Relationship between crack initiation stress and uniaxial compressive strength of brittle rocks

Abstract

Clarifying the reasonable value range of the stress threshold for brittle rock under uniaxial compression has high theoretical and practical significance for predicting the failure of an engineering rock mass. Although much attention has been directed toward the experimental investigation of the ratio of crack initiation stress to uniaxial compressive strength (CI/UCS) in recent years, the ratio’s reasonable value range has not be accurately obtained owing to the lack of relevant theoretical work. By combining renormalization group theory, a rock damage constitutive model, and a CI identification method, this study derived the theoretical expression of CI/UCS for brittle rock and calculated the reasonable value range of CI/UCS as 0.43–0.52. The value range of CI/UCS was verified by 8 experimental results obtained for Longmaxi shale with different bedding angles, and the results of previous experiments on 385 brittle rocks with different lithologies obtained from different locations. On this basis, the main factors affecting CI/UCS in brittle rocks were analyzed, and the applicability of the theoretical calculation results was discussed. The relevant research results are of great interest to theoretical research on the rock stress threshold and can be useful as guidelines in engineering practice.