Andrea Benedetto

Reliability of signal processing technique for pavement damages detection and classification using ground penetrating radar

Ground penetrating radar (GPR) signal processing is a nondestructive technique, currently performed by many agencies involved in road management and particularly promising for soil characteristics interpretation. The focus of this paper is to assess the reliability of an optimal signal processing algorithm for pavement inspection. Preliminary detection and subsequent classification of pavement damages, based on an automatic GPR analysis, have been performed and experimentally validated. A threshold analysis of the error is carried out to detect possible damages and check if they can be predicted, while a second threshold analysis determines the nature of the damage. An optimum detection procedure is performed. It implements the classical Neyman-Pearson radar test. All the settings needed by the procedure have been estimated from training sets of experimental measures. The overall performance has been evaluated by looking at the usual receivers operating characteristic. The results show that a reasonable performance has been achieved by exploiting the spatial correlation properties of the received signal, obtained from an appropriate analysis of GPR images. The proposed system shows that automatic evaluation of subgrade soil characteristics by GPR-based signal analysis and processing can be considered reliable in a number of experimental cases.

Novel perspectives in bridges inspection using GPR

Bridge engineers increasingly prefer to use the Ground-Penetrating Radar (GPR) technique. GPR can yield data with very high spatial resolution, the data can be acquired rapidly and even during traffic, causing very low interferences. This paper presents a novel GPR system that is designed and developed for bridge applications. In addition it proposes a new algorithm for cracks tracking in a three-dimensional domain. The effectiveness and accuracy of the procedure have been calibrated and validated on four different bridges. In this paper, three-dimensional visualisations of cracks and two-dimensional tomographies and sections are shown to demonstrate the potentialities of the GPR system associated to the signal-processing algorithm.

GPR applications for geotechnical stability of transportation infrastructures

Nowadays, severe meteorological events are always more frequent all over the world. This causes a strong impact on the environment such as numerous landslides, especially in rural areas. Rural roads are exposed to an increased risk for geotechnical instability. In the meantime, financial resources for maintenance are certainly decreased due to the international crisis and other different domestic factors. In this context, the best allocation of funds becomes a priority: efficiency and effectiveness of plans and actions are crucially requested. For this purpose, the correct localisation of geotechnically instable domains is strategic. In this paper, the use of Ground-Penetrating Radar (GPR) for geotechnical inspection of pavement and sub-pavement layers is proposed. A three-step protocol has been calibrated and validated to allocate efficiently and effectively the maintenance funds. In the first step, the instability is localised through an inspection at traffic speed using a 1-GHz GPR horn launched antenna. The productivity is generally about or over 300 Km/day. Data are processed offline by automatic procedures. In the second step, a GPR inspection restricted to the critical road sections is carried out using two coupled antennas. One antenna is used for top pavement inspection (1.6 GHz central frequency) and a second antenna (600 MHz central frequency) is used for sub-pavement structure diagnosis. Finally, GPR data are post-processed in the time and frequency domains to identify accurately the geometry of the instability. The case study shows the potentiality of this protocol applied to the rural roads exposed to a landslide.

GPR experimental evaluation of subgrade soil characteristics for rehabilitation of roads

One of the most crucial problem in roads rehabilitation regards the pavement damage. Usually it is easy to localize the damage, but it is always difficult to identify the causes. The rehabilitation can be compromised, if the cause is not removed. The GPR technique is used by many Agencies involved in roads management. It is nondestructive and it is promising for soil characteristics interpretation, such as moisture or density. A classification of pavement damage, based on GPR analysis, is already performed and experimentally validated. The causes of damage are often referable to water intrusion in subgrade or clay intrusion in sandy subgrade. This is why we principally investigate how the moisture and the soil density influence the dielectric constant. The outcomes of a laboratory experimental survey are here discussed. Different soils have been considered. The GPR responses of each soil have been investigated, considering different moistures. The dielectric properties are highly correlated with the water content and the water status in soil. A significant correlation between dielectric properties and soil density is shown; this correlation is not so relevant as the previous. Any generalization is not reliable, but the study proves that the GPR evaluation of subgrade characteristics is possible.

