ABSTRACT
The well-known linear relations between void ratio (e) and stress in logarithmic scale (lnσ) in one-dimensional (1D) consolidation under loading, unloading, and reloading are explained as a conventional elastoplastic behavior. However, it is experimentally known that even in the elastic region in the conventional model (e.g., under reloading and cyclic loading), the plastic strain develops. For instance, when vertical load increases on an overconsolidated clay in oedometer tests, the void ratio approaches gradually the normal consolidation line in the e–lnσ relation with development of the plastic strain. Also, the plastic strains develop during cyclic loadings with constant amplitude of stresses in shear tests. To model such behaviors, which cannot be described by conventional plasticity, some advanced elastoplastic models have been proposed: the subloading surface model (Hashiguchi and Ueno 1977; Hashiguchi 1980), the bounding surface model (Dafalias and Popov 1975), and the anisotropic hardening model (Mroz, Norris, and Zienkiewicz 1981), as well as others. Since these models have two or more yield surfaces, they are called multisurface models.
