[en] The reflection coefficient of GPR waves encountering embedded thin layers is commonly estimated using a plane wave, far field approximation. But when the thin layer is situated in the near field of the antenna, the spherical nature of the waves and the possible propagation of a lateral wave into the layer may have a strong influence on the measured reflected amplitude. In this work, we studied through 2D FDTD simulations the behavior of a radar wave interacting with thin layers of different thicknesses. The snapshots and radargrams showed a large influence of the layer thickness on the wave propagation. For the very thin layers, the evanescent wave plays a major role and the plane wave approximation gives a good estimation of the reflection coefficient. For thicker layers, the specific inclination of each multiple reflection has to be taken into account, as well as the lateral wave propagation. On the basis of these observations, we determined which analytical method should be used for the analytical prediction of the reflection coefficient, as a function of the layer thickness.
Disciplines :
Civil engineering
Author, co-author :
Van der Wielen, Audrey; Belgian Road Research Center
Courard, Luc ; Université de Liège - ULiège > Département ArGEnCo > Matériaux de construction non métalliques du génie civil
Nguyen, Frédéric ; Université de Liège - ULiège > Département ArGEnCo > Géophysique appliquée
Language :
English
Title :
Detection of near-field, low permittivity layers with Ground Penetrating Radar: analytical estimation of the reflection coefficient
Publication date :
2014
Event name :
15th International Conference on ground Penetrating Radar - GPR 2014
Event organizer :
UCL - TU Delft - The University of Edimburgh - Universita degli studi ROMA III
Event place :
Bruxelles, Belgium
Event date :
30 June - 4 July 2014
Audience :
International
Main work title :
Proceedings of 15th International Conference on ground Penetrating Radar
Editor :
LAMBOT, Sébastien
Peer reviewed :
Peer reviewed
Funders :
F.R.S.-FNRS - Fonds de la Recherche Scientifique ULiège - Université de Liège
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