The thesis describes the application of anchors in mining and tunneling and gives an up-to-date overview about anchor types, design principles and the interaction mechanisms between anchors and rockmass. A constitutive model was developed, implemented and tested for the 2- and 3-dimensional numerical codes FLAC and FLAC3D to simulate non-linear anchor behaviour including unloading and reloading. The interaction between rockbolts and rockmass was studied in detail via numerical simulations for 5 Vietnamese coal mines. An extended version of the so-called c-Φ reduction method and a new introduced reinforcement factor were applied to quantify the effect of bolting. Mine specific and generalised relations were deduced to quantify the influence of anchor length and distance between anchors on the effect of bolting.

Ces travaux de thèse portent essentiellement sur la modélisation, l’analyse et la commande des convertisseurs de type MMC intégrés dans un contexte MTDC. Le premier objectif de ce travail est d’aboutir à un modèle dynamique du convertisseur MMC, exprimé dans le repère $dq$, permettant d’une part, de reproduire avec précision les interactions AC-DC, et d’exprimer, d’autre part, la dynamique interne du convertisseur qui peut interagir également avec le reste du système. Le modèle développé peut être linéarisé facilement dans le but de l’exploiter pour l’étude de stabilité en se basant sur les techniques pour les systèmes linéaires à temps invariant. Ensuite, selon le modèle développé dans le repère dq, différentes stratégies de contrôle sont proposées en fonction de systèmes de contrôle-commande existantes dans la littérature mis en places pour le convertisseur MMC. Étant donné que l’ordre du système est un paramètre important pour l'étude des réseaux MTDC en présence de plusieurs stations de conversion de type MMC, l’approche de réduction de modèles à émerger comme une solution pour faciliter l’étude. En conséquence, différents modèles à ordre réduit sont développés, et qui sont validés par la suite, par rapport au modèle détaillé, exprimé dans le repère dq. Finalement, les modèles MMC développés ainsi que les systèmes de commande qui y ont associés sont exploités, pour l’analyse de stabilité en petits signaux des réseaux MMC-MTDC. Dans ce sens, la stratégie de commande associée à chaque MMC est largement évaluée dans le but d’investiguer les problèmes majeurs qui peuvent surgir au sein d’une configuration MTDC multi-constructeurs / This thesis deals with the modeling and control of MMCs in the context of MTDC. The first objective is to obtain an MMC model in dq frame which can reproduce accurately the AC- and DC- interactions, while representing at the same time the internal dynamics which may interact with the rest of the system. This model is suitable to be linearized and to study its stability, among other linear techniques. Then, based on the developed dq model, different control strategies are developed based on the state-of-the-art on MMC controllers. Since the order of the system may be a limiting factor for studying MTDC grids with many MMCs, different reduced-order models are presented and compared with the detailed dq model. Finally, the developed MMC models with different controllers are used for the MTDC studies. The impact of the chosen controllers of each MMC is evaluated, highlighting the potential issues that may occur in multivendor schemes.

