In this study the stabili ty and stress distribution of anisotropic jointed rock slopes under external loading were examined. The influence of joint orientation and mechanical characteristics on the engineering behaviour of jointed rock slopes were included in the investigation. A total of four physical models were developed by using blocks of light-weight concrete and gypsum mortar to simulate intact rocks and joints respectively. The models were built within a confining frame such that plane strain conditions were maintained throughout the experiments. The stress-strain relationship and the strength of the model blocks were determined from laboratory tests. An empirical equation was established to represent the strength envelope of the model material and rocks in general. The normal and shear properties of the model rock JOints were examined, and were described by mathematical expressions in order to facilitate the numerical studies. Results from the physical modelling studies showed that localised failure regions were induced and three types of failure modes were identified. The stability and stress distribution wi thin the models were found to be significantly influenced by the properties and system of the jointing. Two computer programs were developed based on the Finite Element Method and Coupled Finite-Boundary Element Method in order to simulate the behaviour of jointed rock masses and assessments of their application were made in comparison with the physical modelling results. A special finite joint element was developed to incorporate the non-linearity and anisotropy behaviour of rock joints. The finite element program was successfully executed and gave reasonable results in which the principal stress distributions were generally in agreement with those obtained from the physical models. The finite-boundary element program on the other hand introduced boundary incompatibility in the system and therefore led to divergency.

[pt] Movimentos de terra em encostas frequentemente causam grandes prejuízos econômicos, ambientais, sociais e, com freqüência, perda de vidas humanas. O mecanismo que desencadeia o processo de movimentação geralmente ocorre em períodos de chuvas intensas, principalmente nas encostas com pouca cobertura vegetal ou naquelas que sofreram mudanças recentes na topografia, geralmente pela execução de cortes. Neste trabalho foram realizadas análises de estabilidade da um trecho da encosta da BR-376, que liga as cidades de Curitiba a Joinville no km 55+800 do oleoduto OSPAR da Transpetro. Em 1995, cortes executados para duplicação da rodovia provocaram instabilidade em certa área da encosta. Em janeiro de 1997, durante um período de fortes chuvas, um novo escorregamento da porção inferior do talude provocou a ruptura do muro existente e uma série de escorregamentos sucessivos, que chegaram a atingir a faixa dos oleodutos. Diante desse cenário, utilizou-se primeiramente o programa de elementos finitos PLAXIS para as análises de estabilidade e posteriormente, a fim de comparação, o programa Slope/W e Sigma/W. Para as análises no PLAXIS foi utilizado o hardening soil model para o solo, com os parâmetros sendo determinados através de ensaios triaxiais com amostras obtidas de dois blocos de solo coletados das encosta. Os efeitos da movimentação da encosta no oleoduto OSPAR foram analisados por programa 3D de elementos finitos, dando-se ênfase às tensões e deformações para se a fim de verificar a integridade do duto. / [en] In densely populated urban areas, landslides generally cause large economic, social and environmental damages as well as, quite frequently, the loss of human lives. The main triggering factor for soil slope failures is the occurrence of heavy rainfalls and the most affected slopes are those with little vegetal covering or that had suffered recent changes in topography, generally due to the execution of cuts and excavations. In this work, stability analyses of a soil slope located at km 55+800 of the Transpetro’s OSPAR oil pipeline were carried out In 1995, the works for the duplication of the BR-376 highway, connecting the cities of Curitiba and Joinville, caused some instability in certain area of the soil slope. Later, in January 1997, during a period of heavy rainfall, a new landslide near the slope toe provoked the failure of the existing retaining wall and triggered a series of successive slides that reached the protected area were the oil pipeline was buried. In order to better understand the mechanics involved in this process, numerical analyses were carried out using the computational programs Slope/W, Sigma/W and Plaxis v.8. The soil behavior was simulated considering the hard soil model, whose constitutive parameters were estimated from triaxial tests. The influence of soil movements on the OSPAR oil pipeline were investigated through a 3D finite element analysis, with emphasis on stress and strain distributions in order to check the pile line structural integrity.

