FDTD simulation of the GPR signal for preventing the risk of accidents due to pavement damages

It is well known that road safety issues are closely dependent on both pavement structural damages and surface unevenness, whose occurrence is often related to ineffective pavement asset management. The evaluation of road pavement operability is traditionally carried out through distress identification manuals on the basis of standardized comprehensive indexes, as a result of visual inspections or measurements, wherein the failure causes can be partially detected. In this regard, ground-penetrating radar (GPR) has proven to be over the past decades an effective and efficient technique to enable better management of pavement assets and better diagnosis of the causes of pavement failures. In this study, one of the main causes (i.e. subgrade failures) of surface damage is analyzed through finite-difference time-domain (FDTD) simulation of the GPR signal. The GprMax 2D numerical simulator for GPR is used on three different types of flexible pavement to retrieve the numerical solution of Maxwell’s equations in the time domain. Results show the high potential of GPR in detecting the causes of such damage

FDTD simulation of the GPR signal for preventing the risk of accidents due to pavement damages

It is well known that road safety issues are closely dependent on both pavement structural damages and surface unevenness, whose occurrence is often related to ineffective pavement asset management. The evaluation of road pavement operability is traditionally carried out through distress identification manuals on the basis of standardized comprehensive indexes, as a result of visual inspections or measurements, wherein the failure causes can be partially detected. In this regard, ground-penetrating radar (GPR) has proven to be over the past decades an effective and efficient technique to enable better management of pavement assets and better diagnosis of the causes of pavement failures. In this study, one of the main causes (i.e. subgrade failures) of surface damage is analyzed through finite-difference time-domain (FDTD) simulation of the GPR signal. The GprMax 2D numerical simulator for GPR is used on three different types of flexible pavement to retrieve the numerical solution of Maxwell's equations in the time domain. Results show the high potential of GPR in detecting the causes of such damage

GPR applications across Engineering and Geosciences disciplines in Italy: a review

In this paper, a review of the main ground-penetrating radar (GPR) applications, technologies, and methodologies used in Italy is given. The discussion has been organized in accordance with the field of application, and the use of this technology has been contextualized with cultural and territorial peculiarities, as well as with social, economic, and infrastructure requirements, which make the Italian territory a comprehensive large-scale study case to analyze. First, an overview on the use of GPR worldwide compared to its usage in Italy over the history is provided. Subsequently, the state of the art about the main GPR activities in Italy is deepened and divided according to the field of application. Notwithstanding a slight delay in delivering recognized literature studies with respect to other forefront countries, it has been shown how the Italian contribution is now aligned with the highest world standards of research and innovation in the field of GPR. Finally, possible research perspectives on the usage of GPR in Italy are briefly discussed

Evaluation of ground penetrating radar responses to changes in graded rocks pavement layers characteristics

