Master of Science / Department of Computing and Information Sciences / Mitchell L. Neilsen / The United States Department of Agriculture (USDA) is currently researching the effectiveness of various earth dam designs and their ability to prevent erosion. This report utilizes experimental results from the USDA experimental hydraulic engineering research unit to develop computational fluid dynamics models using OpenFOAM. Several variations of smooth and stepped dam models are created and analyzed with OpenFOAM on multiple cores using Message Passing Interface. In this report, seven dam designs are analyzed to extract flow velocities and pressures and animations. This data and OpenFOAM models are helpful for determining potential erosion conditions.

nÃo hà / A evoluÃÃo das anÃlises de estabilidade de taludes na Engenharia GeotÃcnica segue de perto o desenvolvimento da MecÃnica dos Solos. Escorregamentos de taludes sÃo uma das formas mais frequentes de movimento de massa. No caso de barragens de terra, trÃs dificuldades sÃo encontradas quando se analisa a estabilidade de taludes: a) a variabilidade dos parÃmetros de resistÃncia do solo; b) dificuldades de se prever as condiÃÃes de fluxo de Ãgua e as pressÃes piezomÃtricas resultantes, e c) dificuldade de antecipaÃÃo das formas mais provÃveis de ruptura, as superfÃcies potenciais a elas associadas e os mecanismos de ruptura envolvidos. Essas dificuldades refletem diretamente no nÃmero de falhas em barragens de terra, que responde por 66% dos acidentes em barragens em todo o mundo. Dados da AgÃncia Nacional de Ãguas apontam que entre 2002 e 2010 foram registrados 800 incidentes com barragens. Como acidentes de grandes proporÃÃes, cita-se a ruptura da barragem de rejeitos de Cataguazes (MG), em marÃo de 2003, que deixou milhÃes de pessoas por semanas sem abastecimento, em razÃo do lanÃamento de soda cÃustica no rio ParaÃba do Sul, bem como o rompimento da barragem de AlgodÃes, em maio de 2009, no PiauÃ. Dessa forma, em razÃo das inÃmeras incertezas nos projetos das barragens, à necessÃria a utilizaÃÃo de metodologia que leve em consideraÃÃo a variabilidade dos componentes envolvidos nas anÃlises de estabilidade de taludes, uma vez que essas incertezas nÃo sÃo consideradas nos mÃtodos determinÃsticos. A anÃlise probabilÃstica de estabilidade de taludes, utilizando o mÃtodo de Monte Carlo, torna-se uma importante ferramenta durante a construÃÃo, enchimento e operaÃÃo de barragens de terra. PropÃe este trabalho uma metodologia simplificada para estimar os parÃmetros hidrÃulicos do solo mediante a retroanÃlise das condiÃÃes de fluxo, comparando as cargas piezomÃtricas medidas no maciÃo, com as calculadas por um programa de computaÃÃo comercial, para, em seguida, estimar a probabilidade de falha nos taludes da barragem de terra. A probabilidade de falha do talude de jusante, anÃlise na condiÃÃo de cheia mÃxima e anÃlise de estabilidade do talude de montante na condiÃÃo de rebaixamento rÃpido, foram realizadas para o caso da barragem Olho dâÃgua, no Estado do CearÃ. / The evolution of slope stability analysis in geotechnical engineering has followed closely the development of soil mechanics . Slope landslides are one of the most frequent forms of mass movement . In the case of earth dams, three difficulties are encountered when analyzing the slope stability: a) the variability of soil strength parameters, b) difficulty of predicting the conditions of water flow and resulting piezometric pressures, and c) difficulty in predicting the most probable forms of rupture, the potential surfaces associated to them, and the rupture mechanisms involved . These difficulties reflect directly on the number of failures recorded with dams, which accounts for 66 % of accidents in dams around the world. Data from the National Water Agency of Brazil show that between 2002 and 2010, 800 incidents were recorded dams. As major accidents, the rupture of tailings in Cataguazes dam in the state of Minas Gerais in March 2003, which left millions of people without water for weeks , due to leakage of caustic soda in the ParaÃba do Sul river , as well as the failure in the AlgodÃo Dam, in May 2009, in Piauà state in northeastern Brazil may be mentioned . Thus, because of the many uncertainties in the projects of dams, the use of a methodology that takes into account the variability of the components involved in the analysis of slope stability of dams is necessary, since these uncertainties are not considered in deterministic methods. The probabilistic analysis of slope stability using the Monte Carlo method, turns out to be an important evaluating tool during construction, filling and operation of earth dams. This work proposes a simplified methodology for estimating soil hydraulic parameters, by means of back-analysis of seepage conditions, comparing the pressure heads measured by standpipe piezometer in the dam, together with those calculated by commercial computing program to, then, estimate the dam slopes probability of failures. The reliability analysis of the downstream slope of the dam in the high level of water condition was done, such as the backslope stability analysis during rapid drawdown of the Olho dâÃgua dam in the State of CearÃ, Brazil.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18569号 / 工博第3930号 / 新制||工||1604(附属図書館) / 31469 / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 清野 純史, 教授 三村 衛, 准教授 古川 愛子 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

