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Utility detection and positioning on the urban site Sense-City using Ground-Penetrating Radar systems
Abstract
This paper presents the design of a novel Ground-Penetrating Radar (GPR) test site that has been integrated into the mini-city demonstrator Sense-City located at University Paris-Est (France). This test site provides several sources of measurement interest expressed by the presence of a multilayered soil with significant dielectric contrasts, and various dielectric pipes and blades buried at various depths in trenches filled with a backfill soil different from the natural soil. This paper presents experimental Bscans associated with the pipe zone acquired by three different GPR systems at frequencies ranging from 300 MHz to 1.5 GHz. The interpretation and comparison of the raw Bscans have allowed to characterize the dielectric properties of the soil layers, and to detect the hyperbola signatures of the buried pipes. The results of this study will help to guide future developments on polarization, operating frequency and signal processing to extract parameters (orientation, dielectric characteristics, position and size) associated with pipes.
... For indirect measurement in the case of underground utilities, validation in a test site with wellknown model answers is essential to train competent operators and analysts, understand the limitation and accuracy of GPR, and establish survey procedures. Some test sites are available worldwide, for example the Mapping the Underworld's test facilities in University of Birmingham [172], mini-city demonstrator Sense-City located at University Paris-Est [186] and also the indoor Underground Utility Survey Lab in The Hong Kong Polytechnic University [187] and Tongji University, Shanghai. ...
... Validation requires a site with known parameters of buried objects like depth, size, materials, etc. Some validation test sites are available worldwide, for example the Mapping the Underworld's test facilities in University of Birmingham [172], mini-city demonstrator Sense-City located at University Paris-Est [186] and also the indoor Underground Utility Survey Lab in The Hong Kong Polytechnic University [187] and Tongji University, Shanghai. ...
... The importance of awareness in spatial inaccuracy and uncertainties in utility location data.Metwaly (2015) [275] 400MHz Holy Mecca, Saudi Arabia No Reflected hyperbola classified sewage and PVC pipes; flood drain shafts and material interface were detected by reflected signals. Sagnard et al. (2016)[186] Yes 900MHz frequency surveygave better images of subsurface; spatial sampling with half wavelength was suggested; TM polarization not suitable for high impedance dielectric pipe. By interpretation and comparison of the Bscan allows characterize the dielectric properties of the soil layers.No Perpendicular-to-pipe scanning technique cannot handle multiple closed objects. ...
The GPR (Ground Penetrating Radar) conference in Hong Kong year 2016 marked the 30th anniversary of the initial meeting in Tifton, Georgia, USA on 1986. The conference has been being a bi-annual event and has been hosted by sixteen cities from four continents. Throughout these 30 years, researchers and practitioners witnessed the analog paper printout to digital era that enables very efficient collection, processing and 3D imaging of large amount of data required in GPR imaging in infrastructure. GPR has systematically progressed forward from “Locating and Testing” to “Imaging and Diagnosis” with the Holy Grail of 'Seeing the unseen' becoming a reality. This paper reviews the latest development of the GPR's primary infrastructure applications, namely buildings, pavements, bridges, tunnel liners, geotechnical and buried utilities. We review both the ability to assess structure as built character and the ability to indicate the state of deterioration. Finally, we outline the path to a more rigorous development in terms of standardization, accreditation, and procurement policy.
... Before locating underground utilities, some preprocessing methods are required, such as background removal algorithm [102] and pipes visibility increase [24]. Existing studies [53,[103][104][105][106][107][108] have been implemented for positioning and mapping utilities. In [105], the interpretation and comparison of the raw B-scans associated with the different pipe zone and three different GPR system frequencies have allowed us to detect the hyperbola signatures of the buried pipes. ...
... Existing studies [53,[103][104][105][106][107][108] have been implemented for positioning and mapping utilities. In [105], the interpretation and comparison of the raw B-scans associated with the different pipe zone and three different GPR system frequencies have allowed us to detect the hyperbola signatures of the buried pipes. The study [107] about the visualization of urban utilities was conducted based on the integrated model of GPR and robotic terrestrial positioning system (TPS). ...
Ground penetration radar (GPR) technology has received in-depth analysis and rapid development in the field of civil engineering. GPR data analysis is one of the basic and challenging problems in this field. This research aims to conduct a comprehensive survey of the progress from 2015 to the present in GPR scanning tasks. More than 130 major publications are cited in this research covering different aspects of the research, including advanced data processing methods and a wide variety of applications. First, it briefly introduces the data collection of the GPR system and discusses the signal complexity in simulated/real scenes. Then, it reviews the main signal processing techniques used to interpret the GPR data. Subsequently, the latest GPR surveys are considered and divided according to four application domains, namely bridges, road pavements, underground utilities, and urban subsurface risks. Finally, the survey discusses the open challenges and directions for future research.
... It can detect early-stage water leakages in different pipe materials, not limited to PVC pipes and metallic pipes, as found in different lab-scale experiments (Ayala-Cabrera et al. 2011;Bimpas et al. 2010;Cataldo et al. 2014;Crocco et al. 2009;Demirci et al. 2012;Glaser et al. 2012;Goulet et al. 2013;Lai et al. 2016Lai et al. , 2017bOcaña-Levario et al. 2018). GPR is widely used as a non-destructive method for detection and mapping of buried, near-surface utilities (e.g., Metwaly 2015; Prego et al. 2017;Sagnard et al. 2016). The primary reason for GPR being used in the detection of pipe-water leakages is the mechanism of dielectric polarization, where water molecules in free form contained in a material are polarized by an incident GPR wave, thus reducing GPR wave velocity. ...
... The basic principle of laser-based scanning is that it will continuously generate a laser beam, which is projected around the pipe-interior. It highlights and profiles the crown shape at each point along the pipe alignment (Read 2004). The limitation of laser-based scanning survey is that it can only be used reliably above the water surface. ...
The invisible and congested world of underground utilities (UU) is an indispensable mystery to the general public because their existence is invisible until problems happen. Their growth aligns with the continuous development of cities and the ever-increasing demand for energy and quality of life. To satisfy a variety of modern requirements like emergency or routine repair, safe dig and excavation, monitoring, maintenance, and upscaling of the network, two basic tasks are always required. They are mapping and imaging (where?), and diagnosis (how healthy?). This chapter gives a review of the current state of the art of these two core topics, and their levels of expected survey accuracy, and looks forward to future trends of research and development (Sects. 24.1 and 24.2). From the point of view of physics, a large range of survey technologies is central to imaging and diagnosis, having originated from electromagnetic- and acoustic-based near-surface geophysical and nondestructive testing methods. To date, survey technologies have been further extended by multi-disciplinary task forces in various disciplines (Sect. 24.3). First, it involves sending and retrieving mechanical robots to survey the internal confined spaces of utilities using careful system control and seamless communication electronics. Secondly, the captured data and signals of various kinds are positioned, processed, and in the future, pattern-recognized with a database to robustly trace the location and diagnose the conditions of any particular type of utilities. Thirdly, such a pattern-recognized database of various types of defects can be regarded as a learning process through repeated validation in the laboratory, simulation, and ground-truthing in the field. This chapter is concluded by briefly introducing the human-factor or psychological and cognitive biases, which are in most cases neglected in any imaging and diagnostic work (Sect. 24.4). In short, the very challenging nature and large demand for utility imaging and diagnostics have been gradually evolving from the traditional visual inspection to a new era of multi-disciplinary surveying and engineering professions and even towards the psychological part of human–machine interaction.
... These anchors are obtained by scanning feature map using the sliding window. The Faster R-CNN defines three scales [8,16,32] and three ratios [0.5, 1.0, 2.0], combing 9 anchor boxes in different shapes. The Mask R-CNN and the MS R-CNN adopt the same design as Faster R-CNN. ...
