Downloads & Free Reading Options - Results

This report presents the results of a new quasi-static algorithm developed to compute the mechanical and scalar transport properties of three- dimensional sphere assemblages. The algorithm incorporates several new techniques, including a shuffling algorithm for generation of initial random granular packings, an improved microcell-adjacency method to accelerate particle-contact search, and a relaxation method to overcome a singularity in the quasi-linear system of equilibrium equations. The calculated Reynolds dilatancy for random dense-packed granular assemblages is found to depend on the interparticle friction, contrary to Reynolds' original hypothesis, and the use of linear contact mechanics is found to be valid near the ideal rigid-particle limit. Triaxial compression tests, employing steel balls as electrically conductive granular particles, confirm our simulation of both mechanical and transport properties, when account is taken of the actual electrical contact resistance between steel balls. The latter is much higher than for Hertzian contact and exhibits a strong dependence on normal load, probably due to asperities and oxide films on the steel-ball surfaces. A major conclusion of our study is that scalar transport can serve as a useful macroscopic probe for stress anisotropy and particle-contact topology in granular media.