Academic literature on the topic 'Ground Penetrating Radar (GPR)'

Ground penetrating radar (GPR) technology has existed for many decades, but it has only been in the last 20 to 30 years that it has undergone great development for use in near surface ground investigations. The early 1980's saw the first major developments in the application of GPR for pavements (i.e. engineered structures designed to carry traffic loads), and it is now an established investigation technique, with generic information included in several national standard guidance documents. Analysis of GPR data can provide information on layer depths, material condition, moisture, voiding, reinforcement and location of other features. Assessing the condition of pavements, in order to plan subsequent maintenance, is essential to allow the efficient long-term functioning of the structure and GPR has enhanced and improved the range and certainty of information that can be obtained from pavement investigations. Despite the recent establishment of the technique in pavement investigation, the current situation is one in which GPR is used routinely for pavement projects in only a minority of countries, and the specialist nature of the technique and the sometimes variable results that are obtained can mean that there is both a lack of appreciation and a lack of awareness of the potential information that GPR can provide. The fact that GPR is still a developing technique, and that many aspects of its use are specialised in their nature, means that there are also several technical aspects of GPR pavement investigations which have not been fully researched, and knowledge of the response of GPR to some material conditions has not been fully established. The overall aim of this EngD research project was to provide improved pavement investigation capabilities by enhancing the methodologies and procedures used to obtain information from GPR. Several discrete research topics were addressed through various research methods including a literature review, fieldwork investigations, experimental laboratory investigations and a review of previously collected data. The findings of the research allowed conclusions and recommendations to be made regarding improved fieldwork methodologies, enhancing information and determining material condition from previously collected GPR data, assessing the effect of pavement temperature and moisture condition on GPR data and also on managing errors and uncertainty in GPR data. During the EngD project, a number of documents and presentations have been made to publicise the findings both within the EngD sponsoring company (Jacobs) and externally, and an in-house GPR capability has been established within Jacobs as a direct result of the EngD project.

Interpretation of ground penetrating radar (GPR) signals can be a key point in the overall operability of a GPR system. In stepped-frequency and Frequency-Modulated Continuous-Wave (FMCW)GPR systems in particular, the target or object of interest is often located by analysis of Fast Fourier Transform (FFT) derived data. Increasing the GPR system bandwidth can improve resolution, but at the cost of reduced penetrating depth. The challenge is to develop high-resolution signal processing strategies for GPR.A number of Fourier based methods are investigated. However, the main response over a target's position can make it difficult to recognise closely spaced targets. The Least-Suare method is found to be the best autoregression-based estimator. However the method requires high Signal-to-Noise ratio to achieve high- resolution. Furthermore a number of subspace-based methods are investigated. Although the MUItiple Signal Classification (MUSIC) method can theoretically offer infinite resolution, they must be seeded with the number of targets actually present. A superimposed MUSIC technique is proposed to suppress false targets. A novel windowed MUSIC (W-MUSIC) algorithm is developed, and it offers high resolution while still able to minimise spurious responses. Since the performance of any FMCW GPR is critically linked to the linearity of the sweep frequency, the non-linearity in the target range estimation is studied. A Novel Short-Time MUSIC method is proposed and higher time and frequency resolution is achieved than the conventional Short-Time Fourier Transform method. In addition a modified Adaptive Sampling method is proposed to solve the non-linear problem by utilising a reference channel in a GPR system.

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>AGÊNCIA NACIONAL DE PETRÓLEO<br>PROGRAMA DE APOIO A NÚCLEOS DE EXCELÊNCIA<br>O presente trabalho tem por objetivo avaliar as potencialidades do método GPR (Ground Penetrating Radar) em investigações de campo que englobam estudos hidrogeológicos, geotécnicos e ambientais. Para o alcance deste objetivo foram realizadas investigações de campo na região sudeste do Brasil procurando verificar a aplicabilidade deste método no conhecimento da subsuperfície. Os estudos englobaram a determinação da estratigrafia do solo identificando suas camadas e respectivas profundidades; a determinação da posição do lençol freático; a localização de estruturas enterradas e a detecção de possíveis anomalias decorrentes de contaminações. As seções obtidas com o GPR permitiram identificar com boa resolução os contrastes bruscos, como a posição do lençol freático e a localização das estruturas enterradas. A identificação dos contatos entre as camadas de solo foi possível quando as propriedades elétricas destes materiais se diferiam bastante. Já no que diz respeito ao mapeamento de regiões contaminadas, ainda se faz necessário à realização de uma maior quantidade de estudos para afirmar a eficiência do GPR para este objetivo. A utilização da técnica da reflectometria no domínio do tempo (TDR) foi muito útil para correlacionar a velocidade de propagação das ondas eletromagnéticas com a profundidade. O seu emprego permitiu aumentar a exatidão da determinação das profundidades dos alvos de interesse.<br>The present work aims to assess the adequacy of the ground penetrating radar as a screening tool in site in site investigation practice in hydrogeological, geotechnical and environmental studies. An extensive site investigation program was carrid out in Southeast Brazil looking for characterizing the subsurface. Tests were performed to determine the statigraphy of soil profiles, the position of the water level, the detection of buried structures and contamination. The results have shown a great deal of success in identifying water levels and buried structures. Soil surface were only identified when abrupt changes in the dielectric constant of the porous media were observed. Howerer, the results so far do not enable to delineate contamination plumes with the accuracy desired. The accuracy of the target depths were greatly improved by using the result of the dielectric constant measured by the time domain reflectometry (TDR)

