In the paper a water content effect in various states on the variability of the electromagnetic waves parameters is discussed. This variation can affect accuracy and repeatability of asphalt and concrete pavement thickness estimation with GPR method. In case of asphalt pavements, tests were carried out using the air-coupled 1.0 GHz antenna and included three approaches: two on asphalt road and one of asphalt slabs. In the case of concrete slabs, tests were carried out using a ground-coupled 1.6 GHz antenna on two slabs: reinforced and unreinforced. A high variability of the electromagnetic wave parameters was observed depending on moisture conditions. The increase in the humidity of the medium causes a reduction in the propagation speed of the electromagnetic wave (increasing the dielectric constant of the medium), increasing of waves time propagation, decreasing of reflection amplitude and increasing of frequency attenuation, which should be considered when determining the thicknesses of the construction layers. Studies showed that not always higher air humidity, atmospheric precipitation and consequently wet surface indicate a higher dielectric constant of the medium. It can be concluded that not only the humidity and ambient temperature affect the change in the dielectric constant, but also other factors not resulting from the construction of the pavement as well as material microstructure.
The article discusses one of the methods of dielectric constant determination in a continuous way, which is the determination of its value based on the amplitude of the wave reflected from the surface. Based on tests performed on model asphalt slabs, it was presented how the value of the dielectric constant changes depending on the atmospheric conditions of the measured surface (dry, covered with water film, covered with ice, covered with snow, covered with de-icing salt). Coefficients correcting dielectric constants of hot mix asphalt (HMA) determined in various surface atmospheric conditions were introduced. It was proposed to determine the atmospheric conditions of the pavement with the use of wavelet analysis in order to choose the proper dielectric constant correction coefficient and therefore improve the accuracy of the pavement layer thickness estimation based on the ground penetrating radar (GPR) method.
Ground-penetrating radar (GPR) surveys and sedimentological outcrop analyses were combined in order to determine the reflection patterns and internal architecture of terrace deposits of the Vistula River at Kępa Zawadowska in the southern part of Warsaw (central Poland). The sedimentary analyses concerned the granulometric composition and lithofacies analysis. The 34 GPR profiles, which were obtained in two outcrops, using a Malå RAMAC/GPR system with 500-MHz and 250-MHz shielded antennas, were up to 100 m long. The most characteristic ground-penetrating radar profiles are presented; they show a high-resolution data set of radar facies. The GPR data suggest the presence of three geophysically different units, namely with high-angle inclined reflections (radar facies 1), with discontinuous undulating or trough-shaped reflections (radar facies 2), and with low-angle reflections (radar facies 3). The internal structure of the fluvial deposits was obtained by integration of the GPR and sedimentological data, which combination provides a more accurate visualisation of sedimentary units than do reconstructions that are based only on standard lithologic point data.
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