Constitutive Modeling for Overconsolidated Clays Based on Disturbed State Concept. I: Theory

The disturbed state concept (DSC) is widely used to capture the cracking, breaking, heating, softening, and hardening behaviors of geomaterials. In this study, a constitutive model for overconsolidated clays is proposed by incorporating the DSC. A new disturbance function describes the effect of the overconsolidation ratio (OCR) on the strength, dilatancy, and deformation of overconsolidated clays. This disturbance function is incorporated into the potential-failure and dilatancy stress ratios, potential-failure and dilatancy lines, and potential-failure and dilatancy surfaces at the current and referenced states. The plastic moduli also pertain to this disturbance function. With the assistance of this disturbance function, the proposed model can capture the strain hardening and volumetric contraction of normally consolidated or slightly overconsolidated clays, as well as the strain softening and volumetric expansion of highly overconsolidated clays under the drained condition. It can also capture the evolution of strength, excess pore pressure, and stress paths under the undrained condition.