An elastoplastic hydro-mechanical model for unsaturated soils

On basis of experimentally determined retention curves, a model is proposed for the description of water content changes inside the macropores of an unsaturated soil. Two aspects of soil behaviour are taken into account: the hysteresis of the water storage mechanism and its dependence on the void ratio. A description is provided of the set of retention curves, enveloping all the possible soil states in the void ratio-water ratio-suction space. This description enables to develop an elastoplastic model, which copes with the hysteretic effect in the retention curve and the onset of irreversible changes in water content during deformation. A hydro-mechanical model for unsaturated soils is then established by coupling the mentioned formulation and the Barcelona Basic Model (BBM). The formulation of the model is presented in the paper and illustrated on two examples.