A shear-transformation-zone model for time-dependent behaviours of clay

Abstract

A shear-transformation-zone (STZ) model is proposed for time-dependent behaviours of clay, in which the viscoplastic deformation is described by the evolution of a temperature-like state variable. The model is featured by rate-dependent dilatancy and a unique critical state stress ratio. In its present form, it has nine parameters, most of which can be handily calibrated, and can predict the rate-dependent undrained shear strength, primary, and secondary creep, as well as stress relaxation for normally consolidated clay under complex stress paths using a single set of parameters. The capabilities of the model have been verified by available experimental results on five different clays.