... In model testing configuration stage, we evaluate an appropriate threshold value of 0.5 for NMS in RPN stage and a score threshold of 0.8 in R-CNN stage. In RPN stage, the anchoring scheme is updated with aspect_scale = [16] , aspect_ratios = ...
Ground penetrating radar (GPR) has been widely used as a non-destructive technique to detect subsurface objects. Manual process and interpretation of GPR data is tedious and time-consuming. To address this challenge, an automatic method based on a deep instance segmentation framework is developed to detect and segment object signatures from GPR scans. The proposed method develops the Mask Scoring R-CNN (MS R-CNN) architecture by introducing a novel anchoring scheme. By analyzing the characteristics of the hyperbolic signatures of subsurface objects in GPR scans, a set of anchor shape ratios are optimized and selected to substitute the predefined and fixed aspect ratios in the MS R-CNN framework to improve the signature detection performance. In addition, transfer learning technique is adopted to obtain a pre-trained model to address the challenge of insufficient GPR dataset for model training. The detected and segmented signatures can then be further processed for target localization and characterization. GPR data of tree roots were collected in the field to validate the proposed methods. Despite the noisy background and varying signatures in the GPR scans, the proposed method demonstrated promising results in object detection and segmentation. Computational results show that the improved MS R-CNN outperforms the other state-of-the-art methods.
... • an utility zone built under the urban test bed Sense-City in Marne-La-Vallée (France) [9]. This zone is under the 10 m wide traffic circle with lawn at the center. ...
... A 3D full-wave FDTD modeling using the commercial software EMPIRE has enabled to analyze EM phenomena as a function of parameters such as soil and pipe permittivity, pipe depth, and antenna polarization and make comparison with experimental results [8], [9]. The complete SFCW GPR made of a pair of shielded bowtie slot antennas (frequency band [0.46 ; 4] GHz) and designed on a FR4 substrate (real relative permittivity ε ′ = 4.4 and thickness e = 1.6 mm) has been modeled in the presence of a semiinfinite soil [7]. ...
The extraction of quantitative information from Ground Penetrating Radar (GPR) data sets (radargrams) to detect and map underground utility pipelines is a challenging task. This study proposes several algorithms included in the main stages of a data processing chain associated with radargrams. It comprises pre-processing, hyperbola enhancing, hyperbola detection and localization, and parameter extraction. Additional parameters related to the GPR system such as the frequency band and the polarization bring data sets additional information that need to be exploited. Presently, the algorithms have been applied step by step on synthetic and experimental data. The results help to guide future developments in signal processing for quantitative parameter estimation.
... Ground penetrating radar (GPR) which provides a solution for the demand above, is a non-invasive technology that emits high-frequency (10 GHz-1 MHz) electromagnetic waves into the ground to explore the structure of geological bodies and image the distribution of the subsurface media (Daniels, 2004). Due to its great sensitivity, high resolution, convenient operation, and non-destructive, GPR is widely applied in many fields, such as geological survey (Alsharahi et al., 2019), bridge evaluation (Biscarini et al., 2020), railway detection (Shapovalov et al., 2022), archaeology (Işık et al., 2022), and so on (Sagnard et al., 2016). Furthermore, it has become more demanding to reconstruct and image the target body parameters with increasingly sophisticated and complicated exploration objects. ...
Full waveform inversion (FWI) of common-offset ground penetrating radar (GPR) data can make up for the defects of the traditional prospecting technology such as destructive, cumbersome, and low efficiency, which also provides a robust and high-precision tool for quantitative assessment of subsurface prospecting. Nonetheless, conventional GPR-FWI is of limited practicality since the deficiency of accurate source wavelet and tremendous computational cost. We develop an efficient source-independent inversion algorithm based on the convolution method to eliminate the influence of source wavelet and enhance the algorithm efficiency to inverse field data. To suppress the noises induced by the convolution and cross-correlation operations, the time window is introduced in the reference trace which is selected automatically by singular value decomposition (SVD). The stochastic strategy reduces the computational cost by source subsampling. The synthetic model of a complex lens body demonstrates that source-independent FWI with time window has more tolerant to the initial model and noise, and the stochastic strategy improves the efficiency with ensured inversion accuracy. In the field GPR data of a sand trough containing two anomalous bodies, our algorithm has good adaptability and can accurately reconstruct the distribution of the permittivity and conductivity of the subsurface media without accurate estimation of the source wavelet. The results above indicate that the proposed algorithm in this study is valid for common-offset GPR data and improves the inversion efficiency by 1.24 to 3.10 times, which shows great potential to promote qualitative assessment in real-time subsurface exploration.
... Both studies indicated the importance of employing GPR surveys before the excavation process. Sagnard et al. [158] applied various GPR systems having different frequencies that range from 300 MHz to 1.5 GHz. The aim of this study was to detect and position the buried pipes in a city in France. ...
The condition assessment of civil engineering concrete-made structures has been a prevalent research area over the last thirty years as a result of concrete deterioration mechanisms that may compromise the integrity and durability of civil infrastructure. Ground Penetrating Radar (GPR) has been extensively used for the inspection and probing of concrete structures. Nevertheless, a comprehensive state-of-the-art review on the developments of condition assessment of concrete-made structures using GPR in a civil engineering perspective is missing in the literature. This paper aims at addressing the abovementioned limitations and contributes to the body of knowledge by leveraging a mixed methodology approach that incorporates the scientometric and systematic analyses on research work related to the condition assessment of civil constructions. Scopus database is used in this study where the state-of-the-art of GPR-based condition assessment models for civil engineering systems is described in conjunction with models' contributions, shortcomings, methodologies, and critiques. These systems include roads, bridges, structures, concrete elements, tunnels, and other civil engineering disciplines such as underground pipes and treatment plants. Finally, future research directions are recommended to guide the civil engineering community in identifying the crucial topics to be explored in the upcoming years.
... Based on this prime study, Ristic et al. [8] performed a finer radius estimation by using a new version of the hyperbola-fitting algorithm. For calibration and QA/QC of different data-processing methods and hardware, several test sites have been built for testing GPR's ability to detect buried pipes at different depths and surrounding media conditions [9,10] using information inferred from signal amplitudes such as fullwaveform inversion (e.g., Klotzsche et al. [11]) to infer filling dielectric properties [12]. ...
The detection of water leakage along its transportation network has important societal impacts, such as avoiding a large volume of water wasted along the waterways or preventing water-related chemical or physical surrounding media deterioration. Among the vast domain of destructive techniques, Ground-Penetrating Radar (GPR) is a common and efficient tool used for detection in many near-surface contexts, and it is particularly efficient in civil engineering cases, such as utility detection, due to its fine resolution and the ease of data acquisition. A peculiar form of signal enhancement appears in GPR profiles recorded over spheres and cylinders where velocity contrasts exist between the body’s material and the surrounding medium. We used this enhancement to detect potential water leakages in water pipes. After exhibiting the signal enhancement effect in a laboratory sandbox experiment using a spherical glass ball, we verified the results with numerical experiments with varied sphere and cylinder sizes and dielectric properties. We then investigated field and numerical experiments of GPR transects above a “real life” water-leaking PVC pipe. Our results show that the water cylinder and water infiltration bulb produced a characteristic signal that could be used for detecting water leakages along water pipes. The largest amplitude in the GPR signal is caused by a bottom pipe reflection enhanced by the water bulb and not by the top of the pipe. We stress the risk of miscalculating the pipe’s depth during velocity estimation when amplitude enhancement conditions are met. Beyond civil-engineering impacts, knowledge on signal amplification phenomena can help GPR data interpretations in sedimentology and hydrogeology studies.
