Experimental techniques for multi-scale description of soil fabric and its dual pore network

Fabric affects many aspects of soil mechanical behaviour. When transport processes are of concern, its dual, the pore network, is the key aspect ruling the soil properties of interest. In this chapter, a review of a few widely used techniques, currently adopted to analyse the pore network at increasing scale, is presented, namely mercury intrusion porosimetry, environmental scanning electron microscopy and electrical resistivity tomography. Details on the techniques, their advantages and limitations, are first covered, followed by the presentation of selected test results. The results highlight how these techniques provide an insight into the pore network, and how they can be usefully exploited in the understanding of different hydro-electromechanical processes ordinarily observed at the phenomenological scale. Attention is focused on unsaturated soils with reference to water retention properties, micro / macrostructure interaction, and role of sample heterogeneity.