An Elasto-Viscoplastic Model for Soft Clay

The purpose of this paper is to present the development of an elasto-viscoplastic model for normally consolidated clay. A three dimensional constitutive equation was derived based on the framework of Perzyna's overstress theory and Modified Cam-Clay model. It was implemented in a finite element program, and applied to analyze time-dependent behavior of soft clay. The influence of two viscous parameters, which can be determined by undrained triaxial compression tests, was studied. The proposed model was verified using observed laboratory responses of several natural clays. The results showed that the model can satisfactorily describe the stress-strain-rate behavior such as strain rate effect, creep and stress relaxation.