Coupled particle-fluid simulations of the initiation of suffusion

Suffusion or internal instability is a major form of internal erosion in cohesionless soils. Hypotheses based on experimental work suggest complex micro-scale influences of stress and material fabric on suffusion. This study presents the results of coupled discrete element method – computational fluid dynamics (DEM-CFD) simulations of permeameter tests. These simulations were carried out to study the influence of micro-scale variables on the initiation of particle transport in gap-graded cohesionless soils with varying fines contents and relative densities. The results highlight the importance of both particle stress and connectivity on the initiation of suffusion. Particles which do not transfer externally applied stress and those with low initial connectivity are shown to be particularly susceptible to suffusion.