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L'étude des matériaux argileux a de nombreuses applications en génie civil et environnemental. Ces applications, telles que l'enfouissement des déchets nucléaires, les risques naturels liés au gonflement et au retrait des sols, et l'extraction d'hydrocarbures, posent des défis technologiques qui nécessitent de comprendre et de prédire le comportement mécanique des argiles, en particulier sur le long terme. Les argiles gonflantes sont des matériaux complexes, poreux et multi-échelles dont les propriétés sont très sensibles à l'eau. Dans cette thèse, nous cherchons à comprendre l'effet de l'eau sur les propriétés mécaniques à court et long terme des argiles. Notre stratégie est de combiner des simulations numériques à l'échelle du nanomètre et des expériences à l'échelle du micromètre afin de mieux comprendre l'interaction entre ces échelles. Nous avons effectué des simulations moléculaires pour quantifier l'effet de l'eau et du cation interfoliaire sur les propriétés de gonflement, élastiques et de fluage des feuillets d'argile, qui à cette échelle sont inaccessibles à l'expérience. Nous avons également effectué une étude comparative de différents modèles de feuillets d'argile de complexité croissante afin de mieux comprendre les interactions qui régissent la cohésion entre les feuillets d'argile. Nous avons mesuré expérimentalement les propriétés de films d'argile autoporteurs bien ordonnés. Nous avons montré l'effet de l'humidité relative et de la nature du cation interfoliaire sur les déformations de ces films d'argile. En particulier, nous avons quantifié le gonflement de ces films induit par l'humidité en combinant microscopie électronique à balayage environnementale et corrélation d'images numériques. Nous avons également effectué des essais de traction et de fluage sur ces films à humidité contrôlée. Nous avons comparé les données obtenues par nos expériences aux résultats des simulations moléculaires. Cette comparaison permet de discuter les mécanismes élémentaires de déformation et les échelles pertinentes pour la compréhension du comportement hydromécanique des argiles / The study of clay-based materials has many applications in civil and environmental engineering. These applications include underground nuclear waste disposal, the natural risks associated to the swelling and shrinkage of soils, and the extraction of hydrocarbons. They pose significant technological challenges that require to understand and to predict the mechanical behavior of clays, in particular on the long term. Swelling clays are complex porous multi-scale materials and their properties are very sensitive to water. In this thesis, we aim at understanding the impact of water on the short-term and long-term mechanical properties of clays. Our strategy was to combine numerical simulations at the scale of the nanometer and experiments at the scale of the micrometer to have a better insight of the interplay between these scales. We performed molecular simulations to estimate the effect of water and of the interlayer cation on the swelling, elastic and creep properties of clay layers, which are inaccessible to experiments at this scale. We also carried out a comparative study of various numerical models of increasing complexity in order to better understand the interactions that governs the cohesion between the clay layers. We measured experimentally the properties of well-ordered self-supporting clay films. We investigated the impact of relative humidity and of the nature of the interlayer cation on the mechanical properties of these clay films. In particular, we quantified the humidity-induced swelling of these films by using a combination of environmental scanning electron microscopy and digital image correlation. We also performed tensile tests and creep tests on these films at controlled relative humidity. We compared the data obtained by our experiments to the results of the molecular simulations. This comparison makes it possible to discuss the elementary deformation mechanisms and the scales relevant to the understanding of the hydromechanical behavior of clays

