Ground Penetrating Radar Scanning Research Articles

Corrosiveness mapping of bridge decks using image-based analysis of GPR data

Abstract Ground Penetrating Radar (GPR), a locating instrument by design, has attracted much interest as a non-destructive inspection technique for bridge decks due to its ease of use and ability to detect corrosion. The most commonly used technique to interpret GPR data is numerical analysis. The assessment method relies on the fact that corroded reinforcing bars, which cause signal attenuation, can be easily identified using GPR scans. However, several other unrelated factors can attenuate GPR signals such as reinforcing bar depth, surface anomalies and reinforcing bar spacing. These anomalies can be falsely interpreted as deterioration using numerical analysis. Image-based analysis overcomes these drawbacks through analyzing the entire GPR profile while considering prior knowledge of the structure characteristics, thus determining the state of bridge deck. The main objective of this research is to develop a systematic framework of the image-based analysis. The framework is supported by various GPR profiles depicting several causes of signal attenuation and their analysis with respect to deterioration or rebar corrosion status. Two case studies are presented and analyzed using numerical analysis, image-based analysis, and other Non-Destructive Evaluation (NDE) techniques. The results are compared to confirm the validity of the proposed methodology. Further validation is done using concrete cores. The developed approach is believed to assist transportation agencies in a more informed decision making process through highlighting areas of actual deterioration.

Site Interiography and Geophysical Scanning: Interpreting the Texture and Form of Archaeological Deposits with Ground-Penetrating Radar

The remarkable potential of geophysical scanning—to assess the internal variability of sites in new ways, to highlight important phenomena in the field, to exercise co-creation of interpretation and commitment to minimal destruction of community partners’ resources, and to aid in the practice of due diligence in avoiding desecration of the sacred—continues to be underutilized in archaeology. While archaeological artifacts, features, and strata remain primary foci of archaeological geophysics, these phenomena are perceived quite differently in scans than in visual or tactile exposures. In turn, new registers of site exploration afforded by geophysical prospection may be constrained by the language of site excavation and visual observation, requiring adjustments in the ways of thinking about and describing what the instruments are measuring. The texture and form of site deposits as rendered in ground-penetrating radar scans can be examined in detail prior to making interpretations of cultural features or stratigraphy. Far more than simple “anomalies” demanding our attention for excavation, patterns in geophysical data can be the focus of extensive archaeological analysis prior to, in conjunction with, or independent from excavation.

Analysis of the capabilities of the detection of underground optical lines using ground penetrating radar scanning technology

Analysis of the capabilities of the detection of underground optical lines using ground penetrating radar scanning technology

A localization method for concealed cracks in the road base based on ground penetrating radar

Phenomenon of concealed cracks is one of the familiar failures in the road base. Accurate concealed crack localization of the road base using ground penetrating radar still suffers from some limitations. To accurately locate the concealed cracks in the road base, an effective concealed crack localization method based on ground penetrating radar is proposed in this article: first, continuous ground penetrating radar scanning and manual point-by-point detection are performed to determine the location of the concealed crack roughly; then the ground penetrating radar–based ellipse method and an improved data processor based on MATLAB are used for processing the data to determine the accurate location of the concealed crack. The proposed method is experimentally validated using a rectangle concrete block with a concealed crack, and the results of the proposed method are compared with that of the previous method. All results indicate that the proposed method can be used to locate concealed cracks fast and well; moreover, the localization accuracy of the proposed method is obviously higher than the previous method; all these lay a good foundation for engineering applications.

An Experimental and Numerical Study on Embedded Rebar Diameter in Concrete Using Ground Penetrating Radar

High frequency ground penetrating radar (GPR) has been widely used to detect and locate rebars in concrete. In this paper, a method of estimating the diameter of steel rebars in concrete with GPR is investigated. The relationship between the maximum normalized positive GPR amplitude from embedded rebars and the rebar diameter was established. Concrete samples with rebars of different diameters were cast and the maximum normalized amplitudes were recorded using a 2.6 GHz GPR antenna. Numerical models using GPRMAX software were developed and verified with the experimental data. The numerical models were then used to investigate the effect of dielectric constant of concrete and concrete cover on the maximum normalized amplitude. The results showed that there is an approximate linear relationship between the rebar diameter and the maximum GPR normalized amplitude. The developed models can be conveniently used to estimate the embedded rebar diameters in existing concrete with GPR scanning; if the concrete is homogeneous, the cover depth is known and the concrete dielectric constant is also known. The models will be highly beneficial in forensic investigations of existing concrete structures with unknown rebar sizes and locations.

