Este trabalho trata da simulação da propagação de ondas eletromagnéticas (1-D) em meios geológicos de propriedades físicas conhecidas (espessura, condutividade e permissividade elétrica), do registro das ondas EM refletidas (dados sintéticos) para uma antena receptora, e do uso desse registro em algoritmos de inversão e otimização que procuram estimar as propriedades físicas dos meios geológicos. Adotou-se modelos geológicos estratificados de pequena espessura (< 1,2 m) e altas frequências para a onda eletromagnética (800, 1000 e 1200 MHz). A propagação da onda eletromagnética é modelada por meio da resolução das equações de Maxwell no método FDTD. Os métodos de inversão Quasi-Newton e Otimização Ant Colony modificado são aplicados sobre os dados sintéticos para estimar os parâmetros elétricos para cada camada geológica. Ambos os métodos foram aplicados alternadamente para aumentar a precisão e a convergência ao longo da profundidade. Os métodos de inversão foram capazes de estimar simultaneamente duas propriedades eletromagnéticas do modelo geológico: a permissividade elétrica e a condutividade elétrica. Os métodos de inversão alcançaram bons resultados quando executados simultaneamente sobre os dados sintéticos em 3 diferentes frequências. Exemplos de estimativas dos perfis de condutividade e permissividade elétricas unidimensionais são apresentados, com e sem inserção de ruídos nos dados. Os resultados indicam que a combinação dos métodos de inversão (ACO modificado e Quasi-Newton) pode fornecer bons resultados para as estimativas dos parâmetros físicos de meios geológicos e geotécnicos em meios rasos. Além disso, essa combinação de métodos de inversão abre novas perspectivas para o processamento de dados georradar multi-canais. As investigações também mostram que a simulação dos perfis sintéticos por meio do método FDTD pode propagar erros em espessuras maiores de subsolo, devido ao fato de ser um método explícito. / This work deals with simulation of a 1-D electromagnetic wave propagating into a geological structure of known physical properties (thickness, electric conductivity and permittivity), the record of the reflected EM wave (synthetic data), and the use of these records in inversion and optimization algorithms to estimate back the physical properties of the geological structure. A stratified and thin (< 1.2 m) geological structure was initially constructed in order to be scanned by high frequency EM waves (800, 1000, and 1200 MHz). The EM wave propagation is simulated by Maxwell equations through FDTD method. The Quasi-Newton inversion and Ant Colony Optimization methods were applied into synthetic data to estimate original physical parameters of each geological layer. Both methods were applied in order to increase precision and convergence along depth. These methods were able to simultaneously estimate two physical properties of the geological structure: electrical permittivity and conductivity. The methods showed good results when applied simultaneously upon synthetic data of all three frequencies. Electric permittivity and conductivity profiles are shown with and without noise in the data. The results indicate that combined inversion methods can show good results to estimate physical properties of thin geological and geothecnical structures. The combined inversion methods open new perspectives to multichannel GPR data processing. The investigations also show that simulation of synthetic data through FDTD can propagate errors when dealing with thick geological structures, due to the fact that FDTD is an explicit method.

Ground penetrating radar (GPR) has been extensively utilized as a highly efficient and non-destructive testing method for infrastructure evaluation, such as highway rebar detection, bridge decks inspection, asphalt pavement monitoring, underground pipe leakage detection, railroad ballast assessment, etc. The focus of this dissertation is to investigate the key techniques to tackle with GPR signal processing from three perspectives: (1) Removing or suppressing the radar clutter signal; (2) Detecting the underground target or the region of interest (RoI) in the GPR image; (3) Imaging the underground target to eliminate or alleviate the feature distortion and reconstructing the shape of the target with good fidelity. In the first part of this dissertation, a low-rank and sparse representation based approach is designed to remove the clutter produced by rough ground surface reflection for impulse radar. In the second part, Hilbert Transform and 2-D Renyi entropy based statistical analysis is explored to improve RoI detection efficiency and to reduce the computational cost for more sophisticated data post-processing. In the third part, a back-projection imaging algorithm is designed for both ground-coupled and air-coupled multistatic GPR configurations. Since the refraction phenomenon at the air-ground interface is considered and the spatial offsets between the transceiver antennas are compensated in this algorithm, the data points collected by receiver antennas in time domain can be accurately mapped back to the spatial domain and the targets can be imaged in the scene space under testing. Experimental results validate that the proposed three-stage cascade signal processing methodologies can improve the performance of GPR system.

