[pt] Este trabalho apresenta resultados de um estudo realizado visando avaliar o mecanismo de ruptura associado ao escorregamento em solo não saturado ocorrido na Vista Chinesa (RJ) em fevereiro de 1988. São apresentados os resultados de um programa que envolveu investigações de campo e de laboratório, através do qual foram definidos os parâmetros necessários à realização de diversas análises. Foram utilizados os programas de computador SWMS-2D (análises de problemas de fluxo permanente/transiente em meios saturados / não saturados) e PC-SLOPE (análise de estabilidade de taludes utilizando de métodos de equilíbrio limite), com os quais procurou-se reproduzir, da maneira mais realista possível, os fenômenos observados na encosta em estudo. / [en] This thesys presents the results of one study aiming to evaluate failure mechanisms associated with the unsaturated soil lanslides which ocurred in Vista Chinesa (RJ) in february, 1988. There are showed the field and laboratory investigation program, which was the basis to define the parameters required for numerical simulations. In these simulations the SWMS-2D(analysis of permanent/transient flow problems in saturated/unsaturated media) and PC-SLOPE (stability analysis using the limit equilibrium methods) programs were used, in na attempt to reproduce as close as possiible the instability phenomena in the slope under investigation. / [es] Este trabajo presenta resultados de un estudio realizado para evaluar el mecanismo de ruptura asociado al deslizamiento de suelo no saturado, hecho que ocurrió en la zona de la Vista Chinesa (Rio de JaneiroJ) en Febrero de 1988. Se presentan los resultados de un programa que abarco investigaciones de campo y de laboratorio, a través del cual fueron definidos los parámetros necesarios a la realización de diversos análisis. Se utilizaron los programas de computador SWMS-2D (análisis de problemas de flujo permanente/transiente en medios saturados / no saturados) y PC-SLOPE (análisis de estabilidad de taludes utilizando métodos de equilibrio límite), con los cuales se intentó reproducir, de la manera más realista posible, los fenómenos observados en el lugar de estudio.

[pt] O método de exploração Sublevel Caving é um dos métodos de extração massiva mais usados na indústria mundial de exploração subterrânea, sendo considerado pela indústria de mineração, num futuro próximo dentre os substitutos naturais das atuais minas a céu aberto. Uma operação Sublevel Caving requer que o maciço rochoso circundante ao minério rompa continuamente e se movimente para dentro do espaço criado pela extração do minério. Análises existentes na literatura consideram apenas configurações parciais do processo Sublevel Caving sem considerar o processo evolutivo da extração, e o dano induzido ao maciço rochoso decorrente deste processo. Esta dissertação desenvolve uma modelagem numérica utilizando o método dos elementos discretos para simular o mecanismo de ruptura e a subsidência causada pelo método de exploração Sublevel Caving, analisando o referido efeito e suas consequências na evolução do mecanismo de ruptura e subsidência no Sublevel Caving. O software comercial Particle Flow Code (PFC2D) foi selecionado para esta modelagem devido à capacidade de simular, em um evento de excesso de tensão, o fraturamento do maciço rochoso e sua desintegração, desta forma, originam-se o fluxo do material e os deslocamentos em grande escala, os quais são considerados fenômenos físicos dominantes que regem a formação da subsidência e fraturamento num processo Sublevel Caving. Os resultados obtidos nesse estudo mostraram-se satisfatórios, reproduzindo adequadamente a superfície de subsidência induzida por Sublevel Caving, conseguindo-se uma simulação física realista da sua evolução desde o início do fraturamento até à subsidência final. / [en] The Sublevel Caving Method is one of the most massive extraction methods used in underground mining industry worldwide and is considered by the mining industry as one of the natural replacements of the current open cut mines in the near future. A Sublevel Caving operation requires that the rockmass surrounding the orebody continually fails and moves into the void created by ore extraction. This dissertation develops a modeling using the discrete element method to simulate the failure mechanism and subsidence caused by Sublevel Caving method. Analyses reported in the literature consider only partial configurations of process Sublevel Caving, without taking into consideration the excavation evolution process, and damage induced to the rock mass resulting from this process. This dissertation analyzes this effect and its consequences on the evolution of failure mechanism and subsidence in Sublevel Caving. Particle Flow Code (PFC2D) was selected for modeling because of its ability to simulate, if the event of excess stress, fracturing and disintegration of the rock mass and large-scale deformation and material flow, to be simulated, which are believed to be the dominant physical phenomena governing the formation of subsidence and fracturing of Sublevel Caving. The results obtained in this study were satisfactory, reproducing properly the surface subsidence induced by Sublevel Caving, allowing physically realistic simulation of its evolution since the beginning of the fracturing to final subsidence.

