Jamming and Fluctuations in Granular Drag

TL;DR

This paper studies how jamming and force fluctuations in granular materials evolve dynamically, revealing that bulk stress collapse causes stick-slip behavior and that force chain interactions lead to depth-dependent fluctuation patterns.

Contribution

It demonstrates that jamming fluctuations are bulk phenomena independent of contact surface and links fluctuation patterns to force chain dynamics at different depths.

Findings

Fluctuations are independent of contact surface.

Jammed states exhibit stick-slip behavior.

Deeper layers show stepped fluctuation patterns.

Abstract

We investigate the dynamic evolution of jamming in granular media through fluctuations in the granular drag force. The successive collapse and formation of jammed states give a stick-slip nature to the fluctuations which is independent of the contact surface between the grains and the dragged object -- thus implying that the stress-induced collapse is nucleated in the bulk of the granular sample. We also find that while the fluctuations are periodic at small depths, they become "stepped" at large depths, a transition which we interpret as a consequence of the long-range nature of the force chains.