A CONSTITUTIVE EQUATION FOR NORMALLY CONSOLIDATED CLAY

Abstract

It is required to construct a more general constitutive equation for soils in order to analyze three-dimensional boundary-value problems in the field of soil mechanics. Since soils are regarded as work-hardening and rate sensitive materials with dilatancy, the equation must be the one which can describe the soil behaviors due to those properties.So far the researches concerned with the constitutive equation of soils may be divided into two categories, i.e., (i) the deformation characteristics at the equilibrium state and (ii) the rate sensitive properties.The objective of this study is to construct a more general and realistic constitutive equation for fully saturated normally-consolidated clays by unifying the results of above two major approaches. Namely, Roscoe's critical state energy theory for clays is extended so that it explains the rate sensitive property by using Perzyna's theory of elasto/viscoplastic continuum and some empirical evidences.It can be concluded that the proposed constitutive equation can more generally describe the behaviors of clays such as creep, stress relaxation and constant strain rate shear processes than those by other investigators, although there remains a work to refine the equation. The equation is expressed in terms of the second order tensor field. Thus, one can apply it to three dimentional problems by means of the finite element method.