DETERMINATION OF THE THICKNESS OF ASPHALT CONCRETE PAVEMENT LAYERS USINGGROUND PENETRATING RADAR PROBING METHODS

When surveying road structures with the use of georadar equipment, the problem of determining the thickness of a thin layer of asphalt concrete is urgent, when the time of passage of an electromagnetic pulse in the layer is less than the spatial duration of the pulse. The second problem is that if the road surface has two thin layers with similar values of dielectric permittivity, then the reflection signal from such a boundary has a small amplitude and is difficult to detect against the background of strong reflection from the lower boundary of the lower layer. The study examines the use of the Wiener deconvolution method to determine the thickness of road surface layers based on georadar data obtained with the georadar. The optimal value of the stabilizing noise/signal parameter for calculating the impulse characteristics of asphalt concrete is determined. A characteristic feature of the obtained pulse characteristics for both the metal sheet and the road surface is that the peak corresponding to the signal reflected from the surface has the maximum amplitude. Due to the approximate nature of the solution to the problem, amplitude oscillations are observed near the peak values. They fade quickly, but can be superimposed on the peaks corresponding to the reflection of the inner layers of road clothing. The application of the deconvolution method to the signal after extracting from it the component corresponding to the reflection from the asphalt concrete surface made it possible to reveal less powerful peaks of the impulse characteristic. These peaks correspond to the inner layers with close dielectric constant values. Measurements were carried out on the section of the road where repair work was being carried out. This makes it possible to obtain control values of the thickness of road surface layers. Measurements were carried out on the repair site after the installation of the asphalt concrete layer. The method was tested on ground-penetrating radar data collected both on a section with an old asphalt concrete surface and on a section of the road immediately after repair. The calculated thicknesses of the layers, obtained by means of the Wiener deconvolution method and additional extraction of the signal reflection from the surface, agree with the previously measured instrumental values.