Isostaticity and Mechanical Response of Two-Dimensional Granular Piles

TL;DR

This study investigates the static structure and mechanical response of two-dimensional granular piles, revealing how isostaticity depends on friction and pile formation, and how these factors influence the mechanical response to perturbations.

Contribution

It provides a detailed numerical analysis of the isostaticity and mechanical response in 2D granular piles considering friction and elastic properties, highlighting the conditions for isostaticity and response divergence.

Findings

Frictionless piles become isostatic in the rigid limit.

Frictional piles' isostaticity depends on formation procedure.

Displacement response diverges in frictionless isostatic piles.

Abstract

We numerically study the static structure and the mechanical response of two-dimensional granular piles. The piles consist of polydisperse disks with and without friction. Special attention is paid for the rigid grain limit by examining the systems with various disk elasticities. It is shown that the static pile structure of frictionless disks becomes isostatic in the rigid limit, while the isostaticity of frictional pile depends on the pile forming procedure, but in the case of the infinite friction is effective, the structure becomes very close to isostatic in the rigid limit. The mechanical response of the piles are studied by infinitesimally displacing one of the disks at the bottom. It is shown that the total amount of the displacement in the pile caused by the perturbation diverges in the case of frictionless pile as it becomes isostatic, while the response remains finite for the frictional pile. In the frictionless isostatic pile, the displacement response in each sample behaves rather complicated way, but its average shows wave like propagation.