Strength Calculation Method of Bedding Rock Based on Improved Hoek-Brown Criterion Considering the Effect of Critical Confining Pressure

Rock is a commonly used building material. Studying rock properties can reduce production time and cost, improve production efficiency and construction safety. Therefore, rock mechanics characteristics, especially strength, have always been a hot field of rock mechanics. Classical strength criteria such as the Mohr-Coulomb (M-C) criterion and Hoek-Brown (H-B) criterion are based on rock strength homogeneity and cannot reflect the characteristics of layered rock strength changing with azimuth. Therefore, it is necessary to modify the classic strength criterion to reflect layered rock anisotropy. Based on existing triaxial test results and rock anisotropic strength properties, an improved H-B criterion for rock anisotropy considering the effect of critical confining pressure is proposed in this paper, which can be used to calculate the strength of layered rocks. Taking slate as an example, the calculation results of the improved H-B criterion show that: 1. the improved H-B criterion can mostly control the mean absolute percentage error (MAPE) of McLamore slate test results within 30%, which is obviously better than the classical H-B criterion and has good extrapolation ability; 2. the material parameters m, n are determined by test results and inversion analysis, which avoids the arbitrariness. The proposed method can be used as a supplementary and alternative method to estimate or calculate the strength of layered rock