Abstract
A century after the first attempts of Wentworth to characterise the shape of cobbles, our understanding of particle morphology is still expanding. A plethora of shape indices has been proposed in the literature to characterise the morphology of individual particles. This study aims to shed light on the merits and limitations of the indices currently used to characterise particle elongation, flatness and compactness, adopting a unified classification framework. Second, new indices are proposed to address the identified shortcomings. Third, a new particle classification system derived from the proposed indices is illustrated. It is shown the new system overcomes the misclassification of a range of particles that are incorrectly classified as bladed in the Zingg system.
Highlights
Particle morphology has been shown to bear significant influence on the mechanical, rheological and hydraulic behaviour of granular materials (e.g. [8,6,17,12,19])
Particle form has been demonstrated to affect the critical state shear strength [11,1], packing [14], fabric [20], flowability [23] and jamming [18] of particulate materials, roundness has been associated with the shear strength [27] and stress concentrations within particulate assemblies [15], while roughness has been shown to control the small strain stiffness [21] normal contact behaviour and bulk deformation [16] of particles with rough surfaces
It is evident that no single shape aspect controls the link between particle morphology and mechanical behaviour
Summary
Particle morphology has been shown to bear significant influence on the mechanical, rheological and hydraulic behaviour of granular materials (e.g. [8,6,17,12,19]). Other aspects of particle shape have been discussed in the literature, such as sphericity and irregularity [5]. The aforementioned aspects of particle morphology affect the physical behaviour of particles in bulk differently. Particle form has been demonstrated to affect the critical state shear strength [11,1], packing [14], fabric [20], flowability [23] and jamming [18] of particulate materials, roundness has been associated with the shear strength [27] and stress concentrations within particulate assemblies [15], while roughness has been shown to control the small strain stiffness [21] normal contact behaviour and bulk deformation [16] of particles with rough surfaces. This study deals with form, as multiple formulae proposed in the literature often lead in contradicting results; a direct comparison of their values is of interest
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