An earth dam and a dike is one kind of hydraulic construction, which is built with highly compacted earth and can be used for the purpose of containing water in a reservoir to secure the water supply, and in flood control. Earth dam and dike can be a safety issue, as it can experience catastrophic destruction due to the slope failure caused by various factors, such as construction materials, vegetation, atmospheric conditions and so on. The aim of this study is to investigate the influence of the saturation degree (or water content) on the stability of earth dam and dikes under the consideration of precipitation and vegetation with the program PCSiWaPro® (developed at the Technical University of Dresden, Institute of Waste Management and Contaminated Site Treatment). The preliminary tests on a physical model have shown that the security and stability has been already severely compromised in the partially saturated region, i.e. the area above the seepage line was in great danger and it came quickly to landslides on the air side. Before the stability analysis could be done for those unsaturated zones, water flow processes and water saturation in the saturated and partially saturated soil area were simulated using the simulation program PCSiWaPro® under transient boundary conditions. The integration of a weather generator into PCSiWaPro® allows a transient water flow calculation with respect to atmospheric conditions (precipitation, evaporation, daily mean temperature and sunshine duration) and removal of water by plant roots and leaves. Finally, with the Program PCSiWaPro® and Gmsh, a 2D dynamic model of water content distribution in the earth dam could be built, incorporating information of not only climate parameters and vegetation but also geometry, soil properties, geohydraulic conditions and time-dependent boundary conditions. The simulation results of several scenarios both in the laboratory and in the field of China and Germany clearly demonstrated that the accordance between measured values and calculated values for water content using the simulation program PCSiWaPro® was very good. In addition, two kinds of stability analysis models (the Infinite Slope Model and the BISHOP’S Model, one kind of the limit equilibrium method), which were both developed from the old Mohr-Coulomb Model, have been improved with the additional consideration of root reinforcement in the upper layer of the slope and soil water in the earth slope. The Infinite Slope Model has been proved to be mainly applied for the surficial landslide; while the BISHOP’S Model is more responsible for the deeper slip landslide forecasting. Then based on the PCSiWaPro® simulation result of water content in the unsaturated slope in the earth bodies from two study sites, Fs (safety of factor) calculation for those earth slopes was derived providing a sufficient forecasting system for the slope-failure-flood. The results have been compared with the calculated Fs values from the old models (without consideration of the influence of water content change on the slope stability) to study how significantly water content increased the risk of slope landslides.

[pt] Itaipu Binacional é uma usina hidrelétrica localizada no Rio Paraná, entre Brasil e Paraguai. A barragem que forma o reservatório é composta por estruturas de concreto, enrocamento e terra. Após o enchimento do reservatório, em 1984, o nível do lago se manteve com variação média de 1,5 m, entre as cotas 219 m e 220,5 m, cotas de operação da usina, apenas em poucas ocasiões foi reduzido abaixo da cota 219 m. Entre os anos de 2012 e 2015, devido à crise hídrica no sudeste do país, Itaipu passou a operar de maneira atípica a fim de suprir a queda na produção energética de outras usinas, isso fez com que a variação do nível do reservatório aumentasse para 4 m e permanecesse mais tempo em cotas abaixo do nível normal. Nesse mesmo período a instrumentação apontou um recalque de aproximadamente 5 cm em um trecho da Barragem de Terra da Margem Esquerda (BTME). Esse recalque está abaixo dos limites previstos, porém foi considerado atípico já que, desde a construção, os recalques medidos variam de 1 a 2 cm. Neste trabalho foram realizadas simulações para análises de fluxo, estabilidade e recalques no referido trecho, considerando a variação do nível do reservatório no período atípico. As análises permitiram observar o comportamento das poropressões no maciço compactado e fundação, determinar os fatores de segurança críticos para o período nos taludes de montante e jusante e em que momento eles acontecem. As simulações também mostraram que o recalque detectado pela instrumentação não é atribuído ao adensamento primário devido à variação do nível do reservatório. / [en] Itaipu Binacional is a hydroelectric plant located on the Parana River,between Brazil and Paraguay. The dam that forms the reservoir is made up of concrete, rock and earth-filled structures. After the reservoir was filled in 1984, the level of the lake remained with an average variation of 1,5 m, between 219 m and 220,5 m (the operating elevation of the plant). The reduction below elevation 219 m only happened in very few occasions. Between the years of 2012 and 2015, due to the water crisis in the southeast of the country, Itaipu began to operate in an unprecedented manner, in order to compensate for the decrease in other energy production plants. Such operation not only caused the reservoir variation level to increase to 4 m, but also made the water level remain below the average readings. In the same period, the instrumentation indicated, in a specific region, a 5 cm settlement of the Left Earth Dam. This fact was considered atypical, because, since the construction, the measured recharges had varied 1 or 2 cm at most. In this work, flow, stability and recharge simulations were performed to analyze the abovementioned region considering the variation of the reservoir level in this uncharacteristic period. With these analyzes it was possible to observe how the porepressures behave in the dam and foundation; what the critical safety factors for the period in the upstream and downstream slopes are; and when they occur. The simulations also showed that the settlement detected by the instrumentation isn t attributed to consolidation due to the variation of the reservoir level.

