Movement Segregation Mechanism And Impact Effect Of Landslide In Different Gradation Grades

The topographic type and lithology characteristics,associated with other factors would determine the collision,pressure,shearing and friction of a mobilized landslide along a hillside or a valley,leading to the fragmentation and disintegration of rock and soil mass in varying degrees and transforming into high speed landslide debris flow.The component particles with varied sizes and compositions during the movement of involve internal collision,friction,and jumping,etc.,therefore governing the shifting,buckling deformation,and collapsing.The research on the movement characteristics and impact mechanism of landslide debris flow in different gradation grades is not only conducive to get deeper understanding of the kinematics and dynamical of landslide debris flow,but also has important scientific significance to make up for the deficiencies in the research of landslide debris flow impact structure and to improve the design of impact-resistant structures.In this paper,the gradation grades of landslide mass are taken as subjects.The inverse grading of deposit from landslide is considered as the geological basis.By using a three-dimensional discrete element method and comparing with model tests in this research,it investigated the influence of landslide mass with varied grading on the kinematics and dynamics parameters evolution characteristics during the moving and impacting progress of landslide.1)The controlled trial was carried out to investigate the movement and impact behavior of mono-size and multi-size landslide material,which suggested the particle segregation and inverse grading of rock fragments can enhance the mobility,average velocity and impact force during the movement of landslide.The causes of inverse grading are the combined effect of these factors such as the Gravity-Free Dispersion,the kinematic sieving,the large particles segregation and the little particles were stopped earlier than the large particles.2)Furthermore,when the particle gradation is certain,the initial particle size distribution is different,the non-dimensional parameters,and₇),were defined to show the progress and the degree of particle-size segregation in the depth and flow directions,which indicated that a wider variation ofcorresponds to a higher kinetic energy retention and a lower energy dissipation,increasing the impact force of a landslide debris flow.3)Definitively,based on the typical gradation grades of landslide mass,the results of existing studies suggested that,the larger the control particle size for a sliding body,it had the stronger flowability,and similarly the greater the average velocity,the higher the peak impact force.The acting heights distributions of equivalent impact force of sliding body were mainly concentrated at the lower third of the maximum deposit thickness.