Using experimentally measured temperature-process-dependent model parameters, the failure analysis and life prediction were conducted for Atmospheric Plasma Sprayed Thermal Barrier Coatings (APS-TBCs) and electron beam physical vapor deposition thermal barrier coatings (EB-PVD TBCs) with Pt-modified -NiAl bond coats deposited on Ni-base single crystal superalloys. For APS-TBC system, a residual stress model for the top coat of APS-TBC was proposed and then applied to life prediction. The capability of the life model was demonstrated using temperature-dependent model parameters. Using existing life data, a comparison of fitting approaches of life model parameters was performed. The role of the residual stresses distributed at each individual coating layer was explored and their interplay on the coating’s delamination was analyzed. For EB-PVD TBCs, based on failure mechanism analysis, two newly analytical stress models from the valley position of top coat and ridge of bond coat were proposed describing stress levels generated as consequence of the coefficient of thermal expansion (CTE) mismatch between each layers. The thermal stress within TGO was evaluated based on composite material theory, where effective parameters were calculated. The lifetime prediction of EB-PVD TBCs was conducted given that the failure analysis and life model were applied to two failure modes A and B identified experimentally for thermal cyclic process. The global wavelength related to interface rumpling and its radius curvature were identified as essential parameters in life evaluation, and the life results for failure mode A were verified by existing burner rig test data. For failure mode B, the crack growth rate along the topcoat/TGO interface was calculated using the experimentally measured average interfacial fracture toughness.

Nickel superalloys are used for high-temperature application in energetic and aerospace industry. They are exposed to aggressive environment at high temperatures with the interactions between fatigue and creep processes, high-temperature oxidation, corrosion and erosion. Lifetime extension of such strained parts while increasing the performance of particular machine is possible by applying protective surface coatings. The subject of this work is to investigate the fatigue failure mechanisms of superalloy Inconel 713LC at 800 °C and to compare these mechanisms between material with a protective coating based on Al-Si and material without coating. The location of initiation fatigue cracks, their propagation and the fatigue crack propagation rate in some areas were analyzed by optical microscopy, scanning electron microscopy and confocal laser scanning microscopy. Based on previous research it was found that the application of the coating AlSi has a positive effect on lifetime of alloy Inconel 713LC. These results were confirmed and estimated in the diploma thesis.

[pt] A avaliação da estabilidade do talude da Mina Robert (Canadá) é feita através do campo de deslocamentos de marcos superficiais e subsuperficiais e possíveis mecanismos de ruptura obtidos a partir da análise tensão- deformação usando-se o programa computacional FLAC (V. 3.30). Adotando-se o emprego dos modelos constitutivos elástico perfeitamente plástico e elasto-plástico com amolecimento, são calculados o fator de segurança e a porcentagem da região de plastificação, e são definidas as características de comportamento cinemático do talude sob condições de carregamento gravitacional. Apresenta-se um estudo de sensibilidade considerando-se tensões cisalhantes e deslocamentos acumulados em função da variação dos parâmetros do maciço rochoso e da inclinação do talude, além de se analisar fatores associados à definição dos mecanismos de ruptura em termos de tensão- deformação. Finalmente, são apresentadas as comparações entre os fatores de segurança calculados em função dos resultados da simulação numérica (FLAC) e os fatores de segurança calculados por equilíbrio limite considerando-se as superfícies potenciais de ruptura provenientes da modelagem computacional. / [en] The evaluation of the stability of the Robert Pit Mine (Canada) is made through the field of displacements of superficial and ground marks and possible rupture mechanisms obtained from the results of tension-deformation analysis by using the program computational FLAC (V. 3.30). Two constitutive models, the elastic perfectly plastic model and elastic-plastic with strain softening model, are used for the determination of safety's factor and plastification area. This work also defines the characteristics of cinematic behavior of the rock slope under gravitat ional condit ions. A sensibility study is realized considering shear stress and displacements in function of the variation of the rock parameters and of the inclination of the slope. The analysis of the factors associated to the definition of the rupture mechanisms in tension-deformation terms is also done. Finally, the comparisons are presented among safety's factors calculated in function of the results of the numerical analysis (FLAC) and safety's factors calculated by limit equilibrium methods in function of the potential rupture surfaces of the computational model. / [es] La evaluación de estabilidad del talud de la Mina Robert (Canadá) se realiza a través del campo de deslocamientos de marcos superficiales y subsuperficiales y posibles mecanismos de ruptura obtenidos a partir del análisis tensión-deformación utilizando el programa computacional FLAC (V. 3.30). Se adopta el empleo de los modelos constitutivos elástico perfectamente plástico y elasto-plástico con ablandamiento. Se calculan el factor de seguridad y el portentaje de la región de plastificación, y son definidas las características de comportamiento cinemático del talud bajo condiciones de recarga gravitacional. Se presenta un estudio de sensibilidad considerando las tensiones cisallantes y deslocamientos acumulados en función de la variación de los parámetros del macizo rocoso y de la inclinación del talud, además de nalisa factores asociados a la definición de los mecanismos de ruptura en términos de tensión - deformación. Finalmente, se presentan las comparaciones entre los factores de seguridad calculados en función de los resultados de la simulación numérica (FLAC) y los factores de seguridad calculados por equilibrio límite considerando las superfícies potenciales de ruptura provenientes del modelo computacional.