... Algumas pesquisas fazem uso dos registros acústicos e radares de penetração no solo, sendo que o primeiro processo utiliza a diferenciação entre os ruídos em condições normais e em situações anômalas, e com a utilização de radares é fornecido o perfil transversal do solo ao redor das tubulações (Hunaidi et al. 2004). No entanto, a utilização desses métodos pode ser demorada e onerosa, principalmente para grandes áreas urbanas devido à saturação de dutos subterrâneos, à proximidade entre eles e aos seus materiais (Sagnard et al. 2016). Há, ainda, um ramo de pesquisa que busca a detecção e localização de vazamentos de forma automatizada através de dados hidráulicos emitidos por sensores de monitoramento, como vazão, pressão e níveis de reservatórios, em conjunto com técnicas de análise de dados (Hu et al. 2021). ...
Os vazamentos nas redes de distribuição de água geram perdas físicas e monetárias, além de gerar riscos as infraestruturas urbanas. Por isso, detectar vazamentos de forma rápida e automática é um passo importante para evitar maiores comprometimentos. Esse artigo apresenta uma metodologia para detectar vazamentos por meio dos dados de monitoramento de qualidade da água e da análise de parâmetros de grafos. Para isso, um grafo é criado com a correlação entre os dados de qualidade assim que são emitidos pelos sensores de monitoramento. Após isso é realizado um ranqueamento de vértices pela métrica PageRank e quando o valor desse ranqueamento se altera é identificado um comportamento anômalo. A metodologia foi testada com a simulação de vazamentos numa rede benchmark e avaliada por meio da acurácia de uma matriz de confusão. Os resultados alcançaram uma taxa 85,6% de acurácia e a qualidade da água se mostrou uma fonte de informação mais vantajosa que a utilização de dados de pressão. ABSTRACT-Leaks in water distribution networks generate physical and monetary losses, in addition to generating risks for urban infrastructure. Therefore, detecting leaks quickly and automatically is an important step to avoid further compromises. This article presents a methodology for leak detection using water quality monitoring data and analysis of graphical parameters. For this, a graph is created with the correlation between the quality data as they are emitted by the monitoring sensors. Then, a ranking of vertices is performed by the PageRank metric and when the value of this ranking changes, an anomalous behavior is identified. The methodology is tested by simulating leaks in a reference network and evaluated through the accuracy of a confusion matrix. The results reached an accuracy rate of 85.6% and the water quality proved to be a more advantageous source of information than the use of pressure data. Palavras-Chave-Redes de distribuição de água; Detecção de vazamentos; Qualidade da água; Teoria dos Grafos. INTRODUÇÃO O fornecimento de água para abastecer as cidades necessita de redes de distribuição de água (RDA) cada vez maiores e mais complexas. Os danos nos elementos da RDA acarretam em grandes impactos no processo de distribuição e também na hidráulica e qualidade da água (Hu et al. 2021). Uma parcela desses danos está ligada aos rompimentos e fissuras nas tubulações; falhas nas juntas; erros nas medições; e furtos, ocasionando perdas por vazamento de uma grande parcela da água captada e tratada (Silva et al., 2021). Estima-se que em 2019 o Brasil perdeu cerca de 38% da água
... 3. Stochastic disturbance (move): Keeps the number of layer interfaces unchanged and randomly selects a floating layer interface to change its position. 4. No change (rho): The number of layers and the position of the interface remain unchanged. ...
Ground penetrating radar (GPR) and transient electromagnetic (TEM) technologies can detect urban underground space efficiently and with good sensitivity. These two technologies have complementary advantages, but they are often used independently in urban underground space detection and rarely used for the integrated interpretation of urban geology. To realize the high-resolution measurement of urban underground space, we take the shallow structure information of GPR as the input information of TEM inversion, and use the transdimensional Bayesian (Trans-Bayes) inversion method to realize an integrated interpretation of TEM and GPR data. The simulation results show that, compared with inversion using only TEM data, an integrated inversion improves the accuracy of the inversion results, retains the lateral smoothness of the two-dimensional model, and reduces the multiple solutions of the TEM inversion. In addition, the richer the layer interface information provided by GPR, the more significant the improvement in inversion quality. We successfully applied GPR and TEM technologies to the accurate detection of an urban underground air-raid shelter area, and verified the superiority of GPR in improving the resolution of TEM shallow geological imaging. The combination of GPR and TEM provides a new idea for the high-resolution measurement of urban underground space geology, and has practical application value in the accurate early warning of underground water gushing and road collapse accidents.
... A 3D GPR data set can be created from several 2D profiles acquired along parallel survey lines, of which the interval should be less than half of the apparent wavelength at the operating frequency (Conyers and Goodman, 1997). Up to now, such a 3D GPR survey method has been used for imaging cracks in buildings and bridges (Orlando and Slob, 2009;Benedetto, 2013;Panisova et al., 2016), pavement thickness evaluation (Zhao and Al-Qadi, 2016), detection of underground utilities (Jeng and Chen, 2012;Sagnard et al., 2016), and archaeology (Leucci and Negri, 2006;Zhao et al., 2013). Nevertheless, a GPR survey along the dense survey lines using a single-channel GPR system is time-consuming. ...
Cavities under urban roads have increasingly become a great threat to the traffic safety in many cities. As a quick, effective, and high-resolution geophysical method, ground penetrating radar (GPR) has been widely used to detect and image near-surface objects. However, the interpretation of field GPR data is still challenging. For example, it is hard to distinguish reflections caused by road cavities or other urban utilities by a conventional 2D GPR survey. The superiority of 3D GPR in data interpretation is demonstrated by a laboratory experiment. Two pipes and a glass-made cavity buried in a sandpit show similar hyperbolic reflections in the 2D GPR profiles, and are hard to be discriminated. In contrast, their geometric shapes and dimensions are readily identified in the 3D image reconstructed from the synthetic 3D GPR dataset. Thus, a car-mounted 3D GPR system with two antenna arrays oriented in different polarization directions is developed, and has detected over 100 cavities in three Chinese cities over the past one year. The field data of two of the cavities are presented. As a result, the cavity depth, horizontal size and height can be accurately estimated from the 3D GPR dataset. Both laboratory and field experimental results indicate that 3D GPR possesses a great potential in detection and recognition of road cavities and utilities in the complicated urban environment.
... An investigation to map and identify the subsurface in Holy Mecca. Sagnard et al., [14] used the GPR in terms of multilayered soil with dielectric, and various dielectric pipes and blades buried at various depths at Paris city. A review of the application of GPR methods presented by Zajícováet al., [15] was about using the GPR in different soil studies [16]. ...
This work aims to analysis and detects the reasons of the collapse of a road in northern Morocco using simulation based on the Finite-Difference Time-Domain method (FDTD) and a real survey by ground-penetrating radar (GPR) method. In the simulation, we test several targets buried in dry soil at the same depth. Depending on the simulation results GPR survey is done in two zones. The first zone shows multiple strong reflections, it indicates the presence of cavities. In the second zone, the profiles show the presence of the cavities and fragile lands saturated. Based on the results of the analysis and investigation experimental results, it is found that the causes of collapses on the road are due to the presence of the cavities and fragile lands saturated with water. This contribution can be effective and successful in studying areas when establishing infrastructure projects to avoid any risks that in the future.
... The rising interest of those aspects are evidenced by the inclusion of the matter in ad-hoc sessions of international workshops and conferences [33][34][35][36] and by the increment of special issues of international journals aiming to provide an enrichment of showcases for urban geophysics [37][38][39]. Nevertheless, some applications can be found in current literature, providing information on cavity individuation [40], geological mapping [41,42], archaeological investigations [43][44][45] and underground pipe detection [46,47]. ...
