Micro-Mechanical Analysis for Residual Stresses and Shakedown of Cohesionless-Frictional Particulate Materials Under Moving Surface Loads

Residual stresses and shakedown have been successfully presented by two-dimensional numerical experiments based on the discrete element method (DEM), wherein a cohesionless-frictional material under moving surface loads was replicated through irregular-shaped particles. With surface loads below the shakedown limit, both permanent deformations and residual stresses cease to accumulate and the numerical structure shakes down after a number of load passes. Corresponding micro-mechanical analyses indicate that strong forces and normal forces make a dominant contribution to residual stresses. Besides, averaged magnitudes of interparticle forces and corresponding total contact numbers initially change with load passes, and their final variation trends will differ as the structure shakes down or not. Furthermore, polar distributions of interparticle forces and contacts have been presented, and variations of their preferential orientations were emphasised. Lastly, the fabric tensor and anisotropy of resultant forces were studied, presenting the anisotropy weakening of macro-stress fields, induced by developments of residual stresses.