Effects of Mobile Telephone Tasks on Driving Performance: A Driving Simulator Study

Mobile phone use while driving is increasing among road users. Although the most of countries made illegal the cell phone use while driving, the drivers still use it both for calling and texting. Several studies investigated the distraction factors related to the use of mobile while driving and the effects on road safety. The main findings of these studies generally demonstrated an increasing of reaction time and decreasing of driving performance especially during not critical driving conditions, while the evaluation of the effects of mobile use during critical driving conditions is not so much investigates. The overall objective of this work is to contribute to the evaluation of the effects of the mobile phone use on driving safety. Specifically the effects of using cellular phone at the same time the driver is faced with making a critical stopping decision are investigated. The experiments are carried out using an interactive driving simulator. Three different road scenarios (urban road, rural road and motorway) are simulated. Thirty subjects take part to the experiments and drive four times each scenario: one time without calling (control scenario) and the other three times answering the calls by hand-held mobile, hands-free mobile and hands-free voice device. The drivers reaction time, the deceleration rate, the speed and the following distance are evaluated. The main effects of driving and calling are observed in the urban scenario, where the decreasing of driving performance is much more evident than in the rural and motorway scenario. Not significant differences on driving performances are found across the three telephone modes. Keywords - mobile phone, hand-held, hands-free, reaction time, driving simulator, driver distraction Language: en

Remote Sensing of Soil Moisture Content by GPR Signal Processing in the Frequency Domain

This paper presents a method, based on ground penetrating radar (GPR) signal processing in the frequency domain, to estimate moisture content in a porous medium without preventive calibration. Several indicators based on high order moments are extracted from the GPR spectra and their dependency on the moisture content is evaluated. Experimental results confirm the theoretical expectations and show the effectiveness of the proposed approach to estimate soil moisture content.

Applications of Ground Penetrating Radar in civil engineering — COST action TU1208

This paper focuses on the use of Ground Penetrating Radar (GPR) in civil engineering. Open issues in this field are identified and desirable advances in GPR technology, application procedures, data processing algorithms and analysis tools, are addressed. European associations, institutes and consortia interested in this topic are mentioned, together with the main relevant international events. The new COST (European COoperation in Science and Technology) Action TU1208 “Civil Engineering Applications of Ground Penetrating Radar” is presented, started in April 2013: this interdisciplinary project offers important research opportunities and will strengthen European excellence in all the fields concerning the success of GPR technique, with a main focus on its applications in civil engineering. Four Working Groups (WGs) carry out the research activities: WGI focuses on the design of innovative GPR equipment, on the building of prototypes, as well as on the testing and optimization of new systems; WG2 focuses on the GPR surveying of pavement, bridges, tunnels and buildings, as well as on the sensing of underground utilities and voids; WG3 deals with the development of electromagnetic forward and inverse scattering methods and of advanced data processing algorithms; WG4 explores the use of GPR in fields different from civil engineering and the integration of GPR with other nondestructive testing techniques. The COST Action TU1208 is still open to the participation of new parties: in this paper, information is provided for scientists and scientific institutions willing to join the Action and participate to its activities.

An overview of ground-penetrating radar signal processing techniques for road inspections

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 applicationsProper choice of the signal processing techniques according to the GPR data sourceOverview of signal processing techniques to use prior to any post-processing stepOverview of signal processing techniques to perform after the GPR data collection

Inferring bearing ratio of unbound materials from dielectric properties using GPR: The case of runaway safety areas

In this paper, the correlation between the dielectric and the strength properties of unbound materials is analyzed, considering that mechanical characteristics of soil depend on particle interactions and assuming that dielectric properties of materials are related to bulk density. The work investigates this topic using ground-penetrating radar (GPR) techniques. In particular, two ground-coupled GPR are used in laboratory and in field experiments to infer the bearing ratio of soil in runway safety areas (RSA). The procedure is validated through CBR tests and in situ measurements using the light falling weight deflectometer (LFWD). A promising empirical relationship between the relative electric permittivity and the resilient modulus of soils is found. The comparison between measured and predicted data shows a reliable prediction of Youngs modulus, laying the foundation for inferring mechanical properties of unbound materials through GPR measurements.

GPR analysis of clayey soil behaviour in unsaturated conditions for pavement engineering and geoscience applications

Clay content is one of the primary causes of pavement damages, such as subgrade failures, cracks, and pavement rutting, thereby playing a crucial role in road safety issues as an indirect cause of accidents. In this paper, several ground-penetrating radar methods and analysis techniques were used to nondestructively investigate the electromagnetic behaviour of sub-asphalt compacted clayey layers and subgrade soils in unsaturated conditions. Typical road materials employed for load-bearing layers construction, classified as A1, A2, and A3 by the American Association of State Highway and Transportation Officials soil classification system, were used for the laboratory tests. Clay-free and clay-rich soil samples were manufactured and adequately compacted in electrically and hydraulically isolated formworks. The samples were tested at different moisture conditions from dry to saturated. Measurements were carried out for each water content using a vector network analyser spanning the 1 GHz–3 GHz frequency range, and a pulsed radar system with ground-coupled antennas, with 500-MHz centre frequency. Different theoretically based methods were used for data processing. Promising insights are shown to single out the influence of clay in load-bearing layers and subgrade soils, and its impact on their electromagnetic response at variable moisture conditions.