Submitted by Franciele Moreira (francielemoreyra@gmail.com) on 2018-09-21T14:50:47Z No. of bitstreams: 2 Dissertação - Nícolas Rodrigues Moura - 2018.pdf: 4165797 bytes, checksum: 86460ffa29b4d346005f977c2f75693e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-09-24T13:21:40Z (GMT) No. of bitstreams: 2 Dissertação - Nícolas Rodrigues Moura - 2018.pdf: 4165797 bytes, checksum: 86460ffa29b4d346005f977c2f75693e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-09-24T13:21:40Z (GMT). No. of bitstreams: 2 Dissertação - Nícolas Rodrigues Moura - 2018.pdf: 4165797 bytes, checksum: 86460ffa29b4d346005f977c2f75693e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-08-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Análises de estabilidade de taludes são predominantemente realizadas em duas-dimensões (2D) por métodos de equilíbrio limite. Os métodos convencionais de equilíbrio limite são alvos de muitas críticas pelo o uso do equilíbrio estático, pressuposições de forças na análise e por possuir o mesmo fator de segurança ao longo de toda a superfície de deslizamento. Para superar essas deficiências, o método proposto por Kulhawy (1969) incorpora o comportamento tensão-deformação do solo com tensões oriundas do Método de Elementos Finitos (FEM) e tem a mesma estrutura dos métodos de equilíbrio dos métodos de equilíbrio de equilíbrio limite clássicos. É também chamado de método aperfeiçoado. Devido à existência de taludes com geometrias complexas, a abordagem tridimensional (3D) é a única capaz de incorporar todos os aspectos geométricos do problema. Esta dissertação é dividida em dois artigos com o tema de estabilidade de taludes pelo o método de Kulhawy em abordagens 2D e 3D. O objetivo primário dessa dissertação é avaliar os principais fatores que influenciam a estabilidade de taludes. O primeiro artigo propôs geometrias variando de convexo a côncavo em um conjunto de propriedades típicas de solos. Duas trajetórias de geração de tensões in- situ foram utilizadas, i.e., construção e escavação. O método GLE foi calculado para fins de comparação. A superfície de deslizamento é muito dependente do histórico de tensão e da forma da face do talude. A diferença relativa no estado de tensões inicial típico alcançou 15% nas análises 2D e 34% nas análises 3D. A análise de sensibilidade do efeito do Poisson no fator de segurança mostrou-se muito relevante. A relação entre os fatores de segurança 2D e 3D são quase lineares independente do estado de tensões, das propriedades de resistência, formato da face do talude, na ordem de 30 a 40%. O segundo artigo propõe análises em barragens construídas em vales estreitos. Três abordagens de análises foram utilizadas: redução de resistência ao cisalhamento (SSR), métodos de Kulhawy e GLE. Condições típicas de fundações são muito variáveis como topografia e deformabilidade. A análise de sensibilidade do módulo de fundação de Young no fator de segurança foi insignificante em 2D e relevantes em 3D. A relação entre o comprimento do aterro (W) e a altura () é uma variável representativa do grau de estreitamento da barragem e na estabilidade de taludes. A análise de deformações planas tende a altas relações W/H e o oposto mostra elevados efeitos 3D. A inclinação da ombreira mostrou-se relevante no fator de segurança apenas em aterros em vales estreitos. Fundações mais rígidas são mais beneficias para o fator de segurança devido à produção de altos efeitos de arqueamento neste cenário. O método de Kulhawy provou-se ser vantajoso pela a incorporação do comportamento mecânico do solo, o uso de tensões mais realísticas nas análises e avaliação da estabilidade local na superfície de deslizamento. Isso aumenta a quantidade de informações úteis e confiáveis para o profissional de engenharia no projeto de taludes. Todas as análises foram realizadas usando o software SoilVision Systems, Saskatchewan, Canadá. Os módulos utilizados foram o SVLOPE, SVSOLID e o SVFLUX (SoilVision Systems Ltd., 2018). A análise de tensão para a simulação de trajetórias de escavação e construção utilizou do solucionador de Equações Diferenciais Parcias (PDE) o FlexPDE 6 (PDE Solutions Inc., 2014). / Slope stability analyses are predominantly performed using the two-dimensional (2D) conventional limit equilibrium methods. Conventional limit equilibrium methods are targets of many criticisms for using static equilibrium, assumptions of forces in the analysis and the same factor of safety along the slip surface. In order to overcome these shortcomings, the method proposed by Kulhawy (1969) incorporates the stress-strain behavior of the soil with stresses from the Finite Element Method (FEM) with the same structure as limit equilibrium methods. It is also called enhanced method. Due to the existence of slopes with complex geometries, the three-dimensional (3D) approach is only able to incorporate all the geometric aspects of the problem. This thesis is divided into two papers with the subject of slope stability analyses by the Kulhawy’s method in 2D and 3D approaches. The primary objective of this thesis is to evaluate major factors that influence slope stability. The first paper proposed geometries ranging from convex to concave in a set of soil properties. Two stress paths were considered, i.e., construction and excavation. The GLE method was computed for comparison purposes. The slip surface is very dependent on the stress history and the shape of slope face. The relative difference in typical initial stress state reached 15% in 2D analyses and 34% in 3D analyses. Sensitivity analysis of effect of Poisson’s ratio on factor of safety was very relevant. The relationship between 2D and 3D factors of safety are nearly linear independent of stress state on order of 30 to 40%. The second paper propose analyses on embankment dams built in narrow valleys. Three approaches of slope stability were used: shear strength reduction (SSR), Kulhawy’s and GLE methods. The typical conditions of foundation sites are very variable as topography and deformability. Sensitivity analysis of Young’s modulus of foundation on factor of safety was insignificant in 2D and relevant in 3D analyses. The ratio between embankment length (W) and height (H) was very important on slope stability. The plane strain analysis tends to high W/H ratio and the opposite shows high 3D effects. The inclination of abutment showed to be relevant on factor of safety only in embankments in narrow valleys. Stiffer foundations are beneficial to the factor of safety due producing high arching effects in this scenario. The Kulhawy’s method proved to be advantageous by the incorporation of mechanical behavior of soil, more realistic stress and local stability evaluation on slip surface. It increases the amount of useful and reliable information to the engineering professional in design of slopes. All analyses were performed using SoilVision Systems suite software, Saskatchewan, Canada. The modules used were SVSLOPE, SVSOLID and SVFLUX (SoilVision Systems Ltd., 2018). The stress analysis for the simulation of excavation and construction trajectories used partial differential equation (PDE) solver, FlexPDE 6 (PDE Solutions Inc., 2014).

