Ripples and Shear Bands in Plowed Granular Media

TL;DR

This study investigates how granular media's deformation behavior changes at a critical volume fraction, revealing a transition from smooth deformation to shear band formation and surface ripples during drag experiments.

Contribution

It identifies a critical volume fraction where granular drag dynamics shift from smooth to oscillatory, linking shear band formation to surface ripple generation.

Findings

Deformation is smooth below the critical volume fraction

Shear bands form and cause ripples above the critical volume fraction

Drag force behavior transitions at the critical volume fraction

Abstract

Monodisperse packings of dry, air-fluidized granular media typically exist between volume fractions from $\Phi$= 0.585 to 0.64. We demonstrate that the dynamics of granular drag are sensitive to volume fraction $\Phi$ and their exists a transition in the drag force and material deformation from smooth to oscillatory at a critical volume fraction $\Phi_{c}=0.605$. By dragging a submerged steel plate (3.81 cm width, 6.98 cm depth) through $300 \mu m$ glass beads prepared at volume fractions between 0.585 to 0.635 we find that below $\Phi_{c}$ the media deformation is smooth and non-localized while above $\Phi_{c}$ media fails along distinct shear bands. At high $\Phi$ the generation of these shear bands is periodic resulting in the ripples on the surface. Work funded by The Burroughs Wellcome Fund and the Army Research Lab MAST CTA