Induced fabric anisotropy of granular materials in biaxial tests along imposed strain paths

In granular materials, loading on an initially isotopic assembly usually induces particle rearrangement, and this is referred to as the induced anisotropy of fabric. A series of biaxial tests are conducted along various strain paths using DEM to investigate the evolution of the induced anisotropy. The evolution of both the overall contact network and the sub-networks (the strong and weak) are examined separately. Results of DEM simulations indicate that the evolution of the fabric deviator in the overall contact network can be described as a power function of the stress ratio prior to the peak stress ratio that depends on the imposed dilation rate. A unique fabric-stress relation is obtained for the strong sub-network, which is independent of the strain path, the initial porosity and the confining pressure. Moreover, deformation instability is observed only along dilatant strain paths, which can be related to the degradation or even collapse of a weak sub-network, even though the strong sub-network dominates the strength of the granular assembly.