An Experimental Study on the Velocity and Particle Distribution of Landslide-Debris Flow Motion under Deflected Terrain Constraints
Constrained and squeezed by lateral protruding terrain during traveling,landslide-debris flows veer off initial kinetic energy direction,occurring lateral eroding,striking or burying the building structures previously evaluated as in the original low-risk zone.This kind of geo-hazard needs to be comprehensively investigated for key geophysical parameter evolutions during the movement,including velocity,composition and gradation,and it is prerequisite for a proper geotechnical control of the geo-disaster.Preceding research on landslide-debris flows seldom addressed the movement behaviors under the influence of topographic deflection,quite possibly due to the big challenge of experimental modeling;therefore,these previous research outputs were without practical significance.In this study,it conducted an improved geo-physical model test to mimic a typical landslide-debris flow.The changes of particle velocity and gradation of landslide-debris were tracked before and after a topographic deflection point and the influence of deflected terrain on the particle movement and accumulation was examined.(1)The velocity of landslide-debris flows decreased significantly at the topographic deflection point and increased sharply to the peak immediately after the point.The movement process of landslide-debris flows consisted of five stages,including rapid accelerating,fluctuated accelerating,intense decelerating due to the deflection topography,gradual decreasing in the moving-accumulation area,and rapid decreasing in the stagnation area.(2)Landslide-debris flow occurred the maximum deposition after arriving at the topographic deflection point.(3)In the accumulation area,the mass ratio of large particles and small particles of landslide-debris flow was 50.7％at the upper layer and 65.1％at the bottom layer,respectively,indicating an obvious particle sorting phenomenon.In the longitudinal and transverse profile along the movement of landslide-debris flow,the mass share of different particle sizes was consistent with the initial state near the deflection point.In the longitudinal profile,the mass share of large particles decreased in a short distance,and then increased with the increase of movement distance,from 28.3％in the initial state to 49.6％in the final;Comparatively,the mass share of small particles increased first and then decreased,from 44.0％in the initial state to 23.5％in the final;along the transverse prefile,the mass share of large particles on the two sides was greater than those in the middle,whereas the opposite was true for small particles.The study provides an insight into the evolution of key geophysical parameter of landslide-debris flow under the action of deflection terrain,and provides a reference to geo-hazard control.
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