Discrete Element Numerical Study on the Influence of Different Three-Dimensional Boundaries on the Triaxial Test of Granite

The boundary has a serious influence on the mechanical properties of the rock, so 27 sets of triaxial simulation tests were established to study the influence of the boundary on the mechanical properties of the rock. Based on Particle-Flow-Code, generating granite by using the grain-based model, at the same time, triaxial tests under the boundaries of rigid, flexible and shell element were established respectively by using the FDM-DEM coupling technology. The results show that the boundary will affect the peak strength, failure shape and stress concentration of the sample. Rigid boundary can easily lead to stress concentration in rock samples. The flexible boundary will cause the actual confining pressure of the rock sample to be larger than the target confining pressure during the triaxial loading process, and significantly increase the residual strength of the sample. While the sample under shell boundary has smallest probability of stress concentration and stable confining pressure. Therefore, the shell boundary should be used in the triaxial test of discrete element simulation.