Evaluation of dielectric-based probes for expansive soils: application to Regina clay

Much experience has been gained with the use of the dielectric methods in granular or fine-grained soil with low to medium plasticity. Empirical equations were proposed to describe the relationship between water content and measured bulk dielectric constant of the soils. However, the proposed empirical equations are generally not considered applicable for highly plastic, expansive soils due to factors such as bound water and high electric conductivity. This paper presents calibration equations for various commercially available dielectric-based probes. The calibration curves have been determined through laboratory calibration using compacted specimens. The differences between the calibration curves and those predicted by the empirical equations, as well as those provided by the manufacturer, are assessed and discussed. The effect of temperature on the response of the probes was also studied.