Many natural soils and engineering geomaterials, such as aggregated soils and
compacted clay pallets, exhibit two levels of porosity corresponding to the inter- and intraaggregate
pores within their hierarchical structure. Mechanical behavior of these materials, in
particular when unsaturated, is an issue of added complexity which should be described an
appropriate constitutive framework. A coupled water retentionโmechanical constitutive
model for unsaturated soils with double porosity is presented here. Based on the multi-scale
experimental results, the model incorporates the inter-particle bonding, fabric and partial
saturation effects in a single framework. It is formulated within the framework of hardening
elasto-plasticity and is based on the critical state concept. The mechanical model is coupled
with the water retention law which itself takes into account the two levels of porosity. The
coupling is made through the expression of the effective stress and the evolution of the
preconsolidation pressure with suction. On the other hand, the mechanical model at the
macro-scale is also coupled with the pore-scale behavior of the materials through an internal
variable which accounts for the evolution of the soil structure. The model is used for
numerical simulation of the behavior of aggregated and bonded soils. Comparison of
numerical simulations and the experimental results show that the model can successfully
address the main features in the behavior of unsaturated soils with double porosity
