Some issues in constitutive modelling of unsaturated soils

The paper reviews a number of issues concerning the general development of constitutive models for unsaturated soils. The physical significance of suction is considered first, followed by a discussion on the respective effects of matric and osmotic components. The number and selection of constitutive variables are then discussed. Their influence on the resulting constitutive models is examined with the assistance of a model classification based on the type of constitutive variables. Finally, a suite of constitutive models are briefly described with emphasis in the coupling between the hydraulic and the mechanical components.