This paper deals with the application of non-destructive geophysical techniques of investigation in the urban environment of the city of Nicosia (Cyprus). The main aim of the research was, in the frame of the Eleftheria Square redesign project, to image subsurface properties in order to reduce the impact of hazards on the old buildings (therefore preserving the cultural heritage of the place), and on the new infrastructure under construction. Since 2008, electrical resistivity tomography (ERT), ground penetrating radar (GPR) and induced electromagnetic method (EMI) were employed during the different phases of the project to provide an understanding of geological stratigraphy, the detection of buried objects (archaeological structures and underground utilities) and the solution of unexpected events (such as water infiltration in the course of works). The geophysical results proved the efficiency of the adopted methods, adding scientific value to the knowledge of the studied area. The new gathered information helped the public administration technicians to plan direct and targeted interventions and to modify the original design of the project according to the discovery of archaeological findings.
... Ground penetrating radar (GPR) [1] can be effectively used to map the location of all kinds of buried services without destroying any structure. This is a crucial task in the frame of civil-engineering works performed in urban areas [2,3]. GPR is capable of finding utilities made of metallic, plastic, concrete, asbestos, and other materials; different underground features can be mapped, as well, such as cavities, chambers, basements, foundations, obstructions, reinforced concrete layers, and more. ...
... Lai et al. (2018) describe various applications of GPR, highlighting the importance for mapping underground utilities in urban contexts both for plastic water pipe leak detection and for detecting voids under roadways and concrete sections of underground utilities. Sagnard et al. (2016) highlighted the problems relating to uncertainties when using GPR acquisitions for utility detection. They designed and built a test site with objects of known size placed at different depths for studying the capability of GPR to investigate, in time and frequency domains, physical phenomena induced by dielectric and conductive utilities, while also monitoring the polarization of the signal for the detection and identification of buried objects. ...
Geophysical investigations could provide a valid tool for the identification of possible causes of settlement phenomena that affect civil buildings. They provide a non-invasive method of obtaining high-resolution information about the subsoil, saving time and money. However, uncertainties related to the accurate interpretation of the acquired data could potentially reduce the value of these methods. For this reason, the integration of non-invasive tests with direct measurements to support geophysical data interpretation is strongly recommended. This is a fundamental step in the process of defining a sufficiently reliable geological model to explain the cause of failure. Among the various geophysical techniques, electrical resistivity tomography and ground penetrating radar offer significant advantages for monitoring the status of the conservation of civil engineering structures and infrastructures. This paper presents the most recent and beneficial advances of the use of electric and electromagnetic geophysical methods in the field of civil engineering, with particular attention to their applications for monitoring subsidence and settlement phenomena. Finally, the possibilities of the joint use of resistivity and electromagnetic methods for studying the causes of the structural decay that affects two precast buildings are monitored and discussed. The results demonstrate the capability of combining non-destructive geophysical techniques with direct data, for evaluating the safety of building constructions and solving geotechnical problems.
... Other key factors influencing the effectiveness of the method are the material properties as well as the position, orientation and size of the reflector [17,18]. Lastly, the resulting GPR data quality greatly depends on the configuration and parameters used in field data acquisition. ...
... Cassidy et al. (2011) confirmed that practical experience plays a remarkable role in determining suitable values for imaging parameters. Some research has tended to skate over the process of 3D image production (Alani et al., 2013;Hugenschmidt and Kalogeropoulos, 2009;Porsani et al., 2012;Sagnard et al., 2016). Lualdi et al. (2003) point out that system resolution and antenna positioning accuracy are vital for high-quality 3D GPR imaging, while denser measurements ensure that image degradation is minimized. ...
GPR has been widely acknowledged as an effective and efficient technique for imaging the subsurface. But the process of constructing 3D GPR images (C-scans) is still subjective and mainly relies upon the operator's knowledge and experience. This study reviews the parameters that affect GPR imaging quality: namely, profile spacing (PS), slice thickness (ST) and interpolations. Feature characteristics that have a crucial influence on imaging quality were also identified. Through conducting 25 carefully designed empirical experiments on concrete as well as subsurface structures, the relationship between 3D imaging parameters and feature characteristics were observed. A general workflow was derived for GPR C-scan generation, which is analogous to the typical signal processing steps used in 2D radargram signal processing (Jol, 2009). Empirical values in workflow were based on the retrieval of known ground-truth data and comparison with the processed images, i.e. the closest to reality. Unlike 2D processing, the workflow for 3D is feature-oriented and case-specific, and the proposed workflow gives guidelines on suitable ranges for 3 major parameters when used in a variety of applications. It was identified that feature shapes and the ratios of feature size to radar footprint are of vital importance. With the proposed flowchart, the often vague “survey experience” is parametrized and standardized, and the upper and lower limits governing the generation of objective and trustworthy 3D GPR images are defined. This workflow for GPR 3D slice imaging also paves the way for GPR feature extraction and change detection commonly adopted in remote sensing.
... Lai et al. (2018) describe various applications of GPR, highlighting the importance for mapping underground utilities in urban contexts both for plastic water pipe leak detection and for detecting voids under roadways and concrete sections of underground utilities. Sagnard et al. (2016) highlighted the problems relating to uncertainties when using GPR acquisitions for utility detection. They designed and built a test site with objects of known size placed at different depths for studying the capability of GPR to investigate, in time and frequency domains, physical phenomena induced by dielectric and conductive utilities, while also monitoring the polarization of the signal for the detection and identification of buried objects. ...
... Based on the geological observation, the study area composed of shell which was believed to be a natural occurring event. Guar Kepah also referred as Guar Kepah hill or Bukit Cengkerang (shell midden) as the site consists of shell middens located on sandy ridges [5]. The study area covered about 14 m X 20 m. ...
A Ground Penetrating Radar (GPR) survey was conducted at Guar Kepah to detect buried object before commencement of archaeological gallery construction. The study area covered around 20 m length and 14 m width. 15 GPR lines were constructed from north to south with 20 m length, 1 m spacing and parallel to each other. The 500 MHz closed antenna had been used in this study. The surface findings were noticed before started GPR survey. The data was analysed and interpreted by using Groundvision software and several filters were applied to radargrams to enhance the data. Based on the result, several anomalies were detected. The surface findings also detected by GPR which cause hyperbolic curve in radargrams. The subsurface layer was detected by GPR survey. The anomalies are assigned to several classes based on the pattern of signals obtained in radargrams.
... A catalogue of available test sites and laboratories, where GPR equipment, methodology and procedures can be tested, was prepared and is available online [13]. Additionally, WG 2 carried out a wide series of case studies where GPR was successfully employed in civil-engineering works and laboratory tests; some examples are found in [14][15][16][17][18][19][20]. ...
This paper aims to present a wide dataset of ground penetrating radar (GPR) profiles recorded on a full-size geophysical test site, in Nantes (France). The geophysical test site was conceived to reproduce objects and obstacles commonly met in the urban subsurface, in a completely controlled environment; since the design phase, the site was especially adapted to the context of radar-based techniques. After a detailed description of the test site and its building process, the GPR profiles included in the dataset are presented and commented on. Overall, 67 profiles were recorded along eleven parallel lines crossing the test site in the transverse direction; three pulsed radar systems were used to perform the measurements, manufactured by different producers and equipped with various antennas having central frequencies from 200 MHz to 900 MHz. An archive containing all profiles (raw data) is enclosed to this paper as supplementary material. This dataset is the core part of the Open Database of Radargrams initiative of COST (European Cooperation in Science and Technology) Action TU1208 “Civil engineering applications of Ground Penetrating Radar”. The idea beyond such initiative is to share with the scientific community a selection of interesting and reliable GPR responses, to enable an effective benchmark for direct and inverse electromagnetic approaches, imaging methods and signal processing algorithms. We hope that the dataset presented in this paper will be enriched by the contributions of further users in the future, who will visit the test site and acquire new data with their GPR systems. Moreover, we hope that the dataset will be made alive by researchers who will perform advanced analyses of the profiles, measure the electromagnetic characteristics of the host materials, contribute with synthetic radargrams obtained by modeling the site with electromagnetic simulators, and more in general share results achieved by applying their techniques on the available profiles.
