Anisotropy of contact networks in granular media and its influence on mobilised internal friction

A Sufian and AR Russell and AJ Whittle, GEOTECHNIQUE, 67, 1067-1080 (2017).

DOI: 10.1680/jgeot.16.P.170

The anisotropy associated with the contact network in granular media is investigated. A unique expression for mobilised internal friction has been discovered using numerical simulations of monodisperse and polydisperse spherical assemblies under two-way cyclic axisymmetric and simple shear load paths. This uniqueness is described by a linear relationship between the macroscopic stress ratio and the geometric configuration of only the strong and non-sliding contacts, where strong contacts are those with a normal force magnitude greater than the mean normal force. A stress-force-fabric expression for arbitrary partitions of the contact network was derived analytically, providing a mathematical connection between the macroscopic state of stress and interparticle characteristics. Numerical simulations revealed that only strong and non-sliding contacts provided a non-zero contribution to the stress-force-fabric expression. Previous studies suggest the dominance of force anisotropy in the complete contact network, but this study indicates that geometric anisotropy of contacts is the dominant contributor in the stress-force-fabric relationship when particular subsets of the contact network are considered.

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