Role of Loading Rate on Cracking Behavior in Granite Disks With Laboratory Experiments and Grain-Based Modeling

The investigation of the tensile properties of rock materials is essential for understanding the failure mechanism of engineering rock masses. In this study, we conducted a series of Brazilian splitting tests on granite specimens under three different loading rates, concurrently monitored using acoustic emission (AE) and digital image correlation (DIC) techniques. The results show that the mechanical parameters of granite disks are positively correlated with the loading rate. The AE waveforms are found to be associated with the lower frequency band, suggesting that this frequency range primarily dominates the failure mechanism in granite disks. Furthermore, the onset of micro-tensile fractures precedes the development of micro-shear ones. The elevation distribution of the fractured surfaces of the granite disks follows a Gaussian function. The fractal dimension increases progressively with the loading rate, whereas the complexity and irregularity of the fractured surface decrease. Moreover, the cracking mechanism of granite disks at the microscale was revealed using grain-based modeling (GBM). The intergranular tensile cracks predominantly form along the radial direction, and the proportion of intergranular shear cracks is the smallest.