Constitutive Equations for Normally Consolidated Clay Based on Elasto-Viscoplast

ABSTRACT This paper is concerned with the elasto-viscoplastic constitutive equation of normally consolidated clay. A three dimensional constitutive equation is derived based on the Perzyna’s elasto-viscoplastic theory and Cambridge theory. Comparing the theoretical results with the experimental results by triaxial compression test, it becomes evident that the derived constitutive equation can explain the behavior not only such time-dependent behavior as creep, stress relaxation and strain rate effect, but also as secondary compression, aging and isotropic stress relaxation. The equation has eight material parameters which can be determined by two undrained strain rate constant triaxial compression tests with different strain rates, usual consolidation and swelling tests. The proposed theory has a feature to be able to determine the secondary consolidation rate from the results of strain rate controlled undrained triaxial compression test.