The Role of Friction in Compaction and Segregation of Granular Materials

TL;DR

This paper explores how friction influences the compaction and segregation behaviors of granular materials, revealing that high friction reduces compaction and causes segregation at high compactivity, with a phase diagram illustrating these effects.

Contribution

It combines thermodynamic hypothesis, mechanical modeling, and geometrical calculations to analyze friction's impact on granular segregation, providing new insights and a phase diagram.

Findings

High friction reduces compaction in granular systems.

Granular mixtures with different frictional properties segregate at high compactivities.

A phase diagram maps segregation behavior against friction coefficients.

Abstract

We investigate the role of friction in compaction and segregation of granular materials by combining Edwards' thermodynamic hypothesis with a simple mechanical model and mean-field based geometrical calculations. Systems of single species with large friction coefficients are found to compact less. Binary mixtures of grains differing in frictional properties are found to segregate at high compactivities, in contrary to granular mixtures differing in size, which segregate at low compactivities. A phase diagram for segregation vs. friction coefficients of the two species is generated. Finally, the characteristics of segregation are related directly to the volume fraction without the explicit use of the yet unclear notion of compactivity.