Shear-induced pressure anisotropy in granular materials of nonspherical particles

TL;DR

This study investigates how shear-induced pressure anisotropy develops in granular materials of nonspherical particles, revealing the influence of interparticle friction on particle alignment, pressure distribution, and shear localization.

Contribution

It introduces a detailed analysis of pressure anisotropy in sheared granular materials of nonspherical particles, highlighting the role of interparticle friction and particle shape.

Findings

Pressure difference depends on interparticle friction $mma$.

High $mma$ leads to localized shear and particle alignment.

Spherical particles maintain uniform pressure regardless of $mma$.

Abstract

When a granular material composed of elongated grains is sheared in a split-bottom shear cell, a pressure difference develops within the material. This pressure difference depends on the interparticle friction ($\mu$), which affects shear localization and particle alignment. For large $\mu$, alignment is confined to a narrow shear band, leading to localized increases in packing density and pressure. For small $\mu$, particles align over a wider region, leading to a nearly uniform packing density and pressure throughout the material. In contrast, spherical particles, regardless of $\mu$, maintain a uniform packing density and pressure throughout the material. We observe a phenomenological similarity to the Weissenberg effect in non-Newtonian fluids, where normal stress differences induce radial pressure gradients, unlike the uniform pressure in Newtonian fluids.