Macro and meso crack evolution of granite specimens with non-straight fissures: A comparison between two bond models

Various flaws in rock mass can weaken mechanical properties of the rock and pose a risk to the safety of underground engineering, with significant implications for design, construction and maintenance. A study of the strength and failure modes of rocks with non-straight fissures can provide a better understanding of fracture mechanisms of rocks. In this study, uniaxial compression tests were carried out on granite specimens with three types of fissures, including straight and arc fissures. The experiments showed that the stress–strain curves and failure modes of the granite specimens were influenced by pre-existing fissures. Compared to straight fissures, arc fissures had less influence on mechanical parameters of the specimens. In order to further investigate the effects of arc fissures, PFC models were constructed, based on calibrated PBM and FJM parameters. Stress–strain curves, mechanical parameters and failure modes of specimens with pre-existing fissures were simulated. The initial cracks around the arc fissure were shifted from the tip of the fissure to the highest point of the arc fissure. Finally, the dip angle of cracks, the stress distribution in the specimens and the local stress evolution around the fissures were further discussed, and the advantages and disadvantages of the two contact models were summarized.