Para o projeto de estruturas com perfis de aço formados a frio, é fundamental a compreensão dos fenômenos da instabilidade local e global, uma vez que estes apresentam alta esbeltez e baixa rigidez à torção. A determinação do carregamento crítico e a identificação do modo de instabilidade contribuem para o entendimento do comportamento dessas estruturas. Este trabalho avalia três metodologias para a análise linear de estabilidade de perfis de aço formados a frio isolados, com o objetivo de determinar os carregamentos críticos elásticos de bifurcação e os modos de instabilidade associados. Estritamente, analisa-se perfis de seção U enrijecido e Z enrijecido isolados, de diversos comprimentos e diferentes condições de vinculação e carregamento. Determinam-se os carregamentos críticos elásticos de bifurcação e os modos de instabilidade globais e locais por meio de: (i) análise com o Método das Faixas Finitas (MFF), através do uso do programa computacional CUFSM; (ii) análise com elementos finitos de barra baseados na Teoria Generalizada de Vigas (MEF-GBT), via uso do programa GBTUL; e (iii) análise com elementos finitos de casca (MEF-cascas) por meio do uso do programa ABAQUS. Algumas restrições e ressalvas com relação ao uso do MFF são apresentadas, assim como limitações da Teoria Generalizada de Viga e precauções a serem tomadas nos modelos de cascas. Analisa-se também a influência do grau de discretização da seção transversal. No entanto, não é feita avaliação em relação aos procedimentos normativos e tampouco análises não lineares, considerando as imperfeições geométricas iniciais, tensões residuais e o comportamento elastoplástico do material. / For the design of cold formed steel members, it is essential to understand the effects of local and global instability, since these members typically have a high slenderness and low torsion stiffness. The determination of critical loads and the associated buckling modes contribute to understand the behavior of these members. This work performs a evaluation of three methods for linear stability analysis of isolated cold-formed steel members in order to determine the elastic critical loads and the corresponding buckling modes. Specifically, Ue and Ze shape members were studied with various length, different boundary conditions and loads. The elastic critical loads and buckling modes are determined by means of: (i) analysis with the Finite Strip Method (FSM), by the computer program CUFSM, (ii) beam finite element analysis based on the Generalized Beam Theory (FEM-GBT), by GBTUL program, and (iii) Finite Element Method with shell analysis using ABAQUS program. Some restrictions and warnings regarding the use of the FSM are presented, as well as limitations of the Generalized Beam Theory and precautions to be taken in the shell models. It is also analyzed the influence of the degree of discretization of the cross section. In the present study, no evaluation was made with respect to normative procedures neither nonlinear analyses considering the initial geometric imperfections, residual stresses and elastoplastic behavior of the material.

