Accurately estimating the stress thresholds (crack closure stress σcc, crack initiation stress σci and crack damage stress σcd) is of great significance to the study of failure mechanisms for hard rock. Uniaxial compression tests were conducted on four types of hard rock to investigate the rationality and applicability of four different identification methods. The stress thresholds obtained by different methods were compared and analyzed. The main research results are as follows. Both the two distinct energy dissipation rate (EDR) methods underestimate the value of σcc, and it is not applicable for hard rock with few primary fractures. Since the method of lateral strain response (LSR) method does not consider the closure process of primary fractures, it underestimates the value of σci. The method of crack volume strain (CVS) or moving point regression (MPR) is recommended to calculate the σci of hard rock. The EDR method overestimates the value of σcd. The method of CVS or MPR is recommended to identify the σcd of hard rock.
Du et al. (Thu,) studied this question.