Fabric evolution of granular materials along imposed stress paths

The stress–strain behavior of a granular material is dominated by its internal structure, which is related to the spatial connectivity of particles, and the force chain network. In this study, a series of discrete element simulations were carried out to investigate the evolution of internal structure and force chain networks in initially isotropic granular materials along various imposed stress paths. The fabric tensor of the strong sub-network, which is the bearing network toward loading, can be related to the applied stresses uniquely. The principal directions of fabric tensor of the strong sub-network coincide with those of stress tensor during the loading process in the Lode coordinate system. The fabric of the whole contact network in the pre- and post-peak deformation stages can be related to the applied stresses as qϕ=Bq/pz$$q_{\phi } = B\left( {q/p} \right)^{z}$$ (B and z are constants depending on loading condition, such as the stress paths and mean stress level) and ϕ1:ϕ2:ϕ3≈σ10.4:σ20.4:σ30.4$$\phi_{1} :\phi_{2} :\phi_{3} \approx \left( {\sigma_{1} } \right)^{0.4} :\left( {\sigma_{2} } \right)^{0.4} :\left( {\sigma_{3} } \right)^{0.4}$$, respectively. At the critical stress state, the deviator of fabric tensor of the strong sub-network is much larger than that of the whole contact network. When plotted on the π-plane, the fabric state of the strong sub-network can be expressed as a Lade’s surface, while the fabric state of the whole network corresponds to an inverted Lade’s surface.