Suffusion refers to a special form of internal erosion characterized by the selective erosion of the finest particles of a soil under the action of an internal fluid flow. In this work, the microscopic mechanism of particle detachment in binary mixtures subjected to suffusion under different flow directions is analyzed. We use the coupled lattice Boltzmann method (LBM) and discrete element method (DEM) to simulate the suffusion process in a granular sample subjected to an anisotropic stress state. When the macro-flow direction is aligned with the principal direction of compression, it is found that the fluid flow is more intense, which increases erosion. The stress anisotropy also influences the detachment direction that is not necessarily correlated with the macroscopic flow direction. The sample’s anisotropic stress state is responsible for directional variations in microstructural properties during the suffusion under different flow directions. From a microscale point of view, a contact sliding index P and a particle detachment index Δ are defined to demonstrate that fluid-induced sliding dominates for particles about to detach.

Suffusion 是一种特殊形式的内部侵蚀，其特征是在内部流体流动的作用下，土壤中最细小的颗粒被选择性侵蚀。在这项工作中，分析了在不同流动方向下扩散的二元混合物中颗粒脱离的微观机制。我们使用耦合晶格玻尔兹曼法 (LBM) 和离散元法 (DEM) 来模拟颗粒样品在各向异性应力状态下的扩散过程。当宏观流动方向与主压缩方向一致时，发现流体流动更强烈，这增加了侵蚀。应力各向异性也影响与宏观流动方向不一定相关的分离方向。样品的各向异性应力状态导致在不同流动方向下的扩散过程中微观结构特性的方向变化。从微观角度来看，接触滑动指数P和粒子脱离指数 Δ 被定义为证明流体诱导的滑动在即将脱离的粒子中占主导地位。