Evaluation of geotechnical properties of saturated soil using dielectric responses

In the field of geotechnical environment, physical parameters of soil such as volumetric water content, degree of saturation, porosity and effective porosity are important hydrological factors. Especially, these parameters can be applied to the analysis of slope failure, groundwater recharge and infiltration of various substances into the ground by rainfall. In the case of a landslide induced by heavy rainfall, landslide monitoring is one of important technologies that detects the distribution of volumetric water content, wetting front movement, and infiltration characteristics for the earth materials. The infiltration of water mainly occurs through pores of porous media. Infiltration of fluid substances is controlled by the connectivity of pore spaces. Therefore, it is explained by the concepts of porosity and effective porosity. In this study, the applicability of dielectric methods and proposed dielectric mixing models (DMMs) are discussed, and a soil column laboratory test is performed for measuring effective porosity of fully saturated sand using the permittivity method. This study showed that the ratios of effective porosity to porosity of saturated standard sands and river sands were 0.856 and 0.843, respectively. Based on the experimental results, using the frequency domain reflectometry (FDR) and frequency domain reflectometry with vector network analyzer (FDR-V) systems, the relative effective porosity is almost over 85% of the relative porosity in the saturated standard sands and river sands. Consequently, the dielectric measurement systems are considered to be effective in measuring the physical parameters of saturated soil. Moreover, this dielectric method can contribute to estimate porosity and effective porosity of saturated porous media because it is easier and faster than the previous in-situ methods.