Ground-penetrating radar (GPR) was firstly used in traffic infrastructure surveys during the first half of the Seventies for testing in tunnel applications. From that time onwards, such ...non-destructive testing (NDT) technique has found exactly in the field of road engineering one of the application areas of major interest for its capability in performing accurate continuous profiles of pavement layers and detecting major causes of structural failure at traffic speed. This work provides an overview on the main signal processing techniques employed in road engineering, and theoretical insights and instructions on the proper use of the processing in relation to the quality of the data acquired and the purposes of the surveys.
•GPR is an increasingly used NDT technique in pavement applications•Proper choice of the signal processing techniques according to the GPR data source•Overview of signal processing techniques to use prior to any post-processing step•Overview of signal processing techniques to perform after the GPR data collection
This paper reports the integration of the Ground Penetrating Radar (GPR) and the Interferometric Synthetic Aperture Radar (InSAR) techniques for the monitoring of the rail-abutment transition area in ...railway bridges. To this purpose, an experimental campaign was conducted on a rail truss bridge located in Puglia, Southern Italy. On one hand, GPR was used to obtain structural details of the subsurface (thickness of the ballasted layer, position of the sleepers, presence of clay/humidity spots) and to identify potential construction-related issues. Parallel to this, InSAR analyses were mainly addressed to monitor subsidence at the rail-abutment transition area. Outcomes of this investigation outlined presence of subsidence at both the areas of transition and have proven the proposed integrated approach as viable to achieve a more comprehensive assessment of the structural integrity of railway bridges.
•Differential settlements at the bridge-infrastructure transition zone are demanding in terms of maintenance required.•An integrated approach combining ground penetrating radar and satellite interferometry is proposed for displacement monitoring purposes.•A case study on a real railway bridge is presented.
A continuous increase in the worldwide demand for high-speed traffic, freight tonnage as well as of the train operating frequency is worsening the decay conditions of many railway infrastructures. ...This occurrence affects economy-related business as well as contributing to rising maintenance costs. It is known that a failure of a railway track may result in tremendous economic losses, legal liabilities, service interruptions and, eventually, fatalities. Parallel to this, requirements to maintain acceptable operational standards are very demanding. In addition to the above, a main issue nowadays in railway engineering is a general lack of funds to allow safety and comfort of the operations as well as a proper maintenance regime of the infrastructures. This is mostly the result of a traditional approach that, on average, tends to invest in high-priority costs, such as safety-related costs, compromising lower-priority interventions (e.g., quality and comfort of the operations). A solution to correct this trend can be moving from a reactive to a proactive action planning approach in order to limit more effectively the likelihood of progressive rail track decay. Within this context, this paper reports a review on the use of traditional and non-destructive testing (NDT) methods for the assessment and health monitoring of railway infrastructures. State-of-the-art research on a stand-alone use of NDT methods or a combination of them for quality control, inspection and maintenance tasks in this subject area is discussed.
This study reviews research developments in non-destructive assessment of linear transport infrastructures. The main focus will be on the integration between satellite remote sensing and ground-based ...techniques. Specifically, the potential of using interferometric synthetic aperture radar (InSAR) and high-frequency ground penetrating radar (GPR) techniques as self-standing and integrated survey methodologies will be discussed. To this effect, an overview on data fusion techniques will be given. The last section of the paper reports recent results achieved by using both GPR systems and the permanent scatterers InSAR technique on a real-life railway.
Multi-Temporal Interferometric Synthetic Aperture Radar (MT-InSAR) techniques are gaining momentum in the assessment and health monitoring of infrastructure assets. Amongst others, the Persistent ...Scatterers Interferometry (PSI) technique has proven to be viable for the long-term evaluation of ground scatterers. However, its effectiveness as a routine tool for certain critical application areas, such as the assessment of millimetre-scale differential displacements in airport runways, is still debated. This research aims to demonstrate the viability of using medium-resolution Copernicus ESA Sentinel-1A (C-Band) SAR products and their contribution to improve current maintenance strategies in case of localised foundation settlements in airport runways. To this purpose, “Runway n.3” of the “Leonardo Da Vinci International Airport” in Fiumicino, Rome, Italy was investigated as an explanatory case study, in view of historical geotechnical settlements affecting the runway area. In this context, a geostatistical study is developed for the exploratory spatial data analysis and the interpolation of the Sentinel-1A SAR data. The geostatistical analysis provided ample information on the spatial continuity of the Sentinel 1 data in comparison with the high-resolution COSMO-SkyMed data and the ground-based topographic levelling data. Furthermore, a comparison between the PSI outcomes from the Sentinel-1A SAR data—interpolated through Ordinary Kriging—and the ground-truth topographic levelling data demonstrated the high accuracy of the Sentinel 1 data. This is proven by the high values of the correlation coefficient (r = 0.94), the multiple R-squared coefficient (R2 = 0.88) and the Slope value (0.96). The results of this study clearly support the effectiveness of using Sentinel-1A SAR data as a continuous and long-term routine monitoring tool for millimetre-scale displacements in airport runways, paving the way for the development of more efficient and sustainable maintenance strategies for inclusion in next generation Airport Pavement Management Systems (APMSs).