... Esto aportaría algo importante a nuestra investigación, como trabajar patrones pequeños de ondas y con características relevantes para construir nuestro algoritmo y simulación, si es el caso. Además de las diferentes aplicaciones que se le han dado dentro de la geofísica [47][48][49][50][51][52], que ve la importancia del estudio de las ondas penetrantes por la información que traen para ser codificada y controlada y, de esta manera, obtener un mejor beneficio, como lo plantean los artículos que en este caso centran su estudio en las GPR [48][49][50][51][52][53][54][55][56][57][58][59][60], pero sin ver lo microscópico del asunto que aportaría mucha información a los modelos por construir. ...
El principal objetivo de esta investigación es conocer las diferentes tecnologías implementadas para la detección de minas antipersonales. Por diferentes medios bibliográficos se estudiaron las últimas actualizaciones empleadas para la detección de objetos enterrados, los factores que afectan la pérdida de energía de las ondas como transmisoras de información entre estos, las características del suelo, la amplitud de la señal emitida, la frecuencia y las condiciones del terreno. En este artículo se informa sobre los medios computacionales, de su trabajo con los diferentes algoritmos para modelar una información acertada de lo que está sucediendo con el fenómeno de detección. Asimismo, se dan a conocer a la comunidad científica los parámetros de susceptibilidad magnética, el porcentaje de agua y porosidad del entorno donde reaccionan las ondas emitidas, la dificultad de la estabilidad de la señal que se ha de capturar para detectar las minas antipersonales, en un contorno geográfico. En la actualidad se están utilizando tubos de PVC, latas y jeringas para su fabricación, y dispositivos de manipulación manual para su activación. Las ondas van a tener un comportamiento diferente ante estos materiales.
... Other key factors influencing the effectiveness of the method are the material properties as well as the position, orientation and size of the reflector [17,18]. Lastly, the resulting GPR data quality greatly depends on the configuration and parameters used in field data acquisition. ...
... Other key factors influencing the effectiveness of the method are the material properties as well as the position, orientation and size of the reflector [17,18]. Lastly, the resulting GPR data quality greatly depends on the configuration and parameters used in field data acquisition. ...
This work presents the ground penetrating radar as a non-destructive solution to detect buried pipes and minimize the impacts to the services in the intervention area such as leakages in the buried utilities, particularly massive in urban areas. An experimental zone was built including various types and configurations of piping. Different antenna frequencies and parameter setting were tested in order to provide an efficient field data acquisition that guarantees accurate results in detection. For shallower pipes, a 2.3 GHz antenna with 2 cm of trace-interval has provided the best results. However, 1 GHz and 800 MHz data have revealed complementary information when surveying deeper pipes.
Rock mass consists of intact rock material and joints. Different joint parameters like orientation, spacing, persistence, aperture, infilling play important role in tunnel excavation. In drill and blast tunnel excavation, the propagation of blast shock wave differs from one rock mass to another rock mass based on their properties, because of which nature of rock fragmentation differs. All these directly affects the outcome of tunnel blasting. This study establishes the relationship between different joint parameters and excavation volume. In order to do so four different tunnel section of same tunnel alignment, with different joint properties were chosen and then collected data was processed to understand how different joint properties lead to different excavation volume within same tunnel. It was found that when the strike of the joint is parallel to the tunnel axis, the excavation volume obtained from blasting is comparatively higher than that when strike of joint is perpendicular to the tunnel axis, because when joints are parallel to the tunnel axis there is minimum reflection of blast wave from joint plane causing it to travel farther, increasing the fragmentation process. Shape analysis of blast fragments and natural rock block obtained from 3DEC was done in order to find the effect on fragmentation process. It was found that both blast fragments and natural rock block have similar percentage of different shape class proving fragmentation process during blasting of rock mass follows joint pattern, since they are the weak surface in rock mass.
Construction of infrastructure development projects in urbanized environment suffers with obstructions like lack of surface free space, underground utilities, traffic and shallow drainage system. These obstructions hamper the work progress as well as major factor for project delay
and cost overruns. Obtain timely solution to these obstructions helpful in meeting the deadlines and reduce the inconvenience to the public. One such case was discussed here, where Mumbai Metro Rail Corporation Limited (MMRCL) proposed to construct a 33.5 km long underground metro rail tunnel between Colaba and SEEPZ. TBM was deployed to make 5.8 m dia tunnel at a depth of 18 m. After 265 m of tunnel excavation, water seepage was encountered with a high discharge flow rate of 60,000–80,000 L/h at Marol Naka station box area. To plug this flow path, Identification of source location or the direction of flow path is the prime concern. Surface investigations to identify this flow path were not possible, due to heavy traffic, shallow underground utilities and congested area. Ground Penetrating Radar (GPR) investigations through boreholes were proposed to delineate the probable water seepage flow path. Five bore holes were drilled over the station box area up to a depth of 25 m. Five sets of tomography investigations were carried out to map the high/low attenuation zones based on the radar wave attenuation characteristics of the subsurface medium. The Frequency Domain Attenuation Tomography (FDAT) analysis was done to characterize the attenuation pattern of observed radar wave signal in the dry as well as in the saturated medium. 3-D subsurface image was generated based on attenuation characteristics to demarcate the probable water seepage flow path in the study area.
KeywordsGround Penetrating RadarCross-hole tomographyWater seepageAttenuationUnderground metro tunnel
The use of modern information and communication technologies is an essential condition for the formation of the transport infrastructure of a smart city. Scientific and methodological approaches are developed to effectively monitor the transport infrastructure of a smart city based on multi-channel metric learning in the Internet of Things. The proposed solutions provide invariance to the type and nature of the movement of objects. The principles of technical implementation of the proposed method are substantiated using the characteristics of unmanned aerial vehicles of a smart city. Adaptive automatic switching of transport infrastructure monitoring channels is implemented in the form of a neural network analyzer software.
The transient electromagnetic method (TEM) is one of the most effective geophysical methods for detecting urban underground space. The underground resistivity distribution obtained by this imaging technique is important for engineers in urban construction and planning. The conventional transdimensional Bayesian (Trans-Bayes) imaging method gives the credible interval of the data model and quantifies the uncertainty in the imaging results. However, due to the large number of calculations needed and the slow speed of TEM forward modelling, the engineering practicality of Trans-Bayes method is poor. To solve this problem, we propose a fast Trans-Bayes imaging approach based on the Bayesian information criterion (BIC) and the adaptive Metropolis (AM) algorithm. Our simulation and field experiments show that this BIC-AM approach can greatly improve Trans-Bayes imaging efficiency while ensuring imaging accuracy. This method may provide fast uncertainty estimates for urban TEM data.
Towed transient electromagnetic method (TEM) is an efficient geophysical method for urban underground space measurement. However, compared with the field environment, the power harmonic noise as urban electromagnetic noise is the key reason for the low signal-to-noise ratio (SNR) of the towed TEM data. We propose an efficient preprocessing method based on a multi-step processing strategy, which can fast suppress power harmonic noise and improve SNR. Firstly, a pure power harmonic noise sample is obtained by the least-square fitting. Secondly, the noise component of the measurement data that is most relevant to this sample is quickly searched by an improved genetic algorithm. Finally, the power harmonic noise component is subtracted from the measurement data, and the SNR is significantly improved. The simulation and field experiments show that the new method can fast and effectively suppress power harmonic noise without signal distortion, and it is especially suitable for towed data processing.
