泥石流启动试验的数值模拟研究

采用离散元颗粒流程序PFC3D(Particle Flow Code)对泥石流启动过程的模型试验进行数值模拟研究.考虑泥石流启动过程中砂土的非饱和特性,在前期研究的基础上对模型进行改进,利用微小颗粒模拟水团,并通过设置黏结模型模拟土颗粒间的基质吸力.将数值模拟结果与室内模型试验进行对比分析,分析得出泥石流的启动表现为后部土体推挤前部土体快速下滑.非饱和状态下,颗粒间的基质吸力提供了一定的土体强度,当渗透力和重力引起的下滑力克服这种颗粒间的黏结力时,土体由非饱和状态逐渐转变为饱和状态,泥石流才会启动.与原有未考虑非饱和特性的数值模拟方法对比,结果表明,使用PFC3D并考虑土体非饱和特性,可以更接近地模拟流滑型泥石流的破坏形态和启动过程.

Numerical Simulation Study on the Experiments of the Initiation of Debris Flow

This paper used Particle Flow Code (PFC3D) to simulate the model experiment of the process of the initiation of debris flow. Based on the previous simulation studies and considering the unsaturated features of sand soil, it simulated water with small granules in the numerical simulation of the initiation phase of sandy debris flow, and set a bond model to simulate the matrix suction between soil particles. Compared with the results of the numerical simulation with laboratory model tests, the result of the study shows that the start of debris flow forms with rear soil pushing the front soil rapid decline. Under the condition of unsaturated, the matrix suction between soil particles provides soil strength. When the penetration and gravity are beyond the bond force between particles, soil turns from unsaturated to saturated and debris flow will start. Compared with the results in the simulated method which does not consider the condition of unsaturated, the method of considering the unsaturated is suitable to simulate the initiation process and failure mode of flow-slip mudslides.