Modelling Fabric Evolution of Granular Materials Along Proportional Strain Paths

A series of biaxial tests are conducted along proportional strain paths using DEM to investigate the evolution of internal structure in the overall contact network and sub-networks (the strong and weak contact networks). The evolution of fabric in the overall contact network along various strain paths varies with the imposed strain ratio and the resulting stress ratio. Along dilatant strain paths, a unique fabric-stress relation is obtained for the strong network as $$ \phi_{1}^{s} - \phi_{2}^{s} = \kappa (t/s) $$ with $$ \kappa $$ being a constant. The weak contact network and its evolution are affected by both the stress ratio and the imposed strain ratio. Deformation instability occurs only along dilatant strain paths and can be related to the degradation of weak network, even though the strong network dominates the strength of the material.