Railway track condition assessment at network level by frequency domain analysis of GPR data

The railway track system is a crucial infrastructure for the transportation of people and goods in modern societies. With the increase in railway traffic, the availability of the track for monitoring and maintenance purposes is becoming significantly reduced. Therefore, continuous non-destructive monitoring tools for track diagnoses take on even greater importance. In this context, Ground Penetrating Radar (GPR) technique results yield valuable information on track condition, mainly in the identification of the degradation of its physical and mechanical characteristics caused by subsurface malfunctions. Nevertheless, the application of GPR to assess the ballast condition is a challenging task because the material electromagnetic properties are sensitive to both the ballast grading and water content. This work presents a novel approach, fast and practical for surveying and analysing long sections of transport infrastructure, based mainly on expedite frequency domain analysis of the GPR signal. Examples are presented with the identification of track events, ballast interventions and potential locations of malfunctions. The approach, developed to identify changes in the track infrastructure, allows for a user-friendly visualisation of the track condition, even for GPR non-professionals such as railways engineers, and may further be used to correlate with track geometric parameters. It aims to automatically detect sudden variations in the GPR signals, obtained with successive surveys over long stretches of railway lines, thus providing valuable information in asset management activities of infrastructure managers

Methodologies for teaching an engineering subject in different countries: comparison and results

Engineering or technical degrees are difficult to teach and, consequently, have always been characterized by a large number of academic failures. Therefore, continuous assessment has been applied to classes of similar content, related to Port and Coastal Engineering during these last years in three different Universities worldwide: University of La Republica (Montevideo, Uruguay), Nova de Lisboa (Portugal) and Cadiz (Spain). This paper presents different methodologies used to teach and evaluate these courses at each University, together with the results of the evaluations of the students who were enrolled during the current and previous stages. Generally, a decrease in the number of students who abandon the classes has been noticed together with an increase in the percentage of students who pass and an improvement of their grades, except at the University Nova de Lisboa were the results have remained stable. In addition, changes experienced in the courses are discussed herein by comparing the percentage of success in the different locations. Moreover, influence of the different methodologies and the possible reasons for these changes are also presented and analysed. As a conclusion, the improvement in educational outcomes has been achieved through the concurrence of different factors: the existence of more frequent written and/or oral exams, practical examples of case studies as well as access to specific tools of new technology and to documentation specifically prepared for the classes and available online. Evidently, the above mentioned tasks require a strong commitment and great effort by the teaching staff. If human resources diminish, as it is happening in Spain and Portugal due to the budget reduction in education, two difficult questions arise: For how long will teachers’ current effort be maintained? What impact will have their complete devotion to teaching in their research performance

COST Action TU1208 – Working Group 2 – GPR surveying of pavements, bridges, tunnels and buildings; underground utility and void sensing

This work aims at presenting the main results achieved by Working Group (WG) 2 "GPR surveying of pavements, bridges, tunnels and buildings; underground utility and void sensing" of the COST (European COoperation in Science and Technology) Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar" (www.GPRadar.eu, www.cost.eu). The principal goal of the Action, started in April 2013 and ending in October 2017, is to exchange and increase scientific-technical knowledge and experience of Ground Penetrating Radar (GPR) techniques in civil engineering, whilst promoting throughout Europe the effective use of this safe non-destructive technique. The Action involves more than 300 Members from 28 COST Countries, a Cooperating State, 6 Near Neighbour Countries and 6 International Partner Countries

Railway Track Condition Assessment at Network Level by Frequency Domain Analysis of GPR Data

