Modeling the combined effect of time and temperature on normally consolidated and overconsolidated clays

Clay is under the coupling influence of both time and temperature in some innovative geomechanical problems. Previous experimental researches have confirmed that time and temperature affect the overconsolidation degree of clay and induce overconsolidated characteristics. However, the experimental findings have not been included in constitutive models so far. This paper presents an innovative thermo-viscoplastic constitutive model based on the unified hardening model for overconsolidated clay. The new model combines the effect of time and temperature on overconsolidation by incorporating a temperature variable and a time variable into the hardening law and simultaneously considers the overconsolidated characteristics of clay by using the unified hardening parameter. The simulated results for laboratory tests show that the proposed model can not only reflect the influence of temperature and strain rate on the preconsolidation pressure, the undrained shear strength and the flow rule, but also describe the failure after undrained heating and creeping.