Résumé : Les dalles de tabliers de ponts et des stationnements sont exposées à des environnements agressifs en particulier au Québec et en Amérique du Nord en raison de l'utilisation de sels de déglaçage et des cycles de gel-dégel. La substitution des armatures d’acier par des armatures en matériaux composites de polymères renforcés de fibres (PRF) constitue une alternative intéressante qui connait beaucoup de succès ces dernières années. Le béton armé de PRF est durable, car l’armature n’est pas sujette à la corrosion électrochimique. Aussi l’armature de PRF possède une résistance en traction élevée et est légère. En Amérique du Nord, l’utilisation des composites de PRF a suscité une attention toute particulière de la part des ingénieurs et des gestionnaires d’ouvrages. Plusieurs organismes dont des ministères de transport spécifient l’armature de PRF comme matériau structural dans leurs devis techniques pour lutter contre la corrosion et allonger la durée de service de leurs infrastructures. Les dalles en béton armé sont souvent soumises à des efforts de cisaillement critiques. Actuellement les méthodes de calcul au cisaillement (à l’effort tranchant) de dalles unidirectionnelles en béton armé de PRF différèrent d’une norme à une autre. En effet, la majorité des équations proposées dans les normes et guides de conception ont dérivées à partir de relations empiriques. Bien que des efforts de recherche considérables aient été consacrés dans ce domaine au cours de la dernière décennie, une meilleure compréhension du comportement au cisaillement et des mécanismes de rupture de dalles unidirectionnelles en béton armé de PRF est encore nécessaire. Dans cette recherche, un programme expérimental visant à étudier le comportement de dalles renforcées avec différents types de barres en PRF a été mis en place. Vingt-deux dalles unidirectionnelles en béton renforcées avec des barres de PRF ont été construites et testées en flexion a quatre points jusqu’à la rupture. Les paramètres d’étude comprennent : le type et le taux d’armature, le diamètre de la barre, l’espacement et la configuration de l’armature ainsi que la résistance en compression du béton afin d’examiner leur effet sur la résistance au cisaillement des dalles. Le comportement des dalles testées a été examiné en considérant le réseau de fissures, la charge ultime ainsi que les modes de rupture. Aussi, une base de données comprenant 203 poutres et dalles unidirectionnelles en béton armé de PRF rompues en cisaillement a été répertoriée et introduite dans les analyses. Les charges de rupture en cisaillement des dalles testées dans le cadre de cette thèse ainsi que celles de la base de données ont été comparées à celles prédites par les équations de calcul proposées par la normes canadiennes CSA S6-06/S1 et CSA S806-12, ainsi que celles des deux guides de calcul ACI 440.1R-06 et JSCE-97. Les analyses effectuées ont montré que les valeurs prédites par les équations de calcul proposées par l’ACI 440.1R-06 sont très conservatrices, alors que celles prédites par celles de JSCE-97 sont en meilleur accord avec les valeurs expérimentales. Aussi, les résultats obtenus ont montré que les équations de la nouvelle norme CSA S806-12 prédisent bien la résistance au cisaillement expérimentale. Toutefois, une amélioration de l'équation de la norme CSAS806-12, conduisant à de meilleurs résultats, est proposée. Par ailleurs, les résultats obtenus dans le cadre de cette thèse ont mené à une meilleure compréhension des mécanismes de rupture et des facteurs principaux qui contribuent à la résistance au cisaillement de dalles unidirectionnelles en béton armée de PRF. Enfin, des recommandations pour des travaux futurs y sont également formulées. // Abstract : Bridge deck and parking garage slabs are exposed to aggressive environments particularly