The subject of this master’s thesis is the diagnostic survey of the industry cast-in-place hall. The thesis contains theoretical and practical part. The theoretical part is focused on available options of diagnostic methods and options of materials evaluation. The practical part contains material assessment of chosen elements of construction. This part of thesis is focused on localizing the position and the diameter of reinforcement in every single element. Next step is focused on the quality of the concrete, particularly compressive strength and modulus of elasticity. The modern machines, like Hilti PS 1000 and Profometer PM-630, are used to localize the position and diameter of reinforcement. The quality of concrete is determined by removed bore core. Evaluation of material characteristics of the structure is in the conclusion.

Le contrôle des chaussées neuves en génie civil est primordial pour assurer sa bonne miseen oeuvre et lui conférer une durée de vie optimale. Dans cet objectif, divers paramètresphysiques nécessitent d'être scrupuleusement calibrés et contrôlés afin d'éviter une dégradation précoce de la chaussée et des problèmes de sécurité pour les conducteurs qui l'empruntent. De plus, les coûts associés à la mise en place et à la maintenance des chaussées sont considérables. Parmi les propriétés qui requièrent une attention particulière, la compacité, qui est indicative de la quantité d'air en volume dans la chaussée, est celle qui nous intéresse dans cette étude. Actuellement, seulement deux méthodes en laboratoire (en Europe) sont considérées comme des méthodes normalisées pour déterminer la compacité. Néanmoins, ces techniques sont destructives et/ou nucléaires ce qui est un frein majeur à leur utilisation. Durant ces deux dernières décennies, de nouvelles techniques électromagnétiques (non nucléaires et non destructives) ont émergé et ont prouvé leur forte utilité dans le domaine de la géophysique et du génie civil et plus particulièrement pour la détermination de la compacité. Cependant, ces nouvelles techniques nécessitent de prendre un certain nombre de précautions pour déterminer la compacité. Tout d'abord, elles permettent de mesurer la permittivité diélectrique du matériau en question. Ainsi pour déterminer la compacité, il est nécessaire d'utiliser des lois de mélange électromagnétiques. L'utilisation de ces modèles requiert une connaissance précise des constituants qui composent la chaussée ainsi que de leurs propriétés (masse volumique et permittivité diélectrique). La première partie de ce travail démontre la pertinence d'utiliser un radar à sauts de fréquences pour déterminer la compacité. L'étude de plusieurs lois de mélange électromagnétiques a été réalisée et les modèles présentant les meilleurs résultats ont été sélectionnés. Cependant, ces techniques font face de nos jours à un problème majeur. En effet, l'utilisation de matériaux recyclés est de plus en plus fréquente pour la construction de nouvelles chaussées ce qui rend la détermination de la compacité encore plus difficile par des méthodes électromagnétiques. Par conséquent, plusieurs méthodologies ont été développées, et sont proposées pour déterminer la compacité d'une nouvelle autoroute qui comporte des matériaux recyclés. La seconde partie de ces travaux de recherche porte sur la caractérisation diélectrique de plusieurs roches qui sont les éléments principaux d'une chaussée. Cette caractérisation est validée de basses à hautes fréquences mais aussi en fonction de la température. Les résultats montrent que à haute fréquence, la permittivité est principalement dépendante de la densité et de la composition chimique de la roche. En revanche, lorsque la fréquence d'investigation diminue et que la température varie, d'autres phénomènes apparaissent et changent dramatiquement le comportement diélectrique de la roche. Il a également été montré que l'eau joue un rôle majeur dans le comportement diélectrique à basse fréquence de la roche. Ces phénomènes se répercutent à "haute fréquence" par de très faibles variations qui pourraient expliquer les déviations obtenues par les méthodes électromagnétiques capacitives qui fonctionnent dans la région du MHz et qui sont également utilisées pour le contrôle de la compacité des chaussées neuves. / The control of new paved road is primordial to ensure its quality as well as its lifetime. Thus, several physical properties need to be well calibrated and controlled in order to avoid early degradations and safety issues for the drivers. Furthermore, the coast associated to the road building and the road maintenance is significant which makes the implementation of asphalt pavement according to the standard even more important. Among the properties that need attentions, the compactness which is indicative of the air void concentration in the asphalt pavement is the one we are interested in. Currently, only two methods in laboratory (in Europe) are considered as standards to assess the compactness. Nevertheless, these techniques are either nuclear or destructive which is a major hindrance. In the past two decades, new electromagnetic (EM) techniques have emerged and proved their great utility for geophysics or civil engineering applications and more importantly for the compactness assessment. However, these non-destructive and non-nuclear methods require many special precautions for the compactness assessment. First of all, they allow to measure the dielectric permittivity of the investigated material. Then to figure out the compactness, the use of EM mixing models is required. This leads to the accurate knowledge of every components constituting the asphalt pavement and their related properties (density and permittivity). The first main part of this work spotlights the relevance of using a step frequency radar for the compactness assessment. The study of several EM mixing models is performed to select the most appropriate ones. Nowadays, one of the challenges to address for these techniques is that the use of recycled materials is more and more commonly implemented for new roads building. Indeed, as the knowledge of the component properties is required, this makes the compactness assessment even more difficult. As a consequence, several methods have been developed and are proposed to assess the compactness of a new paved highway containing recycled asphalt pavement. The second main part of this research is the dielectric characterization of many rocks which are the main component of the asphalt pavement. This characterization is validated from low to high frequencies and also as a function of the temperature. The results show at high frequency that the permittivity is mainly dependent on the density and the chemical composition of the rock. However, as the frequency decreases and the temperature varies, this is not longer true and additional phenomena appear and drastically change the dielectric behavior of the rock. Also, it has been shown that the water plays a major role on the dielectric behavior at low frequency. This phenomena are reflected partially by small variations at "high frequency" that could explained the deviations obtained for capacitive techniques which work in the MHz region and which are used also for the compactness assessment.