Effective quality assurance and quality control inspections of new roads as well as assessment of remaining service-life of existing assets is taking priority nowadays. Within this context, use of ...ground penetrating radar (GPR) is well-established in the field, although standards for a correct management of datasets collected on roads are still missing. This paper reports a signal processing method for data acquired on flexible pavements using GPR. To demonstrate the viability of the method, a dataset collected on a real-life flexible pavement was used for processing purposes. An overview of the use of non-destructive testing (NDT) methods in the field, including GPR, is first given. A multi-stage method is then presented including: (i) raw signal correction; (ii) removal of lower frequency harmonics; (iii) removal of antenna ringing; (iv) signal gain; and (v) band-pass filtering. Use of special processing steps such as vertical resolution enhancement, migration and time-to-depth conversion are finally discussed. Key considerations about the effects of each step are given by way of comparison between processed and unprocessed radargrams. Results have proven the viability of the proposed method and provided recommendations on use of specific processing stages depending on survey requirements and quality of the raw dataset.
Effective maintenance of railways requires a comprehensive assessment of the actual condition of the construction materials involved. In this regard, Ground-Penetrating Radar (GPR) stands as a viable ...alternative to the invasive and time-consuming traditional techniques for the inspection of these infrastructures. This work reports the experimental activities carried out on a test-site area within a railway depot in Rome, Italy. To this purpose, a 30 m-long railway section was divided into ten sub-sections reproducing different various physical and structural conditions of the track-bed. For more detail, combinations of varying scenarios of fragmentation and fouling of the ballast were reproduced. The set-up was then investigated using different multi-frequency GPR horn antenna systems. The effects of the different physical conditions of ballast on the electromagnetic response of the material were analysed for each scenario using time- and frequency-domain signal processing techniques. Parallel to this, modelling was provided to estimate fouling content. Interpretation of results has proven the viability of the GPR method in detecting signs of decay at the network level, thereby proving this technique to be worthy of implementation in asset management systems.
Health monitoring of ballast in railway infrastructure is crucial to assure long-term structural stability. An efficient and sustainable management of maintenance operations is therefore fundamental ...for asset owners in setting up strategic and effective action plans. Amongst the available methods to assess the conditions of railway infrastructure, non-destructive technologies (NDT) are gaining popularity due to their capability to overcome main drawbacks from conventional routine methods, such as digging trenches and visually inspecting sections along the track. The present study reports an overview on the use of the ground penetrating radar (GPR) and the interferometric synthetic aperture (InSAR) technologies for a sustainable monitoring of railway infrastructure. Main conventional and non-destructive methods utilised for maintenance of railway ballast materials are presented, with a special focus on their sustainability. A review about research methods on the use of GPR and InSAR technologies for railway infrastructure monitoring is also reported, including main investigations carried out in the laboratory and the real-life environments. Furthermore, a conceptual framework based on an integrated approach between satellite-based and ground-based investigations is proposed, where network- and local-level information can be merged for a more effective detection of critical sections and the implementation of an advanced predictive maintenance system.
•Non-destructive assessment of a road flexible pavement.•Development of an experimental-based model for road pavement stiffness assessment.•Integration and modelling of data from GPR (2 GHz horn ...antenna) and LFWD equipment.•Development of a time-efficient methodology (quantitative and qualitative modelling).
This work proposes an experimental-based model for the assessment of the stiffness of a road flexible pavement using ground-penetrating radar (GPR – 2 GHz horn antenna) and light falling weight deflectometer (LFWD) non-destructive testing (NDT) methods. It is known that the identification of early decay and loss of bearing capacity is a major challenge for effective maintenance of roads and the implementation of pavement management systems (PMSs). To this effect, a time-efficient methodology based on quantitative and qualitative modelling of road stiffness is developed. The viability of using a GPR system in combination with LFWD equipment is also proven.
•Data crashes show that more than 280,000 victims of road crashes are pedestrians.•The majority of road crashes are caused by poor driver oversight of road users.•Augmented Reality technology could ...enable future systems to detect dangers earlier.•Several AR video and audio warnings are tested in a driving simulator study.•AR effectiveness in improving the safety of pedestrian crossings is demonstrated.
In this paper, the potential of using Augmented Reality (AR) technology to improve the safety of pedestrian crossings was tested, by means of virtual information provided to a driver approaching a zebra crossing area. To achieve this objective, a driving simulator study was carried out. The effectiveness of the system was tested, and the results of the developed simulation tests, with and without AR warning to inform the driver of a pedestrian crossing ahead, were compared. Specifically, AR warnings were tested under two different situations: a visible pedestrian crossing the roadway and a non-visible pedestrian, made invisible by certain obstacles, and who is about to cross the roadway. Two different virtual warnings were tested - in both cases - on a sample of forty-six participants: a flashing red arrow above the pedestrian, and the same visual warning but with an additional audible warning system. The effects of the audible warnings were studied by comparing the driving performances (decelerations, speeds and distances) and surrogate safety measures (Time-to-Collision (TTC) and Time-to-Zebra (TTZ)) with those recorded under reference conditions (without the audible warnings). Positive effects of AR were observed. Specifically, when the AR warnings were activated, drivers started to decelerate well before the pedestrian crossing, with a low deceleration rate and high TTC and TTZ. This study confirmed the great benefits that AR and connected vehicle technologies could bring to the overall safety conditions on the road network, especially under risky situations and difficult maneuvers. The driving simulator is certainly an effective solution for studying and evaluating such technologies, as well as studying their impact on driving performance.
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