in the North American regions resulting from the excessive use of de-icing salts. Fiber-reinforced-polymer (FRP) reinforcements have emerged as a practical and sustainable anti-corrosive reinforcing material with superior tensile strength to overcome the corrosion problem. High comfort level and increase use of the material is currently seen. Protection and regulations policies of some Public North American agencies currently include GFRP reinforcing bars as premium reinforcement. Shear behaviour in RC slabs is examined since most of the bridge deck and parking garage slabs are shear critical. However, there is still no agreement in FRP design codes and guidelines for shear strength equations. Several design code equations are still based on empirical relationships while recent developments are based on shear theories. The complex nature of shear phenomena which is influenced by many parameters, in addition to the existence of various schools of thoughts in shear, makes it difficult to find a general agreement on a unified equation. Huge research efforts are being established, however better understanding for the shear behaviour and failure mechanisms for unidirectional FRP RC slabs is still needed. In this research study, an experimental program was designed to investigate the shear behaviour of one-way concrete slabs reinforced with different types of FRP bars. A total of twenty one concrete slabs reinforced with FRP bars in addition to a steel reinforced slab were constructed and tested to failure under two-point loading. The variation in the concrete contribution to the shear strength V[subscript c] is investigated with respect to FRP reinforcement properties. Newly developed GFRP bars with high modulus, which were not previously investigated in the literature, are used. Different FRP reinforcement properties were included in the study such as reinforcement ratio, modulus of elasticity and axial stiffness, type of bars, and reinforcement configuration. Also, normal concrete and high strength concrete were considered in the research program. Analysis of the experimental results included the general behavior of the tested slabs, crack patterns, ultimate capacities, and modes of failure, load deflection relationships as well as the concrete and reinforcement strains. Test results of the present investigation indicate an influence of the reinforcement type, bar diameter, and the shear stiffness of the bars on the mode of failure and the shear strength. The experimental investigation and analysis of test results provided better understanding of concerning mechanisms of failure and factors contributing to the shear capacity of FRP RC slabs. A refined shear model to the CSA S806-12 is introduced and found to provide better results compared to the existing design codes and guidelines. The model is based on regression analysis of an experimental database. The database is assembled from twenty five different studies in addition to the present investigation. The used database includes 203 unidirectional members reinforced with FRP bars (without shear reinforcement) failing in shear. The model was evaluated through the experimental concrete shear capacities (V[subscript c exp]) of the database and found to provide good predictions. The experimental shear capacities of the database ( V[subscript c exp]) was compared to their corresponding predicted shear capacities (Vcpred ) using CSA S806-12, CAN/CSA-S6.1S1, ACI 440.1R-06, and JSCE-97. It was found that the ACI guide is very conservative. It can be noted that using this guide in its present form may reduce the economic competitiveness of fibre-reinforced polymers. JSCE recommendations are in better agreement with the test results. The Canadian CSA S806-12 equation was found to be in good fit with the experimental shear capacities.

