Ingeniero Civil / El presente trabajo de título analiza el método de consolidación por vacío y su aplicabilidad para el mejoramiento de un relave integral. El estudio se basa en la comparación de resultados obtenidos a partir de un modelo experimental, modelaciones numéricas de elementos finitos y soluciones analíticas recopiladas de la literatura técnica. El modelo experimental aplica succión generada por una bomba de vacío sobre una columna de relave integral saturado y monitorea la evolución temporal de la deformación vertical, simulando la aplicación de esta técnica en suelos depositados en la cubeta de un tranque de relaves. Además, se realizan simulaciones numéricas de elementos finitos con el software Abaqus para reproducir las condiciones del modelo experimental y poder capturar las mediciones de laboratorio. El comportamiento elasto-plástico del material se simula con el modelo constitutivo Cam-Clay Modificado (MCCM). La calibración de los parámetros de compresibilidad y de conductividad hidráulica del material se realiza con ensayos de laboratorio considerando dos estados de depositación y otros parámetros se adoptan de los trabajos de Cifuentes y Verdugo (2007) y Conejera (2016). La aplicación de -80 kPa de vacío induce deformaciones verticales en la columna de relave integral que son equivalentes a las inducidas por la aplicación de 3,5 - 4 metros de material de relleno. El fenómeno de consolidación de vacíos se puede simular numéricamente con un software de elementos finitos y el uso de un modelo constitutivo elasto-plástico, como Cam-Clay Modificado (MCCM). Los parámetros críticos para modelar apropiadamente el fenómeno son los parámetros de compresibilidad y la conductividad hidráulica del material. Si bien estos parámetros se pueden estimar con ensayos estándares de laboratorio, se requieren algunos ajustes para estimar el asentamiento máximo y el tiempo de consolidación.

A deformação dos solos é, atualmente, objeto de intensas pesquisas em todo o mundo movidas pelas necessidades da engenharia geotécnica. Este trabalho, que aborda o tema nos aspectos teórico e experimental, inicia-se revendo as relações constitutivas elasto-plásticas e o modelo Cam-Clay, cuja formulação matemática é apresentada de um modo diferente do usual. O modelo é construído de forma sistêmica a partir das equações elasto-plásticas gerais. Na parte experimental investiga-se o comportamento de um solo siltoso remoldado, quando submetido a ensaios triaxiais com diferentes trajetórias de tensão após adensamento isotrópico. Por fim comparam-se resultados experimentais e teóricos. Conclui-se que o modelo comporta-se melhor nas trajetórias de tensão em que não há diminuição da tensão octaédrica, embora preveja deformações volumétricas exageradas. Por sua vez, nas trajetórias em que há diminuição da tensão octaédrica, a diferença entre o comportamento previsto e o observado é grande, revelando que o modelo não deve ser aplicado nesses casos. / Soil deformation is today a subject of intense research all over the world motivated by the necessities of the geotechnical engineering. This work, which approaches the theme in both theoretical and experimental aspects, reviews the elastoplastic constitutive relations and the Cam-Clay model, and examines the behavior of a remoulded silty soil when subjected to different stress paths. Following a brief exposition of some basic Continuum Mechanics concepts, the elastic and elastoplastic constitutive equations are presented in a general form, which serve as a basis for several soil models. After a discussion about soil behavior and its representation by models, the Cam-Clay mathematical formulation is presented in an unusual form: it begins with the general elastoplastic constitutive equations, the elastic stress-strain relation, the yield function and the hardening law being given. The plastic stress-strain relation in deduced. In the experimental part the behavior of a remoulded silty soil from the Escola Politécnica Foundation Experimental Field is investigated. Oedometric, isotropic and triaxial compression tests (that were performed as part of the research) are described and analysed. Among them the triaxial tests with different stress paths after isotropic consolidation constitute the principal subject of analysis. Finally the Cam-Clay equations are integrated along the tests stress paths and the experimental e theoretical results are confronted. The conclusions is that the model behaves better in stress paths where there is no octabedral stress reduction, although even then it predicts exaggerated volumetric strains. In its turn, in stress paths where there is an octahedral stress reduction the difference between predicted and observed behavior is large, revealing that the model should not be applied in such cases.

