Modelling of time-dependent behaviour of soft soils using simple elasto-viscoplastic model

The purpose of this study was to present the development of an elasto-viscoplastic constitutive model to describe the time-dependent behaviour of soft soils. The elasto-viscoplastic model was established within the framework of Perzyna's overstress theory and the Modified Cam Clay model. The stress-strain relationship was solved by using an implicit backward Euler method of stress with updated algorithm, and implemented in a finite element program. Different types of tests were simulated using the EVP-MCC model to simulate the time-dependent behaviour of soft soils under different loading conditions, such as the strain rate effects on preconsolidation pressure as well as on undrained shear strength; the primary, secondary consolidation behaviour and stress effects on secondary compression coefficient C?e; the creep and stress relaxation features under different stress levels. It was shown that the model could satisfactorily describe the time-dependent behaviour of normally consolidated or slightly overconsolidated clayey soils along different loading paths. Time-dependent properties behaved in multiple stages triaxial tests, and field and laboratory pressuremeter tests had also been successfully simulated by the proposed EVP-MCC model.