Dans les années 2000, les composants de puissance en carbure de silicium (SiC) font leur apparition sur le marché industriel offrant d'excellentes performances. Elles se traduisent par de meilleurs rendements et des fréquences de découpage plus élevées, entrainant une réduction significative du volume et de la masse des convertisseurs de puissance. Le SiC présente de plus un potentiel important de fonctionnement en haute température (>200°C) et permet donc d'envisager de placer l'électronique dans des environnements très contraints jusqu'alors inaccessibles. Pourtant les parts de marche du SiC restent limitées dans l'industrie vis à vis du manque de retour d'expérience concernant la fiabilité de ces technologies relativement nouvelles. Cette question reste aujourd'hui sans réponse et c'est avec cet objectif qu'a été menée cette étude axée sur le vieillissement et l'analyse des mécanismes de dégradation sur des composants de puissance SiC pour des applications haute température. Les tests de vieillissement ont été réalisés sur des transistors MOSFET SiC car ces composants attirent les industriels grâce à leur simplicité de commande et leur sécurité "normalement bloqué" (Normally-OFF). Néanmoins, la fiabilité de l'oxyde de grille est le paramètre limitant de cette structure. C'est pourquoi l'étude de la dérive de la tension de seuil a été mesurée avec une explication du phénomène d'instabilité du VTH. Les résultats ont montré qu'avec l'amélioration des procédés de fabrication, l'oxyde du MOSFET est robuste même pour des températures élevées (jusqu'à 300°C) atteintes grâce à un packaging approprié. Les durées de vie moyennes ont été extraites grâce à un banc de vieillissement accéléré développé pour cette étude. Des analyses macroscopiques ont été réalisées afin d'observer l'évolution des paramètres électriques en fonction du temps. Des études microscopiques sont conduites dans l'objectif d'associer l'évolution des caractéristiques électriques par rapport aux dégradations physiques internes à la puce. Pour notre véhicule de test, la défaillance se traduit par un emballement du courant de grille en régime statique et par l'apparition de fissures dans le poly-Silicium de la grille. Pour finir, une étude de comparaison avec des nouveaux transistors MOSFET a été réalisée. Ainsi l'analogie entre ces composants s'est portée sur des performances statiques, dynamiques, dérivé de la tension de seuil et sur la durée de vie moyenne dans le test de vieillissement. Le fil rouge de ces travaux de recherche est une analyse des mécanismes de dégradation avec une méthodologie rigoureuse permettant la réalisation d'une étude de fiabilité. Ces travaux peuvent servir de base pour toutes analyses d'anticipation de défaillances avec une estimation de la durée de vie extrapolée aux températures de l'application visée / Since 2000, Silicon Carbide (SiC) power devices have been available on the market offering tremendous performances. This leads to really high efficiency power systems, and allows achieving significative improvements in terms of volume and weight, i.e. a better integration. Moreover, SiC devices could be used at high temperature (>200°C). However, the SiCmarket share is limited by the lack of reliability studies. This problem has yet to be solved and this is the objective of this study : aging and failure mechanisms on power devices for high temperature applications. Aging tests have been realized on SiC MOSFETs. Due to its simple drive requirement and the advantage of safe normally-Off operation, SiCMOSFET is becoming a very promising device. However, the gate oxide remains one of the major weakness of this device. Thus, in this study, the threshold voltage shift has been measured and its instability has been explained. Results demonstrate good lifetime and stable operation regarding the threshold voltage below a 300°C temperature reached using a suitable packaging. Understanding SiC MOSFET reliability issues under realistic switching conditions remains a challenge that requires investigations. A specific aging test has been developed to monitor the electrical parameters of the device. This allows to estimate the health state and predict the remaining lifetime.Moreover, the defects in the failed device have been observed by using FIB and SEM imagery. The gate leakage current appears to reflect the state of health of the component with a runaway just before the failure. This hypothesis has been validated with micrographs showing cracks in the gate. Eventually, a comparative study has been realized with the new generations of SiCMOSFET

Chemo-mechanics studies the material behavior and phenomena at the interface of mechanics and chemistry. Material failures due to coupled chemo-mechanical effects are serious roadblocks in the development of renewable energy technologies. Among the sources of renewable energies for the mass market, hydrogen and lithium-ion battery are promising candidates due to their high efficiency and easiness of conversion into other types of energy. However, hydrogen will degrade material mechanical properties and lithium insertion can cause electrode failures in battery owing to their high mobilities and strong chemo-mechanical coupling effects. These problems seriously prevent the large-scale applications of these renewable energy sources. In this thesis, the atomistic and continuum modeling are performed to study the chemical-mechanical failures. The objective is to understand the hydrogen embrittlement of grain boundary engineered metals and the lithium insertion-induced fracture in alloy electrodes for lithium-ion batteries. Hydrogen in metallic containment systems such as high-pressure vessels and pipelines causes the degradation of their mechanical properties that can result in sudden catastrophic fracture. A wide range of hydrogen embrittlement phenomena was attributed to the loss of