Cette thèse étudie la rétention d’eau à haute HR et le retrait sous température modérée des bétons CEMI et CEMV de l’Andra, en lien avec leur microstructure.Pour étudier l’origine des variations de Sw à haute HR, du béton est séché à HR= 92-100%. Pour les deux bétons, l’échantillonnage influe significativement sur Sw. Pour le CEMI, à HR=100%, la taille joue aussi, en lien avec un mécanisme de séchage par désorption de surface ; à HR=92&98%, ce béton n’est plus sensible aux effets de surface ; il est sensible aux conditions expérimentales. Pour le CEMV, l’effet de la taille existe quelle que soit l’HR, mais il est peu sensible aux conditions expérimentales.A partir de 60°C, le retrait de dessiccation présente quatre phases en fonction de la perte de masse relative. Pour le béton CEMI séché jusqu’en phase 3 ou 4, la possible rigidification de la matrice solide est investiguée par un essai couplé de poro-élasticité et transport de gaz. Pour un même échantillon en phase 3 puis en phase 4, on mesure une légère augmentation du Ks ; la perméabilité au gaz est significativement plus sensible au confinement. Par contre, la rigidification du matériau est limitée en comparaison de l’effet d’échantillonnage.Au MEB, les phases et la morphologie des bétons sont quantifiées. Le CEM I et le CEM V ont des phases solides identiques, mais le CEM V comprend des phases spécifiques (ajout de laitiers et cendres volantes). Les C-S-H du CEM V ont un rapport C/S globalement plus bas que le CEM I. Ce rapport reste similaire pour trois gâchées différentes. Par contre, l’occurrence de pores millimétriques varie significativement, du fait de modes de mise en oeuvre sensiblement différents / This thesis focuses on water retention at high relative humidity (RH) (92-100%) and dessiccation shrinkage under moderate temperature (60-80°C) for two high performance concretes CEMI and CEMV (from Andra), in relation with their microstructure.To investigate the origins of the variations in water saturation degree Sw at high RH, both concretes are dried at RH=92, 98 and 100%, from the fully saturated state. For both concretes, sampling affects significantly Sw. For CEMI at 100%RH, sample size also affects Sw, due to surface drying (desorption); at 92 and 98%RH, CEMI is no longer sensitive to surface drying effects; it is sensitive to experimental conditions (RH, T). CEMV is affected by sample size whatever the RH, but not by experimental conditions.From 60°C drying temperature, the relationship between shrinkage and relative mass loss presents four distinct phases. CEMI concrete is dried at 65°C until phase 3 or 4, and then submitted to a coupled poro-mechanical and gas permeability test. For the same sample tested in phase 3 and then 4, a difference in solid skeleton incompressibility modulus Ks is measured, which is significantly lower than the differences in Ks due to sampling.With the Scanning Electron Microscope, the solid phases and morphology of both concretes are quantified. CEM I and CEM V comprise identical phases, even portlandite, yet CEM V concrete has some specific phases, owing to the addition of slag and fly ash. The C-S-H in CEM V have a lower C/S ratio than in CEM I. The (C/S) ratio remains similar when comparing between three different batches. Besides, millimetric pores vary significantly, owing to differences in manufacturing

Lors du forage des puits d'hydrocarbure, une pâte de ciment est coulée dans l'espace annulaire entre le cuvelage en acier et les formations géologiques traversées. Pompée à l'état liquide, cette pâte de ciment fait sa prise le long du puits sous différentes conditions de température et de pression. La gaine de ciment ainsi mise en place a pour principales fonctions de promouvoir l'étanchéité pour protéger le casing contre la corrosion, de fournir le support mécanique pour assurer la stabilité du puits et d'isoler les différents fluides dans les couches traversées. Au cours de sa vie dans le puits, depuis le forage à la complétion et de la production à l'abandon, la gaine de ciment est soumise à différentes sollicitations mécaniques et thermiques qui peuvent l'endommager et altérer ses principales fonctions. La réponse de la pâte de ciment soumis à ces sollicitations dépend non seulement des conditions d'hydratation mais aussi de l'histoire des chargements précédemment appliqués. La prédiction du comportement de la gaine de ciment doit donc se faire à l'aide d'une modélisation numérique qui nécessite une loi de comportement pour la pâte de ciment. Le but de cette thèse est d'établir une loi de comportement de la pâte de ciment en cours d'hydratation pendant le jeune-âge (les 144 premières heures). Pour ce faire, des essais calorimétriques, de mesures de vitesse des ondes et des essais œdométriques ont été réalisés sur une pâte de ciment pétrolier classe G (w/c = 0,44) en cours de prise. Les conditions d'hydratation explorées vont de 7 à 30°C pour les températures et de 0,3 à 45MPa pour les pressions. Les résultats expérimentaux ont montré que les déformations volumiques de la pâte de ciment dues à son hydratation (retrait macroscopique) sont considérablement influencées par la contrainte sous laquelle la pâte de ciment s'hydrate. Plus la contrainte d'hydratation est élevée, plus élevé est le retrait macroscopique à 144 heures. Inversement, les déformations irréversibles dues à un cycle de chargement mécanique à cet âge sont moins importantes pour les contraintes plus élevées. Les résultats ont également montrés qu'au cours de la prise du ciment, il existe un temps critique à partir duquel l'application des cycles de chargement mécanique crée des déformations résiduelles dans la pâte de ciment. Ce temps critique arrive à un degré d'hydratation relativement constant, compris entre 0,18 et 0,20. Le modèle « Boundary Nucleation and Growth » a été utilisé pour étudier la dépendance de ce temps critique à la pression et à la température. Pour la modélisation du retrait macroscopique et de la réponse contrainte – déformation de la pâte de ciment, un modèle élasto-plastique chemo-poro-mécanique couplé, prenant en compte la désaturation du milieu, a été développé. Ce modèle utilise une surface de charge fermée de type Cam-Clay et une loi plastique associée. La loi d'écrouissage dépend des déformations volumiques plastiques et du degré d'hydratation. Les paramètres du modèle ont été évalués pour simuler le retrait macroscopique de la pâte de ciment hydratée sous différentes contraintes et températures. A un degré d'hydratation donnée, le modèle permet également de simuler la réponse contrainte-déformation due à un chargement mécanique / When drilling oil & gas well, cement slurry is pumped between the casing and the rock formation. This cement slurry sets at different conditions of temperature and pressure. The role of this cement sheath is to provide zonal isolation of different fluid along the well, to protect the casing against corrosion and to provide mechanical support. During the life of the well, from drilling to completion, production and P&A (plug and abandonment), the cement sheath is submitted to various mechanical and thermal loading that can potentially damage its properties and alter its performance. The behavior of cement paste submitted to theses solicitations depends both on the hydration condition and the loadings previously applied on the cement paste. The prediction of cement sheath behavior should be done by numerical modeling, which needs a constitutive law for cement paste. The purpose of the present work is to establish a constitutive law of cement paste during its hydration at early age (first 144 hours). The approach is based on combined calorimetric, wave velocities and oedometric tests on an oil-well class G cement paste with water-to-cement ratio equals 0.44. The hydration conditions explored are 7 to 30°C for temperature and 0.3 to 45MPa for pressure. The experimental results showed that the volumetric strain due to cement hydration (macroscopic shrinkage) depends considerably on the hydration pressure. At 144 hours of hydration, the macroscopic shrinkage increases with the hydration pressure increase. But, the residual strain due to application of mechanical cycle at this age is less for cement hydrated under higher pressure. The experimental results revealed that during the hydration there is a critical time after which, the application of mechanical loading can potentially induce residual strain in cement paste. This time is reached at constant hydration degree between 0.18 and 0.20. The Boundary Nucleation and Growth model was used to model the pressure and temperature dependence of this critical time. A coupled elasto-plastic chemo-poro-mechanical model is developed to simulate the macroscopic shrinkage of cement paste hydrated at different conditions of temperature and pressure. A modified Cam-Clay type yield surface with associate flow rule is used. The hardening law depends both on the degree of hydration and on the plastic volumetric strain. At constant degree of hydration, the developed model permits to simulate the stress – strain behavior of cement paste due to the mechanical loading

