Loose wide-grading soils are commonly found in the source areas of debris flows, and in landslides after an earthquake. During rainfall events, fine particles (fines) in the soils gradually migrate downward, and eventually the loss of fines results in an increase in the pore volume of the soil and a reduction in the stability of the soil skeleton, which can lead to subsequent slope failure. To gain more understanding of the fine migration process at the microscopic scale, a 3D discrete element-fluid flow sequentially coupled model is developed, based on Darcy’s Law, to simulate fluid flow through a porous medium and calculate the transportation of soil solids. The erosion model is verified using experimental data. Parametric studies are carried out to investigate the effects of coarse particle size. The results reveal that changes in pore structure caused by fine particle migration can change the local permeability of the material. For the case of the average pore throat diameter to fine particle ratio (\(J\)) of 2.41, changes in local porosity with time from internal erosion in the sample can be divided into four stages: (1) a rapid increase with some variations in porosity, (2) a slow increase in porosity, (3) a rapid increase in porosity, and (4) a steady state with no change in porosity. Not all stages are present for all value of \(J\). Stages (1) (2) (4) are present for 2.48 ≤ \(J\le\) 2.58 and stages (1) (4) are present for \(J\) ≤ 2.24 and \(J\hspace{0.17em}\)≥ 2.74. A sharp increase in the fine’s erosion possibility occurs for a \(J\) value lies between 2.58 and 2.74. The erosion possibility sensibility shows an exponential relationship with \(J\). The model provides an effective and efficient way to investigate the process of pore blockage and internal soil erosion.

在泥石流源区和地震后的滑坡中通常发现松散的宽梯度土壤。在降雨事件中，土壤中的细颗粒（细颗粒）逐渐向下迁移，最终细颗粒的损失导致土壤孔隙体积增加和土壤骨架稳定性降低，这可能导致随后的倾斜失败。为了在微观尺度上更好地了解精细迁移过程，基于达西定律开发了3D离散元素-流体流顺序耦合模型，以模拟流过多孔介质的流体并计算土壤固体的迁移率。使用实验数据验证了侵蚀模型。进行参数研究以研究粗粒度的影响。结果表明，由细颗粒迁移引起的孔结构变化可以改变材料的局部渗透性。对于平均孔喉直径与细颗粒之比（\（J \））为2.41，样品内部腐蚀引起的局部孔隙率随时间的变化可分为四个阶段：（1）孔隙率有些变化而迅速增加;（2）孔隙率缓慢增加，（ 3）孔隙率迅速增加，以及（4）孔隙率没有变化的稳定状态。并非所有阶段都存在\（J \）的所有值。存在阶段（1）（2）（4）的条件为2.48≤ \（J \ le \） 2.58，存在阶段（1）（4）的条件为\（J \）≤2.24 和\（J \ hspace {0.17em } \） ≥2.74。当\（J \）值介于2.58和2.74之间时，细粉的腐蚀可能性会急剧增加。腐蚀可能性敏感性与\（J \）呈指数关系。。该模型为研究孔隙阻塞和内部土壤侵蚀的过程提供了一种有效的方法。