滑坡碎屑流颗粒分选效应的数值模拟

Numerical Simulation Study of Solids Segregation in Landslide Debris Flow

大量粗细不均匀的碎屑岩粒及孤大块石在滑坡碎屑流运动过程中的相互作用产生颗粒分选效应,影响了滑坡碎屑流的运移堆积特征及致灾效应。以模型试验的资料和数据为依据,运用三维颗粒离散元素法,建立滑坡碎屑流颗粒流数值模型,从滑体运动堆积过程中不同粒径组分的分布位置和动能两方面研究了滑坡碎屑流颗粒分选效应的形成过程,探讨了颗粒分选效应的形成机制。结果表明:滑坡碎屑流运动过程中,粗颗粒组分易获得较大速度并向滑体表层及前缘运移,细粒组分运动速度较慢,并向滑体底层及后部聚集,这种颗粒分选效应最终导致了滑体反粒序分布结构的形成。滑坡碎屑流颗粒分选效应是由振动筛分、小颗粒耗能较大率先停积、大颗粒碰撞分离等动力学机理共同作用的结果。

The interactions between the component particles of a mobilized landslide debris flow with varied sizes cause solids segregation,therefore governing the dynamic characteristics and geohazard potential level of landslide debris flow.From the aspects of the distribution and kinetic energy of different particle size components of a mobilized landslide debris flow,the forming process and formation mechanism of solids segregation were investigated in the present study by using a three-dimensional discrete element method together with the results of model testing.The results of existing studies suggest that the large particle components tend to get large speeds and migrate to the surface and front edge of the sliding body.The fine-grained components move slowly and accumulatetoward the bottom and back of the sliding body.This solids segregation effect eventually leads to the inverse grading form of the landslide deposits.Solids segregation in landslide debris flows is a consequence of the kinematic sieving,the preferential sedimentation of little particles and the collision of large particles.