L'objectif de ce travail est de contribuer à une meilleure prédiction de la rupture des Anévrismes de l'Aorte Abdominale. Pour ce faire, des simulations par éléments finis ont été mises en oeuvre sur des anévrismes modèles dans des conditions proches de la réalité physiopathologique, i.e. en tenant compte de l'anisotropie de la paroi anévrismale, du caractère poreux du thrombus et des Interactions Fluide-Structure. Dans la première partie, une étude statique en l'absence du thrombus a permis de mettre en évidence l'influence de la géométrie de l'anévrisme et du comportement mécanique (isotrope ou anisotrope) de la paroi sur la distribution des contraintes, i.e. la rupture potentielle de l'anévrisme, ainsi que sur l'évolution du module de Peterson. Dans la seconde partie, une modélisation poro-hyperélastique du thrombus est proposée, en s'appuyant sur des données expérimentales de la littérature. La prise en compte de ce comportement et des Interactions Fluide-Structure montre que la pression intra-thrombus demeure du même ordre de grandeur que la pression intra-luminale, conformément à des mesures in vivo réalisées par ailleurs. Enfin, nous montrons que ceci n'est pas en contradiction avec une réduction du risque de rupture potentielle de l'anévrisme. / The aim of this work is to contribute to a better prediction of the Abdominal Aortic Aneurysm rupture (AAA). For that purpose, finite elements simulations have been performed on idealized AAA models under physiopathological like conditions, by taking into account the aneurysmal wall anisotropy, the intra-luminal thrombus porosity and the Fluid-Structure Interactions. In the first part, the influence of the aneurysm geometry and its wall properties (isotropic or anisotropic hyperelasticity) on the wall stress distribution and the Peterson's modulus has been studied in a static analysis and without taking into account the thrombus. In the second part, based on the experimental results from the litterature, a porohyperelastic model has been proposed for the thrombus. By considering such behavior for the thrombus and the Fluid-Structure Interactions, we observe that the intra-thrombus pressure is the same order as the intra-luminal pressure, which is consistent with in vivo measurements. Our results show that despite this unchanged pressure, the maximum wall stress decreases leading to a decrease of the aneurysm potential rupture.

Lors du forage des puits d'hydrocarbure, une pâte de ciment est coulée dans l'espace annulaire entre le cuvelage en acier et les formations géologiques traversées. Pompée à l'état liquide, cette pâte de ciment fait sa prise le long du puits sous différentes conditions de température et de pression. La gaine de ciment ainsi mise en place a pour principales fonctions de promouvoir l'étanchéité pour protéger le casing contre la corrosion, de fournir le support mécanique pour assurer la stabilité du puits et d'isoler les différents fluides dans les couches traversées. Au cours de sa vie dans le puits, depuis le forage à la complétion et de la production à l'abandon, la gaine de ciment est soumise à différentes sollicitations mécaniques et thermiques qui peuvent l'endommager et altérer ses principales fonctions. La réponse de la pâte de ciment soumis à ces sollicitations dépend non seulement des conditions d'hydratation mais aussi de l'histoire des chargements précédemment appliqués. La prédiction du comportement de la gaine de ciment doit donc se faire à l'aide d'une modélisation numérique qui nécessite une loi de comportement pour la pâte de ciment. Le but de cette thèse est d'établir une loi de comportement de la pâte de ciment en cours d'hydratation pendant le jeune-âge (les 144 premières heures). Pour ce faire, des essais calorimétriques, de mesures de vitesse des ondes et des essais œdométriques ont été réalisés sur une pâte de ciment pétrolier classe G (w/c = 0,44) en cours de prise. Les conditions d'hydratation explorées vont de 7 à 30°C pour les températures et de 0,3 à 45MPa pour les pressions. Les résultats expérimentaux ont montré que les déformations volumiques de la pâte de ciment dues à son hydratation (retrait macroscopique) sont considérablement influencées par la contrainte sous laquelle la pâte de ciment s'hydrate. Plus la contrainte d'hydratation est élevée, plus élevé est le retrait macroscopique à 144 heures. Inversement, les déformations irréversibles dues à un cycle de chargement mécanique à cet âge sont moins importantes pour les contraintes plus élevées. Les résultats ont également montrés qu'au cours de la prise du ciment, il existe un temps critique à partir duquel l'application des cycles de chargement mécanique crée des déformations résiduelles dans la pâte de ciment. Ce temps critique