岩土体颗粒级配对滑坡碎屑流冲击作用的影响研究

Influence of Gradation on the Impact Effect of Landslide Debris Flow

滑体的运动、堆积及冲击力等因素决定了滑坡碎屑流的致灾程度,不同粒径大小及组成的颗粒在运动过程中,产生碰撞、摩擦、跳跃等作用,影响着滑坡碎屑流的致灾程度。运用三维离散元素法,对比模型试验,以控制粒径为参数,探讨岩土体不同级配对滑体的堆积形态、运动速度及冲击力等动力学特征的影响。研究结果表明:各滑体模型运移堆积过程中均呈现出显著的反序分离特性;对于控制粒径相同,而颗粒级配不同的初始滑体,虽然堆积形态基本一致,但细小碎屑颗粒增大了滑体的运动速度,大粒径块石增加了滑体冲击力;在不同的控制粒径下,控制粒径越大,滑体流动性越强,滑体平均速度峰值和冲击力峰值越大;细小碎屑物质的反序现象会增大滑体动能,其显著的摩擦耗能作用会缩减滑体冲击能,粗大块石促进了滑体内部的能量传递,增大滑体冲击力。

The movement, accumulation, impact of a mobilized landslide debris flow associated with other factors would determine the degree of damage, and its component particles with varied sizes and compositions during the movement involve internal collision, friction, and jumping, etc. , therefore governing the geohazard potential level. Accordingly, it is of great scientific significance to determine the dynamic characteristics and impact force of landslide debris flow in different gradation for structural design of architecture in mountainous area and the planning and prevention work of landslide disaster. By using a three-dimensional discrete element method and comparing with model tests, in this research it took the control grain size （d60） as input and investigated the influence of rocksoil mass with varied grading on the dynamic characteristics such as deposition form, velocity and impact force of landslide debris flow. The results of existing studies suggested that all the processes of migration and accumulation of landslide debris flows simulated by sliding models exhibited significant particle segregation phenomenon, which eventually led to the inverse grading form of landslide deposits. For the initial sliding body with the same control particle size but different grain compositions, although the deposition forms were generally similar, the fine particles actually increased the velocity of the sliding body while the large grains increased the impact force of the sliding body; Under different control particle sizes, 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. It can conclude that the segregation of fine particles compositions would increase the kinetic energy of a sliding body, while its frictional energy dissipation would significantly reduce the impact energy of landslide debris flow. The collision and segregation of coarse grains compositions could promote the energy transfer inside the sliding body and increase the impact force of landslide debris flow.