Simulating Progression of Internal Erosion in Gap-Graded Sandy Gravels Using Coupled CFD-DEM

Loss of fine particles or suffusion in soils induced by seepage is an important problem that may cause dam or dike failures. This paper aims to study the evolution mechanisms of suffusion in gap-graded sandy gravels using coupled computational fluid dynamics and discrete-element method (CFD-DEM). In the simulation, five groups of sandy gravel including four groups of gap-graded sandy gravel and a benchmark linearly graded sandy gravel were studied. Changes in flow rate, evolution of porosity in different layers, and spatial and temporal redistributions of particles in the samples during suffusion under upward seepage were studied. Simulation results show that when the fine particle content is the same, the total fine erosion ratio is larger when the stability index (H/F)min of the gap-graded sandy gravel is lower. The porosities of five layers of the gap-graded sandy gravel change continuously with infiltration time. A slight decrease in the fine grain content appears in the upper layers, while a sharp reduction in the fine grain content occurs in the bottom layer. The study provides a mechanics basis for the prediction and prevention of suffusion in gap-graded sandy gravels. (c) 2019 American Society of Civil Engineers.