Wall effects on granular heap stability

TL;DR

This study examines how lateral walls influence the stability and angles of granular heaps, revealing size-dependent regimes and confirming experimental and simulation results through a stress redirection model.

Contribution

It introduces a model explaining wall effects on granular heap stability based on stress redirection, accounting for different regimes depending on bead size.

Findings

Wall effects increase pile angles as gap width decreases.

Two regimes observed: constant bead count for large beads, constant length for small beads.

Experimental results align with numerical simulations and the stress redirection model.

Abstract

We investigate the effects of lateral walls on the angle of movement and on the angle of repose of a granular pile. Our experimental results for beads immersed in water are similar to previous results obtained in air and to recent numerical simulations. All of these results, showing an increase of pile angles with a decreasing gap width, are explained by a model based on the redirection of stresses through the granular media. Two regimes are observed depending on the bead diameter. For large beads, the range of wall effects corresponds to a constant number of beads whereas it corresponds to a constant characteristic length for small beads as they aggregate via van der Waals forces.