No / The famous Celtic site of Entremont, well known for its head cult and warrior statues, is a heritage gem of southern France. This naturally inhibits further excavation there, but the authors show just how much can be achieved through an integrated package of remote mapping techniques. Their exemplary methodology produced more than a high resolution plan of the unexcavated part of the site; this type of integrated procedure generates ground-breaking research, without breaking any ground. Here the investigation mobilised arguments for pre-urban monuments, and the activities, enclosures, entrances and circulation of the oppidum.

GPR data interpretation is often difficult due to complex geological environments, reflections ambiguity and time-depth conversion uncertainty. Thanks to the geophysical fields interoperability it is possible to compare results of related survey methods. Radargrams from three model sites were processed and interpreted in an usual way to uniformly amplify all recorded reflections. Results were compared with ERT and EM (DEMP) data within integrated interpretation. GPR data interpretation was extended and new geological and geomorphological interpretations were uncovered. The GPR processing sequence was modified and simplified following outcomes from the integrated interpretation to ease different methods results comparison. Adapting a velocity model to precise time- depth conversion hasn't showed improvements. Key words: ground penetrating radar, electrical resistivity tomography, dipole electromagnetic profiling, integrated interpretation, integrated inversion, GPR processing optimization, sedimentary environment, velocity model

Nesta pesquisa foram realizados levantamentos geofísicos utilizando os métodos eletromagnético indutivo - EMI (equipamento EM38) e GPR - Ground Penetrating Radar, visando localizar redes de interferências, tais como, tubulações metálicas, cabos elétricos e conduítes de plástico instalados nas linhas 6 e 7 do Sítio Controlado de Geofísica Rasa do IAG/USP. Os dados EMI foram afetados pelo drift instrumental devido à variação de temperatura. A sua correção foi efetiva por meio do uso de uma função quadrática, realçando os alvos mais profundos. A aquisição em distância permitiu detectar alvos metálicos no subsolo com boa precisão e a aquisição em tempo permitiu fazer um mapeamento regional de alvos metálicos no subsolo. Os melhores resultados foram obtidos com a aquisição em distância, com os sensores posicionados a 10 cm de altura, devido às anomalias ficarem mais nítidas, onde a influência da condutividade do background foi reduzida. Os perfis GPR 2D obtidos com a antena de 400 MHz permitiram detectar os alvos até 1 m de profundidade e com a antena de 200 MHz foi possível detectar quase todos os alvos metálicos e não-metálicos instalados nas linhas estudas do SCGR. Para o GPR quase-3D, na forma de depth slices, foram importantes para estimar as dimensões dos alvos e melhorar a visualização dos resultados. Os resultados obtidos com os métodos EMI e GPR são complementares, sendo ambos recomendados no mapeamento de interferências no subsolo, tendo aplicações diretas nas áreas de planejamento urbano e infra-estrutura nos grandes centros urbanos. / This research was conducted geophysical surveys using inductive electromagnetic - IEM (EM38 equipment) and GPR - Ground Penetrating Radar methods, to locate network interference, such as metal pipes, electric cables and plastic conduit installed in lines 6 and 7 of test site of the IAG/USP (SCGR). IEM data were affected by instrumental drift due to temperature variation. The correction was effective through the use of a quadratic function, highlighting the deeper targets. The acquisition targets identified in the distance underground metal with good accuracy and acquisition time allowed to make a survey of regional targets metal underground. The best results were obtained with the acquisition in distance with the sensors placed at 10 cm in height, due to deficiencies become more clear, where the influence of the background conductivity was reduced. The 2D GPR profiles obtained with the antenna of 400 MHz to detect the target by 1 m depth and the antenna of 200 MHz was possible to detect almost all metal targets and non-metallic lines installed in the study SCGR. GPR to the quasi-3D in the form of depth slices, were important for estimating the size of the targets and improve the visualization of results. The results obtained with the IEM and GPR methods are complementary, and both are recommended in mapping interference underground, with direct applications in the areas of urban planning and infrastructure in urban centers.

