Effectiveness of 2D FDTD Ground Penetrating Radar Modeling for Bridge Deck Deterioration Evaluated by 3D FDTD

He, Zhan; Belli, Kimberly; Wadia-Fascetti, Sara; Rappaport, Carey M.

doi:10.1109/igarss.2008.4779605

Cited by 4 publications

(2 citation statements)

References 15 publications

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“…Twodimensional simulations are less expensive in terms of computation resources, and it is more feasible to analyze large regions than 3D models. More importantly, 2D and 3D models are both based on the physical basis of radar wave propagation, and when they are used together for the same model, the shapes of waveforms (including the peak arrival times) are consistent with each other (Belli et al, 2009;Zhan et al, 2009). Therefore, the FDTD-2D code is used for our purpose.…”

Section: Numerical Simulation Of the Lprmentioning

confidence: 99%

Layering Structures in the Porous Material Beneath the Chang'e‐3 Landing Site

Ding

Xiao

et al. 2020

Earth and Space Science

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The lunar penetrating radar (LPR) onboard the Chinese Chang'e-3 (CE-3) mission obtained high-resolution profile data for the continuous ejecta deposits of the Ziwei crater. Geological background suggests that the continuous ejecta deposits contain few large boulders, and the ejecta deposits were largely originated from the pre-impact regolith. Using the top~50 ns of radar data, we estimate the bulk density and porosity for the ejecta deposits based on hyperbolic echo patterns in the radargram that are caused by subsurface boulders. The physical properties are close to those of typical lunar regolith. Numerous subparallel and discontinuous short layers are visible in the radargram of the continuous ejecta deposits. The dielectric coefficients of the layering structures are estimated, and their permittivity is slightly larger than that of typical lunar regolith and less than that of basaltic rocks. Cratering physics together with the geological context of this area suggest that the layering structures are most likely ground gravels and/or melt-welded breccias that were sheared due to the horizontal momentum of the impact ejecta. This interpretation is indicative of the origin of the enigmatic layering structures in regolith core samples returned by the Apollo and Luna missions. The results also highlight the importance of ejecta emplacement in shaping the structure of lunar regolith. Plain Language Summary Large discrepancies existed in previous geological interpretations using the Chang'e-3 high-frequency LPR data. A comprehensive review of previous studies that used the Chang'e-3 radar data noticed that most previous studies agree that the top~50 ns of the radargram is restricted within the continuous ejecta deposits of the Ziwei crater. Analyses for the stratigraphy of the landing site suggested that the continuous ejecta deposits were largely composed by pre-impact regolith. Using the high-frequency LPR data, we reconstructed the depth profiles of physical parameters (i.e., relative permittivity, bulk density, and porosity) for the continuous ejecta deposits of the Ziwei crater, which are similar with those of typical lunar regolith. Many subparallel and discontinuous layers are observed in the radargram, which were not deciphered before. We carried out numerical simulations to study the nature of the layering features. Results suggest that these structures have a permittivity slightly larger than that of typical lunar regolith. Geological context of the landing site suggested that the layering structures are likely shear bands within the continuous ejecta deposits, and they may be composed by ground rock fragments and/or melt-welded breccia, which were laterally deformed due to the horizontal momentum of the ejecta deposits.

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Section: Numerical Simulation Of the Lprmentioning

confidence: 99%

Layering Structures in the Porous Material Beneath the Chang'e‐3 Landing Site

Ding

Xiao

et al. 2020

Earth and Space Science

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“…Finite-difference time-domain (FDTD) method, a powerful tool for numerical modeling, is an appropriate tool for EM wave propagation simulation [ 9 ]. Although most of the research using the FDTD method has focused on the detection of underground objects, such as faults and caves, tunnel inspections, pipes, and landmines [ 10 , 11 , 12 , 13 ], this method has recently been applied to bridge assessment and inspection as well as pavement surface-moisture removal [ 14 , 15 , 16 ]. Microstructure and density of AC pavement research using the FDTD method, however, is still limited.…”

Section: Introductionmentioning

confidence: 99%

Development of a Numerical Model to Predict the Dielectric Properties of Heterogeneous Asphalt Concrete

Cao

Al-Qadi

2021

Sensors

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Ground-penetrating radar (GPR) has been used for asphalt concrete (AC) pavement density prediction for the past two decades. Recently, it has been considered as a method for pavement quality control and quality assurance. A numerical method to estimate asphalt pavement specific gravity from its dielectric properties was developed and validated. A three-phase numerical model considering aggregate, binder, and air void components was developed using an AC mixture generation algorithm. A take-and-add algorithm was used to generate the uneven air-void distribution in the three-phase model. The proposed three-phase model is capable of correlating pavement density and bulk and component dielectric properties. The model was validated using field data. Two methods were used to calculate the dielectric constant of the AC mixture, including reflection amplitude and two-way travel time methods. These were simulated and compared when vertical and longitudinal heterogeneity existed within the AC pavement layers. Results indicate that the reflection amplitude method is more sensitive to surface thin layers than the two-way travel time methods. Effect of air-void content, asphalt content, aggregate gradation, and aggregate dielectric constants on the GPR measurements were studied using the numerical model.

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