An overview is initially presented to bring into light the important microstructural effects on different compacted clayey soil properties. Experimental data coming from microstructural studies on different compacted clayey soils with dominant bimodal pore size distribution (i.e., aggregated type or with shielding skeleton) are analysed to provide a comprehensive picture of different phenomenological (macroscopic) features of soil behaviour. A microstructural model, already developed to take into account microstructural aspects on water retention curves, was used to explain hydraulic properties and their evolution along hydro- mechanical paths. The key point of the model is the introduction of the dependence of the microvoid volume (with saturated aggregates) on water content.