Esta tese apresenta o estudo da transição para um escoamento tridimensional da esteira de um cilindro oscilando. Esta é a transição secundária do escoamento ao redor de um cilindro, sendo a primária a própria esteira de von Kármán. A investigação é realizada na mesma faixa de número de Reynolds (Re) que ocorre a transição da esteira de um cilindro fixo: 200 Re 400. O estudo envolve simulações numéricas diretas bi- e tridimensionais do escoamento incompressível ao redor de um cilindro oscilando usando o método dos elementos espectrais. A transição também é analisada através do estudo de estabilidade linear do escoamento. O método de Gaston Floquet é adequado para a análise de estabilidade a perturbações tridimensionais devido à periodicidade característica da esteira de von Kármán. Além disto, o método é mais geral e não é aplicado somente a equações autônomas com soluções periódicas: ele também pode ser usado em análises cujo campo base é estacionário como a análise da transição primária da esteira de um cilindro. Mostra-se que a transição da esteira para tridimensionalidade é influenciada pela oscilação do cilindro. As oscilações podem atrasar a transição quando em amplitudes baixas e com escoamento a um número de Reynolds até 260. Em outros casos, a transição é similar à observada no escoamento ao redor um cilindro fixo. Além disso, quando há mudança de padrões de desprendimento de vórtices devido às oscilações, desencadeiam-se modos instáveis diferentes dos observados na esteira de um cilindro fixo. A comparação dos resultados da análise de estabilidade de Floquet com simulações numéricas diretas e experimentos publicados mostra na maioria dos casos que, apesar de ser uma análise de estabilidade linear, muitas características da análise persistem além do limiar de estabilidade. As situações com discrepâncias são identificadas nesta tese, como padrão de desprendimento diferentes em simulações bi- e tridimensionais na mesma situação. As causa das discrepâncias são estudadas através das simulações numéricas diretas e considerações sobre o sistema linearizado e a abrangência da análise de estabilidade. Em adição, mostra-se que há um limiar de amplitude de oscilação acima do qual a dinâmica da esteira, e portanto a transição secundária, é afetada. Abaixo deste limiar, retoma-se o comportamento do escoamento ao redor de um cilindro fixo. / This thesis presents the investigation of the transition to a three-dimensional flow in the wake of an oscillating circular cylinder. This is the secondary transition of the flow around a circular cylinder, while the primary transition leads to the von Kármán wake. The investigative work is performed in the Reynolds number (Re) range which occurs the secondary transition of the wake o a circular cylinder: 200 Re 400. The study consists of two- and three-dimensional direct numerical simulations of the incompressible flow around an oscillating circular cylinder by means of the spectral/hp method. The transition is also analyzed through linear stability study of the flow. The Gaston Floquet method is an appropriate method for this linear stability analysis to three-dimensional perturbations due to the typical periodicity of the von Kármán wake. Furthermore, the Floquet method is of a general kind and it is not specifically applied to autonomous equation with periodic solutions: it can be employed in analysis with a stationary base flow like the primary transition of the wake of a circular cylinder. The thesis shows that the transition to a three-dimensional wake is affected by the cylinder oscillation. The oscillations can delay the transition when they have low amplitudes and the flow has Reynolds number below 260. In other situations, the transition is similar to that observed in the flow of a fixed circular cylinder. In addition, when there is a change in the vortex shedding pattern due to the oscillatory motion, the observed unstable modes are different than those in a wake of a fixed circular cylinder. The comparison of the results from the Floquet stabilty analysis with the ones from direct numerical simulations and published experiments shows that in most cases, despite the linearization for the stability analysis, many features of the analysis persist beyond the instability threshold. The discrepant features observed are specified in this thesis, e.g. vortex shedding patterns different in two- and three-dimensional simulations with the same parameters. The cause of the discrepancies are studied through direct numerical simulations and careful considerations on the linearized system and the range of the stability analysis. In addition, this thesis shows that there is a threshold amplitude of oscillation for which the wake dynamics, therefore the secondary transition, is affected. Below this threshold, the wake behaves the same way as in the flow around a fixed circular cylinder.

