LAUSR

This study attempted to explore the evolution of fractures and microcracks at the macro- and micro-scale. Based on the hypothesis of the Weibull distribution for micro-strength parameters, a series of grain distinct element models was established. For intact heterogeneous rock, microcrack development was first investigated quantitatively. The results showed that microcrack distribution changes from diffusion to localization as stress increases. This process is affected by the microcrack propagations and coalescences. Moreover, the microcracks whose dips are less than 45° are the most popular, with this type of microcrack accounting for approximately 70% of the total. The number of microcracks whose dip angles are larger than 50° clearly increases after the peak stress. Second, the relationship between the fracture and microcrack was studied. The evolution of the damage process and fracture length in the macro-scale can be divided into three stages. The microcrack number development at the micro-scale had a good correspondence with the macro-failure process. Moreover, the length increment of the fracture was closely associated with an increase in the microcrack number. Finally, the numerical results were verified by experimentally by acoustic emission (AE) and scanning electron microscopy (SEM).