arrive à un degré d'hydratation relativement constant, compris entre 0,18 et 0,20. Le modèle « Boundary Nucleation and Growth » a été utilisé pour étudier la dépendance de ce temps critique à la pression et à la température. Pour la modélisation du retrait macroscopique et de la réponse contrainte – déformation de la pâte de ciment, un modèle élasto-plastique chemo-poro-mécanique couplé, prenant en compte la désaturation du milieu, a été développé. Ce modèle utilise une surface de charge fermée de type Cam-Clay et une loi plastique associée. La loi d'écrouissage dépend des déformations volumiques plastiques et du degré d'hydratation. Les paramètres du modèle ont été évalués pour simuler le retrait macroscopique de la pâte de ciment hydratée sous différentes contraintes et températures. A un degré d'hydratation donnée, le modèle permet également de simuler la réponse contrainte-déformation due à un chargement mécanique / When drilling oil & gas well, cement slurry is pumped between the casing and the rock formation. This cement slurry sets at different conditions of temperature and pressure. The role of this cement sheath is to provide zonal isolation of different fluid along the well, to protect the casing against corrosion and to provide mechanical support. During the life of the well, from drilling to completion, production and P&A (plug and abandonment), the cement sheath is submitted to various mechanical and thermal loading that can potentially damage its properties and alter its performance. The behavior of cement paste submitted to theses solicitations depends both on the hydration condition and the loadings previously applied on the cement paste. The prediction of cement sheath behavior should be done by numerical modeling, which needs a constitutive law for cement paste. The purpose of the present work is to establish a constitutive law of cement paste during its hydration at early age (first 144 hours). The approach is based on combined calorimetric, wave velocities and oedometric tests on an oil-well class G cement paste with water-to-cement ratio equals 0.44. The hydration conditions explored are 7 to 30°C for temperature and 0.3 to 45MPa for pressure. The experimental results showed that the volumetric strain due to cement hydration (macroscopic shrinkage) depends considerably on the hydration pressure. At 144 hours of hydration, the macroscopic shrinkage increases with the hydration pressure increase. But, the residual strain due to application of mechanical cycle at this age is less for cement hydrated under higher pressure. The experimental results revealed that during the hydration there is a critical time after which, the application of mechanical loading can potentially induce residual strain in cement paste. This time is reached at constant hydration degree between 0.18 and 0.20. The Boundary Nucleation and Growth model was used to model the pressure and temperature dependence of this critical time. A coupled elasto-plastic chemo-poro-mechanical model is developed to simulate the macroscopic shrinkage of cement paste hydrated at different conditions of temperature and pressure. A modified Cam-Clay type yield surface with associate flow rule is used. The hardening law depends both on the degree of hydration and on the plastic volumetric strain. At constant degree of hydration, the developed model permits to simulate the stress – strain behavior of cement paste due to the mechanical loading

No presente trabalho analisa-se o comportamento do aço de reforço ante à corrosão, com o uso dos inibidores: nitrito de sódio, fosfato de sódio e etalonamina, na água de poros contaminada com cloreto, e no concreto com a finalidade de analisar seus resultados e seus mecanismos diferenciados. Para cumprir este objetivo o presente trabalho divide-se em duas etapas: uma primeira etapa baseada em simular sinteticamente a água de poro de um concreto, cuja solução é KOH 28g/l+NaOH 4g/l. Essa água de poro é simulada em ambiente marinho, cuja solução é KOH 28g/l + NaOH 4g/l+NaCl 35g/l, e a esta solução referência incorporamse os inibidores (20g/l da cada um). Realizaram-se ensaios de espectroscopia de impedância eletroquímica (EIE) (após 3 e 72 horas de imersão) e curvas de polarização (após 72 horas de imersão) com vistas a obter respostas da cinética da corrosão ante a cada solução. Obteve-se o melhor comportamento para a água de poros. No caso da água de poro contaminada por cloretos, o melhor comportamento se obteve para o inibidor nitrito de sódio. Na segunda etapa adotou-se apenas o inibidor nitrito de sódio, pois estatisticamente as eficiências dos três inibidores