When granular materials are subjected to proportional strain loading paths, they manifest a variety of behaviours depending on the initial void ratio of the specimen as well as on the imposed dilatancy/contractancy rate. The specific behaviour of granular assemblies is linked not only to the local properties but also to the disordered nature of the grain packing. This can be expressed by a micromechanical description of the contact distribution. A micromechanical approach developed earlier for the modelling of granular material behaviour has been used to simulate proportional strain tests on loose and dense sand. The model is based on the description of the contact distribution within the granular assembly. The numerical simulations show that the model can accurately reproduce the macroscopic behaviour and, in addition, provide microstructural information. The results of the simulations show that the mechanical state of each contact - and therefore the overall behaviour of the granular assembly - is dependent on the direction of the macroscopic loading as well as on the geometrical description of the packing.
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