Nesta pesquisa foram realizados levantamentos geofísicos utilizando os métodos eletromagnético indutivo - EMI (equipamento EM38) e GPR - Ground Penetrating Radar, visando localizar redes de interferências, tais como, tubulações metálicas, cabos elétricos e conduítes de plástico instalados nas linhas 6 e 7 do Sítio Controlado de Geofísica Rasa do IAG/USP. Os dados EMI foram afetados pelo drift instrumental devido à variação de temperatura. A sua correção foi efetiva por meio do uso de uma função quadrática, realçando os alvos mais profundos. A aquisição em distância permitiu detectar alvos metálicos no subsolo com boa precisão e a aquisição em tempo permitiu fazer um mapeamento regional de alvos metálicos no subsolo. Os melhores resultados foram obtidos com a aquisição em distância, com os sensores posicionados a 10 cm de altura, devido às anomalias ficarem mais nítidas, onde a influência da condutividade do background foi reduzida. Os perfis GPR 2D obtidos com a antena de 400 MHz permitiram detectar os alvos até 1 m de profundidade e com a antena de 200 MHz foi possível detectar quase todos os alvos metálicos e não-metálicos instalados nas linhas estudas do SCGR. Para o GPR quase-3D, na forma de depth slices, foram importantes para estimar as dimensões dos alvos e melhorar a visualização dos resultados. Os resultados obtidos com os métodos EMI e GPR são complementares, sendo ambos recomendados no mapeamento de interferências no subsolo, tendo aplicações diretas nas áreas de planejamento urbano e infra-estrutura nos grandes centros urbanos. / This research was conducted geophysical surveys using inductive electromagnetic - IEM (EM38 equipment) and GPR - Ground Penetrating Radar methods, to locate network interference, such as metal pipes, electric cables and plastic conduit installed in lines 6 and 7 of test site of the IAG/USP (SCGR). IEM data were affected by instrumental drift due to temperature variation. The correction was effective through the use of a quadratic function, highlighting the deeper targets. The acquisition targets identified in the distance underground metal with good accuracy and acquisition time allowed to make a survey of regional targets metal underground. The best results were obtained with the acquisition in distance with the sensors placed at 10 cm in height, due to deficiencies become more clear, where the influence of the background conductivity was reduced. The 2D GPR profiles obtained with the antenna of 400 MHz to detect the target by 1 m depth and the antenna of 200 MHz was possible to detect almost all metal targets and non-metallic lines installed in the study SCGR. GPR to the quasi-3D in the form of depth slices, were important for estimating the size of the targets and improve the visualization of results. The results obtained with the IEM and GPR methods are complementary, and both are recommended in mapping interference underground, with direct applications in the areas of urban planning and infrastructure in urban centers.

Les travaux de cette thèse concernent l'étude d'une méthode d'évaluation des constantes diélectriques du béton d'ouvrage à risque par une approche problème inverse. Pour cela des mesures radar de type GPR et un modèle électromagnétique de ces mêmes mesures seront utilisés. Les deux premiers chapitres de la thèse présentent les concepts clés, le contexte et un historique des travaux déjà réalisés dans le domaine. Le chapitre 2 propose en outre une adaptation des travaux déjà réalisés à la recherche de gradients de propriétés diélectriques dans le béton en profondeur. Cette recherche préliminaire nous a permis de redéfinir le processus de mesures pour le rendre plus adapté à nos besoins. Ainsi le chapitre 3 présente une campagne de mesure réalisée à l'aide d'un nouveau dispositif radar sur des corps d'épreuve conditionnés de telle sorte que la répartition de la teneur en eau soit maîtrisée. Dans ce chapitre, nous détaillons également un nouveau modèle numérique 3D du dispositif qui nous permet de simuler nos mesures de façon réaliste Ces simulations sont nécessaires à l'expression du problème inverse. à partir de ces mesures, dans le quatrième chapitre, nous définissons tout d'abord le problème inverse, puis en utilisant des mesures sur les corps d'épreuves saturés, pouvant être considérés comme homogènes d'un point de vue diélectrique, nous résolvons ce problème inverse par un algorithme d'optimisation basé sur celui de Levenberg-Marquardt. Les résultats obtenus par notre processus d'inversion sont cohérents avec les valeurs physiques que l'on pouvait attendre et sont indépendants des valeurs données à nos inconnues lors de l'initialisation. Ces résultats correspondent effectivement à un minimum de la fonction coût qui mesure la distance entre mesures et simulations. Nous avons ensuite étudié des stratégies pour diminuer le temps de calcul de notre processus d'inversion. Une première approche consiste à utiliser un modèle simplifié en 2D du dispositif, qui permet d'initialiser l'inversion 3D avec un point plus proche de la solution. Une autre idée consiste à utiliser au mieux les performances d'une machine multiprocesseurs en parallélisant le code 3D. Dans le chapitre 5 nous nous intéressons à des mesures sur des corps d'épreuve en béton dont la teneur en eau est une fonction affine de la profondeur. Dans ces conditions nous avons fait l'hypothèse, en première approche, que les constantes diélectriques suivent aussi ce type de loi. Après avoir redéfini les inconnues de notre problème inverse et adapté l'algorithme, nous