Elastoplastic constitutive model for unsaturated soils

Surface tension acts at the interface between water and air. The surface tension attracts soil particles in unsaturated soil, making the soil stronger and stiffer.
In order to consider the effect of surface tension (suction) on deformation strength characteristics, this study proposes an elastoplastic model in which the normal consolidation line, which defines the soil existence area, is shifted by the degree of saturation, Sr, and a moisture property curve in which the degree of saturation varies continuously with the density. Using this model, the collapsing behavior during consolidation and shear was successfully expressed in a reasonable manner.

Kikumoto, M., Kyokawa, H., Nakai, T. and Shahin, H. M. : A simple elasto-plastic model for unsaturated soils and interpretations of collapse and compaction behaviours, of the 5th International Conf. on Unsaturated Soils (UNSAT 2010), Barcelona, Spain, pp.849-855, 2010.