Suffusion refers to the detachment and migration of fine particles through voids among coarse particles and is one of the major causes of slope failure. This study investigates the seepage-induced suffusion and slope instability using a hierarchical multiscale finite–discrete element method (FEM–DEM). An erosion law with the critical hydraulic gradient for the onset of suffusion is proposed. Two examples, including one-dimensional suffusion and biaxial compression tests, are performed to verify the proposed scheme. Emphases are placed on reproducing suffusion and progressive slope failure process under seepage flow. The results indicate that a shear band is initiated from the slope toe and gradually extends to the crest. The increase of erosion rate accelerates the process of suffusion and slope failure, whereas a higher critical hydraulic gradient plays an opposite role. In addition, fines loss caused by suffusion occurs mainly on the slope surface, especially near the slope toe. Microscopic analyses on locally embedded representative volume elements (RVEs) indicate that RVEs inside the shear band experience severe deformation and microstructural changes, manifested by the rearrangement of soil skeletons and variation of contact force chains.

渗流是指细颗粒通过粗颗粒之间的空隙脱离和迁移，是边坡破坏的主要原因之一。本研究使用分层多尺度有限离散元法 (FEM-DEM) 研究渗流引起的渗流和边坡失稳。提出了具有临界水力梯度的渗流开始侵蚀规律。两个例子，包括一维渗透和双轴压缩测试，进行验证所提出的方案。重点是在渗流下再现渗流和渐进式边坡破坏过程。结果表明，剪切带从坡脚开始，逐渐延伸到坡顶。侵蚀速率的增加加速了渗流和边坡破坏的过程，而较高的临界水力梯度则起相反的作用。此外，渗流造成的细粉流失主要发生在坡面，尤其是坡脚附近。对局部嵌入的代表性体积元（RVEs）的微观分析表明，剪切带内的RVEs经历了严重的变形和微观结构变化，表现为土壤骨架的重新排列和接触力链的变化。