3D Particle-Scale Displacement Gradient to Uncover the Onset of Shear Bands in Sand

In situ synchrotron micro-computed tomography (SMT) scans of a specimen composed of uniform silica sand were acquired at multiple strains during a triaxial compression test. Individual sand particles were identified and tracked through multiple strain increments. The paper presents the concept of displacement gradient to expose the inception of shear bands (strain localization) in sheared sand. Each particle’s neighboring particles were identified and translation fields for all particles were calculated. The second order norm between the particle translation vector and neighboring particles translation vectors were averaged, resulting in a relative displacement value for each particle. The relative displacement concept is effective to uncover the onset of localized shearing within sheared granular materials.