| Clay has a wide distribution in the world and is widely used in geotechnical engineering.Clay presents a lot of special and complex mechanical properties.Above all,the shear strength of clay is influenced by the stress states,which means the influence of the intermediate principal stress,should be taken into account.Besides,the stress-strain relationship of clay is sharply affected by the stress history or the overconsolidated degree.Compared with the normally consolidated clay,the overconsolidated clay shows different stress-strain properties.Then,the stress-strain behavior reflects time-dependence clearly.The different stress rates or strain rates result in the different stress-strain relationships.To bring the time-dependence or rate-dependence into the stress-strain relationship of clay,the relation between creep and overconsolidation is established and the concepts of creep-consolidation as well as stress-consolidation are proposed.A method to calculate the elastoplastic strain during reloading is proposed and introduced into the original one–dimensional equivalent time model for both stepped loading and continuous loading.On the basis of the above one-dimensional stress-strain relationship,unified hardening parameter,and SMP criterion with its corresponding transformed stress space,the unified hardening elastic viscoplastic model for clay with different overconsolidated degrees is proposed.The proposed model can describe the influence of general stress state,different overconsolidated degrees and various stress or strain rate as a whole.Only one parameter is added in the new model compared with the original equivalent time model.Twenty four tests,including undrained triaxial compression and extension,on Hong Kong Marine Deposits with different overconsolidated degrees as well as different constant shear strain rates are used to confirm the validity of the propose elastic viscoplastic constitutive model. |
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