Abstract: Initial fabric anisotropy can greatly affect the shear behavior of particulate materials during shear. The bedding plane effect induced by particle orientation is one of the main fabric anisotropic factors that may affect other factors. It is hard to experimentally examine the effect of bedding direction of particles on the shear behavior of particulate materials, such as sand. A 2D discrete element method (DEM) is employed in this paper to study the influence of different orientations of oval particles on the behavior of dense assemblies under simple shear. As well as the macroscopic shear behavior, the evolution of particle orientation, contact normal, and inter-particle contact forces within the samples with different initial bedding angles during shear have been extensively examined. It was found that the initial bedding direction of the particles has great influence on the non-coaxiality between the directions of principal stress and principal strain increment. The bedding direction also affects the strength and dilatancy responses of DEM samples subjected to simple shear, and the samples with larger bedding angles exhibit higher shear strength and larger volume dilation. A modified stress-force-fabric relationship is proposed to describe the effect of particle bedding direction on the shear strength of samples, and the new equation can better describe the stress-force-fabric relationship of assemblies with initial anisotropic fabrics compared with the existing model.

Key words: Initial fabric anisotropy; Particle orientation; Simple shear; Non-coaxiality; Discrete element method (DEM)

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