foram muito similares. Analisou-se o nitrito de sódio em amostras reais de concreto armado contaminado com cloreto de sódio. Para isso se elegeram dois tipos de cimentos (CP IV e CP V) e três relações água-cimento (a/c-0.4, a/c-0.5, a/c- 0.65). Para simular o ambiente marinho, realizaram-se ensaios acelerados de cloretos. Comparam-se métodos de análises simuladas sinteticamente e reais, concluindo-se em ambos meios, embora fossem um solido e outro líquido o inibidor Nitrito de Sódio aumento a sua eficiência com os ciclos de exposição. / In this paper it is analyzed the behavior of reinforcing steel against corrosion using inhibitors: sodium nitrate, sodium phosphate and ethanolamine in water contaminated with chlorides pore and concrete, in order to analyzing the results and different mechanisms. To meet the objective of this work, it was divided into two stages, a first stage based on synthetically simulate the pore water of a concrete, through the following solution KOH 28g/l+NaOH 4g/l, this same solution simulated pore water to a marine environment it would be KOH 28g/l + NaOH 4g/l+NaCl 35g/l, it is then incorporated into both reference solutions inhibitors in a proportion, (20g/l de cada um). Assays were performed electrochemical impedance spectroscopy (EIE) (last 3 hours and 72 hours of immersion) and polarization curves (last 72 hours of immersion) in order to obtain responses corrosion kinetics in each solution. the best performance was obtained in the pore water. In the case of water contaminated with chlorides pore, the best performance was obtained in the presence of sodium nitrite inhibitor. In the second step was performed only with the inhibitor sodium nitrate, as statistically efficiencies of the three inhibitors were similar. Sodium nitrate was analyzed in real samples of reinforced concrete contaminated with chlorides of sodium. So they were chosen two types of cement CP- IV and CP-V, cement water three relationships 0.4, a/c-0.5, a/c- 0.65. In this case to simulate the marine environment, accelerated tests were performed chloride. They were compared the methods of analysis, simulated synthetically and simulated in real concrete.

Legionella pneumophila, o agente etiológico da doença dos Legionários, é conhecida por desencadear a formação de poro em membranas de macrófagos derivados de medula óssea (BMMs) por mecanismos dependentes do sistema de secreção do tipo IV conhecido como Dot/Icm. Neste trabalho, foram utillizados vários mutantes de L. pneumophila em combinação com camundongos nocautes para investigar os fatores bacterianos e do hospedeiro envolvidos na formação de poro em BMMs. Observamos que apesar da atividade do Dot/Icm, a formação de poro não ocorre em BMMs deficientes para caspase-1 e Nlrc4. A formação de poro foi temporalmente associada com a secreção de IL-1b e precedeu a lise celular e a piroptose. A formação de poro foi dependente do Dot/Icm, mas independente de várias proteínas efetoras, da multiplicação bacteriana e da síntese de novo de proteínas. A flagelina, a qual é conhecida em ativar o inflamassoma de Nlrc4, foi necessária para a formação de poro; a bactéria mutante flaA falhou em induzir a permeabilização celular. Consequentemente, a transfecção da flagelina purificada foi suficiente para desencadear a formação de poro independente da infecção. Utilizando 11 diferentes espécies de Legionella, nós observamos alta formação de poro em resposta à L. micdadei, L. bozemanii, L. gratiana, L. jordanis e L. rubrilucens, e essa resposta estava correlacionada com a expressão de flagelina por essas espécies. Além disso, verificamos que as proteínas Asc e Caspase-11 apresentam fenótipo intermediário na formação de poro, sugerindo que outras vias podem estar envolvidas no processo. Observamos também que a formação de poro desencadeada por L. pneumophila difere daquela induzida pelo ATP. Em conjunto, nossos resultados sugerem que a formação de poro não é uma resposta específica de L. pneumophila nem o resultado de dano da membrana induzido pelo Dot/Icm. Ao invés disso, a formação de poro é uma resposta do hospedeiro altamente coordenada, dependente dos componentes do inflamassoma Nlrc4 e caspase-1 e é desencadeada em resposta a bactérias que expressam o sistema de secreção do tipo IV e flagelina. / Legionella pneumophila, the etiological agent of Legionnaires disease, is known to trigger pore formation in bone marrow-derived macrophages (BMMs) by mechanisms dependent on the type IVB secretion system known as Dot/Icm. Here, we used several mutants of L. pneumophila in combination with knockout mice to assess the host and bacterial factors