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-07-20T12:25:34Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) documento.pdf: 6110083 bytes, checksum: e763b9e4b979081c4ada6fef0eb596a6 (MD5) / Made available in DSpace on 2017-07-20T12:25:34Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) documento.pdf: 6110083 bytes, checksum: e763b9e4b979081c4ada6fef0eb596a6 (MD5) Previous issue date: 2015-08-03 / ANP-PRH26 / Aimportânciadageomecânicaedoestudodeesquemasdeacoplamentoentreageomecânica e fluxo multifásico têm sido cada vez mais importantes e utilizados pela indústria a medida que formações cada vez mais profundas vêem sendo descobertas e exploradas. O entendimento do comportamento do estado de tensão em um reservatório permite produzir um melhor entendimento das implicações geomecânicas que ocorrem durante a fase de explotação, isso porque durante esta fase, as alterações na poro-pressão conduzem perturbações no equilíbrio mecânico afetando o estado de tensão de formações profundas, de maneira a alterar as propriedades da rocha tais como permeabilidade e porosidade. No entanto, a simulação acoplada (hidromecânica) em um grande campo heterogêneo implica na solução de equações de fluxo e mecânica, associadas a um grande número de graus de liberdade que torna esse tipo de abordagem inviável e computacionalmente cara. Neste contexto, um simulador geomecânico-linhas de fluxoé apresentado dentro de um algoritmo sequencial iterativo. Neste trabalho, aplica-se o método de elementos finitos com volume de controle para o subproblema poro-mecânico que fornece um campo de velocidade de Darcy pós-processado e a porosidade como entradas para o subproblema de transporte. Este subproblema é resolvido através do método de decomposição de operador, no qual basea-se em um esquema preditor-corretor com os passos preditor e corretor discretizados pelos esquemas baseados em tempo de vôo e volumes finitos, respectivamente. Simulações numéricas de injeção de água foram comparadas com soluções encontradas na literatura, mostrando bons resultados. Em problemas dominados pela advecção, envolvendo um reservatório naturalmente fraturado, a abordagem implementada foi capaz de predizer a distribuição do campo de saturação ao longo de toda simulação. Além disso, para avaliar a resposta geomecânica, simulações numéricas foram realizadas em um grande sistema de reservatório-rocha capeadora em uma fase de recuperação primária de hidrocarboneto, mostrou que a formulação apresentada provou ser: uma alternativa promissora para simulação hidro-geomecânica tradicional; úteis para o modelo de fluxo de redução de ordem nos casos em que o comportamento geomecânico são mais importantes do que o comportamento de fluxo e de uma ferramenta complementar para simulação geomecânica convencional. / The importance of geomechanics and the study of coupling between geomechanics and multiphase flow have been increasingly recognized and used by the industry as deeper formations are discovered and exploited. The knowledge of the state of stress in a reservoir yields a better understanding of the geomechanical implications during exploitation stage, because during the primary recovery stage, changes in pore pressure leads to perturbations inthemechanicalequilibrium,affectingthestressstateintheformationsinawaythatalters the rock properties such as permeability and porosity. However, the coupled simulation (hydromechanical) in large field heterogeneous models involves stress and flow equations solving, associated with a large number of degrees-of-freedom which becomes infeasible and computationally costly. In this context, a geomechanical-streamline simulator is presented within a iteratively coupled framework algorithm. In the present work, we applied control volume finite element method for the poromechanics subproblem which provides a Darcy velocityfieldthroughapost-processingvelocityprocedureandporosityasinputfieldstothe transportsubproblem.Suchsubproblemissolvedbymeansofanoperatorsplittingmethod, which is based on a predictor-corrector scheme with the predictor and corrector steps discretized by a time-of-flight and a finite volume based schemes, respectively. Numerical simulations of water-flooding are compared to the numerical results available in literature, showing good results. In convection-dominated problems, involving a naturally fractured reservoir, the approach was able to predict the saturation distributions for the whole simulation correctly. Furthermore, to appraisal the geomechanical response, numerical simulation was performed in a large reservoir-caprock system in a primary hydrocarbon recovery stage, showing that the formulation presented proved be: an promising alternative to traditional hydro-geomechanical simulation; useful for flow model order reduction in cases where the geomechanical behavior are more important than the flow behavior and a complementary tool for conventional geomechanical simulations.