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-05-23T18:23:25Z No. of bitstreams: 1 fernandohenriquedeoliveira.pdf: 7733433 bytes, checksum: ed0bfbea1ebdeec7443503ad20027a67 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-05-24T17:33:19Z (GMT) No. of bitstreams: 1 fernandohenriquedeoliveira.pdf: 7733433 bytes, checksum: ed0bfbea1ebdeec7443503ad20027a67 (MD5) / Made available in DSpace on 2018-05-24T17:33:19Z (GMT). No. of bitstreams: 1 fernandohenriquedeoliveira.pdf: 7733433 bytes, checksum: ed0bfbea1ebdeec7443503ad20027a67 (MD5) Previous issue date: 2018-02-23 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Esta dissertação apresenta uma proposta de controle discreto baseado em reali-mentação de estados aplicado à fonte de alimentação das cargas magnéticas do Sirius. A fonte é formada por associações em série e em paralelo de módulos de menor po-tência para que, em conjunto, possam atender às exigências requeridas de tensão e de corrente dos magnetos. Cada módulo é constituído de dois estágios, um de entrada e outro de saída, em que o segundo é o objeto de estudo deste trabalho. O estágio de saída é constituído por um conversor ponte completa associado a um filtro de terceira ordem. Inicialmente é feita a modelagem do estágio de saída e apresentado um modelo apropriado a uma quantidade genérica de módulos associados em série. Em seguida é feita a discretização da planta e o controle em espaço de estados. Para a alocação dos pólos do sistema em malha fechada é utilizado o Regulador Quadrático Linear Digital. Entretanto, quando módulos são associados, aumenta-se consideravelmente a ordem do sistema e torna-se inviável a medição de todos os estados da planta. Então, é proposto um observador ótimo de ordem reduzida para que este seja capaz de fornecer ao con-trolador os estados que não são medidos. A análise de estabilidade permitiu verificar a robustez do controle em conjunto com o observador de estados. Na associação de módulos em paralelo foram consideradas que as correntes da saída de cada módulo são parcelas do estado que corresponde à corrente das cargas magnéticas. Baseado nesta premissa e no controle feito para o arranjo de módulos em série, foi proposta uma estratégia de controle para o arranjo em paralelo. Os resultados em simulação, tanto para a configuração de módulos em série quanto em paralelo, permitem verificar os desempenhos dinâmicos do controlador e observador de estados. / This dissertation presents a proposal of a discrete-time state-feedback control law applied to the Sirius magnetic source power supply. In order to meet the magnets' required voltage and current levels the source is formed by series and parallel associa-tion of modular converters. Each module is made up of two stages, input and output, in which the later is addressed this work. The output stage is constituted by a full bridge converter associated with a third-order filter. Initially a mathematical model is obtained for a single module. This model is later extended to represent the connection of several modules in series. Then the plant is discretized and state feedback law is designed to control the system. The optimal technique Digital Linear Quadratic Regu-lator was used to place the closed-loop poles. However, when modules are associated, due the order of the system it becomes impracticable to measure all the states. Then an optimal reduced order observer is proposed to provide to controller the states that are not measured. An stability analysis is performed in order to verify the controller robustness. For the association of modules in parallel was considered that the output currents of each module are the parcels of the state corresponding to the current of the magnetic loads. Based on this premise and in the previously control design for the series modules association, is proposed a control topology for the parallel arrange-ment. Simulation results were obtained, for the both configuration of modules series and parallel, and the performances of the controller and state-observer were verified.

