Dynamic friction behaviors of slip surfaces in granite and implications for large rapid rockslides with long runouts on the southeastern Tibetan Plateau: Constraints from an experimental investigation

Abstract

Large rapid rockslides with long runouts are the most destructive type of landslide in nature. The dynamic friction behavior of the slip surface of this type of landslide controls its initial acceleration during motion in the source section. To explore the dynamic friction behaviors of the slip surfaces in granite rockslides, a series of high-velocity friction experiments were conducted on simulated slip surfaces in granite. The samples were collected from two rockslides on the southeastern Tibetan Plateau. The experimental results revealed that the dynamic friction behaviors of the slip surfaces were slip-weakening, i.e., decreases in their dynamic friction coefficients with increasing displacement, at velocities ≧0.01 m/s. The pattern of the slip-weakening was single-stage weakening at velocities <0.1 m/s, and multi-stage weakening at velocities ≧0.1 m/s. The weakening was velocity-dependent when gouge was produced at velocities ≤0.1 m/s, and complex slip-weakening once partial melting occurred at velocities ≥0.5 m/s. The dynamic friction behaviors of the slip surfaces had no certain correlation with the normal stress at velocities ≧0.01 m/s. Variable dynamic friction behaviors of slip surfaces in granites clarify that the application of the Coulomb friction model to rapid rockslides is questionable, and that the volume-dependent effect of their friction coefficients in the source sections is uncertain. The dynamic friction behaviors of the slip surfaces in the granites from the two rockslides in this study imply that extreme reductions in their slip surfaces' friction coefficients could have occurred in the source sections and led to significant initial accelerations before entering the transition sections. Their slip-weakening was likely velocity-dependent at a velocity range from 0.1 to 0.1 m/s.