Experimental study on the rift plane of granite under uniaxial compression

In this paper, uniaxial compression tests were carried out on granite specimens with different rift plane orientations to investigate the effect of the rift plane on the fracture mechanisms. The spatial distribution of acoustic emission and the corresponding fractal dimension are calculated and analyzed to describe the evolution of the microcracks. The results show the compression strength is much higher when the loading direction is perpendicular to the rift plane. Stress thresholds for crack initiation and crack damage are identified using the volumetric strain. The stress threshold for crack initiation is found to be 53% of the failure stress, independent of the rift plane orientation. The spatial distribution of acoustic emission events reveals that when the rift plane is parallel to the loading direction the microcracks spreading is more scattered than that when the rift plane is perpendicular to the loading direction. The larger fractal dimension in the former case during the whole compression process also validates this conclusion. Due to the anisotropy of the specimen, the fractal dimension shows a trend of overall increase during the compression and reaches a stable value before the specimen fails. The fractal dimension of acoustic emission events can be a quantitative characteristic serving as an early warning for the coming failures.