Bounding Surface Hypoplasticity Model for Sand

A comprehensive constitutive model for sand is formulated within the general framework of bounding surface hypoplasticity. The distinctive feature of this model is the dependence of the loading and plastic strain rate directions on the stress rate direction. This property renders the model hypoplastic. The model can simulate different features of sand behavior under loading conditions, which range from simple monbtonic to complex cyclic at different amplitudes and directions. In particular, the successful simulation of the response under "rotational shear" is one of the distinctive properties of the model, and it is mainly due to its hypoplastic character. The importance of such predictive capability in practice is related to the phenomenon of liquefaction, which may occur under such cyclic loading conditions of a complex nature, entailing cyclic changes of both principal stress values and principal stress directions. The paper presents a step-by-step calibration procedure of the different constants and a comparison of a series of test results and model simulations.