Modeling the mechanical behavior of compacted unsaturated soils against stress and suction changes is complex. One reason is that the structure mostly depends on the initial moisture content and compaction energy applied. Herein, it is proposed an alternative method to model this kind of soils based on its Pore Size Distribution (PSD), as a possible characterization of its structure. This latter can be obtained by means of the Mercury Intrusion Porosimetry test (MIP). The proposed model should permit the prediction of the volumetric deformations produced as a consequence of stress and suction changes. In order to do this, relationships have been developed to be applied to every pore size considered. The integration over all the sizes leads to the calculation of macroscopic values. Those relationships use fundamental physical principles. In order to determinate the stress-strain behavior, it has been considered that volumetric deformation moduli, both for changes in mean stress and suction, are function of pore size. Finally, the preliminary model equations have been applied to simulate suction controlled oedometer tests, including the subsequent sample’s collapse observed for different values of vertical stress. The investigated soil is a compacted silty clay for which the initial pore size distribution is known.