[pt] São abordados alguns aspectos relativos à execução de análises probabilísticas em projetos de geotecnia. Apresenta-se um resumo dos conceitos de probabilidade e estatística, utilizados ao longo do trabalho. Descreve-se uma metodologia para a obtenção dos dados necessários à análise probabilística, incluindo a quantidade e a localização de amostras, o cálculo das médias e variâncias dos parâmetros do solo e a quantificação das incertezas relativas a estes valores. Apresenta-se o procedimento de execução dos três métodos probabilísticos mais utilizados em geotecnia com ênfase especial para o Método do Segundo Momento de Primeira Ordem. São executadas análises probabilísticas considerando, separadamente, variações de altura e inclinação de um talude de mineração sob condições drenadas. Avalia-se também a aplicação da metodologia de análise probabilística em situações não-drenadas, através da análise da estabilidade de um quebra-mar sobre argila mole. / [en] Some aspects about probabilistic analysis of stability in geotechnical engineering are studied in this thesis. A summary about basic concepts of probability and statistics used along this work is presented. The methodology for obtaining the data needed for probabilistic analysis is described, including quantity and localization of samples, computation of mean and variance of soil properties and determination of uncertainties about these values. The procedures of three probabilistic methods which are useful in geotechnics are presented, with special emphasis on the first order second moment method (FOSM). Probabilistic analysis are made considering independent changes of height and inclination of a mine slope under drained conditions. The application of probabilistic analysis of a breakwater above a soft clay deposit under undrained conditions is also presented. / [es] Se abordan algunos aspectos relativos a la ejecución de análisis probabilístico en proyectos de geotecnia. Se presenta un resumen de los conceptos de probabilidades y estadísticas, utilizados a lo largo del trabajo. Se describe una metodología para la obtención de los datos necesarios para el análisis probabilístico, incluyendo la cantidad y la localización de las muestras, el cálculo de las medias y variancias de los parámetros del suelo y la cuantificación de los errores relativos a estos valores. Se presenta el procedimientode ejecución de los tres métodos probabilísticos más utilizados en geotecnia con énfasis especial para el Método del Segundo Momento de Primer Orden. Se realizan análisis probabilísticos considerando, separadamente, variaciones de altura e inclinación de un talud de mineración en condiciones drenadas. También se evalúa la aplicación de la metodología de análisis probabilística en situaciones no-drenadas, a través de el análisis de la estabilidad de un quebra olas sobre arcilla blanda.

[pt] Na abordagem determinística compara-se o método do equilíbrio limite com o método dos elementos finitos na análise 2D da estabilidade de taludes em solo, determinando-se o valor do fator de segurança para vários exemplos de aplicação. No método dos elementos finitos quantifica-se a região da potencial superfície de ruptura que se comporta sob extensão, analisando-se a ocorrência de anisotropia de resistência ao longo da potencial superfície de deslizamento para situações envolvendo diferentes tipos de solo, ângulos de inclinação do talude e sequências de escavação. Conclui-se que o efeito da anisotropia é pouco significativo quando o ângulo de atrito do solo exceder a 10 graus. Por outro lado, devido à crescente aplicação da abordagem probabilística na prática da engenharia geotécnica, foram realizadas análises de confiabilidade de taludes empregando os métodos de Monte Carlo, do hipercubo latino e o método das estimativas pontuais alternativas, comparando-se os diferentes resultados obtidos e discutindo as principais vantagens da aplicação destes métodos. / [en] In the deterministic approach the limit equilibrium method and the finite element method are compared for 2D analysis of soil slope stability, calculating the value of the safety factor in several numerical examples. In the finite element method the region of soil under strain extension is determined and the occurrence of strength anisotropy is investigated along the potential sliding surface for situations involving different types of soil, angles of slope inclination and excavation sequences. It is concluded that the effect of the anisotropy is negligible when the angle of friction is higher than 10 degress. Moreover, due to the increasing application of the probabilistic approach in the practice of geotechnical engineering, some reliability analyses were carried out using the Monte Carlo method, the Latin hypercube method and the method of alternative point estimates, comparing their different outputs and discussing the main advantages of their application in the analysis of soil slope stability problems.

