Crossover from quasi-static to dense flow regime in compressed frictional granular media

TL;DR

This study explores how frictional granular media transition from a quasi-static state to dense flow, revealing critical behavior and diverging correlation lengths without shear band formation at the transition.

Contribution

It demonstrates that the transition to dense flow in granular media behaves as a critical phase transition with diverging correlation lengths.

Findings

Correlation lengths diverge approaching the transition

Transition behaves as a critical phase transition

No shear band formation at instability onset

Abstract

We investigate the evolution of multi-scale mechanical properties towards the macroscopic mechanical instability in frictional granular media under multiaxial compressive loading. Spatial correlations of shear stress redistribution following nucleating contact sliding events and shear strain localization are investigated. We report growing correlation lengths associated to both shear stress and shear strain fields that diverge simultaneously as approaching the transition to a dense flow regime. This shows that the transition from quasi static to dense flow regime can be interpreted as a critical phase transition. Our results suggest that no shear band with a characteristic thickness has formed at the onset of instability.