Elastic and electromagnetic waves of small perturbation allow the characterization of a particulate material without causing any permanent effects.

The physical interpretation of these measurements (i.e., elastic and electromagnetic wave parameters) permits inference with important information about the particulate material and its process. 

Indeed, soils are particulate and multi-phase materials (i.e., air, fluid, soils).

Thus, soil properties and the interaction among distinct phases can be captured using elastic and electromagnetic wave parameters. 

The interpretation can be local or global, depending on the scale of interest.

Most subsurface soils are unsaturated; thus, the importance of unsaturated soil mechanics has been increasingly emphasized since the pioneering works in the 1950's and 1960' s. 

In unsaturated soils, suction pressure in pore water due to capillarity gives additional force to soil systems, 

increasing the state of stress and shear strength.

Furthermore, all forms of conduction and diffusion processes are related to the size and connectivity of menisci. 

Such effects are not readily evaluated within the framework of conventional soil testing methods.

In this study, a drying cell was newly developed to effectively assess the characteristics of unsaturated particulate materials with the aid of elastic and electromagnetic waves. 

The elastic wave allows interference with the evolution of effective stress while the electromagnetic wave gives an insight into conduction and diffusion processes.