montrons que le processus d'inversion fourni des résultats cohérents en ce qui concerne la permittivité diélectrique, mais insatisfaisant pour la conductivité. Après analyse de ces résultats nous avons proposé diverses pistes pour améliorer et valider la méthode d'inversion. Finalement en comparant l'ensemble des résultats, il apparaît que notre méthode d'inversion permet de caractériser des gradients de permittivité, mais pas de conductivité. Cela représente néanmoins une avancée significative pour la mesure de la teneur en eau dans les bétons, facteur principal influençant la constante diélectrique de ce matériau, dans le contexte du contrôle non destructif des ouvrages du génie civil. / That thesis aims to propose an assessment method of the concrete electromagnetic properties by using radar measurements in a context of building sustainability, by inverse problem. For that purpose Ground Penetrating Radar (GPR) measurements are used as well as a numerical model of the radar device. The first two chapters of the thesis present the key concepts, the context of the study, as well as the history of the research on that topic in particular in our laboratory. Chapter 2 also expands those early works on the search of electromagnetic properties of concrete in depth. That preliminary work helped us to develop a measurement device that is more fitted to our needs. Chapter 3 presents a measurement campaign that was carried out by using a new measurement device on specially made reinforced concrete slabs whose water content is monitored. In that chapter a 3D model of the device is also described. That model allows us to simulate the measurements very precisely. Those simulations are a critical link on the inverse process. Chapter 4 details the formulation of the inverse problem for the case of concrete slabs saturated with water, which can be therefore considered to have homogeneous electromagnetic properties. The problem is solved by using an optimization algorithm based on Levenberg-Marquardt method. The values obtained by the inverse process are physically acceptable and independent of the values given to the unknowns when initializing the algorithm. Those values are the minimum of the cost function that computes the distance between measured and simulated electromagnetic fields. We then studied some strategies to reduce the computing time of the inverse process. A first approach consists in the use of a 2D simplified model of our device to initialize the 3D inversion with values closer to the searched solution. Another idea is to better take advantage of all the resources of a multiprocessor computer by implementing a parallel version of the 3D code. In chapter 5 we focus on the concrete slab with water content being an affine function of depth. We define the new parameters that represent the unknowns of our problem and we adapt the previous algorithm. Then we show that the inverse process gives satisfying results with regard to the dielectric permittivity only. We suggest some ways to improve the method. Finally we conclude that our method allows to retrieve the permittivity of the concrete, but not its conductivity. Nevertheless that result represents a significant step for the measuring of water content in reinforced concrete in particular when a gradient is present, by using radar measurements.

Made available in DSpace on 2015-02-24T19:48:39Z (GMT). No. of bitstreams: 1 ZuleideMCL.pdf: 3563963 bytes, checksum: d530c00861412b2b316c4040482b9f16 (MD5) Previous issue date: 2004-03-10 / This doctorate thesis concerning on the Characterization of the Environmental Dynamics of the Coastal Area of the Municipal district of Galinhos, Septentrional Coast of Rio Grande do Norte State, is located in the influence area of the Guamar? Petroliferous Pole, having as general objective the understanding of the active coastal dynamics in the region of Galinhos, whose specific objectives were: To study the variation of the coast line in the decades of 1954, 1967,1988, 1996, 2000, from remote sensing products; To elucidate the hypothesis of the region of Galinhos to have been an old system of islands barriers, using as basic tool the penetration radar in the soil - GPR; To monitor and to characterize the coastal dynamics of the study area starting from monthly data of beach profiles, sedimentological analysis, hydrodynamic data and environmental characterization data; which were used to feed the database of the N-NE network of Environmental Monitoring of Areas under Influence of the Petroliferous Industry;(REDE05/FINEP/CNPq/CTPETRO/ PETROBRAS). This research is justified, of the environmental point of view, by involving the mangrove ecosystem considered one of the most delicated environments of the State. From the viewpoint of the petroleum exploration, the systems of islands barriers are favorable for hydrocarbons reservoirs and, consequently important targets to the oil and gas industry, becoming this region attractive in comparison with similar lithified environments. With the results of the variability study in the position of the coast line in the Municipal district of Galinhos/RN from the analysis of remote sensing images, it was possible to investigate the changes in the coast line in temporal scale; the use of directional filters allowed to emphasize linings in the direction NE and to identify submerged features such as sandwaves. The use of GPR enabled the confirmation of paleochannels existence and thus confirmed the hypothesis that the Galinhos spit was formed from an old system of