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IGARSS 2019, IEEE International Geoscience and Remote Sensing Symposium, Yokohama, JAPON, 28-/07/2019 - 02/08/2019; Ground Penetrating Radar (GPR) is a widely used tool in the management and monitoring of pavement structures. In this paper, we focus on the detection of thin inter-layer debondings between the hot mix asphalt layers of pavement structures. A Stepped-Frequency Radar (SFR) associated with a Support Vector Regression based Linear Prediction (LP-SVR) method is used to detect thin debondings. The performance of SFR with the LP-SVR method is analyzed according to various used frequency bandwidths on the experimental data.

In civil engineering, roadway structure evaluation is an important application which can be carried out by ground penetrating radar. This paper focuses on the estimation of the time delay and interface roughness of civil engineering structure, like pavements. The influence of interface roughness is taken into account in the signal model. Therefore, we propose a new method which allows to efficiently estimate the time delay and interface roughness. Like in [1], the modified MUSIC is used for time delay estimation. In interface roughness estimation, we propose a modified orthogonal propagator method (OPM) to estimate the interface roughness with estimated time delay. While in [1], maximum likelihood method is applied, which needs multiple dimensional search. The proposed method is tested on the experimental data. The experimental results show the performance of the proposed method.

Resume La selle de Vaucresson est une orthese active qui se situe entre le siege moule et la coquille de verticalisation. Elle a connu au cours de ces dernieres annees une evolution lui permettant d’etre aussi prescrite a des enfants dont la fonction motrice globale est de niveaux 3 et 4 selon le systeme de classification de Palisano (Global Motor Function Classification System : GMFCS). Son objectif est a la fois postural et orthopedique. Le cahier des charges de la selle sera etabli apres une evaluation precise des troubles neuromoteurs et orthopediques de l’enfant. Les nouveaux rappels proprioceptifs participeront a l’organisation du referentiel axial de l’enfant. Ces afferences proprioceptives devront etre mises en place precocement pour obtenir de meilleurs resultats.

MCD2016, 8th International conference on Mechanisms of Cracking and Debonding in Pavements, NANTES, FRANCE, 07-/06/2016 - 09/06/2016; The paper gives an overview of the ongoing experiment to survey debonding areas within pavement structure during accelerated pavement testing on the Ifsttar's fatigue carrousel. Several defects have been embedded during the construction phase and have been probed by different NDT techniques. Among them, the paper focuses on radar NDT&E techniques which have been used to detect and locate the artificial defects at the early stage of the experiment and then to perform the survey at different loading cycles. Besides, the test-site has been used to test different GPR materials, including the 3D GPR technology. The experiment has also motivated some related studies in the field of GPR data modelling and data processing, which are summarized in the paper. The experiment is expected to be pursued beyond 300 loading kcycles to reach larger pavement degradations.

This paper focuses on the development and validation of an innovative method for estimating volumetric water content in concrete mixtures. A supervised learning method (support vector machine) has been used to resolve the inverse problem, i.e., generate in-laboratory calibration curves correlating the controlled water content in various concrete mixtures with the frequency-dependent complex dielectric permittivity originating from the coaxial electromagnetic transition line. An extrapolation procedure using a frequency-power-law model has been developed and validated for estimating the complex permittivity over a broad frequency bandwidth. Implementation of this extrapolation method allows considering various physical phenomena (i.e., polarisation versus water content) that typically affect the dielectric behaviour of concrete as a function of frequency. The two-step estimation procedure (involving extrapolation and support vector regression methods) proposed in this paper has been validated on a wide array of moisture-controlled concrete specimens in the laboratory. The procedure helps building calibration curves that rely on both complex effective permittivity and volumetric water content, taking into consideration the frequency dependence.

International audience; This paper presents the rigorous efficient PILE (Propagation Inside-Layer-Expansion) numerical method [1] to calculate the impulse response of the field scattered by three homogeneous media separated by two random rough surfaces. Here, the study is applied to ground penetrating radar (GPR) (nadir angle, Ricker pulse, near or/and far field) for nondestructive pavement survey by taking the roughness of the surfaces into account and by calculating the contribution of each echo coming from the multiple scattering inside the layer. The PILE method starts from the Method of Moments (MoM), and the impedance matrix is inverted by blocks from the Taylor series expansion of the inverse of the Schur complement. Its main use is that it is rigorous, with a simple formulation and has a straightforward physical interpretation. Actually, this last property relies on the fact that each block of the impedance matrix is linked to a particular and quasi-independent physical process occurring during the multiple scattering process between the two rough surfaces. Furthermore, the PILE method allows us to use any fast method developed for a single interface.

In civil engineering, conventional methods used to estimate the thickness of pavements assume flat interfaces. In contrast, this study uses a rigorous electromagnetic method called propagation-inside-layer-expansion (PILE) to simulate the radar backscattered signal at nadir from a rough pavement made up of two rough interfaces separating homogeneous media. The statistical distribution of the first two echoes is studied by comparison with the default flat case, together with their frequency behaviour. Within the scope of road pavement survey by ground penetrating radar, the scattering model is finally used to assess the performance of the estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm, one of the well-known high-resolution time-delay estimation techniques.

In the field of civil engineering, sounding the top layer of carriageways, i.e., the pavement layer, is classically performed using standard ground-penetrating radar (GPR), whose resolution is bandwidth dependent. The layer thickness is deduced from both the time delays of backscattered echoes and the known dielectric constant of the medium. This paper focuses on superresolution and high-resolution techniques, which serve to improve the time resolution of GPR signals, and presents a parametric technique and five subspace methods, namely, estimation of signal parameters via rotational invariance techniques (ESPRIT), multiple-signal classification (MUSIC) algorithm, Min-Norm, and their polynomial versions root-MUSIC and root-Min-Norm. The performance of these algorithms will be compared in terms of resolution power as well as root-mean-square error on the estimated thickness. The paper also presents the results of computer tests and radar measurements in the far field.