Microscopic Investigation of Suffusion-Induced Particle Migration and Clogging in Gap-Graded Soils: Effects of Particle Shape and Fines Content

Hydraulic infrastructures, such as embankments, dams, and levees, are highly vulnerable to suffusion under complex mechanical and hydraulic loading conditions, posing serious threats to their structural integrity. To better understand the underlying micromechanics of suffusion in gap-graded soils, this study investigates fine particle migration and microstructural evolution, with a focus on the effects of coarse particle shape and fines content. A coupled multibody dynamics and discrete element method framework is employed to generate soil specimens with varying fines contents and particle morphologies, while the suffusion process is simulated using the coupled computational fluid dynamics and discrete element method, enabling the thorough examination of the interactions between fluid flow, particle migration, and force chain evolution during seepage infiltration. The results reveal that the particle shape plays a crucial role in determining the stability of force chains and fine particle migration patterns. A novel motion-based classification of fine particle migration during suffusion is introduced, encompassing four distinct mechanisms: clogging, voiding, detour, and punching. Following a rapid fines loss period during early seepage infiltration, the remaining fine particles primarily stabilize in a clogging state. The concept of tortuosity is proposed to characterize migration complexity, with results showing a nonmonotonic relationship with particle aspect ratio. Additionally, a clogging ratio is developed to quantify the accumulation of fine particles in clogging states. This study provides insights into the complex behaviors of fine particle migration in gap-graded soils, establishing a foundational framework for a better understanding of suffusion dynamics in hydraulic infrastructures.