Understanding modern carbonate depositional systems gives valuable insights into the interpretation of ancient carbonate systems. Ancient carbonate strand plains have the potential to act as productive hydrocarbon reservoirs because of their relatively high porosity. Unfortunately, they are difficult to identify in the rock record because of the lack of work done on modern analogues. San Salvador Island in the Bahamas hosts a well-exposed and easily accessible Holocene strand plain, ideal as a modern analogue. Sandy Hook, located on the southeast part of the island, consists of approximately 35 ridge-swale features that show signs of four distinct zones of deposition. In this study, 20 sediment samples were collected from one meter in depth, and throughout each zone. The sediment analysis reveals remarkably consistent grain-size distributions across the four zones. Carbon-14 ages were taken from the sediment samples. They revealed ages decreasing from 2617 ± 188 YBP to modern moving seaward through zone 4. The ages reveal depositional rates of 0.08 to 0.29 meters of accretion per year. Four pseudo-3D GPR surveys were acquired in Zones B, C, and D, and a 2D GPR survey was acquired that spanned the three zones. The pseudo-3D surveys revealed consistent reflectors through the width of the survey indicating that the 2D surveys represent more than the single line. The 2D survey reveals semi-parallel seaward-dipping reflectors (representing fair-weather deposits) that are truncated by sigmoidal seaward-dipping reflectors (high-energy storm deposits). Indicating that Sandy Hook was built through both fair-weather deposits and high-energy storm events.

High cost is a current problem with modern radar systems. Software-defined radios (SDRs) offer a possible solution for low-cost customizable radar systems. An SDR is a radio communi- cation system where, instead of the traditional radio components implemented in hardware, many of the components are implemented in software on a computer or embedded system. Although SDRs were originally designed for wireless communication systems, the firmware of an SDR can be configured into a radar system. With new companies entering the market, various types of low- cost SDRs have emerged. This thesis explores the use of a LimeSDR-Mini in a short-range radar through open software tools and custom code. The LimeSDR-Mini is successfully shown to detect targets at a short range. However, due to the instability of the LimeSDR-Mini, the consistent detection of a target is not possible. This thesis shows how the LimeSDR is characterized and how timing synchronization and instability issues are mitigated. The LimeSDR-Mini falls short of operating reliable in a radar system and other SDR boards need to be explored as viable options. Test setups using coaxial cables and test setups using antennas in an outdoor environment show the instability of the LimeSDR-Mini. The transmitter and the receiver are asynchronous. The timing difference varies slightly from run to run, which results in issues that are exacerbated in a short-range radar. The bleed-through signal is the signal leakage from the transmitter to the receiver. The bleed-through signal prevents the detection of targets at a short-range. Feed-through nulling is a signal processing technique used to eliminate the bleed-through signal so that short- range targets can be detected. The instability of the LimeSDR-Mini reduces the effectiveness of feed-through nulling techniques.