La stabilité des exploitations à ciel ouvert (mines ou carrières) excavées dans des massifs rocheux dépend de leur géométrie, des caractéristiques géométriques de la fracturation (orientation et espacement) du massif et des caractéristiques mécaniques du massif et des discontinuités. L'évaluation du risque d'instabilité rocheuse dépend de la quantité et la qualité des informations disponibles sur le massif rocheux et des méthodes d'analyse mises en œuvre pour évaluer le comportement mécanique de l'assemblage de blocs rocheux. Différents sites de talus naturels, d'excavation routière et de carrières et mines à ciel ouvert présentés dans le mémoire montrent que les informations connues peuvent beaucoup varier d'un site à l'autre. Les étapes de collecte et de synthèse des données, puis de modélisation afin d'analyser la stabilité d'une pente rocheuse conduisent à des incertitudes. Le mémoire traite plus particulièrement de l'influence des incertitudes géométriques et différentes méthodes de regroupement des fractures en familles sont explorées. La combinaison du travail proposé par différents auteurs conduit à une nouvelle méthode nommée PSMY. Cette méthode ainsi que la méthode spectrale ont été programmées sous l'environnement Mathematica et les résultats sont comparés à des regroupements "manuels" réalisé avec le logiciel DIPS. Les méthodes de regroupement sont présentées selon le pourcentage d'orientations classé par la méthode. L’orientation et l’espacement des familles de fractures sont ajustées à des lois statistiques. Les paramètres statistiques sont comparés en fonction de la méthode regroupement. Ces paramètres influencent la construction d'un modèle géométrique du massif rocheux appelé DFN (Discrete Fracture Network). L'influence des regroupements sur l'analyse de stabilité est étudiée à partir de modélisation stochastiques à l'équilibre limite utilisant les logiciels SWEDGE et RESOBLOK. Ces logiciels ne prennent pas en compte les mêmes incertitudes et en sortie ils fournissent des indicateurs de stabilité différents. Une analyse de sensibilité des indicateurs (nombre de blocs instables, volume moyen du bloc instable, volume total instable) aux méthodes de regroupement et aux orientations de talus est réalisée. Une analyse de variance permet de préciser l'influence de ces deux facteurs. Une évaluation de l’état de stabilité global du massif, en fonction de la cohésion et de l'angle de frottement est proposée. L'influence de la méthode de modélisation est évoquée en comparant des calculs tridimensionnels à l'équilibre limite et des modélisations bidimensionnel et tridimensionnels en éléments discrets rigides ou déformables. Un couplage entre le logiciel RESOBLOK (équilibre limite) et LMGC90 (éléments discrets) permet de comparer les analyses pour une même géométrie. Pour le cas de la déviation d'Ax-les-Thermes et certaines configurations géométriques instables l’influence des paramètres de modèles sur stabilité du talus est testée. Plusieurs variantes sont comparées. La simulation d’une excavation en 3D multi phases est réalisée et l’indice de mobilisation est étudié pour comparer les divers types de contacts dans LMGC90 par rapport à l’éventuel glissement des blocs dans les étapes successives / The stability of open-cast operations (mines or quarries), excavated in rock mass depends on their geometry, the geometrical characteristics of the rock mass fractures (orientation and spacing) and the mechanical characteristics of the rock mass and the discontinuities. The assessment of the rock instability risk depends on the quantity and quality of the available information on the rock mass and the analysis methods used for the evaluation of the mechanical behavior of the rock block collection. Different sites of natural rock slopes, of road cuts, and of open-cast mines and quarries, described in the present document, show that the known information can vary a lot from one site to the other. The steps of data gathering and analysis, then the modelling step used to analyze the stability of the rock slope, lead to uncertainties. The present work deals in particular with the influence of the geometrical uncertainties, and the different clustering methods, to define families of fractures, are examined. The combination of works suggested by several authors leads to a new method called PSMY. This method, together with the spectral method, was coded in the Mathematica platform, and the obtained results are compared with "hand-made" clusters, done with the DIPS software. The clustering methods are presented according to the ratio of classified orientations. The orientation and spacing of fracture families are fitted by statistical law. The statistical parameters are compared according to the clustering method used. These parameters have an influence on the construction of the rock mass geometrical model, called DFN (Discrete Fracture Network). The influence of the clusters on the stability analysis is studied from the stochastic models based on the limit equilibrium analysis, in the SWEDGE and RESOBLOK software. These programs do not take into account the same uncertainties, and as a result, they give different stability indicators. A sensitivity analysis of these indicators (number of unstable blocks, average volume of unstable blocks, and total volume of unstable blocks) versus the clustering methods used, and the orientation of the slopes, is carried out. A variance analysis allows an evaluation of the influence of these factors. The assessment of the global stability condition of the rock mass, depending on the cohesion and the friction angle, is proposed. The influence of the modeling method is analyzed by comparing 3D calculations using the limit equilibrium calculations, and 2D and 3D models using discrete rigid and deformable blocks. A coupling between RESOBLOK (limit equilibrium) and LMGC90 (discrete elements) allows the comparison of results on the same original geometry. For the case of Ax-les-Thermes road-cut, and for various unstable geometries, the influence of the model parameters is tested. Several cases are compared. The 3D simulation of an excavation, at different steps, is performed, and the mobilization index is studied, in order to compare several types of contacts, within the LMGC model, in relation to the possible sliding of blocks, at those different steps