[pt] Neste trabalho se faz uma análise numérica da influência da temperatura na estabilidade de um talude em rocha. Com esta finalidade, analisou-se um escorregamento de rocha que ocorreu na cidade do Rio de Janeiro, Brasil, no ano 2009. Nos estudos feitos, depois do escorregamento, por parte de Geo-Rio (Geo-Rio, 2009) não se encontrou nenhuma evidência de algum fator desencadeante, como água subterrânea, pluviosidade, sobrecarga na crista do talude, que poderia haver desencadeado o escorregamento; por tal motivo se fez a consideração de que o fator desencadeante poderia ser a flutuação da temperatura na rocha. Chavez (Chavez, 2007) fez um trabalho experimental para avaliar a influência das oscilações térmicas na estabilidade de um maciço rochoso, isto ajudou para determinar as equações de variação da temperatura, e assim poder definir as condições de contorno para a modelagem. A modelagem se faz no software 3DEC (3 Dimensional Distinct Element Code) (Itasca, 2007). O software representa o meio descontínuo através de uma montagem de blocos, esta característica é de utilidade, já que pode representar, de forma aproximada, as geometrias dos blocos que escorregam. O método numérico que utiliza o 3DEC é o método de elementos distintos ou discretos. Na análise foi feita em duas etapas, na primeira a temperatura do modelo se mantem constante, e na segunda a temperatura do modelo varia respeito ao tempo. Dentro destas duas etapas também foi mudado o ângulo de atrito. Os resultados obtidos indicaram que quando se tem flutuação da temperatura, com alta frequência, e um menor valor de ângulo de atrito, se geram as condições para que aconteça o escorregamento do talude. / [en] This research made a numerical analysis of the influence of the temperature on the stability of the rock slope. For this purpose, it analyzed a landslide of rock that occurred in the Rio de Janeiro, Brasil, in 2009. The studies made by Geo-Rio (Geo-Rio, 2009) after the landslide, did not find any evidence of a triggering factor, such as underground water, rainfall, overload on the top of the slope, which could be triggered the slipping; therefore was done the consideration that the triggering factor could be the fluctuation of the rock temperature. Chavez (Chavez, 2007) made an experimental study to evaluate the influence of the temperature fluctuation on the stability of the rock mass; this helped to determine the equations of the variation of the temperature, and be able to define the boundary conditions for the numerical model. The modeling was done in 3DEC software (3 Dimensional Distinct Element Code) (Itasca, 2007). The software represents the discontinuous medium such as assemblage of discrete blocks; this feature is useful because it can represent, approximately, the geometries of the slide blocks. The numerical method that 3DEC uses is the discrete element method. The analysis was done in two stages, the first stage the temperature model keeps constant, and in the second stage the temperature of the model varies with respect to time. In these two stages was also changed the angle of friction. The results indicated that when one has fluctuation of the temperature, with high frequency, and slow value of the angle friction are generated the conditions for that the slope slipping.

