Kinematic models for non-coaxial granular materials. Part II: evaluation

In this paper we present results of numerical simulations for the evaluation of kinematic models for non-coaxial granular materials by the distinct element method (DEM). Strain-rate controlled monotonic and cyclic un-drained simple shear tests were specifically designed and evaluation criteria established for this purpose. The models examined are the double-shearing model, the double-sliding free-rotating model, and the double slip and rotation rate model (DSR2 model) proposed by the authors (see the accompanying paper). It is shown that the assumption used in the double-shearing model appears to not be in agreement with the DEM data. It is also shown that in the double-sliding free-rotating model the energy dissipation requirements appear to be unduly restrictive as a constitutive assumption. The DSR2 model, which is a hybrid of discrete micro-mechanics and continuum modelling, gives better agreement with the results of our DEM simulations, than either the double-shearing model or the double-sliding free-rotating model.