Local and global avalanches in a 2D sheared granular medium

TL;DR

This study investigates the statistical properties of avalanches in a 2D sheared granular medium, revealing scale-free distributions, asymmetries, and relationships between local and global events, with insights from experiments, simulations, and theoretical comparisons.

Contribution

It provides new experimental and numerical evidence of avalanche statistics in sheared granular materials, highlighting scale-free behavior and theoretical connections.

Findings

Avalanche size distributions follow power-laws with variable cut-offs.

Avalanches are mainly triggered from shear bands.

A simple relation links local and global avalanche counts.

Abstract

We present the experimental and numerical studies of a 2D sheared amorphous material constituted of bidisperse photo-elastic disks. We analyze the statistics of avalanches during shear including the local and global fluctuations in energy and changes in particle positions and orientations. We find scale free distributions for these global and local avalanches denoted by power-laws whose cut-offs vary with inter-particle friction and packing fraction. Different exponents are found for these power-laws depending on the quantity from which variations are extracted. An asymmetry in time of the avalanche shapes is evidenced along with the fact that avalanches are mainly triggered from the shear bands. A simple relation independent from the intensity, is found between the number of local avalanches and the global avalanches they form. We also compare these experimental and numerical results for both local and global fluctuations to predictions from meanfield and depinning theories.