Integrated Processing of Image and GPR Data for Automated Pothole Detection

AbstractA pothole is a severe pavement distress that can compromise pavement rideability and safety and can be the cause of expensive damage claims. The detection and evaluation of potholes are predominantly manual and time-consuming. Although sensing technologies such as global positioning systems (GPS), stereovision systems, and ground penetrating radar (GPR) now can be combined to collect pavement condition data for assessment, the raw data returned by these sensors are often processed individually and separately. This isolated approach to data processing hinders the potential efficiency and effectiveness of multisensor systems. This paper proposes a method to integrate the processing of two-dimensional images and GPR data to automate accurate and efficient pothole detection. First, the images and GPR scans are preprocessed to filter out noise and enhance the essential clues related to potholes. Second, a novel pothole detector was designed by investigating the patterns of GPR signals reflected by poth...

Pavement Working Platforms Constructed with Large-Size Unconventional Aggregates

As a sustainable construction practice, recent research efforts of the Illinois Department of Transportation (DOT) have been focused on an engineered approach for developing construction specifications and performance validation of the use of large-size virgin and recycled unconventional aggregates in soft subgrade remediation. The Illinois DOT Bureau of Design and Environment has issued a special provision that specifies certain gradation bands for improved aggregate subgrade to allow enhanced use of large rocks from both primary crusher type virgin and recycled sources. Nevertheless, laboratory tests are usually inadequate for characterizing the properties and engineering behavior of large-size unconventional aggregates. Therefore, the recent field performance evaluation study using accelerated pavement testing was initiated at the University of Illinois with 12 full-scale pavement working platforms constructed with selected large-size virgin and recycled materials, including reclaimed asphalt pavement, recycled concrete aggregate, and demolition waste. For in-depth performance testing and evaluation, this paper describes test section construction and quality control sequences conducted at different phases of the study, including state-of-the-art field aggregate and pavement layer imaging techniques. The rutting performance trends of test sections were investigated in light of innovative test devices and techniques, including variable energy penetration testing, geoendoscopy, transverse ground-penetrating radar scans, as well as postfailure trenching images. Penetration of large rocks into the soft subgrade was effective in achieving a stable construction platform. Moreover, reclaimed asphalt pavement as a granular pavement layer was prone to large permanent deformations.

The effect of noise on the estimation of rebar radius by inversion of GPR scan data

Ground Penetrating Radar (GPR) is largely used nowadays in civil engineering applications as an effective technique of structural monitoring. This paper describes a method using radargram acquired by the GPR for estimating the radius of a steel rebar buried in a concrete massif, which is assumed to be homogeneous and isotopic. Considering the forward problem under B-scan procedure, a closed form mathematical formula was derived for the hyperbola trace appearing as the diffraction pattern provided by a circular steel bar. This equation relates the observed hyperbola parameters in the obtained radargram to the characteristics of the object and those of the host medium where the object is buried. The inverse problem was solved in two steps. Using the extracted raw data in terms of the hyperbola characteristics and Hough transform, the coordinates of the peak hyperbola are identified. Then the wave speed, the rebar radius as well as the coordinates of the rebar centre are estimated by a curve fitting procedure which is based on the selection of an arbitrary set of points on the considered hyperbola. The effect of noise resulting from variations affecting the electromagnetic wave speed was assessed. The noise was assumed to be a random variable and to act additively on the actual ordinates of the hyperbola. The obtained results have shown that the estimation of the rebar radius is very sensitive to the considered level of noise. Noise impedes the retrieval of a bar radius if its magnitude exceeds 5%.

GPR scan assessment at Mekaad Radwan Ottoman – Cairo, Egypt

Mekaad Radwan monument is situated in the neighborhood of Bab Zuweila in the historical Cairo, Egypt. It was constructed at the middle XVII century (1635 AD). The building has a rectangle shape plan (13×6m) with the longitudinal sides approximately WNW-ESE. It comprises three storages namely; the ground floor; the opened floor (RADWAN Bench) and the living floor with a total elevation of 15m above the street level. The building suffers from severe deterioration phenomena with patterns of damage which have occurred over time. These deterioration and damages could be attributed to foundation problems, subsoil water and also to the earthquake that affected the entire Greater Cairo area in October 1992. Ground Penetrating Radar (GPR) scan was accomplished against the walls of the opened floor (RADWAN Bench) to evaluate the hazard impact on the walls textures and integrity. The results showed an anomalous feature through the southern wall of RADWAN Bench. A mathematical model has been simulated to confirm the obtained anomaly and the model response exhibited a good matching with the outlined anomaly.

