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The natural deposition of soils results in significant fabric anisotropy, and its influence on suffusion remains unclear. In this study, a series of gap‐graded soil samples with different particle shapes and bedding angles are generated and implemented into the coupled computational fluid dynamics‐discrete element method (CFD‐DEM) simulations to investigate the migration of fine particles within the coarse grain matrix. Macroscopic results, including mass loss, void ratio variation, and soil deformation, as well as microscopic particle trajectory, force chain network, and contact orientation are analyzed. In addition, drained triaxial tests on samples before and after erosion are carried out. All results turn out that the greater the bedding angle, the more severe the loss of fines and the more significant the soil deformation. Three different migration characteristics can be identified according to soil anisotropy degree, that is, when the bedding angle is 0°, the migration of fine particles remains relatively stable; when the bedding angle is 30° and 60°, the particle migration shows a gradual change throughout the erosion; when the bedding angle is 90°, the fine particles migrate significantly in the very early stages of suffusion. Besides, the aspect ratio (AR) of the particle is found to be beneficial for both erosion resistance and soil strength. [ABSTRACT FROM AUTHOR]

Internal erosion involves the loss of fine particles within the matrix of coarse particles under seepage flow, posing a severe threat to hydraulic structures. This paper focuses on internal erosion considering anisotropic stress conditions. The influence of the anisotropic stress state, represented by vertical stress equal to, bigger than, or smaller than horizontal stress, was investigated using coupled computational fluid dynamics (CFD) and the discrete element method (DEM). Results show that the loss of fine particle specimens under anisotropic stress conditions is greater than that for samples under isotropic stress states, as the loss of fine particles leads to an evolution of anisotropy into isotropy, with local contact force chains gradually forming spatially isotropic structures. The strong force chains of specimens under triaxial compression were also found to develop a dominant orientation in the vertical direction, leading to clogging in the upward migration of fine particles and increasing the critical hydraulic gradient. In addition, the evolution of void ratio, hydraulic drag force, connectivity, and coordination number has also been analyzed to exhibit the influence of stress anisotropy on internal erosion. [ABSTRACT FROM AUTHOR]

Influence of particle angularity on the suffusion in gap-graded granular soils remains unclear up to now. In this study, systematical numerical simulations that consider the particle shape as quasi-spherical polyhedra in different angularity are performed with the coupled discrete element method (DEM) and the computational fluid dynamics (CFD) approach. The suffusion of six gap-graded soil samples with 25% fines content is examined by imposing an upward seepage flow. Conventional triaxial tests are also conducted on the pre-eroded and post-eroded specimens to study the coupling influence of angularity and suffusion on the mechanical characteristics of granular soils. Fines loss, vertical displacement, soil strength, volume flow rate, microstructural analyses of force networks, the cumulative percentage of contact force, and the anisotropy of contact are investigated. Results turn out that the angularity intensifies the internal erosion resistance as the fines loss decreases significantly with the increasing angularity. The soil peak strength and friction angle are approximately linearly correlated with angularity. Erosion-induced particle redistribution reduces the degree of anisotropy of contact normal and contact normal force. This study may improve our understanding of the effect of particle angularity on suffusion with both microscopic and macroscopic evidence. [ABSTRACT FROM AUTHOR]