Systematic description of the effect of particle shape on the strength properties of granular media

Emilien Azéma,Jean-Yves Delenne,Nicolas Estrada,Farhang Radjai,Itthichai Preechawuttipong

doi:10.1051/epjconf/201714006026

Abstract

In this paper, we explore numerically the effect of particle shape on the mechanical behavior of sheared granular packings. In the framework of the Contact Dynamic (CD) Method, we model angular shape as irregular polyhedral particles, non-convex shape as regular aggregates of four overlapping spheres, elongated shape as rounded cap rectangles and platy shape as square-plates. Binary granular mixture consisting of disks and elongated particles are also considered. For each above situations, the number of face of polyhedral particles , the overlap of spheres, the aspect ratio of elongated and platy particles, are systematically varied from spheres to very angular, non-convex, elongated and platy shapes. The level of homogeneity of binary mixture varies from homogenous packing to fully segregated packings. Our numerical results suggest that the effects of shape parameters are nonlinear and counterintuitive. We show that the shear strength increases as shape deviate from spherical shape. But, for angular shapes it first increases up to a maximum value and then saturates to a constant value as the particles become more angular. For mixture of two shapes, the strength increases with respect of the increase of the proportion of elongated particles, but surprisingly it is independent with the level of homogeneity of the mixture. A detailed analysis of the contact network topology, evidence that various contact types contribute differently to stress transmission at the micro-scale.

Highlights

In many particulate materials found in nature and industry, scientists and engineers need to quantify the effect of complex particle shapes
A systematic numerical analysis of the effect of particle shape properties on the quasistatic rheology of sheared granular media, as well as packings composed of mixtures of two shapes was presented in the framework of Contact Dynamics simulations
The shape of the particles is systematically varied from spherical shape to angular, non-convex and elongated or platy shape

Summary

Introduction

In many particulate materials found in nature and industry, scientists and engineers need to quantify the effect of complex particle shapes. (B-a) Platy (elongated in 2D), (B-b) Non-convex and (B-c) Angular shapes These methods were primarily dedicated to the characterization of particles in the field of Sedimentology. A possible way for studying this problem is to analyze simplified systems with “idealized non-spherical” particles With this respect, Discrete Element Methods are well suited for this type of simulations even if introducing particle shape in numerical simulations give raise to various technical difficulties such as contact detection and force calculation between particles of arbitrary shape. The main objective of this work was to analyze numerically the effect of particle shape on the strength properties by varying systematically the shape from spheres to angular, non-convex and elongated/platy shape, as well as by considering mixture of shape

Particle shape parameters

Packing construction

Particle connectivity and origins of strength

Findings

Conclusions