Nuclear power generation is being regarded as a solution to ever increasing demand for electricity, and concerns over global warming and climate change due to the use of fossil fuels. Although nuclear power generation is considered to be reliable, economical, clean, and safe, the wastes produced from the nuclear fuel cycle are not, and can remain hazardous for hundreds of thousands of years. An international consensus has developed over the past several decades that deep geologic disposal of low, intermediate, and high level radioactive wastes is the best option to protect the biosphere. In this thesis, both regional scale and sub-regional scale models are created to simulate groundwater flow and transport for a representative Canadian Shield setting, honouring site-specific topography and surface water features. Sub-surface characteristics and properties are derived from numerous geoscience studies. In addition, a regional scale model is developed, centred on the Bruce Nuclear Power Development (BNPD) site near Tiverton, Ontario, and located within the Michigan Basin. Ontario Power Generation (OPG) has proposed a Deep Geologic Repository (DGR) for low & intermediate level waste (L&ILW) at the BNPD site. Paleoclimate simulations using various combinations of parameters are performed for both the Canadian Shield Sub-Regional model, and the Michigan Basin Regional model. Fracture zone permeability is a very important parameter when modelling crystalline rock settings. Migration of a unit tracer representing glacial recharge water can occur to depth in fractures of high permeability. Representative rock compressibility values are necessary as compressibilities are used to calculate storage coefficients, and the one-dimensional loading efficiency; these affect the subsurface propagation of elevated pore pressures due to glacial loading at surface. Coupled density-dependent flow and transport in paleoclimate simulations affects deep flow systems and provides a measure of flow stability, as well as increasing the mean life expectancy at depth. Finally, hydromechanical coupling is a very important mechanism for reducing vertical hydraulic gradients during a glaciation event when a hydraulic boundary condition equal to the pressure at the base of an ice-sheet is applied at ground surface. Pore water velocities are reduced, thereby retarding migration of surface waters into the subsurface environment.

Nuclear power generation is being regarded as a solution to ever increasing demand for electricity, and concerns over global warming and climate change due to the use of fossil fuels. Although nuclear power generation is considered to be reliable, economical, clean, and safe, the wastes produced from the nuclear fuel cycle are not, and can remain hazardous for hundreds of thousands of years. An international consensus has developed over the past several decades that deep geologic disposal of low, intermediate, and high level radioactive wastes is the best option to protect the biosphere. In this thesis, both regional scale and sub-regional scale models are created to simulate groundwater flow and transport for a representative Canadian Shield setting, honouring site-specific topography and surface water features. Sub-surface characteristics and properties are derived from numerous geoscience studies. In addition, a regional scale model is developed, centred on the Bruce Nuclear Power Development (BNPD) site near Tiverton, Ontario, and located within the Michigan Basin. Ontario Power Generation (OPG) has proposed a Deep Geologic Repository (DGR) for low & intermediate level waste (L&ILW) at the BNPD site. Paleoclimate simulations using various combinations of parameters are performed for both the Canadian Shield Sub-Regional model, and the Michigan Basin Regional model. Fracture zone permeability is a very important parameter when modelling crystalline rock settings. Migration of a unit tracer representing glacial recharge water can occur to depth in fractures of high permeability. Representative rock compressibility values are necessary as compressibilities are used to calculate storage coefficients, and the one-dimensional loading efficiency; these affect the subsurface propagation of elevated pore pressures due to glacial loading at surface. Coupled density-dependent flow and transport in paleoclimate simulations affects deep flow systems and provides a measure of flow stability, as well as increasing the mean life expectancy at depth. Finally, hydromechanical coupling is a very important mechanism for reducing vertical hydraulic gradients during a glaciation event when a hydraulic boundary condition equal to the pressure at the base of an ice-sheet is applied at ground surface. Pore water velocities are reduced, thereby retarding migration of surface waters into the subsurface environment.

