The brittle fracture is the most studied process in rock mechanics fields, especially the post-failure behavior of rock is one of the key issues for rock mechanical problems. However, even at present, it is still difficult to obtain complete stress-strain curve of brittle rocks in the laboratory experiments. Therefore, a new Distinct Element Method (DEM) code for the uniaxial compression tests with radial strain control was developed and Class II behavior of rock was simulated. The simulation results show good agreement with the complete stress-strain curve obtained from the laboratory experiment with radial strain control. These imply that the DEM simulation may be a strong tool for the analyses of rock failure mechanisms such as class II behavior. The post-failure behavior of rock was discussed in detail by using a newly developed DEM code. The simulation results suggest that the loading control methods strongly affect the failure mechanisms and processes of rocks under uniaxial compression (Class I and II). Moreover, it is also found that the key to understand the Class II behavior of rock is the localized deformation, such as shear band. A clear shear band appears in the axial strain controlled uniaxial compression test, and a significant increase of the axial strain occurs with the crack surface slips along the shear band. As a result, complete stress-strain curve of the entire rock shows the Class I behavior. On the other hand, clear shear band does not appear in the radial strain controlled uniaxial compression tests, because formation of shear band does not grow due to the unloading in a critical state. Since clear shear band is not formed, most local small parts of the rock still keep elastic behavior, and as a result, the complete stress-strain curve of the entire rock shows Class II behavior.
展开▼