The development of an interactive computer model for managing geologic hazards databases is vital and long overdue. As highway rockslopes continue to age and become more unstable and earthen dams are subjected to ever increasing flood events, a more proactive management system is required in order to provide timely information to planners and emergency personnel on demand. In recent years, deaths have occurred associated with both highway rockslides and earthen dam failures in southwest Virginia. In February 1991, a rockfall event occurred on Route U.S. 11 in the City of Radford, VA, which resulted indirectly in a highway accident and fatality. The incident made all parties aware that rockfalls from aging highway roadcuts within the city limits pose some threat to the motoring public (Watts et al., 1996). Additionally, in June 1995, the Timberlake dam in Lynchburg, VA, failed due to flash flooding from intense summer storms. Two people died on highways downstream of the dam, even though emergency personnel were on the scene. The lack of organized critical information about the dam, its downstream flood inundation zone, and its emergency action plan contributed to the tragedy. The outcome of the ensuing litigation is pending. In the case of the City of Radford, a user-friendly interactive database containing structural stereonet analysis, digital images, hazardous slope conditions, and maintenance records would provide a proactive approach to rockslope maintenance by allowing the slopes to be ranked in terms of geologic and traffic conditions. Appropriate remediation measures can then be taken in the most cost-effective manner. In the case of the Timberlake dam failure, a database containing critical information about the dam, its upstream watershed characteristics, downstream flood inundation zones, and emergency action plan could have been accessed by state geologists and emergency dispatchers. Appropriate measures could have been taken to deal with the event as it was unfolding. / Master of Science

[pt] Esta dissertação tem como objetivo principal estudar um caso real do comportamento de taludes de grande altura em um projeto de mineração situado no Peru, em termos de deslocamentos e fatores de segurança, considerando uma escavação com uma profundidade que se aproxima de 900 m. As análises tensão x deformação foram executadas pelo método dos elementos finitos, em modelos bi e tridimensionais, considerando o modelo constitutivo de Mohr-Coulomb para os seis diferentes tipos de rocha encontrados na área do projeto. Também foram investigados os efeitos da geometria 3D em análises pseudo-estáticas, tendo em vista a mineração estar situada em região de atividade sísmica, bem como a distância da pilha de material estéril em relação à borda da escavação. De modo geral observou-se que os deslocamentos horizontais e o fator de segurança estático são maiores em analises 3D, enquanto que os deslocamentos verticais resultaram superiores nas análises 2D. Os efeitos da pilha de estéril nos valores do fator de segurança foram pouco significativos, mas a configuração da superfície potencial de ruptura varia de acordo com a distância da pilha à escavação. O fator de segurança pseudo-estático em análises 3D depende da orientação considerada para a força pseudo-estática horizontal. / [en] The main objective of this thesis is to investigate the mechanical behavior of rock slopes of great height in a mining project located in Peru, in terms of displacements and safety factors, considering that the excavation has almost reached the depth of 900m. The stress – strain analyses were carried out by the finite element method considering bi and three-dimensional models and the Mohr-Coulomb constitutive model for the six different types of rock found in the area of the project. The 3D geometrical effects on pseudo-static analyzes were also investigated, since the mine is situated in a region of seismic activity, as well as the influence of the distance of the waste material from the edge of the excavation. In general, it was observed that the horizontal displacements and the static safety factor are larger in 3D analysis while the vertical displacements were superior in 2D models. The effects of the waste dump on the values of the safety factor were insignificant, but the configuration of the potential failure surface varied according to its distance from the excavation. The pseudo-static safety factor in 3D analysis depends on the orientation considered for the horizontal pseudo-static force.

