Snell's Law for Shear Zone Refraction in Granular Materials

TL;DR

This study demonstrates that shear zones in layered granular materials refract at material boundaries following Snell's law, with the shear zone's width and path influenced by material properties and boundary configurations.

Contribution

It reveals that shear zone refraction in granular materials obeys Snell's law and introduces the concept of a granular lens affecting shear zone behavior.

Findings

Shear zones refract at material boundaries following Snell's law.

Shearing through a granular lens results in a broad shear zone.

Shear zone width varies with material properties and boundary conditions.

Abstract

We present experiments on slow shear flow in a split-bottom linear shear cell, filled with layered granular materials. Shearing through two different materials separated by a flat material boundary is shown to give narrow shear zones, which refract at the material boundary in accordance with Snell's law in optics. The shear zone is the one that minimizes the dissipation rate upon shearing, i.e.a manifestation of the principle of least dissipation. We have prepared the materials as to form a granular lens. Shearing through the lens is shown to give a very broad shear zone, which corresponds to fulfilling Snell's law for a continuous range of paths through the cell.