Orientador: Osvaldo Luís Manzoli / Resumo: Materiais porosos constituem uma grande gama de materiais que podem ser encontrados na natureza ou em forma artificial. Rochas reservatório é um exemplo importante desse tipo de material, sendo o estudo delas a motivação principal desse trabalho. O estudo de rochas reservatório, de onde são extraídos gases e petróleo, consiste em um problema físico no qual os sistemas mecânico e hidráulico são acoplados. O acoplamento ocorre pois as deformações (no sistema mecânico) inuenciam as pressão (no sistema hidráulico), que por sua vez inuenciam as tensões (sistema mecânico). As equações governantes do sistema mecânico são mostradas e as do hidráulico deduzidas. Para a resolução do problema, o Método dos Elementos Finitos (MEF) foi utilizado para ambos os sistemas físicos, logo, as equações governantes são apresentadas em sua forma fraca e, então, aproximada pelo MEF. Numericamente, o acoplamento pode ser tratado de diferentes maneiras, seja considerando um dos sistemas de maneira bem pobre tal como fórmulas empíricas simplistas, seja considerado os sistemas de maneira individual, ou então de maneira completa. Essa última maneira de considerar um acoplamento, o acoplamento total, é formulada, programada e testada nesse trabalho. Para validar a implementação, dois problemas foram analisados: Problema de Terzaghi e Problema Mandel, ambos com solução analítica conhecidas. Os resultados obtidos numericamente comparados aos analíticos indicam que o método totalmente acoplado foi bem implem... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Porous materials constitute a wide range of materials that can be found in nature and arti cially. Reservoir rock is an important example of this kind of material, which is the main motivation of this work. The study of reservoir rocks, from which gases and oil are extracted, consists of a physical problem in which mechanical and hydraulic systems are coupled. The coupling occurs because the deformations (in the mechanical system) in uence the pressure (in the hydraulic system), which in turn in uence the stresses (mechanical system). The governing equations of the mechanical system are shown and those of the hydraulic system are deduced. To solve the problem, the Finite Element Method (FEM) is used for both physical systems, so the governing equations are presented in their weak form and then approximated according to the FEM. Numerically, the coupling can be handled in di erent ways, either by considering one of the systems in a very poor way by using simplistic empirical formulas, by considering the systems individually, or in a complete manner. The latter one, the fully-coupled treatment, is formulated, programmed and tested in this work. To validate the implementation, two problems has been analyzed: Terzaghi Problem and Mandel Problem, both with known analytical solutions. The comparison between the results obtained numerically and analytically indicates that the fully coupled method has been well implemented in both 2D and 3D cases. The numerical oscillation existing i... (Complete abstract click electronic access below) / Mestre

Le but de cette thèse est de mettre en place un nouveau modèle de comportement hydromécanique permettant de prendre en compte les anisotropies initiale et induite et l'impact de l'endommagement mécanique sur la perméabilité. Afin de construire ce modèle, une nouvelle approche de modélisation permettant d'étendre les lois de comportement mécaniques des matériaux isotropes aux matériaux anisotropes est développée. Cette approche, employée dans le cadre des milieux continus à variables internes, est utilisée pour construire une loi de comportement elasto-viscoplastique qui distingue les régimes de sollicitation en compression et en traction. Un tenseur de second ordre est introduit pour décrire l'anisotropie induite suite à des sollicitations de traction et une variable interne scalaire est utilisée pour traduire le durcissement/adoucissement du matériau suite à des sollicitations de compression. Sous des sollicitations complexes, ces deux mécanismes sont couplés et l'effet de fermeture/réouverture des fissures est traité. Le couplage endommagement-perméabilité est ensuite modélisé par l'introduction d'une loi phénoménologique reliant la perméabilité intrinsèque du matériau aux variables internes de la mécanique.Ce modèle a été appliqué dans le cas des ouvrages souterrains du site de Bure afin de comprendre les mécanismes d'altération des propriétés hydromécaniques autour des galeries et des alvéoles de stockage causée non seulement par les opérations de creusement mais également par les surpressions dues à la production d'hydrogène gazeux suite à la corrosion des parties métalliques des modules de déchets. / This thesis aims to introduce a new hydromechanical constitutive model taking into account both initial and induced anisotropies and the impact of the mechanical damage on the permeability. To build this model, a new modeling approach is developed allowing the extension of mechanical behavior laws from isotropic materials to transversely isotropic materials. This approach is used, within the framework of continuous media with internal variables, to propose an elasto-viscoplastic behavior law that distinguishes between compressive and tensile loading regimes. A second order tensor is introduced to describe the induced anisotropy due to tensile loadings, and a scalar internal variable is employed to account for hardening and softeningof the material due to compressive loadings. Under complex loadings, these two mechanisms are coupled, and the effect of cracks closing/reopening is taken into consideration. The damage-permeability coupling is modeled by the introduction of a phenomenological law linking the material intrinsic permeability to the mechanical internal variables.The developed model is applied to the case of the underground drifts of Bure site in order to better understand the mechanisms of hydromechanical properties alteration, around drifts and storing cells. Not only the impact of the excavation operations is considered but also the consequences of the overpressures caused by the produced hydrogen due to the corrosion of the metallic parts of nuclear waste containers.