The article presents an imaging approach for ground penetrating radar prospecting over a heterogeneous background soil characterized by a dielectric permittivity variation along depth. The proposed approach is based on a linear model of the electromagnetic scattering phenomenon, where the soil inhomogeneity in the reference scenario is accounted for by introducing an equivalent permittivity function. Such a function notably simplifies the computation of the kernel of the relevant linear integral equation to be inverted. Then, the data inversion is carried out in a regularized way by resorting to the truncated singular value decomposition scheme. A procedure for estimating the equivalent permittivity function, typically unknown in practical situations, is also proposed. Reconstruction results achieved from full-wave simulated data and real data collected in a controlled test site are provided to demonstrate the effectiveness and the reliability of the proposed imaging approach.
This paper describes in detail the applicability of the developed ground-penetrating radar (GPR) model with a kinematic GPR and self-tracking (robotic) terrestrial positioning system (TPS) surveying setup (GPR-TPS model) for the acquisition, processing and visualisation of underground utility infrastructure (UUI) in a real urban environment. The integration of GPR with TPS can significantly improve the accuracy of UUI positioning in a real urban environment by means of efficient control of GPR trajectories. Two areas in the urban part of Celje in Slovenia were chosen. The accuracy of the kinematic GPR-TPS model was analysed by comparing the three-dimensional (3D) position of UUI given as reference values (true 3D position) from the officially consolidated cadastre of utility infrastructure in the Republic of Slovenia and those obtained by the GPR-TPS method. To determine the reference 3D position of the GPR antenna and UUI, the same positional and height geodetic network was used. Small unmanned aerial vehicles (UAV) were used for recording to provide a better spatial display of the results of UUI obtained with the GPR-TPS method. As demonstrated by the results, the kinematic GPR-TPS model for data acquisition can achieve an accuracy of fewer than 15 centimetres in a real urban environment.
It is difficult to systematically classify and detect objects buried in tillage soil layers. There is no effective way to detect destructive objects in the soil. This paper presents a method and model of intelligently classifying hard objects of electromagnetic wave based on Finite Difference Time Domain (FDTD), especially the volume and shape of the object can destroy agricultural machinery in farming. It aims to improve the environmental detection technology of agricultural machinery and break through the limit of intelligent equipment. Firstly, in order to calculate the energy amplitude loss function of plane electromagnetic waves in farmland soil layer, the optimal Soil Layer and Electromagnetic Wave Model (SEM) is determined by using Blackman-Harris pulse as the excitation source; The absorption boundary condition of Uniaxial Perfectly Matched Layer (UPML) is also determined by test. Secondly, the forward modeling is performed by REFLEX and MATLAB software programming, the grid type forward modeling results, compared to electromagnetic wave results and real-time forward measured data by GPR in layered soil, there were verification and analysis. Measuring the relationship between different phase amplitude and electromagnetic wave energy between different materials, proved by experiment, the optimized 750 MHz excitation source function was verified experimentally and accuracy rate reached to 0.98 or 0.99 with FDTD model. The precision of actual depth and calculated depth of the object are not more than 0.02 m. The multi-channel amplitude analysis of five kinds of material of electromagnetic waves of metal, wood, PVC plastic, dry hard stone, and glass is obtained by SEM in different soil layers, and the classification accuracy is 100%, the optimal value of energy discrimination peak amplitudes of these five materials are 0.0183, 0.0028, 0.0043, 0.0069 and 0.0087. The research shows that the FDTD difference method is used to simulate the propagation mechanism of electromagnetic waves in the soil. The SEM of GPR forward modeling can be established efficiently and accurately. The results can provide theoretical and technical support for the GPR soil matter or objects classification system and agricultural machine farming modules to detect objects buried in the soil layer.
More than half of the world's population resides in urban areas, which has resulted in increased demand for utility services. Properly designed and well-managed utility infrastructure systems play an important role in the sustainability of cities. The complexity of underground utilities is highly problematic, as it has many types of service lines comprised of different materials. Damage to underground utilities during excavation is a serious problem that can result in casualties, injuries, project delays, disruptions in costly services, and large repair costs. Missing depth information, inaccurate available utility position data, and lack of visual guidance for utility locations have been identified as the major reasons for utility strikes during excavation operations. These accidents can be prevented if the machine operator is aware of the utility location with reference to the equipment position. In this paper, a novel approach is presented to model underground utilities for a machine guidance system to provide visual guidance to the operator. This approach is useful for avoiding catastrophic utility strike accidents and promoting safe excavation operations. Two case studies were conducted for reviewing the proposed methodology and its application in the machine guidance system. The underground utility data was collected by using GPR in combination with a highly accurate RTK GPS system. An uncertainty buffer zone is proposed that enclosed the true location of the utility as an extra safety measure to avoid a utility strike during excavation. The objective of this research is to devise a simple and easy process to model the underground utilities for a machine guidance system to promote safe excavation.
This paper describes in detail the development of a ground-penetrating radar (GPR) model for the acquisition, processing and visualisation of underground utility infrastructure (UUI) in a controlled environment. The initiative was to simulate a subsurface urban environment through the construction of regional road, local road and pedestrian pavement in real urban field/testing pools (RUTPs). The RUTPs represented a controlled environment in which the most commonly used utilities were installed. The accuracy of the proposed kinematic GPR-TPS (terrestrial positioning system) model was analysed using all the available data about the materials, whilst taking into account the thickness of the pavement as well as the materials, dimensions and 3D position of the UUI as given reference values. To determine the reference 3D position of the UUI, a terrestrial geodetic surveying method based on the established positional and height geodetic network was used. In the first phase of the model, the geodetic network was used as a starting point for determining the 3D position of the GPR antenna with the efficient kinematic GPR surveying setup using a GPR and self-tracking (robotic) TPS. In the second phase, GPR-TPS system latency was quantified by matching radargram pairs with a set of fidelity measures based on a correlation coefficient and mean squared error. This was followed by the most important phase, where, by combining sets of “standard” processing routines of GPR signals with the support of advanced algorithms for signal processing, UUI were interpreted and visualised semi-automatically. As demonstrated by the results, the proposed GPR model with a kinematic GPR-TPS surveying setup for data acquisition is capable of achieving an accuracy of less than ten centimetres
Most historic urban areas have a lack information regarding subsoil and buried structures (such as old utilities, private cellars, etc.). Therefore, when planning new engineering interventions, limited information of subsoil composition leads to greater risk when conserving and reclassifying historic urban areas. Obtaining information about potential sources of risk for infrastructures is important for civil engineering. However, only high-resolution information improves the management of important activities involving historic urban infrastructure. Although direct measurements can alleviate a lack of information concerning the subsoil, they are, generally, expensive, invasive and interferes with everyday use of the site for long periods. Therefore, the use of low or non-invasive technologies to quickly and accurately analyse the subsoil is preferable and strongly recommended. For this purpose, a new discipline, recently termed Urban-Geophysics, is developing rapidly. This paper describes an application of Urban-Geophysics in a historically important Italian town. In order to characterize the subsoil and identify the presence of natural voids and unknown anthropic underground structures such as cellars, an extensive geophysical investigation based on use of Electrical Resistivity Tomography and Ground Penetrating Radar to perform a survey in the town of San Benedetto del Tronto (Marche region, Italy) with a total time frame of around two days was carried out. Previously unknown buried structures and geological discontinuities were highlighted by using these geophysical techniques. In order to support and confirm the interpretation of the geophysical data, geotechnical drillings were carried out. Finally, direct data validated and supported the non-invasive geophysical results. The combined results have provided valuable information to the local authorities and engineers involved in the decision-making process for the construction of new underground structures.