Traditional slope stability analysis and design methods, such as limit equilibrium method and continuum numerical methods have limitations in investigating three dimensional large scale rock slope stability problems in open pit mines associated with stress concentrations and deformations arising due to intersection of many complex major discontinuity structures and irregular topographies. Analytical methods are limited to investigating kinematics and limit equilibrium conditions based on rigid body analyses. Continuum numerical methods fail to simulate the detachment of rock blocks and large displacements and rotations. Therefore, there is an urgent need to try some new methods to have a deeper understanding of the open pit mine rock slope stability problems. The intact rock properties and discontinuity properties for both DRC and DP rock formations that exist in the selected open pit mine were determined from tests conducted on rock samples collected from the mine site. Special survey equipment (Professor Kulatilake owns) which has a total station, laser scanner and a camera was used to perform remote fracture mapping in the research area selected at the mine site. From remote fracture mapping data, the fracture orientation, spacing and density were calculated in a much refined way in this dissertation compared to what exist in the literature. Discontinuity orientation distributions obtained through remote fracture mapping agreed very well with the results of manual fracture mapping conducted by the mining company. This is an important achievement in this dissertation compared to what exist in the literature. GSI rock quality system and Hoek-Brown failure criteria were used to estimate the rock mass properties combining the fracture mapping results with laboratory test results of intact rock samples. Fault properties and the DRC-DP contact properties were estimated based on the laboratory discontinuity test results. A geological model was built in a 3DEC model including all the major faults, DRC-DP contact, and two stages of rock excavation. The built major discontinuity system of 44 faults in 3DEC with their real orientations, locations and three dimensional extensions were validated successfully using the fault geometry data provided by the mining company using seven cross sections. This was a major accomplishment in this dissertation because it was done for the first time in the world. Numerical modeling was conducted to study the effect of boundary conditions, fault system and lateral stress ratio on the stability of the considered rock slope. For the considered section of the rock slope, the displacements obtained through stress boundary conditions were seemed more realistic than that obtained through zero velocity boundary conditions (on all four lateral faces). The fault system was found to play an important role with respect to rock slope stability. Stable deformation distributions were obtained for k₀ in the range of 0.4 to 0.7. Because the studied rock mass is quite stable, it seems that an appropriate range for k₀ for this rock mass is between 0.4 and 0.7. Seven monitoring points were selected from the deformation monitoring conducted at the open pit mine site by the mining company using a robotic total station to compare with numerical predictions. The displacements occurred between July 2011 and July 2012 due to the nearby rock mass excavation that took place during the same period were compared between the field monitoring results and the predicted numerical modeling results; a good agreement was obtained. This is a huge success in this dissertation because such a comparison was done for the first time in the world. In overall, the successful simulation of the rock excavation during a certain time period indicated the possibility of using the procedure developed in this dissertation to investigate rock slope stability with respect to expected future rock excavations in mine planning.

[pt] A preocupação com a preservação ambiental e a sustentabilidade, cada vez mais presente em todos os aspectos da vida do mundo atual, conduz, mais e mais, à busca por fontes de energia limpa, renovável e minimamente agressivas ao meio ambiente. Dentro desse quadro, as usinas hidrelétricas reversíveis - UHRs - retornam mais uma vez como alternativa para matrizes de energia ao produzir energia incomparavelmente mais limpa e racional do que fontes tais como termoelétricas, muito utilizadas na regulação dos picos de consumo de energia. Entretanto, por sua operação peculiar, com ciclos curtos e frequentes de enchimento e rebaixamento do nível de água de seus lagos, o projeto para reservatórios das UHRs não está perfeitamente contemplado nos procedimentos normativos brasileiros usuais para o projeto de usinas hidrelétricas, carecendo de orientações adequadas para o tratamento das margens desses lagos, cuja instabilidade pode levar a problemas econômicos e ambientais bastante inconvenientes. Atento a este problema, este trabalho apresenta um resumo das principais metodologias de análise de estabilidade de taludes sujei-tos a rebaixamento rápido e identifica as potencialidades e limitações dos métodos de equilíbrio limite e numéricos usualmente utilizados, especialmente para o caso das UHRs. Foram apresentadas soluções de tratamento de taludes das margens de reservatórios para usinas reversíveis. O caso das rupturas às margens do reservatório da usina hidrelétrica de Santa Branca é apresentado para ilustrar a gravidade do problema e contribuiu para identificar as limitações para que os referidos métodos sejam efetivamente aplicados. A conclusão do trabalho é que estudos de