Orientador: Osvaldo Luís Manzoli / Abstract: This work presents a numerical method based on Discrete Fracture Model (DFM) and the Finite Element Method (FEM), where the fractures are approximated by a reduced model. The flow along and across the fracture is described by a simplified set of equations considering both conductive fractures and barriers. The coupled hydromechanical model is composed of a linear poroelastic Biot medium and a nonlinear model based on damage mechanics for the fractures, which captures the nonlinear normal deformation and shear dilation according to the Barton-Bandis model. Both flow and geomechanical models are approximated using the finite element model. Fractures are explicitly represented by three-node standard finite elements with high aspect ratio (i.e. ratio between the largest and the smallest element dimensions) and appropriate constitutive laws. These interface high aspect ratio elements represent a regularization method which continuously approximate the discontinuous pressure and displacement fields on a narrow material band around the fracture. The complete mathematical formulation is presented together with the algorithm suggested for its numerical implementation. The efficiency of the proposed method is demonstrated through numerical examples, as well as the effects of fractures in the hydraulic properties of porous rocks and its dependency of the stress state. / Resumo: Este trabalho apresenta um método numérico baseado no Modelo de Fratura Discreta (MFD) e no Método dos Elementos Finitos (MEF), onde as fraturas são aproximadas por um modelo reduzido. O fluxo ao longo e através da fratura é descrito por um conjunto simplificado de equações, considerando tanto fraturas condutoras quanto barreiras. O modelo hidromecânico acoplado é composto por um meio poroelástico linear e um modelo não linear para fraturas, baseado na mecânica do dano e que captura a deformação normal não linear e a dilatância ao cisalhamento de acordo com o modelo de Barton-Bandis. Os modelos de fluxo e geomecânico são aproximados usando o método dos elementos finitos. As fraturas são explicitamente representadas por elementos finitos triangulares de três nós com elevada razão de aspecto (isto é, a razão entre a maior e a menor dimensão do elemento) e leis constitutivas apropriadas. Esses elementos de elevada razão de aspecto representam um método de regularização que aproxima de forma contínua os campos de pressão e deslocamento descontínuos em uma estreita faixa material ao redor da fratura. A formulação matemática completa é apresentada juntamente com o algoritmo sugerido para sua implementação numérica. A eficiência do método proposto é demonstrada através de exemplos numéricos, bem como os efeitos de fraturas nas propriedades hidráulicas de rochas porosas e sua dependência do estado de tensão. / Mestre

Integrated theoretical and experimental analysis is carried out in this work to investigate the fundamental failure mechanisms and flow patterns involved in the process of fluid injection into dense granular media. The experimental work is conducted with aqueous glycerin solutions, utilizing a novel setup based on a Hele-Shaw cell filled with dense dry sand. The two dimensional nature of the setup allows direct visualization and imaging analysis of the real-time fluid and grain kinematics. The experimental results reveal that the fluid flow patterns show a transition from simple radial flow to a ramified morphology while the granular media behaviors change from that of rigid porous media to localized failure that lead to development of fluid channels. Based on the failure/flow patterns, four distinct failure/flow regimes can be identified, namely, (i) a simple radial flow regime, (ii) an infiltration-dominated regime, (iii) a grain displacement-dominated regime, and (iv) a viscous fingering-dominated regime. These distinct failure/flow regimes emerge as a result of competition among various energy dissipation mechanisms, namely, viscous dissipation through infiltration, dissipation due to grain displacements, and viscous dissipation through flow in thin channels and can be classified based on the characteristic times associated with fluid injection, hydromechanical coupling and viscoelastoplasticity. The injection process is also analyzed numerically using the discrete element method (DEM) coupled with two fluid flow scheme, a fixed coarse grid scheme based on computational fluid dynamics (CFD) and a pore network modeling scheme. The numerical results from the two complementary methods reproduce phenomena consistent with the experimental observations and justify the concept of associating the displacement regimes with the partition among energy dissipation mechanisms. The research in this work, though fundamental in nature, will have direct impacts on many engineering problems in civil, environmental and petroleum engineering such as ground improvement, environmental remediation and reservoir stimulation.