Performance Assessment of Secondary-Roadway Infrastructure in Iowa after 2011 Missouri River Flooding

AbstractThe Missouri River flooding in 2011 caused significant damage to secondary roadway infrastructure systems in western Iowa. This paper documents results of an investigation designed to evaluate unpaved roads and bridge approaches in the flood-affected areas. In situ testing was conducted as flood waters receded and several months later to evaluate performance and recovery conditions. In situ tests included falling weight deflectometer, dynamic cone penetrometer, and ground penetrating radar scanning. Field results indicated statistically significant differences over time in roadway support characteristics between flooded and nonflooded areas. Support characteristics in some flooded areas did not recover over the duration of the research reported in this paper (7–8 months after flooding). Multivariate statistical analysis indicated that the dynamic composite stiffness of the flooded unpaved roads was highly dependent on the stiffness of the underlying subgrade layer. Voids were detected in culvert a...

Estimating Features of Underground Utilities: Hybrid GPR/GPS Approach

Ground penetrating radar (GPR) is capable of detecting, locating, and characterizing underground utilities in a non-destructive manner. However, processing raw GPR scans to estimate the buried depth and radius of underground utilities remains a challenge in practice, which can be attributed to two main constraints: (1) the necessity of the GPR scanning trajectory being perpendicular to the centerline of the utility to be scanned and (2) the requirement of knowing either the velocity of the GPR electromagnetic (EM) waves traveling through heterogeneous soils or the range of the utility’s radius. This paper presents a novel method to overcome the two limitations by simultaneously estimating the radius and the buried depth of underground utilities based on GPR scans and auxiliary global positioning system (GPS) data. First, GPR scans are pre-processed to extract raw data points. Thereafter, a generic hyperbola equation is proposed to model GPR raw data, which incorporates the relative angles between buried utilities and GPR scanning trajectories. The very important point (VIP) algorithm then is developed to estimate the radius and depth utilizing auxiliary GPS data. The proposed new method was validated using GPR field scans obtained under various settings and was found to increase the accuracy of estimating the buried depth and radius under a general scanning condition (i.e., when both the EM wave velocity and the range of the radius are unknown and the GPR scanning trajectory is not perpendicular to the centerline of the buried utility).

Application of ground penetrating radar for locating buried impediments to geotechnical exploration and piling

Geotechnical exploration in strata containing boulders pose problems leading to wear and tear of equipment and time and cost over-runs due to the inability to foresee their presence. In addition, piling through such strata, particularly on hill slopes, is also a vexing problem, especially in the case of large diameter piles, which are commonly used for high-rise buildings. In locations, where buildings had already existed and are now demolished for redevelopment, there could also be buried impediments like old foundations or active utilities and other objects. Ground penetrating radar (GPR) could help in locating the buried objects and obstructions to drilling, excavation, and piling. The study described here deals with the instance of a site, admeasuring 21 m by 30 m, of a demolished building where a high-rise is being planned. Owing to unavailability of plans of the forty-year old building, which was demolished, GPR scanning has been used successfully to locate several of the buried footings and some boulders. The available antennae had central frequencies of 80 and 200 MHz. It was possible to get adequate information through these for carrying out exploration and preliminary selection of the locations of the pile foundations for the new building. Apart from visual interpretation of the radargram, digital classification using support vector machines (SVM) has been carried out. The inputs for the classification have been derived through the application of Hilbert transform to the signal amplitudes after post-processing of the radar data.

Combined ground-penetrating radar (GPR) and electrical resistivity applications exploring groundwater potential zones in granitic terrain

Frequent failures of monsoons have forced to opt the groundwater as the only source of irrigation in non- command areas. Groundwater exploration in granitic terrain of dry land agriculture has been a major concern for farmers and water resource authorities. The hydrogeological com- plexities and lack of understanding of the aquifer systems have resulted in the failure of a majority of the borehole drillings in India. Hence, a combination of geophysical tools comprising ground-penetrating radar (GPR), multielectrode resistivity imaging (MERI), and vertical electrical sounding (VES) has been employed for pinpointing the groundwater potential zones in dry land agricultural of granitic terrain in India. Results obtained and verified with each other led to the detection of a saturated fracture within the environs. In GPR scanning, a 40-MHz antenna is used with specifications of 5 dielectric constant, 600 scans/nS, and 40 m depth. The anomalies acquired on GPR scans at various depths are confirmed with low-resistivity ranges of 27-50Ω ma t 23 and 27 m depths obtained from the MERI. Further, drilling with a down-the-hole hammer was carried out at two recom- mended sites down to 50-70 m depth, which were compli- mentary of VES results. The integrated geophysical anoma- lies have good agreement with the drilling lithologs validat- ing the MERI and GPR data. The yields of these bore wells varied from 83 to 130 l/min. This approach is possible and can be replicated by water resource authorities in thrust areas of dry land environs of hard rock terrain around the world.

