The characteristic state
Simulations of cyclic biaxial tests on samples composed of 2D irregular polygonal particles were performed to investigate the properties of the characteristic state, transition state between contraction and dilation. Two aspect ratios of 2D angular particules and different states of initial fabric are considered. The stress ratio at characteristic state is found to be much more sensitive to initial anisotropy than to density changes. Fabric is the kind of anisotropy that seems to influence the most the characteristic state. Constant amplitude cycling does not erase the influence of the initial anisotropy of fabric which was not expected. Then, in the framework of usual soil modelling where the material is supposed to be in an initially isotropic state, the usual models for the characteristic state are only valid for constant cyclic strain amplitude loadings where the mean anisotropy throughout the cycles remains low.
Keywords: DEM, Granular Material, Aspect Ratio, Cycles, Biaxial Test, Anisotropy