No description available.

The Bahamas Island archipelago grows by the precipitation and secretion of calcium carbonate. A majority of this growth is by lateral accretion of shoreline sedimentary deposits. Previous research is not clear on whether the growth is largely due to eustasy, sediment input from catastrophic events, or a combination of both. The Bahamas is an ideal location for studying Holocene carbonate generation and deposition, but there is limited research on the analysis of strandlines in relation to lateral accretion. Carbonate strandline deposits are commonly classified as low-energy beach ridge deposits. Previous researchers have primarily focused on ooid shoals and subtidal regions. Understanding the mechanisms of platform and shoreline growth in the Bahamas is important for creating petroleum reservoir analogs for exploration. We use ground penetrating radar (GPR) to image and interpret the internal fine-scale stratigraphy of Bahamian carbonate strand plains and thereby constrain our understanding of the processes by which the islands grow. Although GPR has been used extensively to analyze the interior of clastic strandline deposits across the world, tropical carbonate settings have received little attention. We are the first to utilize GPR to study strand plains in Crooked Islands, The Bahamas, our primary location for 2D GPR data acquisition. We integrate our interpretation of these data with a 3D GPR data volume collected on Pleistocene eolianites on San Salvador Island, The Bahamas. We used a GSSI (Geophysical Survey Systems, Inc.) bistatic 400-MHz antenna with a field frequency filter of 100"“800 MHz for all datasets. GPR allowed visualization of the interior of the strand plains down to a depth of about 2 m with high resolution. Data processing was performed using state-of-the-art petroleum industry techniques (e.g., gain control, deconvolution, migration, seismic attribute computation) to better visualize the reflectivity. Our data constrains a model that the lateral accretion of carbonate sediment preserved in strandline was deposited in a combination of storm processes and gradual sediment progradation, rather than one or the other. Our conclusions help determine that The Bahamas is ideal for GPR imaging of strandlines due to being assessable, high data quality, no clastic influence, and a dry environment during parts of the world

Concrete bridge decks in Utah are experiencing observable deterioration due primarily to freeze-thaw cycles and the routine application of deicing salts during winter maintenance activities. Given the need for increasingly cost-effective strategies for bridge deck maintenance, rehabilitation, and replacement (MR&R), the Utah Department of Transportation (UDOT) initiated this research to ultimately develop a protocol offering guidance as to whether deteriorated bridge decks should be rehabilitated or replaced. While threshold values for various non-destructive condition assessment methods were proposed in earlier UDOT research, this work focused on implementing the recommended test criteria. Twelve bridges were identified by UDOT engineers for inclusion in the study, and data were collected from each deck to determine whether the bridge decks warranted rehabilitation or replacement based on the proposed threshold values. Several evaluation techniques were employed to assess concrete bridge deck condition, including visual inspection, hammer sounding and chaining, dielectric measurements, ground-penetrating radar imaging, resistivity testing, half-cell potential testing, and chloride concentration testing. The condition assessment testing confirmed that chloride-induced corrosion of reinforcing steel is the primary mechanism of deck deterioration and that inadequate cover over the upper steel mat facilitated accelerated corrosion damage in many instances. The bridge deck condition analyses produced from the results of non-destructive testing were compared to the visual inspection ratings assigned to each deck by UDOT. Concrete bridge deck condition data should be collected regularly through inspection and monitoring programs to facilitate prioritization of MR&R strategies for individual bridges and to evaluate the impact of such strategies on the overall condition of the network. Performance indices based on selected condition assessment parameters should be developed for use in bridge management activities, and mathematical deterioration models should be calibrated in order to forecast both network-level and project-level conditions and predict funding requirements for various possible MR&R strategies. Further research, including statistical analyses of the data presented in this report, should be completed to develop relevant mathematical deterioration models for predicting the service lives of concrete bridge decks in Utah.

No description available.