Influence of antenna polarization and dielectric contrast on ground penetrating radar signals from non- metal pipe

Abstract

Ground penetrating radar (GPR) usage in detecting subsurface non-metal objects is investigated as there are many factors which can affect the strength of GPR signals such as the frequency of GPR antenna, the size, shape and the dielectric properties of the objects as well as the dielectric properties of the soil. This study involves the detection of GPR signal from a polyvinyl chloride (PVC) pipe of 0.15m in diameter and buried at a fixed depth of 0.5m from the soil surface in a testbed. Data collections were made using 500MHz and 800MHz GPR antennas which were placed directly above the soil surface, and in perpendicular or parallel orientation to the buried PVC pipe. Dielectric properties of the soil and the pipe content were varied by changing the amount of water added to them respectively. The results were shown by graphs of peak to peak amplitude of the detected GPR signals versus the soil conditions characterizing the soil-pipe dielectric contrast. Regardless of the antenna orientations, it was found that stronger GPR signals were obtained using the 500MHz antenna compared to those obtained using the 800MHz antenna. In addition, no significant difference is observed in signal strength collected using the 500MHz antenna in both perpendicular and parallel orientations. The results also show that there is a gradual increase in signal strength with increasing soil-pipe dielectric contrast irrespective of the orientations of the antenna. As a conclusion, depending on the level of the dielectric contrast, it is always more favourable to use the 500MHz GPR antenna to detect the PVC pipe.