DEM Analysis of Fabric Evolution and Behavior of Granular Geomaterials in True Triaxial Test with Flexible Boundary

Abstract

The fabric of granular geomaterials used in roads and embankments is related to properties such as shear strength, permeability and liquefaction resistance. To evaluate the fabric evolution and behavior of geomaterials, a series of the true triaxial test simulations with flexible boundaries under general stress states in this study were performed using the three-dimensional discrete element method (DEM). First, the stress states at the axial strain of 20%, which indicates that the stress under the critical state conforms to the Matsuoka-Nakai criterion, were examined. Then the uniqueness of the coordination number and non-uniqueness of void ratio and invariant of anisotropic fabric tensor under the critical state were investigated based on the contact density, which indicates the relative number of contacts in different orientations. In particular, the contact density at the critical state under different mean effective principal stresses with its effects on the invariant of anisotropic fabric tensor were discussed. It was found that the contribution of the contact density to the fabric anisotropy decreased as the mean effective principal stress increased due to geometric limitations.