Maintenance of aging buried infrastructure and reinforced concrete are critical issues in the United States. Inexpensive non-destructive techniques for mapping and imaging infrastructure and defects are an integral component of maintenance. Ground penetrating radar (GPR) is a widely-used non-destructive tool for locating buried infrastructure and for imaging rebar and other features of interest to civil engineers. Conventional acquisition and interpretation of GPR profiles is based on the arrival times of strong reflected/diffracted returns, and qualitative interpretation of return amplitudes. Features are thereby generally well located, but their material properties are only qualitatively assessed. For example, in the typical imaging of buried pipes, the average radar wave velocity through the overlying soil is estimated, but the properties of the pipe itself are not quantitatively resolved. For pipes on the order of the radar wavelength (<5-35 cm), pipe dimensions and infilling material remain ambiguous. Full waveform inversion (FWI) methods exploit the entire radar return rather than the time and peak amplitude. FWI can generate better quantitative estimates of subsurface properties. In recent decades FWI methods, developed for seismic oil exploration, have been adapted and advanced for GPR with encouraging results. To date, however, FWI methods for GPR data have not been specifically tuned and applied on surface collected common offset GPR data, which are the most common type of GPR data for engineering applications. I present an effective FWI method specifically tailored for common-offset GPR data. This method is composed of three main components, the forward modeling, wavelet estimation and inversion tools. For the forward modeling and iterative data inversion I use two open-source software packages, gprMax and PEST. The source wavelet, which is the most challenging component that guarantees the success of the method, is estimated with a novel Sparse Blind Deconvolution (SBD) algorithm that I have developed. The present dissertation indicates that with FWI, GPR can yield better quantitative estimates, for example, of both the diameters of small pipes and rebar and their electromagnetic properties (permittivity, conductivity). Also better estimates of electrical properties of the surrounding media (i.e. soil or concrete) are achieved with FWI.

Ground Penetrating Radar (GPR) is an effective tool to measure the geological properties. A lot of information can be interpreted from the GPR data, such as soil water content. One of the common approaches is to determine the apparent electrical permittivity from the transmission velocity of the impulse electromagnetic wave, and to use empirical relationships to estimate the soil water content. For example, Ferre equation &amp; Topp equation are all expressing the relationship between soil water content and electrical permittivity. However, this method has some limitations; most notably the necessity to determine the velocity from a known depth to a reflecting surface. Therefore, another approach using the frequency dependent attenuation represented by a parameter called Q* was tested and studied in this thesis. The Q* method was evaluated using laboratory measurements, which consists of a series of experiments. A new empirical model was established using experiments where Q* was estimated from measurements on a soil sample with known water contents using two types of antennas (1.6 GHz &amp; 2.3 GHz). Finally, the adaptability of Topp equation and Ferre equation were verified, and a new empirical equation was defined. What’s more, the other method using Q* was proved to be feasible.

Ground penetrating radar (GPR) has been used as a railway substructure investigation tool since the late 1990’s and has seen significant development since then. To use GPR as a more effective tool for substructure investigation, a GPR substructure characterization model was developed. This dissertation provides a detailed description of railway track components, track geometry, soil properties and classification and substructure design. The historical background of GPR is discussed together with GPR principles, basic GPR equations, hardware and accessories as well as GPR data collection, processing and interpretation. Other in situ investigation techniques namely the dynamic cone penetrometer (DCP), light weight deflectometer (LWD) , Pencel pressuremeter, surface wave testing, remote video monitoring (RVM), multi-depth deflectometers (MDD) and continuous track modulus measurement techniques are also discussed. A comparison between the different track investigation techniques was also done, with reference to sample rate, cost, effectiveness and value. Two sites in South Africa were selected for the investigation, one with good substructure conditions used for heavy haul coal export close to Vryheid (KN test section) and the other a general freight line with poor substructure conditions near Rustenburg (NT test section). These two sites were selected to develop a GPR substructure characterization model as they provided conditions ranging from poor to very good. This was supported by the analysis of the in situ soil sampling and testing. The calculation of the track substructure modulus from RVM deflection measurements showed three times higher values for the KN test section compared to the NT test section. The subballast and subgrade thickness, the GPR ballast fouling (GBF) index as well as the GPR moisture condition index was used for the classification ranges used in the model. The subballast and subgrade layer roughness values were calculated and used for the substructure classification. The GBF index and the GPR moisture condition roughness were used for the GPR fouling index classification. The GPR deliverables were divided into four classes (i.e. very good, good, moderate and poor). The evaluation of the characterization model showed that a traditional in situ investigation will cost approximately 3.7 times more than that of a GPR investigation. It would also take two thirds of the time to complete the GPR investigation compared to the traditional in situ investigation. The study showed that GPR can be used to develop a substructure characterization model and that it would be more cost effective and efficient than traditional in situ investigation techniques. GPR surveys provide continuous measurements of the track structure condition and can therefore provide a continuous classification unlike the discreet and fragmented nature of in situ investigations. However, in situ tests can be done at certain intervals within the GPR survey or at point where the GPR classification is not clear. The best solution for railway track characterization can therefore be obtained by using GPR and in situ classification in combination.<br>Dissertation (MEng)--University of Pretoria, 2012.<br>Civil Engineering<br>unrestricted

Thesis (M.S.)--Missouri University of Science and Technology, 2009.<br>Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed February 18, 2009) Includes bibliographical references (p. 104-107).

Thesis (M.S.)--West Virginia University, 2006.<br>Title from document title page. Document formatted into pages; contains v, 128 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 106-107).