islands barriers. The results of the granulometric analyses indicated that in the summer period the sediments in the profiles A and B in the foreshore portion were classified with the granulometry of sand with scattered gravel and in the shoreface were constituted by sand, but in the winter period these same morphologic compartments were constituted by sand with sparse gravel and siltic sand respectively. In the profile C, in the summer and in the winter, the shoreface and foreshore compartments presented predominantly constituted by sand with sparse gravel. The hydrodynamic results showed that the largest wave heights were registered in the month of February (62 cm) and the highest period of 1,00 m/s in the month of May, the sense of the coastal currents was kept among the quadrants SW and NW, and the winds coming from NE were predominant. The analysis of the beach profiles demonstrated that in the profile A, although it had occurred erosion and deposition during the monitored months, the morphology of the referred profile was kept constant. In the profiles B and C, there were abrupt changes in the morphology, during the monitored months, having been identified a cyclic pattern in the features of the foreshore zone sometimes forming longitudinal sandy bars and in other times forming berm. These results evidenced, therefore, that studies of this nature are of fundamental importance for the coastal zoning, aiming subsidies to the organs managers in the closing of decisions as for the implantation of enterprises in the area, and for the industry of the petroleum through generation of information that subsidize the implementation and location of petroliferous structures adequate to this environment / Esta tese de doutorado sobre a caracteriza??o da din?mica ambiental da regi?o costeira do munic?pio de Galinhos, Litoral Setentrional do Rio Grande do Norte, acha-se inserida na ?rea de influ?ncia do P?lo Petrol?fero de Guamar?, tendo como objetivo geral o entendimento da din?mica costeira atuante na regi?o de Galinhos, cujos objetivos espec?ficos foram : estudar a varia??o da linha de costa nas d?cadas de 1954, 1967, 1988, 1996 e 2000, a partir de produtos de sensoriamneto remoto; elucidar a hipotese da regi?o de Galinhos ter sido um antigo sisitema de ilhas barreiras, utilizando como ferramneta b?sica o radar de penetra??o no solo - GPR; monitorar e caracterizar a dinamica costeira da ?rea em estudo a partir de dados mensais da perfis praiais, analise sedimentologica, dados hidrodin?micos e dados de caracteriza??o ambiental; este conjunto de dados foram utilizados para alimetar o banco de dados da Rede NNE de monitoramneto ambiental das ?reas sob influ?ncia da industria petrol?fera (REDE05/FINEP/CNPq/CTPERO/PETROBRAS). Esta pesquisa se justifica, do ponto de vista ambiental, por envolver ecossistemas de alta fragilidade como dunas, praias e manguezais. Do ponto de vista da explora??o do petr?leo, os sistemas de ilhas barreiras s?o prop?cios para reservat?rios de hidrocarbonetos e, por conseguinte, alvos importantes para a ind?stria do petr?leo e g?s tornando esta regi?o atrativa na compara??o com dep?sitos similares litificados. O estudo da variabilidade na posi??o da linha de costa no Munic?pio de Galinhos/RN a partir da an?lise de imagens de sensores remotos, foi poss?vel investigar as mudan?as na linha de costa em escala temporal; a utiliza??o de filtros direcionais permitiu enfatizar lineamentos de dire??o NE e identificar fei??es submersas tais como sandwaves. A utiliza??o do GPR possibilitou a comprova??o da exist?ncia de paleocanais confirmando a hip?tese de que o spit de Galinhos foi formado a partir de um antigo sistema de ilhas barreiras. Os resultados das an?lises granulom?tricas indicaram que no per?odo de ver?o os sedimentos nos perfis A e B na por??o de estir?ncio foram classificados como de granulometria areia com cascalho esparso e na antepraia foram constitu?dos por areia, j? no per?odo de inverno estes mesmos compartimentos morfol?gicos apresentaram-se com areia com cascalho esparso e areia siltosa respectivamente No perfil C, tanto no ver?o como no inverno, os compartimentos de estir?ncio e antepraia apresentaram-se predominantemente por areia com cascalho esparso. Os resultados hidrodin?micos mostraram que as maiores alturas de onda foram registradas no m?s de fevereiro (62 cm) e o maior per?odo de 1,00 m/s no m?s de maio, o sentido das correntes litor?neas se manteve entre os quadrantes SW e NW, e os ventos provenientes de NE foram predominantes. A an?lise dos perfis praiais demonstrou que no perfil A, embora tenha ocorrido tanto eros?o como deposi??o durante os meses monitorados, a morfologia do referido perfil permaneceu constante. Nos perfis B e C, ocorreram mudan?as bruscas na morfologia, durante os meses monitorados, tendo sido identificada uma ciclicidade nas fei??es da zona de estir?ncio ora formando barras arenosas longitudinais ora formando berma. Estes resultados evidenciaram, portanto, que estudos desta natureza s?o de fundamental import?ncia para o zoneamento costeiro, dando subs?dios aos ?rg?os gestores na tomada de decis?es quanto ? implanta??o de empreendimentos na regi?o, e para a ind?stria do petr?leo atrav?s de gera??o de informa??es que subsidiam a implementa??o de estruturas petrol?feras adequadas ao ambiente estudado

