Friction vs Texture at the Approach of a Granular Avalanche

TL;DR

This study analyzes the granular texture near the stability limit of a granular bed, revealing the coexistence of weak and strong contact phases and identifying a subset of highly frictional, coherent contacts that influence destabilization.

Contribution

It introduces a novel criterion for friction mobilisation in 2D granular packings, uncovering the bimodal texture and the role of coherent weak contacts in destabilization.

Findings

Bimodal granular texture with weak and strong phases.

Existence of a coherent subset of highly frictional weak contacts.

Coherent weak contacts oppose force chains and influence stability.

Abstract

We perform a novel analysis of the granular texture of a granular bed close to stability limit. Our analysis is based on a unique criterion of friction mobilisation in a simulated two-dimensional packing. In this way, we recover the bimodal character of granular texture, and the coexistence of weak and strong phases in the sense of distinct contacts populations. Moreover, we show the existence of a well-defined subset of contacts within the weak contact network. These contacts are characterized by their important friction, and form a highly coherent population in terms of fabric. They play an antagonistic role with respect to force chains. We are thus able to discriminate between incoherent contacts and coherent contacts in the weak phase, and to specify the role that the latter plays in the destabilisation process.