Abstract A comprehensive data package of cyclic simple shear tests was used to critically check and revise a plasticity model for sand. These cyclic simple shear tests were performed using Monterey No. 0/30 sand with different relative densities and under complex loading conditions including asymmetrical cyclic loading with various initial shear stresses and overburden pressures. The newly revised model carries several novel concepts: using a strain increment dependent flow rule and loading/unloading criterion that results in explicit integrations of stress-strain model equations; the density dependency extended to more ingredients of the model structure, especially to plastic shear and bulk moduli that achieves ‘one set of model parameters for one sand’ for cyclic loading responses; and the appropriate use of three intrinsic history dependent variables, i.e., the latest stress reversal point, the virgin loading (i.e. maximum pre-stress) stress ratio, and the accumulated plastic deviatoric strains that contribute greatly to the enhanced capabilities of the revised model. The model is first calibrated based on three symmetrical cyclic loading responses. Using the single set of model parameters, the model is then used to predict the sand behavior under asymmetrical cyclic loadings and different initial confining pressures. Lastly, the model predictions are checked against empirical correlations established between cyclic resistance ratio (CRR) with initial shear stresses and confining pressures, or the commonly referred to K α and Κ σ effects. The obtained model predictions not only compare relatively well with the test data, but the K α and Κ σ effects based on model predictions follow the trend of empirical relationships too.

Highlights In this paper, a bounding surface hypo-plasticity model for sand [31–37] is revised based on the behavior of sand demonstrated in a comprehensive package of simple shear test data [41]. The model simulations are compared with the test results under various loading conditions including asymmetric cyclic loading with varying initial confining stresses for different densities of Monterey No.0/30 sand [41]. The systematic comparisons demonstrate the revised model is capable of capturing not only the complex contractive/dilative behaviors, but also the commonly referred K α, and K σ effects, which are critical to the evaluation of cyclic resistance to liquefaction for sandy soils. Specifically, the technical merit and novel propositions of the revised model are:1. It is demonstrated in this study that the stress (or strain) increment dependent flow rule is not only necessary for the complex loading conditions such as rotational shear, but also for K o (<1) consolidation conditions encountered in most field engineering cases. 2. The new proposed strain dependent flow rule and loading/unloading criterion result in explicit integrations of stress-strain model equations to obtain stress increments from given strain increments with the need of iterations . 3. The density dependency of model parameters ( elastic moduli and critical state relations and newly proposed plastic shear and bulk moduli) made the 'one set of model parameters for one sand' possible. 4. The success of the newly revised model relies a great deal upon the appropriate use of three intrinsic history dependent variables, i.e., the latest stress reversal point, the virgin loading (i.e. maximum pre-stress) stress ratio, and the accumulated plastic deviatoric strains.