Modeling sand behavior in constant deviatoric stress loading

Constant Deviatoric Stress (CDs) loading involves application of a constant deviatoric (shear) stress to the soil while the applied mean normal stress is being varied. Loose granular soils exhibit a unique behaviour under such loading. In these soils, significant contraction can initiate before the soil reaches the critical state condition. In saturated soils, this can lead to the generation of pore pressures and substantial loss of strength, which can result in flow slides in soil masses. While the initiation of such behaviour has been investigated experimentally in a number of previous studies, ability of constitutive models to predict such behaviour has been rarely verified. In this paper, a critical state constitutive model is used to examine the initiation and severity of volume contraction of sands subjected to CDs loading. The model, which has been described in detail elsewhere, is briefly summarized and used to investigate effects of factors such as density, consolidation pressure, anisotropic consolidation, etc. on the initiation of volume contraction in loose sands. Predicted effects are then compared with test data where such data is available.