  The paper addresses the underlying source of two forms of induced anisotropy
in granular materials: contact orientation anisotropy and contact force
anisotropy. A rational, mathematical structure is reviewed for the manner in
which fabric anisotropy emerges and evolves during loading. Fabric is expressed
as an orientation density, and transport phenomena such as convection, contact
generation, and diffusion control the rate of fabric evolution during loading.
The paper proposes specific measurable forms for all terms, based upon the
micro-mechanics of particle interactions. Discrete element (DEM) simulations
are used to verify and quantify these terms, so that the theory can be applied
to general loading conditions. The DEM simulations are of densely packed
durable spheres, and the emphasis is on soil behavior at large strains,
specifically on fabric and strength at the critical state. Once the theory has
been developed and quantified, it is applied to predict the effect of the
intermediate principal stress on strength.
