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Deep geological repositories (DGR) are considered an effective long-term solution for radioactive waste disposal. Sedimentary (argillaceous formations) and crystalline rocks are currently under investigation worldwide as potential host formations for DGR. Their low porosity (<1-2 %) and very low hydraulic conductivity result in diffusion-dominated solute transport. There is a need to investigate their diffusion properties in detail, the long-established diffusion methods do not allow an evaluation of the spatial relationship between tracers and the characteristics of the geological medium. The aim of this project was to measure diffusion coefficients in low-porosity rocks (< 2%) using X-ray radiography and iodide tracer. The method is a non-destructive technique based on the principle of X-ray attenuation; it provides temporal- and spatially-resolved information of a highly attenuating tracer diffusing in a sample. Samples from the Cobourg Formation, an Ordovician argillaceous limestone from the Michigan Basin, and from the Lac du Bonnet batholith, an Archean granitic pluton were used in this study. X-ray radiography data from the Cobourg Formation indicate tracer accumulation occurs on dark argillaceous layers in the rock characterized by clay minerals and organic matter. It is proposed that the I– tracer solution underwent photo-chemical oxidation, leading to the formation of I2, a highly reactive volatile iodine species and I3–, which readily reacted with humic substances contained in the clay- and organic rich zones in the limestone samples. In the case of the granitic samples, attempts at measuring diffusion coefficients encountered several challenges. The results indicate that tracer signal can be detected, however diffusion signal is masked by imaging errors and noise.

Orientador: Joel Carneiro de Castro / Banca: Maria Rita Caetano Chang / Banca: Luiz Carlos Weinschütz / Resumo: Os membros Lontras (Formação Campo Mourão) e Rio Segredo (Formação Taciba) constituem uma sucessão marinha de folhelhos e arenitos turbidíticos, que está encaixada entre diamictitos glaciais daquelas formações. O folhelho Lontras tem uma centena de metros na faixa aflorante norte catarinense, contendo em sua porção superior a fácies "folhelho várvico", na verdade um estrato com gradação de siltito a folhelho (Tde) em escala milimétrica e que é considerado como sendo o turbidito distal da sucessão. O turbidito Rio Segredo tem de 15 a 25 m e consiste de estratos gradacionais portando sequência Bouma em diversas escalas: muito delgado (1 a 3 cm; Tde e Tcde), delgado (3 a 10 cm; Tcde e Tbcde), médio (10 a 30 cm; Tbcde e Tabcde), espesso (30 a 100 cm; Tabc) e muito espesso (acima de 1,0 m; Tabc). Há ainda uma divisão "superior" do Membro Rio Segredo normalmente com 10 a 20 m de espessura, que contém turbiditos areno-argilosos muito delgados (Tcde e Tde). Foram levantados sete perfis faciológicos de detalhe, escala 1:50, de modo a registrar turbiditos com até 5 cm de espessura (1 mm no perfil). Posteriormente, quatro desses perfis foram cronocorrelacionados em uma seção norte-sul: Forcação, Wiegand, Laeisz e Dona Emma, numa extensão de 28 km. A esta seção foi acrescido o perfil Taiózinho, localizado 30 km a oeste do Forcação, entre os dois últimos (semelhança faciológica com o Laeisz). Identificaram-se sete sistemas deposicionais, com uma média de 3 m de espessura por sistema e contidos em três sequências de alta frequência. Os sistemas deposicionais são formados por ciclos turbidíticos de origem marinha, encontrados principalmente nos perfis Laeisz e Taiózinho, com uma organização ascendente de adelgaçamento e granodecrescência. Outros ciclos turbidíticos... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The Lontras shale and overlying Rio Segredo sandstone are members of Campo Mourão and Taciba formations, corresponding to shelf marine and turbidite deposits; they are encased in glacial diamictites of those formations. The Lontras shale is 100 m thick in northern Santa Catarina outcrop belt and it displays a "varved shale" facies in its upper portion. In reality, it represents many mm-scale beds with Bouma sequence Tde, and therefore distal, argillaceous turbidites. The Rio Segredo Member is 15 to 25 m thick and contain beds of different thicknesses: very thin (1 to 3 cm; Tde and Tcde), thin (3 to 10 cm; Tcde and Tbcde), and medium beds (10 to 30 cm; Tbcde and Tabcde). Also, thick (30 to 100 cm) and very thick beds (thicker than 1 m) displays massive or graded sandstones with disperse laminations and cross-laminations resembling Ta, Tb and Tc intervals of Bouma sequence. There is also a Rio Segredo "upper" division with 10 to 20 m thick, consisting of very thin turbidites (Tcde and Tde). Seven detailed facies logs were constructed at 1:50 scale, to represent even 5 cm thin beds (1 mm). Later, four of the logs were put in a north-south stratigraphic section (28 km in length): Forcação, Wiegand, Laeisz and Dona Emma, in a 28 km extension. A fifth log, Taiózinho (distant 30 km west of Forcação), was added to the section between the last two logs, because of its facies similarity with Laeisz log. Seven depositional systems are identified, averaging 3 m thick in, thickness, and they belong to high frequency sequences. The systems are composed of turbidite cycles of marine origin, found mainly in Laeisz and Taiózinho logs: they form thinning- and fining-upward cycles. Turbidite cycles of deltaic origin are observed in Forcação and Dona Emma logs as thickening-up and coarsening-up cycles. In the latter, are included... (Complete abstract click electronic access below) / Mestre

Made available in DSpace on 2014-06-11T19:26:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-04-17Bitstream added on 2014-06-13T19:06:23Z : No. of bitstreams: 1 andrade_lrm_me_rcla.pdf: 1854084 bytes, checksum: 37c55097ff800285da56aac3723135e2 (MD5) / Os membros Lontras (Formação Campo Mourão) e Rio Segredo (Formação Taciba) constituem uma sucessão marinha de folhelhos e arenitos turbidíticos, que está encaixada entre diamictitos glaciais daquelas formações. O folhelho Lontras tem uma centena de metros na faixa aflorante norte catarinense, contendo em sua porção superior a fácies “folhelho várvico”, na verdade um estrato com gradação de siltito a folhelho (Tde) em escala milimétrica e que é considerado como sendo o turbidito distal da sucessão. O turbidito Rio Segredo tem de 15 a 25 m e consiste de estratos gradacionais portando sequência Bouma em diversas escalas: muito delgado (1 a 3 cm; Tde e Tcde), delgado (3 a 10 cm; Tcde e Tbcde), médio (10 a 30 cm; Tbcde e Tabcde), espesso (30 a 100 cm; Tabc) e muito espesso (acima de 1,0 m; Tabc). Há ainda uma divisão “superior” do Membro Rio Segredo normalmente com 10 a 20 m de espessura, que contém turbiditos areno-argilosos muito delgados (Tcde e Tde). Foram levantados sete perfis faciológicos de detalhe, escala 1:50, de modo a registrar turbiditos com até 5 cm de espessura (1 mm no perfil). Posteriormente, quatro desses perfis foram cronocorrelacionados em uma seção norte-sul: Forcação, Wiegand, Laeisz e Dona Emma, numa extensão de 28 km. A esta seção foi acrescido o perfil Taiózinho, localizado 30 km a oeste do Forcação, entre os dois últimos (semelhança faciológica com o Laeisz). Identificaram-se sete sistemas deposicionais, com uma média de 3 m de espessura por sistema e contidos em três sequências de alta frequência. Os sistemas deposicionais são formados por ciclos turbidíticos de origem marinha, encontrados principalmente nos perfis Laeisz e Taiózinho, com uma organização ascendente de adelgaçamento e granodecrescência. Outros ciclos turbidíticos... / The Lontras shale and overlying Rio Segredo sandstone are members of Campo Mourão and Taciba formations, corresponding to shelf marine and turbidite deposits; they are encased in glacial diamictites of those formations. The Lontras shale is 100 m thick in northern Santa Catarina outcrop belt and it displays a “varved shale” facies in its upper portion. In reality, it represents many mm-scale beds with Bouma sequence Tde, and therefore distal, argillaceous turbidites. The Rio Segredo Member is 15 to 25 m thick and contain beds of different thicknesses: very thin (1 to 3 cm; Tde and Tcde), thin (3 to 10 cm; Tcde and Tbcde), and medium beds (10 to 30 cm; Tbcde and Tabcde). Also, thick (30 to 100 cm) and very thick beds (thicker than 1 m) displays massive or graded sandstones with disperse laminations and cross-laminations