Nonlinear distinct element modeling of the microstructural compression-hardening effect on the progressive failure and associated acoustic emission of brittle rock

The linearly bonded particle model (LBPM) and moment tensor method (MTM) have been combined and applied to simulate the progressive failure of rock and associated acoustic emission (AE). However, LBPM-MTM cannot characterize the compression-hardening response of a rock microstructure or its effect on progressive failure and AE. We propose a nonlinear bonded particle model (NBPM) to address this with MTM. Results revealed that NBPM could reproduce the compression-hardening response of Xinzhuang sandstone far better than LBPM. For the LBPM case, the proportion of the tensile force and concentration zones changed slightly during compression, while the results of the NBPM significantly increased. Microcracks in the NBPM case emerged later than in the LBPM case. Compared to the LBPM-MTM case, the NBPM-MTM case has more microcracks and AE events, and more energy is released near the peak stress. The correlation between the accumulative AE event count and magnitude via NBPM-MTM complied with the Gutenberg-Richter law much better than via LBPM-MTM. Overall, the magnitude of a single AE event with NBPM-MTM is greater than with LBPM-MTM. Our NBPM-MTM was proven to be more feasible and accurate in characterizing the progressive failure of rock and its associated AE than the traditional LBPM-MTM.