Quasistatic rheology, force transmission and fabric properties of a packing of irregular polyhedral particles

TL;DR

This study uses contact dynamics simulations to compare the shear behavior and force transmission in packings of irregular polyhedral particles versus spherical particles, revealing shape-dependent differences in shear strength and fabric anisotropy.

Contribution

It introduces a harmonic approximation of granular fabric and elucidates how particle shape influences force anisotropy and contact types in dense packings under shear.

Findings

Polyhedra packings exhibit higher shear stress and dilatancy than sphere packings.

Force anisotropy is the main contributor to enhanced shear strength in polyhedra.

Different contact types contribute uniquely to force transmission and fabric anisotropy.

Abstract

By means of contact dynamics simulations, we investigate a dense packing composed of polyhedral particles under quasistatic shearing. The effect of particle shape is analyzed by comparing the polyhedra packing with a packing of similar characteristics except for the spherical shape of the particles. The polyhedra packing shows higher shear stress and dilatancy but similar stress-dilatancy relation compared to the sphere packing. A harmonic approximation of granular fabric is presented in terms of branch vectors (connecting particle centers) and contact force components along and perpendicular to the branch vectors. It is found that the origin of enhanced shear strength of the polyhedra packing lies in its higher force anisotropy with respect to the sphere packing which has a higher fabric anisotropy. Various contact types (face-vertex, face-face, etc) contribute differently to force transmission and fabric anisotropy. In particular, most face-face contacts belong to strong force chains along the major principal stress direction whereas vertex-face contacts are correlated with weak forces and oriented on average along the minor principal stress direction in steady shearing.