SUMMARYThis paper proposes a general formulation of an elastoplastic model adapted to unsaturated soils. This formulation enters within the framework of two independent state variables descriptions. The choice of a particular effective stress combined with suction is made. The definition of this effective stress is based on the formulation of an equivalent pore pressure which is an essential point of this type of models. It will be discussed in this paper.This general formulation can be seen as a methodology allowing to adapt in a straightforward way most of elastoplastic behaviour models classically used in saturated soils mechanics to unsaturated states. It is shown that this synthesis can include most of recent models developed within the same framework.The last part of this paper is devoted to the adaptation of an existing complex elastoplastic model (CJS model) to unsaturated states using the methodology previously exposed. The model thus obtained is validated on various loading paths including oedometric, isotropic or triaxial compressions and also wetting tests simulating collapse phenomenon.This model extension shows the easiness introduced by the proposed methodology to adapt a given elastoplastic model to unsaturated states. Its validation illustrates by the way the abilities of the extended model to reproduce complex volumetric responses of an unsaturated soil.
SUMMARYThis paper presents a constitutive model for unsaturated soils with only 13 parameters. Its development is based on the concept of bounding surface plasticity under a critical state framework. The definition of effective stress via an equivalent pore pressure and the introduction of suction effects into a general plastic hardening mechanism are inspired from the work of Pereira et al. (Ph.D. Thesis, 2005) and that of a few others. Despite the minimal number of parameters, this model can simulate correctly complex volumetric behaviour and post-peak softening, as well as a few other classic typical behaviours of unsaturated soils. The model is validated using experimental data both on saturated and unsaturated soils. Its efficiency has been highlighted by comparing its outputs with those from the Barcelona Basic Model and from another advanced model CJS-NS. The numerical studies revealed the necessity of additional experimental data for a more complete validation of the model and its future improvement.
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