Measuring layer thicknesses with GPR – Theory to practice

Al-Qadi, Imad L.; Lahouar, Samer

doi:10.1016/j.conbuildmat.2005.06.005

Cited by 216 publications

(98 citation statements)

References 5 publications

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“…(2), derived from the Fresnel reflection coefficients [1], ε r1 and ε r2 are the respective relative dielectric permittivities of the two materials and 1 is the inclination of the incident ray ( Fig. 2 (a)).…”

Section: 2mentioning

confidence: 99%

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Static Detection of Thin Layers into Concrete with Ground Penetrating Radar

Wielen

Courard

Nguyen

2012

Restoration of Buildings and Monuments

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Ground Penetrating Radar (GPR) is a nondestructive technique particularly well adapted to the inspection of concrete structures and can help to determine the structure inner geometry or to detect damaged areas. When the GPR is used on structures containing thin layers, for example the sealing layer of a concrete bridge deck or the void into a masonry wall, it is important for the radar user to know the minimum thickness required to detect and estimate the thickness of those layers.The theory of thin layer detection is based on a sine wave but, in reality, most commercial GPR systems emit a large frequency band wavelet, which undergoes attenuation into the layer. To analyze the influence of those realistic conditions on the reflection coefficient of a thin layer, we combined experimental measurements and numerical FDTD simulations. The experimental results matched the numerical predictions well, presenting a fast attenuation compared to the theoretical predictions. Nevertheless, for thicknesses inferior to λ/11, the reflection coefficient could still be considered as linearly dependent of the thickness to wavelength ratio.

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Section: 2mentioning

confidence: 99%

“…Among all the non-destructive methods, the Ground Penetrating Radar (GPR) is well adapted to inspect multilayer structures because only a percentage of the energy is reflected at every interface. An inspection can thus reveal the thickness and electromagnetic properties of two layers or more, if the conditions are favorable [1].…”

Section: Introductionmentioning

confidence: 99%

Static Detection of Thin Layers into Concrete with Ground Penetrating Radar

Wielen

Courard

Nguyen

2012

Restoration of Buildings and Monuments

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“…Different equations are utilized to approximate this zone [4]. Vertical resolution is often considered as ¼ of the wavelength [5][6], but in field measurements it is sometimes considered as 1/2 of the wavelength [7] [8]. Spatial resolution is largely dependent on the beam of the antenna because the footprint at different depths depends on the energy cone transmitted.…”

Section: Laboratory Datamentioning

confidence: 99%

GPR resolution in cultural heritage applications

Pérez-Gracia

Capua

González-Drigo

et al. 2010

Proceedings of the XIII Internarional Conference on Ground Penetrating Radar

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Abstract-The non-destructive study of historical buildings, archaeological sites and other Cultural Heritage structures requires high resolution methodologies and a good knowledge of the potential of the different methods. Laboratory measurements provide valuable information about the ability to detect different targets and to determine structural problems, but these data must be compared to the results obtained in real and complex structures. In this work, we present experimental GPR measurements made in order to determine the spatial resolution under laboratory conditions. These results were compared to the data obtained in different GPR surveys applied to Cultural Heritage. The information obtained in drillings, in visual inspections and in old documentation about the historical buildings and archaeological sites is used to determine the resolution in each case.

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“…Full waveform inversion methods can give good estimation of thin layers parameters [1][2][3], but they also require an antenna calibration, as well as a large computing cost. The faster alternatives to these methods exploit the reflection coefficient of the layer to determine its properties [4][5][6]. The reflection coefficient, R, is the proportion of the incident wave reflected by the layer.…”

Section: Introductionmentioning

confidence: 99%

Detection of near-field, low permittivity layers with ground penetrating radar: Analytical estimation of the reflection coefficient

Wielen

Courard

Nguyen

2014

Proceedings of the 15th International Conference on Ground Penetrating Radar

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Abstract-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.Index Terms-GPR, thin layers, lateral wave, spherical reflection, plane wave approximation, evanescent wave.

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Measuring layer thicknesses with GPR – Theory to practice

Cited by 216 publications

References 5 publications

Static Detection of Thin Layers into Concrete with Ground Penetrating Radar

Static Detection of Thin Layers into Concrete with Ground Penetrating Radar

GPR resolution in cultural heritage applications

Detection of near-field, low permittivity layers with ground penetrating radar: Analytical estimation of the reflection coefficient

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