Mesoscopic damage evolution characteristics of jointed sandstone under different loading conditions

To reveal the influence of different loading conditions on the damage evolution of jointed sandstone, the numerical model with realistic mesostructure was established using CT scans and RFPA(3D). Moreover, uniaxial compression tests of similar simulated specimens were performed. Three-dimensional fractures were extracted and reconstructed. A digital image-based rock microscopic scale fractured box dimension algorithm was written in MATLAB to analyze the three-dimensional fractal features of the AE fields. Studies have revealed that plane-to-plane and point-to-plane loading are both the mixed failure of tension and compression. Whereas point-to-point loading is a compression failure, and multi-point loading is a tensile failure. There are significant variations in damage characteristics and evolution of multi-point loading; the specimen's fractal dimension is 2.5622, which is the largest, and it has the most significant crack propagation, the most complicated rupture mode, and a relatively good damage effect. The fractal dimension determined by the AE field can quantitatively assess the mesoscale damage evolution. The research findings are significant in understanding the rules of jointed sandstone breakage and energy consumption, in addition to searching for an effective and energy-saving rock-breaking technology.