Study on the meso-structure development in direct shear tests of a granular material

Stress induced anisotropy phenomenon has been the main interest of many researches, especially in granular materials. Discrete element method (DEM) is one of the important methods for the study of meso-mechanics of granular materials. Based on previous studies, a 3D meso-fabric statistical method have been established, which can be used for quantitative analysis of 3D meso-fabric development in DEM numerical simulation of granular materials under external loads. Taking the direct shear test of sand as an example, the stress induced anisotropy of sand in 3D under the shearing loads has been studied systematically. According to the analysis results: the magnitude of anisotropy significantly develops during shear tests and gradually become steady after the peak, and the principal directions of anisotropy rotates consistent with the principal stress direction; the connectivity between the particles decreases and a series of particle skeletons are formed in the sample which undertake the main external loads. Furthermore, the stress state does also influence the evolution of anisotropy and force chain networks. (C) 2017 Elsevier B.V. All rights reserved.