Overconsolidated (OC) clays are commonly encountered in geotechnical engineering and are subjected to threedimensional (3D) stress conditions. This study proposes a unified plastic potential function for triaxial and 3D general stress conditions, by incorporating the overconsolidation parameter and intermediate principal stress parameter. This function can effectively capture the coupling influence of the overconsolidation degree and intermediate principal stress on the dilatancy characteristics of OC clay. Additionally, it possesses a simple form and clear physical significance, making it easily applicable in constitutive models. Then, a simple bounding surface model in triaxial stress conditions is established by adopting the dilatancy relation and the model is extended to general 3D stress conditions by the transformed method based on spatially mobilized plane (SMP) strength criterion. Finally, the performance of the proposed model is validated through various triaxial shearing tests under a wide range of overconsolidation ration (OCR) and the simulation results of the proposed model are compared with those of the SANICLAY model. The comparative analysis indicates that the proposed model effectively describes the complex characteristics of OC clays by simple theory and it demonstrates significant advantages in deformation and pore water pressure simulation due to the advanced dilatancy relation.
