Crack propagation and strength characteristic of sandstone with structural defects under extensive true triaxial tests by using DEM simulation
Fan Feng, Tong Zhang, Jamal Rostami, Shaojie Chen, Xingdong Zhao, Jiadong Qiu
Abstract
The stability of rock masses is significantly affected by the existence, frequency, and condition of the structural features such as planes and joints. The failure characteristics and strength of such features, their conditions and stability should be studied to understand the behavior of rock mass. In the present study, Particle flow code in three dimensions (PFC3D), which is a discrete element program, was used to conduct extensive simulation of true triaxial compressive tests on sandstone with structural defects. The results of the simulation were validated by comparing the crack growth pattern with those of laboratory testing. The main focus of this study was on the effects of structural plane dip angles (α) and polyaxial stress states on the crack propagation, failure mode and peak strength of sandstone. The results indicate that the minimum principal stress (σ 3 ) has a predominant influence on the generation of anti-wing cracks. Increase in σ 3 can promote the propagation range of the anti-wing crack under the same intermediate principal stress (σ 2 ). The increase in σ 2 lowers the non-uniform deformation of specimen which was affected by the structural plane. The increasing rate of peak strength with equal σ 3 gradient of specimens exhibits a linear relationship with σ 2 under true triaxial compression. However, the resulting strength is different under various α. σ 3 has a more pronounced influence on the peak strength of specimens with structural plane than σ 2 . σ 3 determines the influence of σ 2 on the peak strength of the specimens. It is also found that the higher σ 3 leads to reduced influence of α on the strength.