Made available in DSpace on 2015-02-24T19:48:43Z (GMT). No. of bitstreams: 1 PedroXN_ate_cap4.pdf: 4119464 bytes, checksum: afcae765da030e3171f973a2422290fb (MD5) Previous issue date: 2006-05-05 / In Fazenda Bel?m oil field (Potiguar Basin, Cear? State, Brazil) occur frequently sinkholes and sudden terrain collapses associated to an unconsolidated sedimentary cap covering the Janda?ra karst. This research was carried out in order to understand the mechanisms of generation of these collapses. The main tool used was Ground Penetrating Radar (GPR). This work is developed twofold: one aspect concerns methodology improvements in GPR data processing whilst another aspect concerns the geological study of the Janda?ra karst. This second aspect was strongly supported both by the analysis of outcropping karst structures (in another regions of Potiguar Basin) and by the interpretation of radargrams from the subsurface karst in Fazenda Bel?m. It was designed and tested an adequate flux to process GPR data which was adapted from an usual flux to process seismic data. The changes were introduced to take into account important differences between GPR and Reflection Seismic methods, in particular: poor coupling between source and ground, mixed phase of the wavelet, low signal-to-noise ratio, monochannel acquisition, and high influence of wave propagation effects, notably dispersion. High frequency components of the GPR pulse suffer more pronounced effects of attenuation than low frequency components resulting in resolution losses in radargrams. In Fazenda Bel?m, there is a stronger need of an suitable flux to process GPR data because both the presence of a very high level of aerial events and the complexity of the imaged subsurface karst structures. The key point of the processing flux was an improvement in the correction of the attenuation effects on the GPR pulse based on their influence on the amplitude and phase spectra of GPR signals. In low and moderate losses dielectric media the propagated signal suffers significant changes only in its amplitude spectrum; that is, the phase spectrum of the propagated signal remains practically unaltered for the usual travel time ranges. Based on this fact, it is shown using real data that the judicious application of the well known tools of time gain and spectral balancing can efficiently correct the attenuation effects. The proposed approach can be applied in heterogeneous media and it does not require the precise knowledge of the attenuation parameters of the media. As an additional benefit, the judicious application of spectral balancing promotes a partial deconvolution of the data without changing its phase. In other words, the spectral balancing acts in a similar way to a zero phase deconvolution. In GPR data the resolution increase obtained with spectral balancing is greater than those obtained with spike and predictive deconvolutions. The evolution of the Janda?ra karst in Potiguar Basin is associated to at least three events of subaerial exposition of the carbonatic plataform during the Turonian, Santonian, and Campanian. In Fazenda Bel?m region, during the mid Miocene, the Janda?ra karst was covered by continental siliciclastic sediments. These sediments partially filled the void space associated to the dissolution structures and fractures. Therefore, the development of the karst in this region was attenuated in comparison to other places in Potiguar Basin where this karst is exposed. In Fazenda Bel?m, the generation of sinkholes and terrain collapses are controlled mainly by: (i) the presence of an unconsolidated sedimentary cap which is thick enough to cover completely the karst but with sediment volume lower than the available space associated to the dissolution structures in the karst; (ii) the existence of important structural of SW-NE and NW-SE alignments which promote a localized increase in the hydraulic connectivity allowing the channeling of underground water, thus facilitating the carbonatic dissolution; and (iii) the existence of a hydraulic barrier to the groundwater flow, associated to the A?u-4 Unity. The terrain collapse mechanisms in Fazenda Bel?m occur according to the following temporal evolution. The meteoric water infiltrates through the unconsolidated sedimentary cap and promotes its remobilization to the void space associated with the dissolution structures in Janda?ra Formation. This remobilization is initiated at the base of the sedimentary cap where the flow increases its abrasion due to a change from laminar to turbulent flow regime when the underground water flow reaches the open karst structures. The remobilized sediments progressively fill from bottom to top the void karst space. So, the void space is continuously migrated upwards ultimately reaching the surface and causing the sudden observed terrain collapses. This phenomenon is particularly active during the raining season, when the water table that normally is located in the karst may be temporarily located in the unconsolidated sedimentary cap / Esta tese apresenta resultados da pesquisa realizada no campo de petr?leo de Fazenda Bel?m-CE (Bacia Potiguar), com o objetivo de entender os mecanismos de gera??o de colapsos de terreno associados ? exist?ncia de um substrato carbon?tico intensamente fraturado e karstificado da Forma??o Janda?ra. A principal ferramenta utilizada foi o imageamento do karst soterrado com GPR (Ground Penetrating Radar). Dois eixos tem?ticos de pesquisa foram desenvolvidos: um eixo de natureza geof?sica, que consistiu no desenvolvimento de metodologias de processamento de dados de GPR, e um eixo de natureza geol?gica, que consistiu do estudo do karst Janda?ra e dos fatores condicionantes da sua evolu??o. Este segundo eixo foi fortemente apoiado no estudo de