Orientador: Maria Teresa FrançosoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e UrbanismoResumo: Esta dissertação apresenta o estudo das respostas do ground penetrating radar às variações nas seguintes características de misturas de britas graduadas para camadas do pavimento: granulometria e massa específica aparente. Para a execução dos ensaios foi utilizada a antena blindada, de transmissão pelo solo, com frequência central de 1,6 GHz, acoplada a uma unidade de controle e armazenamento de dados. A fim de avaliar a sensibilidade do GPR às variações na granulometria comparou-se dois tipos de mistura, uma de graduação densa e uma de graduação aberta: respectivamente a BGS da Faixa B da especificação 141/2010 ¿ ES do DNIT e a base drenante da especificação ET-DE-P00/008 do DER/SP, que foram compactadas em uma caixa de madeira de 40 × 40 × 15 cm confeccionada para este fim. A fim de avaliar a sensibilidade às variações da massa específica aparente foram realizados levantamentos com ambas as misturas nas seguintes condições: teor de umidade variando ±1,0% em relação à umidade ótima; no estado solto e compactadas a 90%; 95%; 98% e 100% do Proctor Modificado. Também foram realizadas simulações numéricas 2D dos ensaios, nas quais se empregou o modelo CRIM e o método FDTD. Os resultados obtidos nas simulações foram condizentes com os resultados obtidos em laboratório, aos quais serviram de apoio. Em todos os ensaios o objetivo foi detectar variações na permissividade dielétrica relativa e relacioná-la à granulometria e às condições de compactação das misturas. Os resultados obtidos demonstram que em função do baixo contraste entre as propriedades físicas das duas misturas comparadas o ground penetrating radar não foi capaz de diferenciá-las. Os resultados também demonstram que o ground penetrating radar é sensível às variações nas condições de saturação, mas que esta sensibilidade não é suficiente para que ele seja utilizado em substituição aos métodos tradicionais de controle de qualidade na execução de camadas granulares, mas indicam que ele pode vir a ser utilizado para identificar heterogeneidades nas camadas executadasAbstract: This thesis presents the study of ground penetrating radar responses to changes in the following characteristics of graded rocks for pavement layers: particle size composition and bulk density. For the execution of the tests, the shielded antenna was used, transmitted by the ground, with a central frequency of 1.6 GHz, coupled to a control and data storage unit. In order to evaluate the sensitivity of GPR to variations in granulometric composition particle size, two compositons were compared, one dense grade and one open grade, respectively, the Curve B from DNIT Specification 141/2010 ¿ ES Curve B and the drainage layer from DER/SP specification ET-DE-P00 / 008., which were compacted in a 40 × 40 × 15 cm wooden box made for this purpose. In order to assess the sensitivity to variations in apparent density, surveys were carried out with both mixtures under the following conditions: moisture content varying ± 1.0% in relation to the optimum humidity; in the loose state and compacted to 90%; 95%; 98% and 100% of the Modified Proctor. 2D numerical simulations of the tests were also carried out, in which the CRIM model and the FDTD method were used. The results obtained in the simulations were consistent with the results obtained in the laboratory, which served as support. In all tests, the objective was to detect variations in the relative dielectric permittivity and to relate it to the granulometry and the conditions of compaction of the mixtures. The results obtained demonstrate that due to the low contrast between the physical properties of the two mixtures compared, the ground penetrating radar was not able to differentiate them. The results also demonstrate that the ground penetrating radar is sensitive to variations in the saturation conditions, but that this sensitivity is not sufficient for it to be used to replace traditional methods of quality control in the execution of granular layers, but indicate that it can come to be used to identify heterogeneities in the executed layersMestradoTransportesMestra em Engenharia Civil01-P-03713/2017CAPE

Experimental and theoretical investigation on road pavements and materials through ground-penetrating radar

Ground-penetrating radar (GPR) is being increasingly used over the last years in a wide range of applications, due to its flexibility and high potential to provide characterization and imaging of structures and materials. Overall, several reasons are contributing to increase the demand for the use of this tool and non-destructive testing techniques (NDTs) in general. Amongst all, it is worth citing technological advances of both hardware and software elements, an intrinsic lower significance of measurements provided by traditional monitoring techniques along with their greater invasiveness in measuring processes and, last but not least, the impacts of Global Economic Crisis on the use of economic resources affecting for years countries worldwide. The combination of such factors has led the interest of several skill profiles spanning from researchers, practitioners and end-users in general, and focused the attention of governments and local authorities on the high capabilities to gather a large amount of information in a relatively short time of surveying. In the field of pavement engineering, GPR has been used since the early 1980s mostly focusing on the geometrical characterization of road structure, by evaluating layer thicknesses. Minor care has been given to the analysis of the main causes of damage and performance properties of pavements, in order to improve management of infrastructural asset through effective and efficient maintenance and rehabilitation actions, as well as to provide best conditions in design of new roads. In that regard, this thesis is aimed to give a useful contribution also in the perspective of road safety issues by improving current processes of management and maintenance of road asset, along with the design of new roads, and provide effective support for the application and practical use of the tools described. Efforts have been spent in order to detect and quantify those physical and strength characteristics of road materials and subgrade soils that are relevant causes of damage, such that an effective planning of supporting actions for maintenance, rehabilitation and design of new roads may be timely performed. Three main topics are addressed, namely: i) the evaluation of moisture spatial field in subgrade soils through a self-consistent frequency-based technique and the analysis of radar support scale in small-scale measurements of water content; ii) the potential to detect and quantify clay content in load-bearing layers and subgrade soils through different GPR tools and signal processing techniques, and iii) the possibility to infer strength and deformation characteristics of both bound, unbound pavement structures, and subgrade soils from their electric properties. The results are encouraging for applications in the field of pavement engineering