La sécurité des procédés est une préoccupation majeure dans l'industrie du raffinage et de pétrochimie. Pour les procédés très exothermiques, l'emballement thermique doit être évité. Ainsi, l'objectif de la thèse est la mise en place d'une méthodologie d'étude de la stabilité thermique dans les réacteurs chimiques qui permet de déterminer les zones opératoires de fonctionnement stable du réacteur. Après le développement d'un modèle dynamique de réacteur, la méthodologie consiste à cartographier les zones de stabilité et d'instabilité du système réactionnel en régime stationnaire et dynamique. Le critère de Van Heerden (régime stationnaire) à été généralisé pour application à des systèmes réactionnels complexes. La méthode de perturbation des états stationnaires (régime dynamique) a aussi été intégrée à la méthodologie avec l'analyse des valeurs propres.Cette méthodologie a été appliquée au procédé d'hydroconversion en lit bouillonnant de charges pétrolières lourdes, ceci à l'échelle pilote et industrielle. Des modèles dynamiques adaptés au procédé pilote et industriel ont été développés. Ils tiennent en compte la complexité de la charge ainsi que le schéma des deux procédés. L'étude de la stabilité stationnaire et dynamique a été réalisée. Des cartographies de stabilité/instabilité en fonction des principaux paramètres du procédé ont été tracées. D'après les résultats obtenus, la plage stable pour réacteur pilote est plus large que pour le réacteur industriel. La variation des paramètres du procédé ont le même effet sur les deux réacteurs. Les cartographies de stabilité obtenues sont un outil indispensable pour l'ingénieur lors du design des procédés ou leur opération. / In refining and petrochemistry process safety is a major issue. For highly exothermic processes it is necessary to ensure in a rigorous way the safe that the process operates in safe conditions, hence avoiding thermal runaway. The objective of this thesis was to develop a methodology to determine the operating conditions of reliable operation of chemical reactors. The methodology relies on stationary and dynamic analysis. The stationary stability analysis based on the Van Heerden criterion was generalized to complex chemical systems. The dynamic analysis applies the perturbation theory to definitely determine if a stationary point is stable according to eigenvalue analysis.The methodology was applied to ebullated-bed technology for residue hydroconversion at pilot and industrial scale. Two comprehensive dynamic models that accurately represent the ebullated-bed pilot plant and industrial process were developed for the study. The models take into account a detailed description of the reactive system and the configuration of the pilot and industrial plants: three phases, kinetics and flow characterization. A stationary and dynamic thermal stability analysis was carried out for both configurations and stable/unstable operating regions were identified. The study showed that the pilot plant reactor can operate in a larger domain of operating conditions compared to the industrial reactor while the parameters have the same effect on both reactors. The resulting reactor operation diagrams are a essential guide for engineers in the reactor design and operation practice.

In recent years, the electric power industry around the world is changing continuously due to transformation from regulated market structure to deregulated market structure. The main aim of the transformation of electric supply industry under open access environment is to overcome the some of the limitations faced by the vertically integrated system. It is believed that this transformation will bring in new technologies, integration of other sources of energy such as wind, solar, fuel cells, bio-gas, etc., which are self sustainable and competitive, and better choice for the consumers and so on. As a result, several new issues and challenges have emerged. One of the main issues in power systems is to support reactive power for maintaining the system voltage profile with an acceptable margin of security and reliability required for system operation. In this context, the thesis addresses some of the problems related to planning and operation of reactive power in power systems. Studies are mainly focused on steady state operation of grid systems, grid connected wind farms and distribution systems as well. The reactive power support and loss allocation using Y-bus approach is proposed. It computes the reactive power contribution from various reactive sources to meet the reactive load demand and losses. Further, the allocation of reactive power loss to load or sink buses is also computed. Detailed case studies are carried out on 11-bus equivalent system of Indian southern region power grid under