Application of high-frequency ground penetrating radar to the reconstruction of 3D sedimentary architecture in a flume model of a fluvial system

Ground penetrating radar (GPR) offers a fast and efficient method for visualizing three-dimensional (3D) images of shallow subsurface structures. We investigated the application of GPR to nondestructive imaging of deposits formed in a small experimental flume using a high-frequency GPR antenna. The GPR measurements, made with a 1.6GHz antenna, were conducted on flume models of sandy fluvial systems. We conducted two experiments, one to reveal the penetration depth and resolution of the GPR antenna and to reconstruct the 3D architecture of fluvial deposits created in a flume, and the other to examine the characteristics of reflection boundaries. The experimental materials were mainly loamy soil. The first experiment showed that a 1.6GHz antenna was suited to laboratory use, offering a depth resolution of 2–3cm in full penetration of a bed 15–24cm thick. GPR scanning yielded an accurate reconstruction of the 3D architecture of a fluvial channel using magnetite marker beds. The second experiment also successfully imaged a 3D architecture using quartz sand instead of magnetite, and loamy soil, which have different relative permittivities. This research shows that GPR is a feasible technique for 3D analysis of experimental flume deposits.

Coastal changes from open coast to present lagoon system in Histria region (Danube delta)

Preoteasa, L., Vespremeanu-Stroe, A., Hanganu, D, Katona, O.,Timar-Gabor, A., 2013. In: Conley, D.C., Masselink, G., Russell, P.E. and O’Hare, T.J. (eds.), Coastal changes from open coast to present lagoon system in Histria region (Danube delta). Proceedings 12 th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 564-569, ISSN 0749-0208. Histria (Istros) is a Milesian colony founded on the Black Sea coast during the 7th c.BC. Nowadays, the remains of the ancient city are located 8 km inland form the Black Sea coast, on the continental edge of the Razelm-Sinoe lagoon system which forms the southern part of the Danube Delta. Significant environmental changes occurred during and after the ancient city’s lifetime, particularly related to dramatic shoreline displacement. The present study deals with the Late-Holocene coastal landscape transformation from the open-coast stage to the present-day lagoon system. Our research includes stratigraphic records by Ground Penetrating Radar scanning of the beach ridges, cores in lagoons and beach ridges and absolute age determination of the paleoshorelines. The study shows that the ancient city decoupling from the sea was due to the beach ridge plain development southward and eastward of the acropolis. The decline of the Histria city, documented during the 7th c. AD, temporally coincides with the decoupling of the city from the open coast as a consequence of the shoreline progradation. Discontinuous chronology and discordant stratigraphy obtained by OSL dating and GPR scanning of successive ridges document intense neotectonic movements which affected Saele-Chituc beach ridge plain. The seismic activity led to the recent drowning of its central part and the formation of the Sinoe lagoon; the same processes acted at the downdrift part of the Dunavat lobe and also in the areas presently occupied by Histria and Nuntasi Lakes. Several areas containing archeological remains are currently below sea-level due to local neotectonics.

Application of ground penetrating radar for coarse root detection and quantification: a review

Because of the crucial role coarse roots (>2 mm diameter) play in plant functions and terrestrial ecosystems, detecting and quantifying the size, architecture, and biomass of coarse roots are important. Traditional excavation methods are labor intensive and destructive, with limited quantification and repeatability of measurements over time. As a nondestructive geophysical tool for delineating buried features in shallow subsurface, ground penetrating radar (GPR) has been applied for coarse root detection since 1999. This article reviews the state-of-knowledge of coarse root detection and quantification using GPR, and discusses its potentials, constraints, possible solutions, and future outlooks. Some useful suggestions are provided that can guide future studies in this field. The feasibility and accuracy of coarse root investigation by GPR have been tested in various site conditions (mostly in controlled conditions or within plantations) and for different plant species (mostly tree root systems). Thus far, single coarse root identification and coarse root system mapping have been conducted using GPR, including roots under pavements in urban environment. Coarse root diameter and biomass have been estimated from indexes extracted from root GPR radargrams. Coarse root development can be observed by repeated GPR scanning over time. Successful GPR-based coarse root investigation is site specific, and only under suitable conditions can reliable measurements be accomplished. The best quality of root detection by GPR is achieved in well-drained and electrically-resistive soils (such as sands) under dry conditions. Numerous factors such as local soil conditions, root electromagnetic properties, and GPR antenna frequency can impact the reliability and accuracy of GPR detection and quantification of coarse roots. As GPR design, data processing software, field data collection protocols, and root parameters estimation methods are continuously improved, this noninvasive technique could offer greater potential to study coarse roots.

