Quantification of fabric evolution in granular material under cyclic loading

Abstract

AbstractFabric influences the macro scale mechanical properties and behavior of granular materials as a continuum and can be represented by an appropriately defined evolving fabric tensor entering the constitutive equations. In this study, the evolution of fabric tensors under cyclic loading is investigated and quantified by a series of cyclic loading DEM tests. Simulations of the DEM data are made by two different continuum evolution rate equations for the contact normal‐based fabric tensor, both within the Anisotropic Critical State Theory (ACST) framework: the first, is a Basic Fabric Evolution (BFE) equation and the second, is a novel Combined Fabric Evolution (CFE) equation, where a quantity related to particle‐based fabric tensor is considered. The comparison with DEM results highlights the capability of the CFE equation in simulating fabric evolution under cyclic loading for different anisotropy, density, and loading conditions. In addition, such simulations are significantly more accurate in comparison with those obtained by the BFE equation. The reason for the superiority of CFE over the BFE is the incorporation of the influence of the particle orientation fabric on contact normal fabric evolution. Analytical evaluation of CFE further identifies a total of seven periodic stable contact normal fabric evolution patterns that exist under cyclic loading, governed by initial void ratio, intensity of anisotropy, and stress amplitude. The limitation of current fabric evolution equations in being able to only reflect the proportional coaxial part of the fabric tensor with respect to the loading direction is discussed.