different loading conditions and also tested on 259-bus equivalent system of Indian western region power grid. A comparative analysis is also carried out with the proportional sharing principle and one of the circuit based approach in the literature to highlight the features of the proposed approach. A new reactive power loss index is proposed for identification of weak buses in the system. The new index is computed from the proposed Y-bus approach for the system under intact condition as well as some severe contingencies cases. Fuzzy logic approach is used to select the important and severe line contingencies from the contingency list. The validation of weak load buses identification from the proposed reactive power loss index with that from other well known existing methods in the literature such as Q-V sensitivity based modal analysis and continuation power flow method is carried out to demonstrate the effectiveness of the proposed index. Then, a short-term reactive power procurement/optimal reactive power dispatch analysis is also carried out to determine the optimum size of the reactive compensation devices to be placed at the weak buses for reactive compensation performance analysis in the system. The proposed approach is illustrated on a sample 5-bus system, and tested on sample 10-bus equivalent system and 72-bus equivalent system of Indian southern region power grid. A comprehensive power flow analysis of PQ type models for wind turbine generating units is presented. The different PQ type models of fixed/semi-variable speed wind turbine generating units are considered for the studies. In addition, the variable speed wind turbine generating units are considered in fixed power factor mode of operation. Based on these models, a comparative analysis is carried out to assess the impact of wind generation on distribution and transmission systems. 27-bus equivalent distribution test system, 93-bus equivalent test system and SR 297-bus equivalent grid connected wind system are considered for the studies. Lastly, reactive power coordination for voltage stability improvement in grid connected wind farms with different types of wind turbine generating units based on fuzzy logic approach is presented. In the proposed approach, the load bus voltage deviation is minimized by changing the reactive power controllers according to their sensitivity using fuzzy set theory. The fixed/semi-variable speed wind turbine generating units are also considered in the studies because of its impact on overall system voltage performance even though they do not support the system for voltage unlike variable speed wind generators. 297-bus equivalent and 417-bus equivalent grid connected wind systems are considered to present the simulation results. A comparative analysis is also carried out with the conventional linear programming based reactive power optimization technique to highlight the features of the proposed approach.

Cette thèse est consacrée à la vérification de l'analogie entre l'instabilité viscoélastique (VEI) et l'instabilité magnéto-rotationnel (MRI) dans un écoulement képlérien, afin de mieux comprendre le transport du moment dans les disques d'accrétion. Le discriminant de Rayleigh élasto-rotationnel est établi pour clarifier le rôle de l'élasticité dans le VEI. L'analyse de stabilité linéaire (LSA) avec le modèle d’Oldroyd-B est effectuée pour prédire les paramètres critiques des modes viscoélastiques. Il fait apparaître également l'influence de l'élasticité, la viscosité polymérique et d'autres paramètres de contrôle pour le VEI. Des expériences bien contrôlées avec des solutions aqueuses de polyoxyéthylène (POE) et de polyéthylène glycol (PEG) sont effectuées. Nous avons observé le mode stationnaire axisymétrique supercritique avec des solutions de faible élasticité et modes désordonnés sous-critiques avec des solutions de grande élasticité. Les formes et les valeurs critiques de ces modes sont en bon accord avec les prédictions théoriques de LSA. Selon l'analogie, le mode axisymétrique stationnaire est probablement l'analogue de MRI standard, tandis que le mode désordonné est probable que l'analogue de MRI hélicoïdale. La thèse contient aussi des résultats théoriques expérimentaux sur quatre autres régimes de rotation et un cas de limite d'élasticité infinie. / This thesis is devoted to the verification of the analogy between the viscoelastic instability (VEI) and the magnetorotational instability (MRI) in a Keplerian flow, in order to get better understanding of the momentum transportation in accretion disks.The elasto-rotational Rayleigh discriminant is deduced to clarify the role of the elasticity in the VEI. The linear stability analysis (LSA) with Oldroyd-B model is performed to predict critical parameters of viscoelastic modes, and it reveals the influence of the elasticity, polymer viscosity on the VEI. Experiments with well controlled aqueous solutions of polyoxyethylene (POE) and polyethylene glycol (PEG) are conducted. We have observed supercritical stationary axisymmetric mode with solutions of small elasticity and subcritical disordered modes with solutions of large elasticity. Both the flow patterns and the critical values of these modes are in good agreement with the LSA predictions. According to the analogy, the stationary axisymmetric mode is likely the analog of the standard MRI while the disordered mode is likely the analog of the helical MRI. The thesis contains also theoretical and experimental results with four other rotation regimes and the limit case of infinite elasticity.