cohesion of interfaces (between grains, inclusion and matrix, or phases) due to interstitially dissolved hydrogen. Our modeling and simulation of hydrogen embrittlement will address the question of why susceptibility to hydrogen embrittlement in metallic materials can be markedly reduced by grain boundary engineering. Implications of our results for efficient hydrogen storage and transport at high pressures are discussed. Silicon is one of the most promising anode materials for Li-ion batteries (LIB) because of the highest known theoretical charge capacity. However, Si anodes often suffer from pulverization and capacity fading. This is caused by the large volume changes of Si (~300%) upon Li insertion/extraction close to the theoretical charging/discharging limit. In particular, large incompatible deformation between areas of different Li contents tends to initiate fracture, leading to electro-chemical-mechanical failures of Si electrodes. In order to understand the chemo-mechanical mechanisms, we begin with the study of basic fracture modes in pure silicon, and then study the diffusion induced deformation and fracture in lithiated Si. Results have implications for increasing battery capacity and reliability. To improve mechanical stability of LIB anode, failure mechanisms of silicon and coated tin-oxide nanowires have been studied at continuum level. It's shown that anisotropic diffusivity and anisotropic deformation play vital roles in lithiation process. Our predictions of fracture initiation and evolution are verified by in situ experiment observations. Due to the mechanical confinement of the coating layers, our study demonstrates that it is possible to simultaneously control the electrochemical reaction rate and the mechanical strain of the electrode materials through carbon or aluminum coating, which opens new avenues of designing better lithium ion batteries. This thesis addresses the nano-chemo-mechanical failure problems in two green energy-carrier systems toward improving the performance of Li-ion battery anode and hydrogen storage system. It provides an atomistic and continuum modeling framework for the study of chemo-mechanics of advanced materials such as nano-structured metals and alloys. The results help understand the chemical effects of impurities on the mechanical properties of host materials with different metallic and covalent bonding characteristics.

The sublevel caving mining method is a mass production method with potentially very low operational costs. The success of this method is dependent on, among other factors, the cavability of the orebody and the overlying rock mass. However, caving of the surrounding rock mass also results in deformations in the cap rock as well as on the ground surface above the orebody being mined. From this follows that any existing infrastructure on the ground surface must be relocated as not to be affected by the mining-induced deformations.This thesis work was undertaken to bring about a better understanding of the rock mass behavior in the cap rock of non-daylighting orebodies, with particular application to the Printzsköld orebody as part of the LKAB Malmberget Mine. Rock testing, field observations and underground mapping was conducted to characterize the rock mass in the caving environment. A methodology for identifying the caving front based on seismic monitoring data was derived by studying the Fabian orebody (which has caved to surface), and using laser scanning data for validation. The methodology was then applied to the Printzsköld orebody to identify the caving front.Numerical modeling was performed for various scenarios of the rock mass as mining proceeded. Modeling included (i) stress analysis to understand stress changes and their effects on the rock mass behavior, (ii) discontinuum numerical modeling to quantify the influence of large-scale geological structures on the cave progression, and (iii) discontinuum cave modeling to simulate possible cave mechanisms in the cap rock more explicitly. Laser scanning together with seismic event data were used to calibrate the numerical models.The numerical simulation results showed that as mining progresses, the cap rock and hangingwall were exposed to stress changes that resulted in yielding. Two failure mechanisms were predominantly at play (i) shear failure (dominant in the cap rock) and (ii) tensile failure (dominant in the hangingwall). The presence of the large-scale structures affected thenearfield stresses through slip along the cave boundaries. The effect of the structures on the far field stresses were less significant.Discontinuum modeling to explicitly simulate failure and caving involved simulating the rock mass as a jointed medium using Voronoi tessellations in 2D, and bonded block modeling (BBM) in 3D. Both the 2D and the 3D modeling results showed fair agreement when comparing the inferred boundary of the seismogenic zone, with that identified from seismic monitoring data. Predictive numerical modeling was conducted for future planned mining to assess future cave development in the cap rock. The results from 3D modeling indicated that cave breakthrough for the Printzsköld orebody is expected when mining the 1023 m level, corresponding to approximately year 2022, as per current mining plans. The 2D model was non-conservative with cave breakthrough predicted to occur when mining the 1109 m level, corresponding to the year 2028.The estimated boundary between the seismogenic and yielded zones, as defined in the Duplancic and Brady conceptual model of caving, was coinciding with, or was close to, the cave boundary in the Printzsköld orebody. This may imply that in some areas the yielded zone was not present and that the Duplancic and Brady model may not be universally applicable. Additional work is required to verify this indication, as well as to fine-tune the modeling methodology.

