Shear Zones in granular materials: Optimization in a self-organized random potential

TL;DR

This paper presents a new model for wide shear zones in granular materials, using a variational principle to identify shear bands as minimal dissipation surfaces in a biased random potential, aligning well with experimental observations.

Contribution

It introduces a generalized variational model for shear zones in granular materials, capturing the complex behavior observed in experiments.

Findings

Numerical simulations match experimental shear zone patterns.

The model predicts measurable properties of shear zones.

Shear bands are identified as minimal dissipation surfaces in a biased random potential.

Abstract

We introduce a model to describe the wide shear zones observed in modified Couette cell experiments with granular material. The model is a generalization of the recently proposed approach based on a variational principle. The instantaneous shear band is identified with the surface that minimizes the dissipation in a random potential that is biased by the local velocity difference and pressure. The apparent shear zone is the ensemble average of the instantaneous shear bands. The numerical simulation of this model matches excellently with experiments and has measurable predictions.