Robustness of Rock Damage Regions Induced by Crack Nucleation

The stress-induced fracture of brittle rocks, as a result of macrocrack evolution, is closely related to the evolution of microcracks. The study of such damage processes provides information about the mechanical behavior of rock cracks. In this study, we conducted research with respect to macrocracks using hypothetical damage regions constituted by correlated microcracks. A Gaussian mixture model was applied to describe the spatial distribution of microcracks. The Kullback–Leibler divergence was used to characterize the geometric variation of damage regions. The results showed that the robustness of the damage region’s geometry became increasingly higher during the damage evolution and the damage region became unchanged after some time. The robustness of the damage regions could be an indicator of the nucleation of macrocracks. Moreover, a fracture nucleation indicator methodology was developed to calculate the point at which nucleation was formed. This study is considered to enhance the understanding of macrocrack nucleation and it is useful to the application of macrocrack recognition and prediction.

This study presented an investigation on the robustness of the damage regions associated with macrocracks. The evolution of calculated damage regions can be considered as a process of macrocrack nucleation. The geometric variation of damage regions was studied. Results showed that the geometry of damage regions became increasingly stable during microcracking. A methodology named fracture nucleation indicator was proposed to define the fracture nucleation point, whereby the damage regions showed great robustness. This study was considered to enhance the understanding of a fracture’s nucleation process and the proposed fracture nucleation indicator was a successful approach to quantitatively define macrocrack nucleation time.