Abstract
Ground penetrating radar (GPR) exploration provides volumetric water content which can be calculated from relative dielectric permittivity of a ground medium. The volumetric water content is calculated using Topp's equation (Topp et al., 1980) in the TDR(Time Domain Reflectmetry) method. This equation has wide applications to soil water content estimation as a simple and easy way. Topp's equation was determined by the relative dielectric permittivity of soils and glass beads which have taken the volumetric water content under 50%. Care must be taken when applying Topp's equation for high water content materials and fine-grained cohesive soils.
It is known that the frequency dependence (dielectric dispersion) is present for soils containing water, but dielectric dispersion has hardly been discussed in Topp et al.(1980).
This report showed the relation between relative dielectric permittivity and volumetric water content less than 90% considering the dielectric dispersion of the soil samples. This result supports the ‘semi-disperse model’ by Wobschall (1977) and will provide the basis for a new indicator of the high accuracy volumetric water content estimation using GPR.