Résumé : Ce projet de maîtrise s’intéresse au comportement ultime d’une structure en acier, contrôlée sismiquement par des amortisseurs élastomères et des contreventements en chevron. Les séismes peuvent causer des dommages considérables quand les infrastructures et les bâtiments ne sont pas construits selon les normes et les techniques appropriées. Par conséquent, réduire l’impact des séismes revient particulièrement à construire des ouvrages sécuritaires en tenant compte bien entendu du paramètre économique. Ainsi Gauron, Girard, Paultre et Proulx ont étudié en 2009, un système de reprise de forces latérales, constitué uniquement de treventements en chevron montés en série avec des amortisseurs en caoutchouc naturel fibré ayant de nombreux avantages. Premièrement, le système reste élastique sous le séisme de design en réduisant les efforts sismiques linéaires par un facteur supérieur à R[indice inférieur d] = 3 par rapport à un cadre conventionnel. Deuxièmement, il est capable de contrôler les déplacements sous la limite du CNBC 2010 (Code National du Bâtiment du Canada 2010), et même de réduire ces derniers dans certains cas. Par conséquent, il permet de réduire les sections des poutres et des poteaux des cadres par rapport à une structure conventionnelle ainsi que les coûts de réparation après un séisme. Toutefois, le comportement à l’état limite ultime d’un tel système, ses limites et ses réserves de sécurité restaient à déterminer. Ainsi, l’objectif global de ce projet de recherche est de déterminer les différents mécanismes de ruine possibles de ce système, d’établir des limites et réserves de sécurité, et de préciser, après avoir formulé certaines recommandations, à quelles conditions il peut être utilisé dans le dimensionnement de nouvelles structures. Pour atteindre les objectifs fixés, deux essais quasi statiques ont été réalisés sur deux cadres en acier dimensionnés avec le système. Des essais dynamiques ont aussi été réalisés afin d’avoir les propriétés viscoélastiques des amortisseurs. Le premier essai a mis en évidence un mécanisme de ruine inattendu et prématuré qui a souligné un défaut majeur dans les connexions des diagonales avec l’amortisseur. Le second essai a révélé un des mécanismes de ruine envisagés initialement où le caoutchouc se déchire après l’initiation du flambement dans la diagonale comprimée. Les résultats expérimentaux ont montré que l’amortisseur constitue le maillon faible du système, et que des efforts parasites peuvent réduire significativement la capacité portante des structures dimensionnées avec un tel système. Dans les deux cas, les résultats ont montré que la méthode de dimensionnement du système tel qu’elle est définie actuellement mérite d’être améliorée. En ce sens, des recommandations relatives au dimensionnement des différents éléments des structures dimensionnées avec le système ont été élaborées, particulièrement en ce qui concerne le caoutchouc et les connexions. // Abstract : This thesis focuses on the ultimate behavior of steel structures, controlled seismically by elastomeric dampers and chevron bracings. Earthquakes can cause considerable damages when infrastructures and buildings are not built considering appropriate standards and technics. Therefore, mitigating the impact of earthquakes means essentially building safe structures by taking account of economic parameters too. Thus Gauron, Girard, Paultre and Proulx studied in 2009 a seismic force resisting system consisting only of chevron braces connected in series with fiber-reinforced natural rubber dampers that offers many benefits. First, the system remains elastic under the design earthquake by reducing linear seismic efforts by a factor of R[subscript d] = 3 compared to a conventional frame. Secondly, it allows to control the displacements under the limits of NBCC 2010 (National Building Code of Canada 2010), and even to reduce them in some cases. Therefore, it allows a reduction of sections of beams and columns of conventional frames and it prevents repairing costs of the structure after an earthquake. However, the ultimate limit state behavior of this system, its limitations and safety reserves have not been determined yet. Thus, the overall objective of this project is to determine the different possible failure mechanisms of the system, to set its limits and safety reserves, and to state after some recommendations, how it can be used in the design of new structures. To achieve these objectives, two quasi static tests were performed on two steel frames designed with the new system. Dynamic tests were also conducted to get the viscoelastic properties of the damping material. The first quasi static test revealed an unexpected and premature failure mechanism that pointed out a major flaw in the connections of the braces with the damper. The second test revealed one of the failure mechanisms originally expected where the rubber tears after buckling of the compression brace. The experimental results have shown that the damper is the weak element in the system, and that additional forces can significantly reduce the structural capacity of structures designed with the system. In both cases, the results have shown that the actual design method of the system should be improved. Thus, recommendations for the design of elements of structures designed with this system have been developed, particularly with regard to the rubber and brace connections.