Characterization of unsaturated particulate materials using elastic and electromagnetic waves

Soils are particulate and multi-phase materials (i.e., air, fluid, solid), thus, their properties capture the interaction among distinct phases. In unsaturated particulate materials, the negative pore-water pressure in menisci at particle contacts increases the interparticle forces, changes the small-strain stiffness, and alters all forms of conduction and diffusion processes. It has been difficult in evaluating such effects in common geotechnical engineering practices. Thus, a drying cell is newly developed to assess the characteristics of unsaturated particulate materials with the aid of elastic and electromagnetic waves. Bender elements (i.e., bimorphs) are installed at the center of metal caps and insulated from unwanted electromagnetic fields, while the metal caps work as electrodes. This configuration allows acquiring elastic and electromagnetic properties simultaneously. Continuous drying tests are performed on laboratory specimens made of three different soils. Overall, experimental test results suggest that unsaturated particulate materials can be assessed effectively using the developed cell with the aid of elastic and electromagnetic waves.