Three-dimensional grain-based model study on triaxial mechanical behavior and fracturing mechanism of granite containing a single fissure

Abstract

In order to investigate the mechanical behavior and failure mechanism of fissured granite under triaxial compression, a three-dimensional grain-based model (GBM3D) was established in particle flow code (PFC) for simulating the triaxial compression of granite specimens with various fissure inclinations (α = 0°, 30°, 45°, 60° and 90°) under different confining pressures (0, 5, 10 and 20 MPa). First, a group of micro-parameters used in GBM3D was calibrated based on the experimental triaxial compression results of intact specimens, the simulation results of fissured specimens based on these parameters are in good agreement with the experimental results. Compared with intact granite, the fissured granite has smaller peak strength, crack damage threshold, elastic modulus and axial peak strain. Confining pressure can improve the mechanical properties of granite at the same fissure angle, and under the same confining pressure, the mechanical properties increase with the increase of fracture angle. With the increase of axial stress, the cracks first emerge from the crack apices and propagate toward the ends of the specimen along the direction of the principal stress, and the cracks penetrate each other and eventually lead to the failure of the specimens. The displacement field shows that the main cracks are all generated at the interfacial locations where large relative displacements occur between the particles. The three-dimensional spatial crack distribution characteristics of the damaged specimens are not only influenced by the confining pressure, but also related to the fissure angle. The confining pressure not only complicates the crack distribution characteristics, but also increases the total count of cracks. As the fissure angle increases, anti-tensile wing crack is more likely to appear in the specimen.