rupture zone. from the ratio of the shear cracks to the tensile cracks when unloading, we find that a lot of tensile cracks will generate immediately if suddenly unloaded, so that the tensile failure occurs. subsequently, the shear and tensile cracks remain stable at a certain value, that is, the specimen fails due to the joint tension and shear. the simulation test is conducted with the analysis of the relationship between the uniaxial compression microcracks and the stress, and it is found therefrom that the stress curve of the sample is mainly subjected to change with the number of microcracks. The findings of this study may serve as to avoiding many work accidents have been incurred by work load relief in recent years
particle flow, unload, mesoscopic rupture mechanism
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