Le creuset est une structure majoritairement composée de matériaux réfractaires destinés à supporter de fortes sollicitations thermomécaniques, dues au contact direct de ses parois internes avec la fonte à 1500°C. L’objectif de cette thèse est de développer un modèle thermomécanique de creuset capable de localiser les zones sensibles de la structure et d’estimer les contraintes. Des blocs de carbone, des structures maçonnées (briques avec mortier) et un pisé carboné sont les principaux constituants du creuset. Afin d’identifier leur comportement, des essais de caractérisation ont été développés pour des températures atteignant les 1500°C. Un modèle de type Cam-Clay modifié est proposé pour modéliser le comportement compactant du pisé. L’influence de la température et des fortes pressions est prise en compte. Une bonne corrélation est obtenue entre les résultats expérimentaux et numériques. Les structures maçonnées, en contact direct avec la fonte, sont fortement sollicitées, ce qui peut conduire à l’ouverture des joints de mortier. La modélisation proposée pour ces structures est basée sur une approche micro-macro où les briques et le mortier sont remplacés par un matériau homogène équivalent, et ce pour différents états d’ouverture de joints. La non-linéarité du comportement est reproduite grâce à un critère d’ouverture en contrainte, qui permet le passage d’un état à un autre. Les propriétés homogénéisées sont obtenues par homogénéisation périodique en s’appuyant sur une approche énergétique. La modélisation d’un essai de la littérature permet la validation du modèle. La modélisation finale du creuset est confrontée aux résultats de l’instrumentation d’un creuset. Une bonne concordance entre ces résultats est obtenue. / The blast furnace hearth is mainly composed of refractory materials to support strong thermo-mechanical loads. Indeed, there is a direct contact between its internal walls and the molten pig iron at 1500°C. The objective of this thesis is to develop a thermo-mechanical model able to locate the sensitive areas and to estimate the stress fields. Carbon blocks, masonries (bricks and mortars) and a carbon ramming mix are the main constituents of the hearth. In order to identify their behaviours, characterization tests have been developed for temperatures up to 1500°C. A modified Cam-Clay model is proposed in order to reproduce the hardening behaviour of the ramming mix. The influences of temperature and pressure are taken into account. Experimental and numerical results are in good agreement. Masonries, submitted to high temperature gradients are highly stressed, which can lead to the opening of the mortar joints. The proposed masonry modelling is based on a micro-macro approach where bricks and mortars are replaced by an equivalent homogenous material for different joint states. The non-linearity of the behaviour is reproduced thanks to a stress criterion, allowing the transition from one state to another. Homogenized properties are obtained by periodic homogenization with an energetic approach. The modeling of a shear test available in the literature allows the validation of this model. The final modelling of a hearth is compared with in-situ instrumentation results. A good agreement is reached between these results.