Detection of leakage in a buried water pipe is a crucial issue, as underground pipes become aged and these pipes are often used as pathways for aggressive chemical agents. Nondestructive geophysical methods for identifying such underground leakages are of vital importance. Leakage detection in buried water pipes is sometimes carried out through use of specific acoustic methods. In this research we have used ground‐penetrating radar (GPR) as an alternative to such acoustic methods, because of the high sensitivity of electromagnetic waves to the presence of water in soil. This paper presents a methodology, illustrated by field‐scale GPR experiments. Four water leakage points in a buried, ductile, iron, main‐water pipe were pre‐designed within a full‐scale (20 m long x 10 m wide) experimental set up. This facility was paved half by reinforced concrete and half by other pavement blocks. Four GPR antennae with five nominal frequencies 200 MHz, 250 MHz and 400 MHz, 600 MHz and 900 MHz were tested. Using a modified algorithm for common offset GPR antennae, in this work we measure the changes in electromagnetic wave velocity and wave reverberation, which sense upward and downward leakages, respectively. Leakages could be identified most clearly with the 600 MHz GPR data. Our result suggests two potential applications in terms of detecting and defining the extent of multiple leakages in old water pipes, and testing and commissioning new pipes before and after pressurized tests.
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SPOT-GPR (release 1.0) is a new freeware tool implementing an innovative Sub-Array Processing method, for the analysis of Ground-Penetrating Radar (GPR) data with the main purposes of detecting and localizing targets. The software is implemented in Matlab, it has a graphical user interface and a short manual. This work is the outcome of a series of three Short-Term Scientific Missions (STSMs) funded by European COoperation in Science and Technology (COST) and carried out in the framework of the COST Action TU1208 “Civil Engineering Applications of Ground Penetrating Radar” (www.GPRadar.eu). The input of the software is a GPR radargram (B-scan). The radargram is partitioned in sub-radargrams, composed of a few traces (A-scans) each. The multi-frequency information enclosed in each trace is exploited and a set of dominant Directions of Arrival (DoA) of the electromagnetic field is calculated for each sub-radargram. The estimated angles are triangulated, obtaining a pattern of crossings that are condensed around target locations. Such pattern is filtered, in order to remove a noisy background of unwanted crossings, and is then processed by applying a statistical procedure. Finally, the targets are detected and their positions are predicted. For DoA estimation, the MUltiple SIgnal Classification (MUSIC) algorithm is employed, in combination with the matched filter technique. To the best of our knowledge, this is the first time the matched filter technique is used for the processing of GPR data. The software has been tested on GPR synthetic radargrams, calculated by using the finite-difference time-domain simulator gprMax, with very good results.
Full wave analysis of a prototype laboratory model of a pipe buried in sandy soil is
used to examine the feasibility of using ground penetrating radar in detecting water pollution in
underground water distribution systems. A wideband microstrip patch antenna with half and
defected ground plane is designed for detection of pollution in buried plastic water pipes. The
contrast in the dielectric constant between pure and polluted water is one of the most important
parameters to be considered for detecting the presence of pollutants. The complex dielectric
permittivity of water is measured and analytically represented by Cole-Cole fit model. The
experimental set up is described and the procedure followed to obtain an effective permittivity
data is outlined. Microwave technique developed in this manuscript is proved as a successful
non-destructive technique in detecting water pollution in buried pipes.
Even though ground penetrating radar has been well studied and applied by many researchers for the last couple of decades, the focusing problem in the measured GPR images is still a challenging task. Although there are many methods offered by different scientists, there is not any complete migration/focusing method that works perfectly for all scenarios. This paper reviews the popular migration methods of the B-scan GPR imaging that have been widely accepted and applied by various researchers. The brief formulation and the algorithm steps for the hyperbolic summation, the Kirchhoff migration, the back-projection focusing, the phase-shift migration, and the ω-k migration are presented. The main aim of the paper is to evaluate and compare the migration algorithms over different focusing methods such that the reader can decide which algorithm to use for a particular application of GPR. Both the simulated and the measured examples that are used for the performance comparison of the presented algorithms are provided. Other emerging migration methods are also pointed out.
This paper proposes a design for GPR test site for underground utilities. A test site with the following parameters: 8 meters in width, 17 meters in length, and 4 meters in depth is the design proposed for construction in Malaysia. Differing samples of pipe sizes and materials are represented as buried objects for GPR survey. The site is designed to meet the changing needs of researchers so as to eliminate most of the commonly known GPR limitations.
We present a 2D/3D topographic migration scheme for ground-penetrating radar (GPR) data which is able to account for variable velocities by using the root mean square (rms) velocity approximation. We test our migration scheme using a synthetic 2D example and compare our migrated image to the results obtained using common GPR migration approaches. Furthermore, we apply it to 2D and 3D field data. These examples are recorded across common subsurface settings including surface topography and variations in the GPR subsurface velocity field caused by a shallow ground water table. In such field settings, our migration strategy provides well focused images of common-offset GPR data without the need for a detailed interval velocity model. The synthetic and field examples demonstrate that our topographic migration scheme allows for accurate GPR imaging in the presence of variations in surface topography and subsurface velocity.
UWB systems based on impulse radio have the potential to provide very high data rates over short distances. In this paper, a new pulse shape is presented that satisfies the FCC spectral mask. Using this pulse, the link budget is calculated to quantify the relationship between data rate and distance. It is shown that UWB can be a good candidate for reliably transmitting 100 Mbps over distances at about 10 meters.
This book, based on Transport and Urban Development COST Action TU1208, presents the most advanced applications of ground penetrating radar (GPR) in a civil engineering context, with documentation of instrumentation, methods, and results. It explains clearly how GPR can be employed for the surveying of critical transport infrastructure, such as roads, pavements, bridges, and tunnels, and for the sensing and mapping of underground utilities and voids. Detailed attention is also devoted to use of GPR in the inspection of geological structures and of construction materials and structures, including reinforced concrete, steel reinforcing bars, and pre/post-tensioned stressing ducts. Advanced methods for solution of electromagnetic scattering problems and new data processing techniques are also presented. Readers will come to appreciate that GPR is a safe, advanced, nondestructive, and noninvasive imaging technique that can be effectively used for the inspection of composite structures and the performance of diagnostics relevant to the entire life cycle of civil engineering works.
The invention of ground-penetrating radar (GPR) technology has facilitated the possibility of detecting buried utilities and has been used primarily in civil engineering for detecting structural defects, such as voids and cavities in road pavements, slabs and bridge decks, but has not been used to assess the condition of buried pipes. Pipe deterioration can be defined as pipes where, for example, cracking, differential deflection, missing bricks, collapses, holes, fractures and corrosion exist. Assessing the deterioration of underground pipes is important for service efficiency and asset management. This paper describes a research project that focused on the use of GPR for assessing the condition of buried pipes. The research involved the construction of a suitable GPR test facility in the laboratory to conduct controlled testing in dry sand. Plastic pipes were chosen for the experiments. A series of laboratory experiments were conducted to determine the validity and effectiveness of standard commercially available GPR technology in assessing the condition of buried utilities with common types of damage. Several types of damage to the plastic pipe were investigated with respect to different GPR antenna frequencies. The GPR surveys were carried out in order to obtain signal signatures from damaged and undamaged pipes buried at 0.5 m depth. These surveys were organised on a grid pattern across the surface of the sand in the test facility. The results presented in this paper show that GPR can identify certain types of damage associated with a buried pipe under these controlled laboratory conditions.
Ground penetrating radar is one of the non-destructive methods useful in locating underground facilities. Little researches had been investigated about the significances of measuring pipes and cables in Hong Kong. In this research, general procedures on how to design the grids and to conduct the radar surveys were reviewed. The main objective was to compare the radar results with the conventional survey methods in three trial sites. Finally, it was crucial to evaluate the use of antenna frequency and the accuracy of the obtained data.