resembling Ta, Tb and Tc intervals of Bouma sequence. There is also a Rio Segredo “upper” division with 10 to 20 m thick, consisting of very thin turbidites (Tcde and Tde). Seven detailed facies logs were constructed at 1:50 scale, to represent even 5 cm thin beds (1 mm). Later, four of the logs were put in a north-south stratigraphic section (28 km in length): Forcação, Wiegand, Laeisz and Dona Emma, in a 28 km extension. A fifth log, Taiózinho (distant 30 km west of Forcação), was added to the section between the last two logs, because of its facies similarity with Laeisz log. Seven depositional systems are identified, averaging 3 m thick in, thickness, and they belong to high frequency sequences. The systems are composed of turbidite cycles of marine origin, found mainly in Laeisz and Taiózinho logs: they form thinning- and fining-upward cycles. Turbidite cycles of deltaic origin are observed in Forcação and Dona Emma logs as thickening-up and coarsening-up cycles. In the latter, are included... (Complete abstract click electronic access below)

Shea Creek est un gisement d'uranium liée à la discordance entre un socle métamorphique et des roches sédimentaires d'origine fluviatile, d'âge Paléo-protérozoïque et situé dans la partie ouest du bassin d'Athabasca. Ce gisement majeur est le plus profond connu actuellement dans le bassin (entre 680 m et 1000 m de profondeur). Il rassemble en un même lieu tous les types de minéralisation associés à une discordance connus de par le monde. Cette étude s'appuie sur l'analyse de plus de 1200 échantillons du halo d'altération qui entoure le gisement et sur l'utilisation des données d'exploration minière. L'objectif est double. Il s'agit d'une part de déterminer des guides sédimentologiques, pétrographiques, minéralogiques et géochimiques pour la prospection des corps minéralisés en zone profonde et d'autre part d'utiliser ces critères pour construire une représentation tridimensionnelle simplifiée (minéralisation et halo d'altération) permettant de préciser le modèle génétique de ce gisement profond. La localisation des différentes zones minéralisées dépend non seulement des phénomènes d'altération liés aux circulations hydrothermales contrôlées par la tectonique, mais aussi de la nature du remplissage sédimentaire et de son évolution diagénétique. L'architecture de la zone minéralisée de Shea Creek montre que les corps minéralisés sont localisés dans des structures en grabben remplies par des alternances de grès propres et de grès argileux souvent préservés de la compaction et de l'altération. La signature minéralogique et géochimique de ces grès suggère un apport provenant de l'érosion de paléo-altérites continentales (régolithe). La très forte concentration en défauts d'ir / Shea Creek is an unconformity-type uranium deposit located in the west part of Atabaska basin. It is related to an unconformity between a metamorphic basement and sedimentary rocks of fluvial origin, of paleoproterozoic age. Shea Creek's particularity is to be the deepest ore deposit ever known in the basin (between 680 m and 1000 m deep). It gathers all types of unconformity hosted mineralization known. More than 1200 samples, taken from halo alteration around the deposit, were analyzed and mining exploration data were used for this study. First, the aim was to determine the markers for prospection of mineral elements in deep area: sedimentological, petrographical, geochemical and mineralogical types. Then, it was to build a simple three-dimensional model (mineralization and alteration halo) using these criteria in order to precise the genetic pattern of this deep deposit. The location of mineralized areas depends on tectonic deformation, on sedimentary filling and diagenetic development. The morphology of Shea Creek’s ore deposit shows clearly that mineralization is located in the grabbens composed by clean sandstones and clay sandstones, often preserved from compaction and alteration phenomena. The mineralogical and geochemical signature of these clay sandstones suggests a contribution from the erosion of continental paleo-alterite (regolith). Beside, the great concentration of radiation induced defects suggests the presence in abundance of uranium in the grabbens from sedimentary state.