A deformação dos solos é, atualmente, objeto de intensas pesquisas em todo o mundo movidas pelas necessidades da engenharia geotécnica. Este trabalho, que aborda o tema nos aspectos teórico e experimental, inicia-se revendo as relações constitutivas elasto-plásticas e o modelo Cam-Clay, cuja formulação matemática é apresentada de um modo diferente do usual. O modelo é construído de forma sistêmica a partir das equações elasto-plásticas gerais. Na parte experimental investiga-se o comportamento de um solo siltoso remoldado, quando submetido a ensaios triaxiais com diferentes trajetórias de tensão após adensamento isotrópico. Por fim comparam-se resultados experimentais e teóricos. Conclui-se que o modelo comporta-se melhor nas trajetórias de tensão em que não há diminuição da tensão octaédrica, embora preveja deformações volumétricas exageradas. Por sua vez, nas trajetórias em que há diminuição da tensão octaédrica, a diferença entre o comportamento previsto e o observado é grande, revelando que o modelo não deve ser aplicado nesses casos. / Soil deformation is today a subject of intense research all over the world motivated by the necessities of the geotechnical engineering. This work, which approaches the theme in both theoretical and experimental aspects, reviews the elastoplastic constitutive relations and the Cam-Clay model, and examines the behavior of a remoulded silty soil when subjected to different stress paths. Following a brief exposition of some basic Continuum Mechanics concepts, the elastic and elastoplastic constitutive equations are presented in a general form, which serve as a basis for several soil models. After a discussion about soil behavior and its representation by models, the Cam-Clay mathematical formulation is presented in an unusual form: it begins with the general elastoplastic constitutive equations, the elastic stress-strain relation, the yield function and the hardening law being given. The plastic stress-strain relation in deduced. In the experimental part the behavior of a remoulded silty soil from the Escola Politécnica Foundation Experimental Field is investigated. Oedometric, isotropic and triaxial compression tests (that were performed as part of the research) are described and analysed. Among them the triaxial tests with different stress paths after isotropic consolidation constitute the principal subject of analysis. Finally the Cam-Clay equations are integrated along the tests stress paths and the experimental e theoretical results are confronted. The conclusions is that the model behaves better in stress paths where there is no octabedral stress reduction, although even then it predicts exaggerated volumetric strains. In its turn, in stress paths where there is an octahedral stress reduction the difference between predicted and observed behavior is large, revealing that the model should not be applied in such cases.

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

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

O modelo cam-clay modificado foi aplicado aos resultados experimentais obtidos para um solo arenoso típico da cidade de São Carlos. Os ensaios de compressão triaxial foram conduzidos em equipamento moderno, com instrumentação interna, segundo distintas trajetórias de carregamento. Verificou-se que os resultados obtidos em termos de modelagem foram satisfatórios, principalmente quando a tensão octaédrica (p\') foi diminuida durante os carregamentos. Nesse caso, tanto em termos de modelagem como de resultados experimentais, houve expansão de volume do solo. Com o aumento da tensão octaédrica, verificou-se a ocorrência de compressão volumétrica do solo. Observou-se que o modelo apresenta uma previsão de deformações axiais maiores do que as observadas experimentalmente nas trajetórias de -30, -50, 30, 40, 50, 60, 120 graus e no ensaio triaxial convencional com \'sigma\' 3 = 100 kPa. Além disso, determinou-se a superfície inicial de plastificação do solo utilizando-se dois critérios que tenderam a fornecer valores de tensão de cedência aproximadamente iguais, notando-se que a condição de fluxo associado não é obedecida. / The modified cam-clay model was used to model experimental results of a sandy soil from São Carlos - SP. Triaxial compression tests were performed using Bishop - Wesley cell with internal transducers to measure axial and radial strains. It was observed that the model fairly fitted experimental results, specially when medium effective stress (p\') is reduced during loading. In this case, both the model and the experimental results, showed volume increase. When (p\') increases the model and the tests showed a tendency to give volumetric compression, although the values were differents. The model yielded strains larger than that measured in the tests when the stress-paths were of -30, -50, 30, 40, 50, 60, 120 degrees and in axial compression test with 100 kPa of confining pressure. Besides that, initial yield surface of soil was calculated from test results using two different criteria which gave about the same yield stress and it is show that normality rule was not satisfied in this soil.

