Morphologies of three-dimensional shear bands in granular media

TL;DR

This paper uses 3D numerical simulations to analyze shear band formation in granular media, revealing correlations among shear intensity, grain motion, and structural properties, and emphasizing boundary conditions' influence.

Contribution

It provides new insights into shear band morphologies and formation mechanisms through detailed 3D simulations and comparison with experimental data.

Findings

Shear bands correlate with shear intensity and grain velocity.

Boundary conditions significantly influence shear band morphology.

Shear bands exhibit strain hardening at large strains.

Abstract

We present numerical results on spontaneous symmetry breaking strain localization in axisymmetric triaxial shear tests of granular materials. We simulated shear band formation using three-dimensional Distinct Element Method with spherical particles. We demonstrate that the local shear intensity, the angular velocity of the grains, the coordination number, and the local void ratio are correlated and any of them can be used to identify shear bands, however the latter two are less sensitive. The calculated shear band morphologies are in good agreement with those found experimentally. We show that boundary conditions play an important role. We discuss the formation mechanism of shear bands in the light of our observations and compare the results with experiments. At large strains, with enforced symmetry, we found strain hardening.