In response to the limitations of the existing a unified state parameter model for clay and sand (CASM) in simulating the mechanical properties of overconsolidated soil

this paper introduces the theoretical framework of the subloading surface Cambridge (SSC) model and constructs an overconsolidated soil model (CASM-o) based on the SSC and CASM. This model not only retains the advantages of CASM in yield surface and plastic potential surface

but also combines the hardening rule of the SSC model for overconsolidated soil

which can better describe the mechanical behavior of overconsolidated soil. Based on the CASM-o

this paper systematically analyzes the overconsolidation characteristics of four typical clays under three stress paths: conventional triaxial drained

undrained

and constant average principal stress. The results indicate that the CASM-o can effectively capture the strain softening and volume expansion phenomena exhibited by overconsolidated soil in triaxial drainage tests

as well as the strain hardening and negative excess pore water pressure characteristics exhibited in undrained tests. This validates the effectiveness and reliability of the CASM-o in simulating the mechanical response of overconsolidated soil under different stress paths.