A compact UWB bowtie-slot antenna (36 multiplied by 23 cm2) fed by a CPW transition is proposed for an improved ground-coupling radar. The antenna has an operating frequency band in the range [0.46 ; 4] GHz. Full-wave modeling using the FDTD approach has allowed to study in details the antenna radiation characteristics in air and in the presence of a soil. Afterwards, a radar system made of a pair of independent shielded bowtie antennas has been considered to probe the sub-surface very close to the air-soil interface. The polarization diversity in the E and H-planes is an important aspect which has been studied in order to further detect the orientation of damages (cracks, delaminations . . . ) in civil engineering structures. Measurements in a dry and wet sand in different system configurations have allowed to first characterize the GPR system and to draw comparisons with numerical results. The ability of the radar to detect small buried objects has been investigated.
Subsurface utility mapping is an important technique for extracting subsurface information about buried utilities such as electric and telephone cables, water and sewage pipes and other infrastructure, particularly in the dense urban areas. Since the Holy Mecca city has many engineering development projects that need geotechnical excavation procedures across a wide inhabited area, there is a great demand for locating and imaging the subsurface utilities before starting the excavation process, particularly whereas there is no available information about the location of subsurface utilities. In this study, a 400 MHz antenna was utilized to map and identify the possible subsurface utilities along the investigated site. The survey was carried out along an asphalt road, roughly perpendicular to the expected direction of the utility infrastructure. Most of the subsurface features consisted of different pipes, cables, shafts, sharp interfaces between the filling and the original soil, sewage and flooding sewers. From the consistent character of the hyperbolic reflected signals along the successive profiles, it was possible to trace pipe lines, cables and vertical shafts. The results of this study highlight the importance of carrying out geophysical surveys before the excavation process particularly in the crowded urban sites, where the misdetection of any of the subsurface utilities may be hazardous.
A ground-penetrating radar (GPR) has been developed for civil engineering applications. Ultra-wide band (UWB) bowtie slot antennas operating at frequencies from 460 MHz to beyond 4 GHz have been designed to be integrated in a ground-penetrating radar (GPR) positioned very close to the soil surface. FDTD modeling has allowed to define the optimal geometrical parameters associated with the ground-coupled radar system that has been studied in two polarization configurations TE and TM. The ability of the GPR system in detecting small discontinuities using polarization diversity has been analyzed considering several buried canonical objects with different dielectric characteristics. Measurements in a sand box have been compared to full-wave simulations.
The purpose of this paper is to present a proposal to locate illegal connections underground using a technique to inject radar signals and collect their measurements. In special analyses, the reflection on the ground in the case of electrical conductors forms a hyperbola. Utilizing the radius of curvature variations of the hyperbola, the texture and tonal intensity of colors, it is possible to identify and differentiate between water pipes, gas pipes, tree roots, and others materials grounded. A testing area was built in a substation, where types of cables, containing branches, simulating clandestine links were buried in ditches. To support the analysis, a computational tool was developed to identify objects through statistical analysis of the radar grams, pixels, colors, and intensity.
This paper reviews the state-of-the-art of inspection techniques and technologies towards condition assessment of water distribution and transmission mains. Pipe condition assessment is the determination of its current condition, including structural health, impact on water quality, and hydraulic capacity. The collection and analysis of relevant data and information is the first and a paramount step to detect and monitor critical indicators to prevent or mitigate catastrophic failures. The technologies include conventional non-destructive inspection and advanced sensor techniques for condition monitoring. This paper focuses on the inspection techniques and technologies for structural deterioration of water pipes. Technologies like smart pipe, augmented reality, and intelligent robots are also briefly discussed and summarized.
Ground penetrating radar (GPR) is a near-surface geophysical technique that can provide high resolution images of the dielectric properties of the top few tens of meters of the earth. In applications in contaminant hydrology, radar data can be used to detect the presence of liquid organic contaminants, many of which have dielectric properties distinctly different from those of the other solid and fluid components in the subsurface. The resolution (approximately meter-scale) of the radar imaging method is such that it can also be used in the development of hydrogeologic models of the subsurface, required to predict the fate and transport of contaminants. GPR images are interpreted to obtain models of the large-scale architecture of the subsurface and to assist in estimating hydrogeologic properties such as water content, porosity, and permeability. Its noninvasive capabilities make GPR an attractive alternative to the traditional methods used for subsurface characterization.
In adapting the prestack migration technique used in seismic imaging to the inversion of ground-penetrating radar (GPR) from time- to depth-sections, we show that the theoretical integral formulation of the inversion can be applied to electromagnetic problems, albeit with three assumptions. The first two assumptions concern the electromagnetic characteristics of the medium, primarily that the medium must be perfectly resistive and non-dispersive, and the third concerns the antennae radiation pattern, which is taken to be 2D. The application of this adaptation of the inversion method is confirmed by migrating actual GPR measurements acquired on the test site of the Laboratoire Central des Ponts et Chaussées. The results show good agreement with the geometry of the structures in the medium and confirm that the possible departure from the assumption of a purely resistive medium has no visible effect on the information concerning the geometry of scattering and reflecting structures. The field experiments also show that prestack migration processing is sufficiently robust with regard to the assumption of a non-dispersive medium. The assumption of a 2D antennae radiation pattern, however, produces artefacts that could be significant for laterally heterogeneous media. Nevertheless, where the medium is not highly laterally heterogeneous, the migration gives a clear image of the scattering potential due to the geometry of structural contrasts in the medium; the scatterers are well focused from diffraction hyperbolae and well localized. Spatial geometry has limited dimensional accuracy and positions are located with a maximum error equal to the minimum wavelength of the signal bandpass. Objects smaller than one wavelength can nevertheless be detected and well focused if their dielectric contrasts are sufficiently high, as in the case of iron or water in gneiss gravels. Furthermore, the suitability of multi-offset protocols to estimate the electromagnetic propagating velocity and to decrease the non-coherent noise level of measurements is confirmed. Our velocity estimation is based on the semblance calculation of multi-offset migrated images, and we confirmed the relevance of this quantification method using numerical data. The signal-to-noise ratio is improved by summing multi-offset results after the addition of random noise on measurements. Thus the adaptation of prestack migration to multi-offset radar measurements significantly improves the resolution of the scattering potential of the medium. Limitations associated with the methods used here suggest that 3D algorithms should be applied to strongly laterally heterogeneous media and further studies concerning the waveform inversion are necessary to obtain information about the electric nature of the medium.
Ground penetrating radar (GPR) polarization is an important consideration when designing a GPR survey and is useful to constrain the size, shape, orientation, and electrical properties of buried objects. The polarization of the signal measured by the receive antenna is a function of the polarization of the transmit antenna and scattering properties of subsurface targets. Circular cylinders represent important environmental and engineering targets such as buried pipes, wires, and rebar. The backscattered fields from cylinders may be strongly depolarized depending on the orientation of the cylinder relative to the antennas, the electrical properties of the cylinders, and the radius of the cylinder compared to the incident wavelength. These polarization dependent scattering properties have important implications for target detection, survey design, and data interpretation.As the radius-to-wavelength ratio of metal and plastic pipes decreases, the backscattering properties become more polarization dependent. When using linearly polarized dipole antennas, metallic pipes and low impedance dielectric pipes are best imaged with the long axis of the dipole antennas oriented parallel to the long axis of the pipes. High impedance, dielectric pipes, are best imaged with the long axis of the dipoles oriented orthogonal to the long axis of the pipes.
Contribution of ultra-wide band and polarization diversity for the non destructive evaluation of civil engineering structures using the ground penetrating radar
- E Tebchrany
E. Tebchrany, Contribution of ultra-wide band and polarization diversity for the non
destructive evaluation of civil engineering structures using the ground penetrating radar,
PhD Thesis University of Marne-la-Vallée, Oct. 2015
- K Lichtenecker
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Application of Polarimetric GPR to detection of subsurface objects
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