involved in pore formation in BMMs. We found that regardless of Dot/Icm activity, pore formation does not occur in BMMs deficient in caspase-1 and Nlrc4/Ipaf. Pore formation was temporally associated with IL-1b secretion and preceded host cell lysis and pyroptosis. Pore-forming ability was dependent on bacterial Dot/Icm but independent of several effector proteins, multiplication and de novo protein synthesis. Flagellin, which is known to trigger the Nlrc4 inflammasome, was required for pore formation as flaA mutant bacteria failed to induce cell permeabilization. Accordingly, transfection of purified flagellin was sufficient to trigger pore formation independent of infection. By using 11 different Legionella species, we found robust pore formation in response to L. micdadei, L. bozemanii, L. gratiana, L. jordanis and L. rubrilucens, and this trait correlated with flagellin expression by these species. Furthermore, we found that Asc and Caspase-11 showed an intermediate phenotype in pore formation, suggesting that other pathways may be involved in this process. We also observed that the pore formation triggered by L. pneumophila differs from the pore induced by ATP. Together, the results suggest that pore formation is neither L. pneumophilaspecific nor the result of membrane damage induced by Dot/Icm activity; instead, it is a highly coordinated host cell response dependent on host Nlrc4 and caspase-1 and on bacterial flagellin and type IV secretion system.

Made available in DSpace on 2014-06-12T17:36:34Z (GMT). No. of bitstreams: 2 arquivo2272_1.pdf: 1584114 bytes, checksum: a3a3fa1c92e9025ca69503845b2e0c3d (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2008 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Nas últimas décadas houve um grande avanço no que diz respeito ao desenvolvimento de modelos constitutivos que melhor representassem o comportamento dos materiais geomecânicos. Um meio contínuo submetido à degradação de suas propriedades mecânicas tem sua resposta constitutiva diferenciada, por isso, torna‐se necessária a adoção de modelos baseados na Mecânica do Dano Contínuo formulados em consistência com os princípios da termodinâmica dos processos irreversíveis, para melhor representá‐lo. Neste trabalho será implementado o modelo de visco‐dano, baseado na mecânica do dano contínuo, e que tem como diferença quanto ao modelo de dano, a introdução da regularização viscosa sendo esta feita através do método de Perzyna. Para validação do modelo serão feitas simulações de ensaios de relaxação de tensões e Creep utilizando a ferramenta numérica CODE_BRIGHT, utilizando o método dos elementos finitos Galerkin, sendo os resultados confrontados com os obtidos através do código numérico COMET. Será analisado um caso de ativação de falha e, a partir deste, analisaremos a sensibilidade através da simulação numérica de vários casos considerando a variação dos parâmetros de grande importância no modelo de visco‐dano

Cette thèse a permis d'évaluer l'effet des changements de morphologie d'un matériau cimentaire soumis à un traitement thermique jusqu'à T (≤ 400°C). Pour cela, nous avons caractérisé expérimentalement le comportement mécanique (en compression uniaxiale, compression hydrostatique avec ou sans déviateur), poro-mécanique (modules d'incompressibilité Kb, Ks et coefficient de Biot b) et hydraulique (perméabilité au gaz), d'un mortier modèle E/C=0,5 suite à un cycle de chauffage/refroidissement. Les essais mécaniques multiaxiaux sont couplés aux mesures de perméabilité, qui servent d'indicateur de la progression de la fissuration du matériau sous contrainte. Nous avons également mis au point un essai original, permettant de quantifier le volume de l'espace poreux interconnecté sous chargement hydrostatique Pc. La création de porosité occluse sous l'effet d'un accroissement du confinement est confirmée, et ainsi la diminution de la rigidité de la matrice solide Ks avec Pc après traitement thermique T>200°C. Nous avons également identifié un effet bouchon (aucun passage de gaz) lors d'un chargement couplé, thermique et en compression hydrostatique du mortier mais aussi de bétons industriels (CERIB et ANDRA). Afin d'analyser l'évolution des propriétés mécaniques et poro-élastiques après traitement thermique, un modèle prédictif thermo-élasto-plastique avec endommagement isotrope et une approche micro-mécanique descriptive, intégrant la présence de micro-fissures, y sont couplés

