The overconsolidation ratio (OCR) is a critical factor in determining the mechanical behaviour of overconsolidated clays. On the basis of the three requirements for the peak strength line, a continuous and smooth peak strength line is constructed from the perspective of the peak stress ratio, and then a new yield function for overconsolidated clays is developed. The developed yield function in the stress space is characterized by an elliptical curve. The evolution of the developed yield function in the stress space is captured by a new hardening parameter, which is constructed by integrating the proposed peak strength surface with the subloading surface concept. By combining the developed yield function with the non-orthogonal plastic flow rule, a non-orthogonal elastoplastic constitutive model of overconsolidated clays is established to consider the influence of the OCR on strength and deformation. The proposed model requires seven material parameters, all of which have a clear physical meaning and can be easily determined via conventional laboratory tests. Three typical stress paths are employed to demonstrate the essential features of the proposed model. The effectiveness of the proposed model is confirmed by comparing the experimental data with corresponding model predictions.
