Hypoplastic Cam-clay model

A rearrangement of the hypoplastic constitutive equation is proposed that enables the incorporation of an asymptotic state boundary surface of an arbitrary predefined shape into the model, with any corresponding asymptotic strain-rate direction. This opens the way for further development of hypoplastic models. To demonstrate the flexibility of the proposed approach, a hypoplastic equivalent of the modified Cam-clay model is developed. A comparison of the predictions of the elasto-plastic and hypoplastic models reveals the merits of the hypoplastic formulation. Although both models predict the same asymptotic states, hypoplasticity predicts a smooth transition between overconsolidated and normally consolidated states, and thus accounts for the non-linearity of the soil behaviour inside the state boundary surface in a natural manner.