Strain Localisation in Sand in Cycles of Triaxial Compression and Extension: Continuum and Grain-Scale Analysis

In this work we present selected results from a recent experimental programme where small sand specimens are subjected to cycles of triaxial compression and triaxial extension: the material is yielded in extension, after which the loading is reversed and the material is yielded in compression a number of cycles are performed. The ways in which extension and compression-like localisation patterns (i.e., dilatant shear banding, and necking respectively) appear, get activated and disactivated on reversal of loading are measured, and discussed in terms of both (continuum) strain yelds and individual grain rotations.