The railway track system is a crucial infrastructure for the transportation of people and goods in modern societies. With the increase in railway traffic, the availability of the track for monitoring and maintenance purposes is becoming significantly reduced. Therefore, continuous non-destructive monitoring tools for track diagnoses take on even greater importance. In this context, Ground Penetrating Radar (GPR) technique results yield valuable information on track condition, mainly in the identification of the degradation of its physical and mechanical characteristics caused by subsurface malfunctions. Nevertheless, the application of GPR to assess the ballast condition is a challenging task because the material electromagnetic properties are sensitive to both the ballast grading and water content. This work presents a novel approach, fast and practical for surveying and analysing long sections of transport infrastructure, based mainly on expedite frequency domain analysis of the GPR signal. Examples are presented with the identification of track events, ballast interventions and potential locations of malfunctions. The approach, developed to identify changes in the track infrastructure, allows for a user-friendly visualisation of the track condition, even for GPR non-professionals such as railways engineers, and may further be used to correlate with track geometric parameters. It aims to automatically detect sudden variations in the GPR signals, obtained with successive surveys over long stretches of railway lines, thus providing valuable information in asset management activities of infrastructure managers

Caracterização Estrutural de Pavimentos Flexíveis através de Métodos de Auscultação Não Destrutivos

Tese de doutoramento em Engenharia Civil apresentada à Faculdade de Ciências e Tecnologia da Universidade de CoimbraThe aim of this work is to contribute to the improvement of the methodologies used in structural pavement evaluation, concerning in particular the backcalculation of layer moduli based on Falling Weight Deflectometer (FWD) together with Ground Penetrating Radar (GPR) test results. The main aspects that are dealt with are the application of GPR to pavement evaluation, the use of FWD data together with layer thickness data obtained from GPR and the improvement of the efficiency of the backcalculation of pavement layer moduli using Artificial Neural Networks (ANN). The advantages in using the GPR equipment, as well as the difficulties that occur during testing and data interpretation are addressed. Procedures to overcome some of the problems associated with this technology and to improve the reliability of GPR use are also recommended. A methodology for structural pavement evaluation using artificial neural networks, based on both FWD and GPR test results is presented. The sensitivity of the proposed method to variations in pavement thickness or to variations in deflections is also addressed. An application of the proposed method to a runway pavement evaluation is presented. The analysis of the results showed the suitability and advantages of the proposed methodology for structural pavement evaluation. From the experience gathered some recommendations for use of ANN in pavement structural evaluation were drawn, in view of obtaining reliable results.O objectivo do presente trabalho é o de contribuir para o aperfeiçoamento das técnicas de ensaio e metodologias de análise para a caracterização estrutural de pavimentos, em particular no que se refere à interpretação de resultados de ensaios de carga com deflectómetro de impacto (FWD) conjuntamente com os do radar (GPR). Os principais aspectos abordados são a aplicação do equipamento radar para pavimentos, a utilização resultados obtidos com o deflectómetro de impacto conjuntamente com espessuras das camadas medidas com o radar e a optimização da interpretação dos resultados de carga utilizando redes neuronais artificiais (ANN). Abordam-se as vantagens da utilização do radar e referem-se algumas das dificuldades inerentes à realização de ensaios e interpretação de resultados. São apresentadas recomendações relativas à resolução de alguns problemas relacionados com a utilização deste equipamento, visando a melhoria dos resultados obtidos. Apresenta-se uma metodologia baseada na utilização de redes neuronais artificiais, para a para a caracterização estrutural de pavimentos com base nos resultados obtidos com do deflectómetro de impacto conjuntamente com os do radar. Analisa-se a influência da variação das espessuras das camadas e das deflexões no comportamento da rede neuronal. Apresenta-se um exemplo da aplicação da metodologia proposta na avaliação de um pavimento aeroportuário. A interpretação dos respectivos resultados permitiu verificar a adequabilidade da metodologia proposta na caracterização estrutural de pavimentos. A experiência recolhida com a utilização desta metodologia permitiu extrair algumas recomendações relativas ao uso de redes neuronais artificiais, tendo em vista a obtenção de resultados fiáveis

Structural evaluation of flexible pavements using non-destructive tests

Tese de doutoramento em Engenharia Civil apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbr

Assessing the pavement subgrade by combining different non-destructive methods

The subgrade provides support to the pavement system and assures an effective distribution of traffic loads in depth. Therefore, a failure in the subgrade will have consequences on the entire pavement behavior. This work presents an integrated approach for the analysis of the road subgrade condition by combining different Non-Destructive Testing (NDT) techniques. Different Ground Penetrating Radar (GPR) systems, both antennas configuration and frequencies, were tested in order to achieve the best methodology for subgrade cracking detection. Additionally, NDT load tests were performed with two deflectometers, Falling Weight Deflectometer (FWD) and Light Weight Deflectometer (LWD), aiming to determine the elastic modulus of the subgrade and consequently detect damaged areas. The tests were conducted at a real scale test section built to simulate pavement foundation layers consisting of clay soil subgrade, frequently used in African countries. The main tests performed are presented and analysed in this paper. Troubleshooting’s are referred mainly related with GPR wave propagation on clayey materials, due to high absorption. Recommendations are made regarding the use of GPR antennas as air-coupled antennas lead to a better identification of pavement layer interfaces while ground-coupled antennas were preferable to detect anomalous areas, namely cracking and debonding. The results showed good agreement between both NDT methods (GPR and load tests) in the identification of the anomalous areas and were validated with some in-situ cores extracted

A review of GPR application on transport infrastructures: Troubleshooting and best practices

The non-destructive testing and diagnosis of transport infrastructures is essential because of the need to protect these facilities for mobility, and for economic and social development. The effective and timely assessment of structural health conditions becomes crucial in order to assure the safety of the transportation system and time saver protocols, as well as to reduce excessive repair and maintenance costs. Ground penetrating radar (GPR) is one of the most recommended non-destructive methods for routine subsurface inspections. This paper focuses on the on-site use of GPR applied to transport infrastructures, namely pavements, railways, retaining walls, bridges and tunnels. The methodologies, advantages and disadvantages, along with up-to-date research results on GPR in infrastructure inspection are presented herein. Hence, through the review of the published literature, the potential of using GPR is demonstrated, while the main limitations of the method are discussed and some practical recommendations are made.European CommissionMinisterio de Ciencia e Innovación (España) | Ref. RYC2019–026604–I /AEI / 10.13039/50110001103

Ballast fouling evaluation with ground penetrating radar

In the transport infrastructures context, the support layers have a fundamental role in the degradation of the track condition, both in structural aspects and in terms of fouling of the materials that comprise them. Particularly in the field of railway research, ballast is the key element, and its fouling leads to track deterioration. Thus, the main focus of this work is based on the evaluation of the ballast fouling using Ground Penetrating Radar (GPR). In order to determine the applicability of the method on the evaluation of railway characteristics, laboratory samples and measurements carried out in situ, on sections of two railways in operation were analysed. In both cases the different ballast fouling levels were evaluated, using specialized software for this approach (temporal analysis); and then comparing these results with results of a frequency analysis in an automatic calculation program. This paper presents the possibilities of testing with GPR equipment by analysing an electromagnetic wave, in the temporal and frequency domain for the purpose of investigating the level of degradation of a railway track. Some recommendations are also made regarding the use of this method, adding the need for future developments in an attempt to reduce the number of destructive tests still practiced nowadays

Ballast fouling evaluation with ground penetrating radar

In the transport infrastructures context, the support layers have a fundamental role in the degradation of the track condition, both in structural aspects and in terms of fouling of the materials that comprise them. Particularly in the field of railway research, ballast is the key element, and its fouling leads to track deterioration. Thus, the main focus of this work is based on the evaluation of the ballast fouling using Ground Penetrating Radar (GPR). In order to determine the applicability of the method on the evaluation of railway characteristics, laboratory samples and measurements carried out in situ, on sections of two railways in operation were analysed. In both cases the different ballast fouling levels were evaluated, using specialized software for this approach (temporal analysis); and then comparing these results with results of a frequency analysis in an automatic calculation program. This paper presents the possibilities of testing with GPR equipment by analysing an electromagnetic wave, in the temporal and frequency domain for the purpose of investigating the level of degradation of a railway track. Some recommendations are also made regarding the use of this method, adding the need for future developments in an attempt to reduce the number of destructive tests still practiced nowadays