ABSTRACT
Cam-clay model (Schofield and Wroth, 1968) is certainly the first elastoplastic model applicable to the practical deformation analysis of ground. This model is certainly very simple, i.e., the number of material parameters is few, and the meaning of each parameter is clear. However, Cam-clay model has problems to describe the following features:
a. Influence of intermediate principal stress on deformation and strength of soils
b. Stress-path dependency on the direction of plastic flow
c. Influence of density and/or confining pressure on the deformation and strength of soils
d. Behavior of structured soils and aged soils
Subloading tij model (Nakai and Hinokio, 2004) can describe properly the features (a) to (c), having the merits of Cam clay model. Feature (a) is considered using tij concept (Nakai and Mihara, 1984). Feature (b) is considered by dividing the plastic strain increment into two components, even though only one yield function and strain hardening parameter is used. Features (c) are considered referring to Hashiguchi’s subloading surface concept (Hashiguchi, 1980) and revising it. However, this model cannot describe the typical behavior of structured soils (feature (d)) which is observed in natural deposited clays.
