Resolved CFD-DEM Modeling of Suffusion in Gap-Graded Shaped Granular Soils

Abstract

The effect of particle shape on the suffusion of gap-graded soils is an essential although poorly understood subject in geotechnical engineering that requires further investigation. This work presents a macroscale and microscale numerical investigation into the effect of particle shape on the suffusion of gap-graded granular materials. Rounded, elliptical, and convex particles with the same volume-equivalent diameter and varying shape coefficients were generated and used to produce samples. Next, a series of resolved coupled computational fluid dynamics (CFD) and discrete-element method (DEM) simulations were performed to provide evidence of the effect of particle shape on the suffusion susceptibility of gap-graded soils. The evolution of particle orientation, moment, and drag force coefficient were analyzed to determine the mechanisms by which particle shape exerts influence. The fine angular particles under seepage flow were found to adjust their orientation, reducing the projected area of the particle perpendicular to the fluid flow direction. Fine particles in high-flow-velocity regions had a smaller projected area and drag force coefficient. The continuous rotation of the irregularly shaped particles during suffusion implies that their migration should counteract the moments exerted by the surrounding particles. In the sample containing various irregularly shaped particles, the initial position of the most irregularly shaped particle was closer to the outlet, implying that irregularly shaped particles are less susceptible to suffusion.