Effect of inter-particle friction on 3D accordance of stress, strain, and fabric in granular materials

The inter-particle friction is mainly related to the roughness of particles, which plays an important role in both macroscopic and microscopic mechanical behaviors of granular materials. Under the real three-dimensional (3D) loads, the multiscale effects of inter-particle friction could be more complex. In this study, a series of true triaxial tests are conducted based on discrete element method (DEM). We identify that the inter-particle friction is key to triggering the disaccord of Lode angles between stress tensor and incremental strain tensor (also fabric tensor) on pi-plane under 3D non-axisymmetric loading paths. A kind of function form is proposed to describe this disaccord, by incorporating the inter-particle friction coefficient mu and intermediate principal stress ratio b. We further observe that the evolution of strong contact network coincides with the overall stress tensor in the Lode coordinator system, irrespective of mu. The disaccord behaviors of overall contact fabric and the macroscopic stress mainly originate from the weak subset of contacts, and then, the inter-particle friction should play an important role on the rearrangements of weak contact network and finally lead to the disaccord behaviors at the macroscopic scale.