Quantification of Soil State Variables Using Electromagnetic Methods

The possibility to quantitatively measure changes in state variables both in laboratory and in situ is the key for the comprehensive assessment and understanding of many problems in geotechnical engineering. The analysis of the processes in unsaturated soils, for example, requires not only pore water pressures but also the information on the water content and the porosity to capture the field soil–water retention relationships. In saturated soils, knowledge of the temporal evolution of the soil density allows a much better understanding of the consolidation and shrinkage behavior, especially with respect to soft soils. Electromagnetic measurement methods allow the quantification of not only the water content but also the porosity of granular and cohesive soils. In particular, the porosity, which determines the dry density of a soil in combination with the specific gravity, is a key parameter influencing many mechanical and hydraulic processes and their governing parameters. The presented contribution introduces different measurement methods in the laboratory and the field for determining water content and density using a variety of sensors.