Abstract
Ground Penetrating Radar is a device which is nowadays largely used in civil engineering applications. Considering a rebar buried in a concrete medium, this work addresses sensitivity of the inverse problem solution associated to identification of the object radius and its depth from B-scan data acquired by the GPR. The approach uses a closed form parameterisation of the hyperbola trace emerging in the radargram as function of the hyperbola apex coordinate along the direction of B-scan, the cover depth, the radius of the object and the relative permittivity of the medium. Estimation of the wave velocity, the hyperbola apex coordinates and the rebar radius was performed through solution of an appropriate nonlinear least mean squares problem. Perturbation analysis was then conducted by assuming that the hyperbola points coordinates, extracted from raw data of radargram, are randomly distributed according to Gaussian densities of probabilities. The effect of the amount of data was also analyzed. The method was implemented in Matlab environment. The obtained results have shown that identification process is extremely sensitive to noise affecting the B-scan raw data, but not to the number of points used in identification.
Highlights
Ground Penetrating Radar (GPR) is commonly used in civil engineering for the localization of supply lines, land mines, pipes and many other buried objects in soils
One of the most important problems to deal with in the field of GPR based detection techniques is to retrieve from the actual radargram the hyperbola characteristics by post-processing of acquired B-scan data and inverse problem solution
Use is made of an appropriate least squares based method in order to assess more effectively sensitivity of the inverse problem solution associated to identification of rebars buried in homogeneous concrete
Summary
Ground Penetrating Radar (GPR) is commonly used in civil engineering for the localization of supply lines, land mines, pipes and many other buried objects in soils. Its use encompasses diagnosis and detection of rebars in reinforced concrete structures. One of the changeling issues in this filed is the localization and the identification of radius of buried steel bars. Detection of a reinforcement steel rebar can be made from the raw data recorded as reflection hyperbola trace in the GPR radargram. The hyperbola has typical shape that varies according to the depth and material of the rebar as well as the surrounding medium dielectric properties. One of the most important problems to deal with in the field of GPR based detection techniques is to retrieve from the actual radargram the hyperbola characteristics by post-processing of acquired B-scan data and inverse problem solution
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