James T. Jenkins
Granular materials are common in nature, in industry, and in the home. They are interesting because they exhibit behaviors characteristic of a solid or a fluid, depending upon the circumstances. They are important because natural hazards, such as slope failure and soil liquefaction, are threats to life and property and because granular materials are involved in many, if not most, industrial processes. Unfortunately, present theories for the prediction of deformations, failure, and flow of granular materials are far less reliable than those for classical solids and fluids.
We will focus on the quasi-static, rate-independent behavior of granular materials and review recent theories for their deformation and failure. These involve incremental relations between stress and deformation that include a dependence on the state of the material. The goal is to identify the appropriate state variables from the consideration of force and moment equilibrium of the individual particles, to incorporate them through suitable averaging into the incremental stress-strain relation, and to describe their evolution with the deformation.