Abstract: Ground penetrating radar (GPR) is becoming an increasingly useful tool for road subsurface characterization. The Florida Department of Transportation (FDOT) has recently obtained a new 1 GHz ground penetrating radar with the ability to make high resolution measurements. Depth profile scan rates of the new radar are about 50 scan/sec and the radar operates on a test van travelling at speeds up to 50 - 55 MHz. The time domain data collected by the GPR allow the determination of thickness of the road surface and subsurface layers and, with appropriate signal processing, the data can provide information about voids and other anomalies within road layer interfaces. This paper will describe the salient features of the Florida DOT ground penetrating radar, recent measurement results, and applications of GPR for road assessments. It will also describe preliminary results of a University of Florida project which is employing advanced signal processing techniques to detect and classify subsurface anomalies in road layers. As a precursor to anomaly detection we are developing improved techniques for finding road layer thicknesses and dielectric constants. The processing techniques being developed include matched filter and slope detection algorithms. A goal of the current work is to develop signal processing techniques that will allow FDOT to evaluate subsurface conditions for large sections of road throughout Florida in a more accurate and rapid manner. It is expected that the GPR and the results of current research will assist the FDOT in more accurately determining road layer thickness profiles, in assessing road subsurface conditions with less coring, and aid in rehabilitating roads with less manpower than is now required. Such capabilities will allow potentially serious problems to be corrected before they become costly and will also provide a useful tool for future road design and improvement.!2
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