Stress-Induced Anisotropy in Granular Masses

Abstract

ABSTRACT Stress-induced anisotropy or fabric in granular masses is discussed on the basis of biaxial compression tests performed on two-dimensional assemblies of oval cross-sectional rods. The fabric of granular mass depends at least on three basic fabric elements: the distribution of the contact normals, the shape of the particles, and the shape of the associated voids. These are discussed in order to define the corresponding anisotropy in terms of a second-rank fabric tensor. It is shown that the principal axes of the fabric tensor rotate gradually toward the principal axes of the stress tensor during the course of monotonic deformation. Generation of new contacts in the direction of the maximum principal compression is closely related to the formation of column-like load paths in that direction and is a major process which leads to the stress-induced anisotropy. The stress-induced anisotropy due to the formation of elongated voids seems to be a contributing factor to the post-peak failure of the material.