La nature est complexe et c’est en toute modestie que les ingénieurs doivent chercher à prédire le comportement des ouvrages dans le sous-sol. La réalisation de projets industriels dans le domaine souterrain, à forts enjeux économiques et sociaux (traversées alpines, stockage de déchets nucléaires), nécessite d’évoluer vers une meilleure compréhension des mécanismes comportementaux des ouvrages à concevoir. Cette amélioration passe par une meilleure représentativité physique des mécanismes macroscopiques et par la mise à disposition d’outils de prédiction adaptés aux attentes et aux besoins des ingénieurs. Les outils de calculs développés dans ce travail s’inscrivent dans cette volonté de rapprocher les attentes de l’industrie et les connaissances liées à la rhéologie des géomatériaux. Ces développements ont ainsi débouché sur la proposition d’un modèle de comportement mécanique, adapté aux roches peu fissurées et assimilables à des milieux continus, intégrant, en particulier, l’effet du temps. Fil conducteur de cette étude, la problématique du sujet de thèse concerne précisément la prise en compte du comportement différé des massifs rocheux dans les modélisations et ses conséquences sur les ouvrages souterrains.Fondé sur des concepts physiques de référence, définis à différentes échelles (macro/méso/micro), le modèle rhéologique développé est transcrit dans un formalisme mathématique dans le but d’être mis en oeuvre numériquement.Les applications numériques proposées s’inscrivent principalement dans le contexte du stockage des déchets radioactifs. Elles concernent deux configurations d’ouvrages rigoureusement différentes : l’excavation du laboratoire souterrain canadien de l’AECL, dans le granite du Lac du Bonnet et le creusement de la galerie GMR du laboratoire de Bure (Meuse/Haute-Marne) dans l’argilite de l’Est. Dans les deux cas, l’utilisation du modèle a permis de mettre en évidence l’apport de la prise en compte du comportement différé sur la représentativité des prédictions numériques du comportement à court, moyen et long termes des ouvrages souterrains / Nature is complex and must be approached in total modesty by engineers seeking to predict the behavior of underground openings. The engineering of industrial projects in underground situations, with high economic and social stakes (Alpine mountain crossings, nuclear waste repository), mean striving to gain better understanding of the behavioral mechanisms of the openings to be designed. This improvement necessarily involves better physical representativeness of macroscopic mechanisms and the provision of prediction tools suited to the expectations and needs of the engineers. The calculation tools developed in this work is in step with this concern for satisfying industrial needs and developing knowledges related to the rheology of geomaterials. These developments led to the proposing of a mechanical constitutive model, suited to lightly fissured rocks, comparable to continuous media, while integrating more particularly the effect of time.Thread of this study, the problematics ensued from the subject of the thesis is precisely about the rock mass delayed behavior in numerical modeling and its consequences on underground openings design.Based on physical concepts of reference, defined in several scales (macro/meso/micro), the developed constitutive model is translated in a mathematical formalism in order to be numerically implemented.Numerical applications presented as illustrations fall mainly within the framework of nuclear waste repository problems. They concern two very different configurations of underground openings: the AECL’s underground canadian laboratory, excavated in the Lac du Bonnet granite, and the GMR gallery of Bure’s laboratory (Meuse/Haute-Marne), dug in argillaceous rock.In this two cases, this constitutive model use highlights the gains to be obtained from allowing for delayed behavior regarding the accuracy of numerical tunnel behavior predictions in the short, medium and long terms