Rate-dependent shear behaviors of rock discontinuities with different joint wall strengths.

Understanding the shear responses of discontinuities with different joint wall strengths (DDJS) under varying shear rates is crucial for evaluating slope dynamic stability in the Three Gorges Reservoir region, China. In this study, direct shear tests were performed on discontinuity replicas featuring three distinct wall strength combinations under three normal stress levels and four shear rates. The investigation explored the rate-dependent shear behaviors of DDJS and their underlying failure mechanisms. Tested results show consistent shear stress behavior under different shear rates for each configuration, with intensified surface damage observed at higher shear rates. Shear stiffness exhibits a decreasing trend with increasing shear rate, particularly under higher normal stress. Peak shear strength decreases non-linearly with the increase in shear rate, with this decrease being less pronounced at higher shear rates. Noted that the variation of peak shear strength versus shear rate remains roughly consistent under various normal loadings. Importantly, the negative shear rate dependence on shear stiffness and peak shear strength diminishes with the increase in discontinuity wall strength difference. Based on experimental observations, a new failure criterion with the inclusion of shear rates was developed to estimate the peak shear strengths of DDJS, further validated by experimental data available in the literature. [ABSTRACT FROM AUTHOR]