Les glissements de terrain sont les risques naturels fréquents dans le monde. D'une part, ils concernent un comportement alterné pour les géomatériaux : le comportement solide décrit classiquement par la géomécanique, et celui fluide après la rupture. D'autre part, ils peuvent être induits par plusieurs facteurs. Par exemple, la géologie, la topographie, la végétation, la variationclimatique, et les activities humaines. Dans les régions tropiques et tempérées, il est bien connu que les glissements de terrain surviennent fréquemment après les pluies intensives, à cause de la saturation des sols non saturés.Comme jusqu'à présent, il n'y a aucun modèle constitutif satisfaisant pour décrire une telle transition pour les géomatériaux non saturés, nos travaux se concentrent d'abord à un modèle unifié, qui associe un modèle hydro-élasto-plastique pour les géomatériaux non saturés, un modèle visqueux de Bingham, et un critère de transition entre les phases solide et fluide. Le modèle unifié permet dedécrire complètement le comportement avant et après la rupture, induite par des conditions hydromécaniques, pour les géomatériaux non saturés dans un cadre unifié.Ensuite, la Méthode des Eléments Finis avec les Points d'Intégration Lagrangiens (MEFPIL), qui bénéficie des avantages des approches Lagrangiennes (suivre les variables internes) et de celles Eulériennes (traiter les grandes transformations), est améliorée et choisie pour effectuer les calculs dans ce cadre. Nous avons introduit une nouvelle formulation hydro-élasto-plastique avec le couplage hydromécanique basée sur la MEFPIL, et l'implanté dans l'Ellipsis (le code basé sur la MEFPIL). En outre, pour inverser la matrice non symétrique de la formulation, un nouveau solver basé sur la méthode stabilisée du gradient bi-conjugué (BiCGSTAB) a été aussi implanté.Enfin, plusieurs benchmarks sont proposés pour valider le comportement mécanique des géomatériaux non saturés décrit par le modèle, et un glissement de terrain heuristique induit par la pluie est simulé, nous pouvons étudier les effets de paramètres divers sur l'infiltration d'eau et sur la rupture. En outre, une simulation du glissement de terrain à Shien (Chine, 2012), avec des paramètres réels est présentée. / Landslides are common natural disasters all over the world. On one hand, they implicate an alternate behaviour for geomaterials: the solid behaviour dealt with classically by geomechanics, and the fluid behaviour after failure. On the other hand, they can be induced by several factors. For example,geology, topography, vegetation, climatic variation, and human activities. In tropic and tempered regions, it is well known that the landslides occur frequently after intense rainfalls, because of saturation effect of unsaturated soils.As there is, up to now, no satisfactory constitutive model to describe such a transition for unsaturated geomaterials, our work is thus focused firstly on a unified model, that associates an hydro-elastoplastic model for unsaturated geomaterials, a Bingham's viscous law, and a transition criterion between solid and fluid states. The model allows to describe both solid and fluid behaviours for unsaturated geomaterials in a unified framework, and is made possible to simulate completely the behaviour of unsaturated geomaterials before and after failure, induced by hydromecanical conditions.Secondly, the Finite Element Method with Lagrangian Integration points (FEMLIP), that benefits from both the Lagrangian approaches (track internal variables) and Eulerian approaches (solve large transformations), is ameliorated and chosen to carry out calculations in this framework. We have introduced a new hydro-elasto-plastic FEMLIP formulation with hydromecanical coupling, and implemented it in Ellipsis (FEMLIP based code). Moreover, in order to inverse nonsymmetric matrixin the formulation, a new solver based on the biconjugate gradient stabilized method (BiCGSTAB) has been also implemented.Finally, several benchmarks are proposed to validate the model for the main features of unsaturated geomaterials, and a heuristic rainfall-induced landslide is simulated, we could study the effects of various parameters on the water infiltration and on the failure. Moreover, a simulation of the Shien landslide in China (2012) with real parameters is presented.