Energy dissipation in granular materials

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Ever since Coulomb's work on equilibrium and the failure of granular slopes, friction and strength of granular soils became firmly linked. More than two centuries later, many theories have been advanced resulting in a near one-to-one proportionality between Coulomb's friction angle and the angle of friction between soil grains. Attempts to verify these theories experimentally yield a surprising indication that the link between macro and micro friction angles is far weaker than past theories implied. Although shear strength characteristics of granular soils appear analogous to those of a frictional system, the lack of a direct link to interparticle friction is not easily rationalizable. This points to a fundamental knowledge gap that possibly explains the many difficulties in describing engineering properties of soils through practically usable models. The proposed project is to substantially close this gap, both in terms of the fundamental understanding of the role of friction in the behavior of granular material and in developing a constitutive model based on adequate physics. Both objectives are connected to the broader topic of the physical mechanisms of energy dissipation in granular materials and its analytical description for modeling purposes. The project is theoretical in its nature but involves particle-level simulations, as well as grain-scale physical experimentation utilizing recent advances in sensing technology.