An unsaturated soil model with minimal number of parameters based on bounding surface plasticity

Abstract This 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. Copyright © 2009 John Wiley & Sons, Ltd.