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

O modelo cam-clay modificado foi aplicado aos resultados experimentais obtidos para um solo arenoso típico da cidade de São Carlos. Os ensaios de compressão triaxial foram conduzidos em equipamento moderno, com instrumentação interna, segundo distintas trajetórias de carregamento. Verificou-se que os resultados obtidos em termos de modelagem foram satisfatórios, principalmente quando a tensão octaédrica (p\') foi diminuida durante os carregamentos. Nesse caso, tanto em termos de modelagem como de resultados experimentais, houve expansão de volume do solo. Com o aumento da tensão octaédrica, verificou-se a ocorrência de compressão volumétrica do solo. Observou-se que o modelo apresenta uma previsão de deformações axiais maiores do que as observadas experimentalmente nas trajetórias de -30, -50, 30, 40, 50, 60, 120 graus e no ensaio triaxial convencional com \'sigma\' 3 = 100 kPa. Além disso, determinou-se a superfície inicial de plastificação do solo utilizando-se dois critérios que tenderam a fornecer valores de tensão de cedência aproximadamente iguais, notando-se que a condição de fluxo associado não é obedecida. / The modified cam-clay model was used to model experimental results of a sandy soil from São Carlos - SP. Triaxial compression tests were performed using Bishop - Wesley cell with internal transducers to measure axial and radial strains. It was observed that the model fairly fitted experimental results, specially when medium effective stress (p\') is reduced during loading. In this case, both the model and the experimental results, showed volume increase. When (p\') increases the model and the tests showed a tendency to give volumetric compression, although the values were differents. The model yielded strains larger than that measured in the tests when the stress-paths were of -30, -50, 30, 40, 50, 60, 120 degrees and in axial compression test with 100 kPa of confining pressure. Besides that, initial yield surface of soil was calculated from test results using two different criteria which gave about the same yield stress and it is show that normality rule was not satisfied in this soil.

[pt] A predição da permeabilidade é uma etapa crítica no fluxo de caracterização e modelagem geológica de reservatórios e essencial para o desenvolvimento de projetos de produção. Estruturas subsísmicas denominadas bandas de deformação (BD) podem diminuir a permeabilidade em até seis ordens de grandeza em relação à rocha matriz de reservatórios areníticos e podem, dessa forma, atuar como barreiras totais ou parciais ao fluxo de fluidos. O presente trabalho pretende contribuir na determinação do comportamento hidráulico de reservatórios propondo um modelo geomecânico analítico para a predição de BD em reservatórios de arenitos. Em termos práticos, o objetivo é prever se em uma determinada porção de um depósito siliciclástico de hidrocarboneto foram atingidas condições para a formação de BD, ou quão próximo se está de uma possível geração dessa feição a fim de se sugerir uma análise da redução de permeabilidade. A proposta se estende na implementação computacional do método e sua aplicação em um estudo de caso de um reservatório arenítico pouco consolidado da margem continental brasileira rico em BD. Os resultados confirmaram a viabilidade do método mostrando que a porção do reservatório analisada atingiu as condições mecânicas para a gênese de BD a partir da idade geológica intitulada de Oligoceno (~ 23 a 35 Ma) para os cenários estabelecidos. / [en] The permeability prediction is a critical step in the flow of geological modeling and reservoir characterization and is essential for the development of production projects. Sub-seismic structures called deformation bands (BD) can reduce permeability up to six orders of magnitude in relation to the host reservoir sandstone and can thus act as total or partial barriers to the fluid flow. The present work intends to contribute in the determination of the hydraulic behavior of reservoirs proposing an analytical geomechanical model for BD s prediction in sandstone reservoirs. In practical terms, the objective is to predict whether the conditions in a given portion of a siliciclastic hydrocarbon deposit have been reached for the localization of BD or how close it is to a possible generation of this feature in order to suggest an analysis of the permeability reduction. The proposal extends to the computational implementation of the method and its application in a case study of a poorly consolidated sandstone reservoir on the brazilian continental margin, rich in BD. The results confirmed the viability of the method by showing that the portion of the analyzed reservoir reached the mechanical conditions for the genesis of BD from the geological age entitled Oligocene (~ 23 to 35 Ma) for the established scenarios.