# Evolution of Internal Granular Structure at the Flow-Arrest Transition

## TL;DR

This study investigates how the internal contact and force network structures in granular materials evolve during shear flow and arrest, revealing that anisotropy predicts stress ratios and that fabric distributions narrow with system size.

## Contribution

It introduces fabric tensors as descriptors of internal granular structure evolution and links anisotropy to stress prediction during shear arrest and flow.

## Key findings

- Bulk stress ratio is predicted by contact and force network anisotropy.
- Fabric tensors at arrest show balanced force and contact anisotropy.
- Distribution of fabric tensors narrows as system size increases.

## Abstract

The evolution of the internal granular structure in shear-arrested and shear-flowing states of granular materials is characterized using fabric tensors as descriptors of the internal contact and force networks. When a dilute system of frictional grains is subjected to a constant pressure and shear stress, the bulk stress ratio is well-predicted from the anisotropy of its contact and force networks during transient flow prior to steady shear flow or shear arrest. Although the onset of shear arrest is a stochastic process, the fabric tensors upon arrest are distributed around nearly equal contributions of force and contact network anisotropy to the bulk stress ratio. The distribution becomes seemingly narrower with increasing system size. The anisotropy of the contact network in shear-arrested states is reminiscent of the fabric anisotropy observed in shear-jammed packings.