Problems involving coupled thermo-poro-chemo-mechanical processes are of great importance in geothermal and petroleum reservoir systems. In particular, economic power production from enhanced geothermal systems, effective water-flooding of petroleum reservoirs, and stimulation of gas shale reservoirs are significantly influenced by coupled processes. During such procedures, stress state in the reservoir is changed due to variation in pore fluid pressure and temperature. This can cause deformation and failure of weak planes of the formation with creation of new fractures, which impacts reservoir response. Incorporation of geomechanical factor into engineering analyses using fully coupled geomechanics-reservoir flow modeling exhibits computational challenges and numerical difficulties. In this study, we develop and apply efficient numerical models to solve 3D injection/extraction geomechanics problems formulated within the framework of thermo-poro-mechanical theory with reactive flow. The models rely on combining Displacement Discontinuity (DD) Boundary Element Method (BEM) and Finite Element Method (FEM) to solve the governing equations of thermo-poro-mechanical processes involving fracture/reservoir matrix. The integration of BEM and FEM is accomplished through direct and iterative procedures. In each case, the numerical algorithms are tested against a series of analytical solutions. 3D study of fluid injection and extraction into the geothermal reservoir illustrates that thermo-poro-mechanical processes change fracture aperture (fracture conductivity) significantly and influence the fluid flow. Simulations that consider joint stiffness heterogeneity show development of non-uniform flow paths within the crack. Undersaturated fluid injection causes large silica mass dissolution and increases fracture aperture while supersaturated fluid causes mineral precipitation and closes fracture aperture. Results show that for common reservoir and injection conditions, the impact of fully developed thermoelastic effect on fracture aperture tend to be greater compare to that of poroelastic effect. Poroelastic study of hydraulic fracturing demonstrates that large pore pressure increase especially during multiple hydraulic fracture creation causes effective tensile stress at the fracture surface and shear failure around the main fracture. Finally, a hybrid BEFEM model is developed to analyze stress redistribution in the overburden and within the reservoir during fluid injection and production. Numerical results show that fluid injection leads to reservoir dilation and induces vertical deformation, particularly near the injection well. However, fluid withdrawal causes reservoir to compact. The Mandel-Cryer effect is also successfully captured in numerical simulations, i.e., pore pressure increase/decrease is non-monotonic with a short time values that are above/below the background pore pressure.

New modelling tools intended to contribute to the development of components for quieter vehicles are developed. The tools are based on continuum models for wave propagation in poro– and visco–elastic media. By using geometric attributes of the studied components, the computational cost may be radically decreased compared to traditional methods. By assigning known analytical functions for one or two of the spatial directions, the spatial dimension of the remaining numerical problem is reduced. This reduction of spatial dimensions is performed in two di↵erent ways. The first one treats wave propagation in infinitely extended homogeneous and hollowed cylindrical rods, or wave guides, consisting of visco–elastic media. The wave solutions obtained are then used to model rubber vibration isolators of finite length by mode–matching the fields to the radial boundary conditions of interest. The second one is a method for modelling rotationally symmetric multilayered structures consisting of poro–elastic, elastic and fluid domains. By using a harmonic expansion for the azimuthal spatial dependence, the original three–dimensional problem is split up into several, much smaller, two– dimensional ones, radically decreasing the computational load. Moreover, using a mixed measurement/modelling approach, the audible frequency range characteristics of a viscous damper from a truck is studied, illustrating the influence of the rubber bushings by which it is attached to surrounding structures. The modelling approaches presented in this thesis are intended as tools aiding the design process of new vehicles, enabling new technology striving for more sustainable vehicle concepts. More specifically, the tools aim to improve the modelling of sound and vibration properties which are often penalised when seeking new, more sustainable vehicle designs. / <p>QC 20120522</p> / Centre for Eco2 Vehicle Design