Measuring the dielectric constant profile of soil cores based on ground-penetrating radar transillumination measurements

Abstract

Testing soil samples for geoengineering and geotechnical applications requires the measurement of various properties. In this study, we propose a simple yet robust method to determine the dielectric constant profile of soil cores. The proposed method measures a set of transillumination signals using an ultra-wideband radar, which records the travel time of microwaves penetrating through cylindrical soil core samples with various path lengths. The shape of the arrival time curve is evaluated using a modified version of the velocity analysis for common mid-point data to obtain the dielectric constant that best describes the shape of the curve. This method can be used to obtain depth profiles of, for example, soils varying in type and water content. Laboratory experiments were conducted with simulated soil core samples with a diameter of 75 mm with various types of soils and varying water content, using an implementation of the proposed measurement system operating in the 0.5–2.8 GHz frequency range. The results show that the proposed approach obtains reasonable values for the dielectric constants of the samples, which are consistent with those predicted using mixing models. Thus, the results demonstrate that the system can perform the automated measurement of the dielectric constant profile of soil cores.