Statistical characterization of shear strength parameters of rock mass for hydropower projects in China

This study performs a statistical analysis on shear strength parameters of rock mass for hydropower projects in China. First, a large database comprising 1139 groups of field direct shear tests on rock mass from 100 hydropower projects in China is compiled. Second, the best-fit probability distributions of shear strength parameters are identified using Akaike Information Criterion (AIC). Finally, new characteristic and design values of shear strength parameters of rock mass are suggested. The results indicate that shear strength parameters increase with increasing quality of rock mass. In particular, the shear strength parameters of discontinuities in rock mass are significantly smaller than those of rock mass itself. The discontinuities in rock mass should be paid more attention during geological investigations. There is a large variation in shear strength parameters, and the variability of cohesion is larger than that of tangent of friction angle. The derived statistics of shear strength parameters of rock mass in this study provide an update to the values suggested in Chinese codes, and serve as a reference for hydropower projects with few site-specific test data and similar geological conditions for partial-factor design of dams.