Microcracking behaviors and acoustic emission characteristics of granite subjected to direct shear based on a novel grain-based model

Abstract

In this study, we numerically examine the microcracking behaviors of Alxa porphyritic granite under direct shear using a novel grain-based model considering particle-scale softening mechanism. Associated acoustic emission (AE) activities were monitored using a moment tensor algorithm, and then the effects of normal stress on the microcracking behaviors and AE characteristics of granite were investigated. The shear fracture systems primarily comprised linked tensile crack arrays, of which the proportion of shear cracks increases with an increase in normal stress. Furthermore, additional intra-grain cracks formed because of the strengthening grain interlocking effect, and the thickness of shear band gradually increased. Moreover, with the normal stress increasing, the decreasing b-value of AE events indicated that the proportion of large-magnitude AE events increased. We reported that the maximum-magnitude AE event in the prepeak stage could be used to identify the crack damage point, which could be considered as a potential failure precursor of granites. The displacement ratio of the peak strength point to crack damage point slightly increased with an increase in normal stress, providing a potential warning indicator for the granite failure. Overall, this study provides certain novel insights into the damage behaviors and failure prediction of granites under direct shear.