Abstract
In the previous chapters it has been shown that the principle of effective stress can be applied to the shear strength, the tensional strength and the volumetric behavior of unsaturated soils. This chapter shows that the critical void ratio plotted against the mean effective stress for samples tested at different suctions align parallel to the virgin consolidation line of the material. This means that the critical state concept also applies to unsaturated materials. Taking into account all these results, an elastoplastic framework that can be used to develop general constitutive models for soils including saturated, unsaturated and compacted materials is presented.
Keywords: Critical state concept, critical void ratio, effective stress, virgin consolidation line, elastoplastic framework, elastic zone, constitutive models, tensional strength, volumetric behavior, effective stress, yield surface, plastic deformations, suction hardening, failure surface, preconsolidation stress.