estruturas k?rsticas aflorantes e na interpreta??o de radargramas do karst soterrado. Um fluxo de processamento adequado para tratar dados de GPR ? proposto a partir da adapta??o de um fluxo usual de processamento s?smico. As principais modifica??es introduzidas est?o associadas com diferen?as fundamentais existentes entre GPR e S?smica, notadamente: pior condi??o de acoplamento entre fonte e solo, fase da wavelet (que ? mista, no GPR), grande n?vel de ru?do (inclusive a?reo), aquisi??o monocanal e maior import?ncia dos efeitos de propaga??o (principalmente dispers?o) na onda eletromagn?tica. A necessidade de um processamento adequado foi ainda mais premente em Fazenda Bel?m devido ? forte presen?a de ru?do a?reo, por se tratar de uma ?rea industrial, e grande complexidade das fei??es k?rsticas soterradas. A etapa chave do fluxo de processamento ? a corre??o dos efeitos de propaga??o. Em meios diel?tricos de perda baixa a moderada, verificou-se que a propaga??o do pulso de GPR impacta fortemente o seu espectro de amplitude, mas provoca muito pouca altera??o no seu espectro de fase. P?de-se assim corrigir os efeitos da propaga??o com uma aplica??o judiciosa de ganhos e balanceamento espectral. Os ganhos foram utilizados para recuperar a perda de amplitude e o balanceamento espectral, para recuperar as componentes da faixa superior de freq??ncia, que s?o mais fortemente afetadas pelos efeitos da propaga??o. Apesar da n?o estacionaridade do sinal do GPR, o balanceamento espectral promove um aumento de resolu??o, o que qualifica esta t?cnica como um bom substituto dos algoritmos de deconvolu??o, garantindo repetitividade e independ?ncia do meio geol?gico. A karstifica??o da plataforma carbon?tica Janda?ra est? associada a, pelo menos, tr?s eventos de exposi??o sub-a?rea relacionadas ?s discord?ncias do Turoniano, Santoniano e Campaniano. Em Fazenda Bel?m, a partir do Mioceno M?dio, o karst Janda?ra foi soterrado por sedimentos silicicl?sticos continentais. Este soterramento preencheu parte das cavidades de dissolu??o e fraturas e, assim, o desenvolvimento do processo de karstifica??o foi bastante atenuado, em compara??o com outros locais da Bacia Potiguar, onde o karst Janda?ra est? exposto. Nas condi??es vigentes em Fazenda Bel?m, identificou-se que os principais fatores condicionantes do surgimento das dolinas e do colapso de terreno s?o: (i) exist?ncia de uma cobertura inconsolidada espessa o suficiente para encobrir o calc?rio, por?m delgada o suficiente para que o seu volume possa ser acomodado nos espa?os vazios dessas estruturas; (ii) ocorr?ncia da interse??o de lineamentos estruturais SW-NE e NW-SE, que promovem um aumento localizado da condutividade hidr?ulica e condicionam a canaliza??o do fluxo hidr?ulico subterr?neo, facilitando a dissolu??o dos carbonatos; e (iii) exist?ncia de uma barreira hidr?ulica vertical, associada ? Unidade A?u-4, que condiciona a circula??o da ?gua subterr?nea a ser predominantemente lateral. Os colapsos de terreno em Fazenda Bel?m seguem o seguinte processo de evolu??o temporal. O fluxo de ?gua se infiltra atrav?s da cobertura sedimentar inconsolidada e promove sua mobiliza??o para o espa?o vazio das estruturas de dissolu??o na Forma??o Janda?ra. Este efeito ? iniciado na base da cobertura sedimentar, onde o fluxo aumenta o seu poder de abras?o, devido ? mudan?a brusca do regime laminar para o regime turbulento, ao entrar no karst. O material remobilizado vai preenchendo, as cavidades intra-acamamento e geram espa?o, de forma remontante, na cobertura sedimentar acima situada, que vai se afinando at? o ponto de colapso, quando ent?o ocorrem as dolinas. Este fen?meno ? especialmente ativo durante a esta??o chuvosa, quando o n?vel est?tico da ?gua, que normalmente est? situado dentro do calc?rio, pode estar temporariamente localizado dentro da cobertura sedimentar

Made available in DSpace on 2015-03-13T17:08:31Z (GMT). No. of bitstreams: 1 PeryclysROA_Cap1.pdf: 1534050 bytes, checksum: 88145cdf2e8bbe54b546fb696fea947a (MD5) Previous issue date: 2005-06-17 / Due to its high resolution, Ground Penetrating Radar (GPR) has been used to image subsurface sedimentary deposits. Because GPR and Seismic methods share some principles of image construction, the classic seismostratigraphic interpretation method has been also applied as an attempt to interpret GPR data. Nonetheless some advances in few particular contexts, the adaptations from seismic to GPR of seismostratigraphic tools and concepts unsuitable because the meaning given to the termination criteria in seismic stratigraphy do not represent the adequate geologic record in the GPR scale. Essentially, the open question relies in proposing a interpretation method for GPR data which allow not only relating product and sedimentary process in the GPR scale but also identifying or proposing depositional environments and correlating these results with the well known Sequence Stratigraphy cornerstones. The goal of this dissertation is to propose an interpretation methodology of GPR data able to perform this task at least for siliciclastic deposits. In order to do so, the proposed GPR interpretation method is based both on seismostratigraphic concepts and on the bounding surface hierarchy tool from Miall (1988). As consequence of this joint use, the results of GPR interpretation can be associated to the sedimentary facies in a genetic context, so that it is possible to: (i) individualize radar facies and correlate them to the sedimentary facies by using depositional models; (ii) characterize a given