A hypoplastic constitutive model for clays

SUMMARY This paper presents a new constitutive model for clays. The model is developed on the basis of generalised hypoplasticity principles, which are combined with traditional critical state soil mechanics. The positions of the isotropic normal compression line and the critical state line correspond to the Modied Cam clay model, the Matsuoka{Nakai failure surface is taken as the limit stress criterion and the nonlinear behaviour of soils with dieren t overconsolidation ratios is governed by the generalised hypoplastic formulation. The model requires v e constitutive parameters, which correspond to the parameters of the Modied Cam clay model and are simple to calibrate on the basis of standard laboratory experiments. This makes the model particularly suitable for practical applications. The basic model may be simply enhanced by the intergranular strain concept, which allows reproducing the behaviour at very small strains. The model is evaluated on the basis of high quality laboratory experiments on reconstituted London clay. Contrary to a reference hypoplastic relation, the proposed model may be applied to highly overconsolidated clays. Improvement of predictions in the small strain range at dieren t stress levels is also demonstrated. Copyright c 2004 John Wiley & Sons, Ltd.