ABSTRACT
It is usually known that the intermediate principal stress and the stress histories have large influences on the deformation and the strength of soil. The influences of these factors, i.e. stress-induced anisotropy, therefore should be considered properly in a constitutive model of soils. In the ordinary models, the influence of the intermediate principal stress is usually modeled by assuming a non-circular shaped yield surface in octahedral plane (or by changing the strength depending on the relative magnitude of the intermediate principal stress), and that of the stress histories is considered by applying kinematic/rotational hardening rule in ordinary stress space. The induced anisotropy, however, can be described simply by using modified stress which suitably reflects the fabric change due to the variations of the intermediate principal stress and the stress histories.