depositional system, and (iii) determine its stratigraphic framework highligthing how it evolved through geologic time. To illustrate its use the proposed methodology was applied in a GPR data set from Galos area which is part of the Galinhos spit, located in Rio Grande do Norte state, Northeastern Brazil. This spit presents high lateral sedimentary facies variation, containing in its sedimentary record from 4th to 6th cicles caused by high frequency sea level oscillation. The interpretation process was done throughout the following phases: (i) identification of a vertical facies succession, (ii) characterization of radar facies and its associated sedimentary products, (iii) recognition of the associated sedimentary process in a genetic context, and finally (iv) proposal of an evolutionay model for the Galinhos spit. This model proposes that the Galinhos spit is a barrier island constituted, from base to top, of the following sedimentary facies: tidal channel facies, tidal flat facies, shore facies, and aeolic facies (dunes). The tidal channel facies, in the base, is constituted of lateral accretion bars and filling deposits of the channels. The base facies is laterally truncated by the tidal flat facies. In the foreshore zone, the tidal flat facies is covered by the shore facies which is the register of a sea transgression. Finally, on the top of the stratigraphic column, aeolic dunes are deposited due to areal exposition caused by a sea regression / O Radar Penetrante no Solo (Ground Penetrating Radar GPR) tem sido utilizado para mapear em detalhe dep?sitos sedimentares, devido ? sua alta resolu??o. Pelo fato de que os m?todos GPR e S?smico t?m princ?pios de forma??o de imagens muito semelhantes, o modelo cl?ssico de interpreta??o s?smica, baseado na sismoestratigrafia, tem sido tentativamente utilizado para interpretar dados de GPR. N?o obstante os grandes avan?os j? realizados em contextos particulares, as adapta??es propostas das ferramentas e conceitos da sismoestratigrafia, para o GPR, ainda s?o inadequadas; isto acontece basicamente porque as interpreta??es atribu?das aos padr?es de termina??o, extra?dos da sismoestratigrafia convencional, n?o representam o registro geol?gico na escala de opera??o do GPR. O problema conceitual reside, pois, em propor um m?todo de interpreta??o que permita n?o s? relacionar produto e processo sedimentar, na escala do GPR, mas tamb?m identificar ou propor ambientes deposicionais e correlacionar estes resultados com os blocos construtores da Estratigrafia de Seq??ncias. O objetivo desse trabalho ? propor uma metodologia de interpreta??o de dados de GPR capaz de realizar esta tarefa, pelo menos no contexto de dep?sitos silicicl?sticos. Para este fim, prop?e-se uma interpreta??o de dados de GPR, baseada na adapta??o de termos e conceitos herdados da sismoestratigrafia, em conjunto com uma metodologia de hierarquiza??o de superf?cies limitantes (bounding surfaces), a exemplo da metodologia proposta por Miall (1988). Como conseq??ncia direta desta combina??o, a interpreta??o dos dados de GPR pode ser associada ?s f?cies sedimentares, dentro de um contexto gen?tico, possibilitando assim: (i) individualizar as radarf?cies e correlacion?-las ?s f?cies sedimentares, com base em modelos de f?cies sedimentares; (ii) caracterizar um determinado sistema deposicional e, principalmente, (iii) determinar seu arcabou?o estratigr?fico, mostrando como ele evoluiu no tempo geol?gico. Para exemplificar a utiliza??o desta metodologia de interpreta??o foram utilizados os dados de GPR adquiridos na ?rea de Galos, que faz parte do spit de Galinhos, localizado no Estado do Rio Grande do Norte. Este spit apresenta grande variedade lateral de f?cies sedimentares e cont?m registros sedimentares que s?o sens?veis ?s varia??es de freq??ncia mais alta do n?vel relativo do mar (ciclos de 4? a 6? ordens). O processo de interpreta??o constou das seguintes fases: (i) estabelecimento de uma sucess?o vertical de f?cies, (ii) caracteriza??o dos produtos sedimentares (radarf?cies), (ii) atribui??o de processos sedimentares dentro de um cunho gen?tico, e finalmente (iv) estabelecimento de um modelo evolutivo para o spit de Galinhos. O modelo prop?e que este spit constitui um sistema do tipo Ilhas Barreiras que ? materializado, da base para o topo, por f?cies de estreito de mar? (tidal inlet), f?cies de plan?cie de mar?, f?cies de praia e f?cies e?lica (dunas). A f?cies de estreito de mar?, na base, ? representada por barras de acres??o lateral que preencheram os estreitos de mar?. Estes dep?sitos s?o truncados lateralmente pela f?cies de plan?cie de mar?. Na zona de intermar? antiga, a f?cies de intermar? encontra-se sobreposta pela f?cies de praia, marcando assim um avan?o relativo da linha de costa. Por fim, no topo da coluna estratigr?fica, est?o depositadas dunas e?licas, denotando o recuo da linha de costa e conseq?ente exposi??o a?rea