Investigating the role of buried-object radius and surface slope in energy efficiency of the developed GPR algorithm

Since ground penetrating radar (GPR) is a portable device, its battery life is very important for finishing scanning problematic area at the first time. Thus, importance of energy-efficient algorithm of GPR that we developed previously becomes more evident. This paper aims to investigate the effect of radius of buried object and layer surface slope on energy efficiency of the developed energy-efficient algorithm of GPR via computer simulations. Simulation models having a layer with wavy rough surface and a buried object were separately created. Critical values of wavy rough surface slope and buried object radius that guarantee energy efficiency at GPR scanning were determined. It was found that critical values changed with relative dielectric constant, conductivity, and depth of the layer or buried object. The simulations were carried out using 2D-finite difference time domain (FDTD) method in Matlab environment. Transverse electric mode and perfectly matched layer were applied while using 2D-FDTD approach.

Simulation Test of Equipment of Non-Contact Detection with GPR

The composite lining model of railway tunnel is set up and then simulation test is presented by non-contact detection with the simple detection equipment of ground penetrating radar (GPR) to study the main technique parameters of the equipment. The results show that the lining can be detected by the way, and the quality of GPR scan obtained in the simulation test decreases with the detection distance increasing. In the GPR scan obtained when keeping ground-coupled shielding antenna of 400MHz 20cm away from the ground(the distant from the bottom of GPR antenna to the surface of lining specimen), a variety of work conditions that has been preset in the experimental design can be identified, moreover, the location and range of both uncompacted backfill and cavity behind the lining etc. approach those that can be get when the antenna sticking to the lining, thus providing satisfactory qualitative interpretation of GPR scan. In addition, the deviation range of GPR non-contact detection is close to that when the antenna sticking to the lining, thus ensuring the detection value accuracy of lining thickness.

Ground‐Penetrating Radar Detection and Three‐Dimensional Mapping of Lateral Macropores: I. Calibration

Preferential flow of water through soil macropores is known to contribute to groundwater and surface water contamination as well as stream bank instability. However, research on the mechanisms and extent of soil macroporosity is limited due to the lack of a practical technique to study macropores in situ without disrupting the site's ecological function. In this paper, we present a ground‐penetrating radar (GPR)‐based methodology for detecting soil macropores smaller than 10 cm in diameter within 1 m of the soil surface and then creating a computerized tomogram of the macropore network. Manual and automated algorithms for macropore detection were tested for scan data collected using a 900‐MHz radar antenna in a field experiment with a silt‐loam soil. Buried polyvinyl chloride (PVC) pipes were used to simulate soil macropores of different diameters and fill contents intersected by GPR scan lines at four different angles. Pipes ≥ 3.00 cm in diameter were clearly detectable regardless of the scan line orientation relative to the target, and pipes with diameters as small as 1.85 cm were detected at perpendicular angles of intersection. In a second field experiment, PVC pipes of varying dimensions were buried at different depths to simulate a macropore network of preferential flow pathways. A branch‐node algorithm was developed that referenced GPR scan line detections to create an accurate computer‐generated three‐dimensional map of the pipe network.

Development of a control system for a multipurpose road repairing machine

In this paper an automatic control system for a multipurpose road pavement repairing machine (ROADMOTO) is introduced. The goal is to achieve cost savings and better work quality by means of automation. Before the actual repair work a GPR (Ground Penetrating Radar), a profilometer or laser scanning techniques are used for collecting information about the road. During the design phase a repair design file is created. The ROADMOTO machine is equipped with a GPS positioning unit and the repair design file can be used for automatic control of road repairing operations. The control system also offers a manual control mode as well as automatic height and slope control modes. This ensures flexibility, because the user can choose the control mode that best suits the situation. The process from data collection and design to automatic machine control is presented as well as the developed prototype system and results of the first tests.