ABSTRACT
Various constitutive models for soil have been developed over the last four decades. In particular, many elastoplastic models have been proposed since Cam-clay models were established by Roscoe et al. (1963; Roscoe and Burland 1968). The constitutive model for soil should be able to describe all types of soil behavior. The behavior of soil is complex, however, due to its nature, that is, its granularity, its multiphase structure, and its inhomogeneity. The typical characteristics of soil can be listed as follows:
1. Multiphase mixture of soil particles, pore water and pore air, saturated and unsaturated soil, and effective stress
2. Elasticity and hypoelasticity 3. Plasticity, hypoplasticity, and dilatancy characteristics 4. Rate sensitivity, viscoelasticity and viscoplasticity 5. Density dependency and con‰ning pressure dependency 6. Strain-hardening and strain-softening characteristics 7. Cyclic deformation characteristics 8. Structural and induced anisotropy 9. Noncoaxiality 10. Deformation localization, bifurcation, and instability 11. Discontinuity 12. Degradation and the growth of microstructures 13. Inhomogeneity and nonlocality 14. Temperature dependency 15. Electromagnetic characteristics, the dieletric constant, and con du ctivity
Some of the characteristics have been included in the formulation of the constitutive models. In particular, elastoplasticity and dilatancy are now included in almost all of the models. However, some of them are not well incorporated into the models.