viabilidade e de projeto de usinas hidrelétricas devem ser aprimorados para incluir as metodologias de estudo de estabilidade na condição de rebaixamento rápido mais atuais, especialmente para taludes marginais, cuja estabilidade condiciona a operação das UHRs, antevendo a possível introdução desta solução na matriz energética brasileira. Por fim, o presente trabalho apresenta recomendações para o aprimoramento dos estudos de viabilidade para a implantação de usinas hidrelétricas reversíveis, considerando o conteúdo dos manuais brasileiros. / [en] Concern about environmental preservation and sustainability, which is increa-singly present in all aspects of life currently, leads to the growth of a search for sources of energy that are clean, renewable and minimally aggressive for the environment. Within this framework, pumped storage power plants - PSPP - return once again as an alternative to energy matrices by producing incomparably cleaner and more rational energy than sources such as thermoelectric, widely used in the regulation of energy consumption peaks. However, due to its peculiar operation, with short and frequent cycles of filling and lowering of the water level of its lakes, the designs of PSPP reservoirs are not entirely covered by the usual Brazilian guidelines for design of hydroelectric plants, lacking appropriate guidance for the treatment of the margins from such reservoirs, whose destabilization can lead to very inconvenient economic and environmental issues. Regardful of this problem, this study presents a summary of the main methods of analysis of stability of slopes subjected to rapid drawdown and identifies the potentialities and limitations of the limit equilibrium methods and numerical methods usually used, especially for the case of PSPP. Slope stabilizations solutions for reservoir banks subjected to rapid drawdowns were presented. The case of the ruptures along the Santa Branca hydroelectric power plant reservoir is presented to illustrate the severity of the problem and has helped to identify the limitations for the effective application of these methods. The conclusion of this study is that feasibility studies and hydropower plant design should be improved in order to include more up-to-date methods of analysis of slope stability under rapid drawdown condition, especially for marginal slopes, which stability conditions the operation of PSPPs, foreseeing the possible introduction of this solution in the Brazilian energy matrix. Finally, this work presents recommendations for the improvement of feasibility studies for the implementation of PSPPs, considering the content of Brazilian guidelines.

[pt] Este trabalho tem por objetivo o desenvolvimento de uma ferramenta numérica para avaliação do fluxo saturado-não saturado em encostas de grandes dimensões, com aplicação na análise de estabilidade dessas áreas. Emprega-se o método dos elementos finitos na solução da equação de Richards, considerando a carga de pressão como variável primária e utilizando formulação adequada para minimização dos problemas de conservação de massa, freqüentemente, associados a esse fato. O modelo constitutivo utilizado para a curva característica e função de condutividade hidráulica é o proposto por Van Genuchten (1980). Para solução da não-linearidade, emprega-se um método quasi- Newton (BFGS). Com o objetivo de minimizar os requisitos de memória computacional, utiliza-se esquema de armazenamento de matriz esparsa, associado ao método de gradiente biconjugado, na solução do sistema de equações. Paralelamente, é apresentado algoritmo de geração de malha tridimensional de elementos finitos, a partir de uma malha superficial de triângulos, representativa da topografia. Análises numéricas são executadas com a finalidade de validação do código gerado, comparando-se os resultados obtidos com aqueles gerados por outros programas já consagrados na literatura técnica. É proposta metodologia para geração de mapas de susceptibilidade a escorregamentos translacionais rasos, empregando-se o método do talude infinito, associado à estrutura da malha de elementos finitos e aos resultados do problema de fluxo, incorporando- se, assim, o efeito do estado de não saturação na resistência do material. / [en] The aim of this work is to develop a numerical tool for the analysis of saturated-unsaturated flow in large scale natural slopes, applied to the study of the stability of these areas. The finite element method is applied to solve the Richard`s equation, taking into account the pressure head as the primary variable and using an adequate formulation to minimize the mass conservation issues. The constitutive model used to the characteristic curve and hydraulic constitutive function is the one presented by van Genuchten (1980). A quasi-Newton method (BFGS) is applied for the solution of the non-linearity. A sparse matrix storage scheme, with the objective of reducing the computational memory requirements, is associated to the bi- conjugated gradient method for the solution of the system of equations. An algorithm of finite elements mesh is presented, which generates the 3D mesh from a triangle superficial mesh representing the relief. Numerical analyses are performed in order to validate the code, by comparing the results with those generated by others widely known codes presented in the technical literature. A methodology for the generation of susceptibility maps to shallow translational landslides is delineated, which employs the infinite slope method to the finite elements mesh structure and the flow problem results, considering the effect of the unsaturated state in the material strength.