MECHANISM ANALYSIS OF THE ACCUMULATION CHARACTERISTICS OF ROCK AVALANCHE

Rock avalanches is generally rapid downslope flowage of rock fragments composed of solid particles and some pore fluid. During rock avalanche slide, particle grading occurs, and certain sedimentation characteristics are exhibited in the deposit. For the study of kinematic sieving process in particle mass movement, the chute experiments have been conducted, and the sequence of particles with different size in vertical section and slide direction section are mainly studied. Then, based on the description of the vertical sorting and horizontal sorting, the grain-size distribution of the deposit zones is analyzed with sieve analysis, which presents larger grains prevail in the upper part of the deposit. The content of large particle exhibits double peak morphology of distribution in the slide direction section. The two distribution characteristics are also founded in Xinmocun rockavalanche and Pusacun rockavalanche, which are macroscopic reflection of the interaction of rock fragment during the particle flows and are important geological evidence for the study of rock avalanche kinematics. Finally, according to lots of chute experiments and case studies, the conclusion is proposed that:the dispersive pressure and kinematic sieving during the movement are main reasons for the formation of the vertical inverse grading and the longitudinal double peak morphology in the rock avalanche deposit. The kinematic sieving process energized by undulated sliding surface, and the momentum between particles.