Cette thèse a deux objectifs principaux: (i) la reconstruction de l'évolution des plaines côtières autour des baies de Chabahar et de Pozm et (ii) L'évaluation des risques côtiers (tsunamis et tempêtes extrêmes) par l'étude des dépôts de haute énergie. Vastes plaines côtières et paleo-rivages protégées par des terrasses marines soulevées sont présents autour des baies de Chabahar et Pozm. Nous avons mise en évidence des changements du niveau marin relatif le long de quatre profils. L'architecture interne des paleo-rivages a été imagée en utilisant le géoradar (GPR). Des analyses sédimentologiques et stratigraphiques des séquences côtières ont été examinées par carottages et tranchées. Les paleo-rivages sont datées entre 4800 et 270 ans BP à des distances respectives de 5 km et de 670 m du rivage actuel. La position spatiale des paléo-rivages montre une chute du niveau relatif de la mer de 15 m au cours des 4800 derniers années. Nous insistons aussi sur le rôle de contrôle des structures géologiques. Les dépôts d'événements (tsunami et tempêtes) ont été étudiés en contexte de côte meuble par Les sédiments sableux et coquilliers d'origine marine, et sur les côtes rocheuses par les dépôt des blocs déplacés. Nous avons appliqué des modèles hydrologiques pour évaluer et comparer la hauteur des vagues et la distance d'inondation. Nos résultats montrent qu'aucun événement de tempête, connu ou potentiel, n'est capable de transporter les blocs observés. Des vagues de tsunamis de l'ordre de 4 m de hauteur sont suffisantes pour transporter les blocs. La côte de Makran a enregistré des indices de paléo-tsunamis probablement générés par de grands séismes dans la zone de subduction. / In this thesis we have two main goals: (i) to reconstruct the Holocene coastal evolution and relative sea-level changes using strandplains around the Chabahar and Pozm bays; and (ii) to evaluate coastal hazards (tsunami and extreme storms) along the Iranian coast of Makran using high-energy deposits. Since the mid-Holocene, the shoreline rimming the bays of Chabahar and Pozm has prograded ~5 km and formed extensive strandplains. We documented relative sea-level changes along four coast-normal profiles. Internal architecture of strandplain imaged using Ground Penetrating Radar (GPR). The sedimentology and stratigraphy of the coastal sequence were studied by coring and trenching. The highest paleo-coastline is located about 5 km inland and stands approximately 15 m above present sea level. Paleo-shorelines date back between 4800 and 270 years BP at respective distances of 5 km to 670 m from the active shoreline. The spatial position of the palaeo-coastlines demonstrates a fall in local sea level of around 15 m during the last ~4800 years. Event deposits attesting to high-energy waves have been studied in low-lying coast by study of Over-washed sandy and shelly marine sediment and on the rocky shore by study of displaced boulder deposits. We applied hydrologic models to estimate the height and inundation distance of exceptional waves. Our results demonstrate that no known or probable storm is capable of detaching and transporting the boulders. Tsunami waves 4 m in height are enough to transport the boulders. We conclude the Makran coast has archived evidence of palaeo-tsunami events generated in the Makran subduction zone.

[pt] No estado do Rio de Janeiro, os movimentos de massa em encostas passaram a representar um dos problemas mais importantes em geotecnia devido ao seu relevo acidentado, forma de ocupação e condições climáticas rigorosas. Visando identificar uma alternativa para avaliar encostas usando métodos não invasivos que possibilitem o trabalho em locais de difícil acesso, com rapidez e aquisição contínua de dados, neste trabalho é exposto uma análise teórica e prática deste processo de avaliação utilizando métodos geofísicos e o monitoramento contínuo da água no solo por meio de sensores. Os levantamentos geofísicos com uso do georadar e da análise multicanal de ondas superficiais para investigação da estratigrafia da encosta estudada, possibilitaram a identificação de três camadas: solo maduro, solo residual jovem e rocha. Para o monitoramento contínuo, são usados sensores de umidade volumétrica, sucção e um pluviômetro durante um período de 6 meses com a coleta de dados a cada 10 minutos. Com a interpretação dos dados coletados, verificou-se uma boa funcionalidade do monitoramento para avaliar as respostas de sucção e umidade volumétrica ao longo de períodos com intervalos irregulares de chuva. Os dados de precipitação e estratigrafia identificados são usados nas análises de infiltração e estabilidade saturada e não saturada, que possibilitaram a identificação de seções críticas com fator de segurança abaixo de 1,5, onde são necessárias intervenções para garantir a segurança da vizinhança. / [en] In the state of Rio de Janeiro, mass movements on slopes have become one of the most important geotechnical problems due to their rugged terrain, occupation and harsh weather conditions. In order to identify an alternative to evaluate slopes using non-invasive methods that enable work in hard to reach places, with rapid and continuous data acquisition, this paper presents a theoretical and practical analysis of this evaluation process using geophysical methods and continuous monitoring ground water through sensors. Geophysical surveys using georadar and multichannel analysis of surface wave to investigate the stratigraphy of the studied slope, allowed the identification of three layers: mature soil, young residual soil and rock. For the continuous monitoring, volumetric humidity and suction sensors and a rain gauge are used for a period of 6 months with data collection every 10 minutes. With the interpretation of the collected data, a good monitoring functionality was verified to evaluate the suction and volumetric humidity responses during periods with irregular rain intervals. The identified precipitation and stratigraphy data are used in the infiltration and saturated stability analyzes, which allowed the identification of critical sections with safety factor below 1.5, where interventions are necessary to ensure the safety of the neighborhood.