Dispersive soils are prevalent in many areas of South Africa and the presence of these soils has not only posed a problem in earth dam construction but has led to problems with a number of road projects. The use of dispersive soils in roadway embankments and structures can lead to serious engineering problems if the soils are not accurately identified before use and appropriate mitigation measures taken. Although the causes and consequences of soil dispersion are well understood, the consistent and positive identification of dispersive soils still remains a problem. Many identification methods have been proposed but none has been completely successful. The current tests used for identification include the pinhole, double hydrometer, crumb and chemical tests, which are generally used in combination to obtain the most reliable outcome. These laboratory tests, however, have not always been entirely consistent, either when used in combination or individually, and it is possible that the reason lies in the actual testing procedures. Recent investigations have shown that in many cases the identification and classification problems appear to be related to inconsistencies in the test methods and testing protocols. This has been highlighted recently at various conferences and presentations in South Africa, with a recommendation that the problem be investigated fully. The main objective of this project was thus to carry out a detailed investigation into the current methods used for the testing and identification of dispersive soils. The test methods were thoroughly analysed and shortcomings identified. The differences in results and interpretation resulting from different test techniques are examined and solutions to overcome the problems proposed. A further objective of this study is the assessment of the interpretation of results obtained from dispersive soil chemical analysis. A pilot study was first carried out, which recognized deficiencies in the identification process resulting from problems with the test methods. The pilot study allowed for the identification of these shortcomings in the test methods and their modification. The modified methods were used in the full study to obtain more consistent and reliable results. The study found the pinhole test as well as the Gerber and Harmse (1987) ESP versus CEC chart to be highly unreliable. The double hydrometer and crumb tests are good indicators of dispersivity if carried out accurately and repeatably using a standard test method. The chemical analysis of the soils should be carried out using the standard methods employed by the Soil Science Society of South Africa. Final rating systems were also found to be unreliable since they put a great deal of weight on the poorly reproducible pinhole test. Emphasis is thus put on the test methods being as simple and unambiguous as possible to promote repeatability and reproducibility of the results. Recommendations are finally made proposing a suite of tests as well as a decision process which should be followed when faced with a potentially dispersive soil. This investigation was aimed solely at the evaluation of test protocols and not the suitability or specification of limits for any rating systems. This should now be assessed using the standard test methods proposed in this thesis. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Geology / unrestricted

An earth dam and a dike is one kind of hydraulic construction, which is built with highly compacted earth and can be used for the purpose of containing water in a reservoir to secure the water supply, and in flood control. Earth dam and dike can be a safety issue, as it can experience catastrophic destruction due to the slope failure caused by various factors, such as construction materials, vegetation, atmospheric conditions and so on. The aim of this study is to investigate the influence of the saturation degree (or water content) on the stability of earth dam and dikes under the consideration of precipitation and vegetation with the program PCSiWaPro® (developed at the Technical University of Dresden, Institute of Waste Management and Contaminated Site Treatment). The preliminary tests on a physical model have shown that the security and stability has been already severely compromised in the partially saturated region, i.e. the area above the seepage line was in great danger and it came quickly to landslides on the air side. Before the stability analysis could be done for those unsaturated zones, water flow processes and water saturation in the saturated and partially saturated soil area were simulated using the simulation program PCSiWaPro® under transient boundary conditions. The integration of a weather generator into PCSiWaPro® allows a transient water flow calculation with respect to atmospheric conditions (precipitation, evaporation, daily mean temperature and sunshine duration) and removal of water by plant roots and leaves. Finally, with the Program PCSiWaPro® and Gmsh, a 2D dynamic model of water content distribution in the earth dam could be built, incorporating information of not only climate parameters and vegetation but also geometry, soil properties, geohydraulic conditions and time-dependent boundary conditions. The simulation results of several scenarios both in the laboratory and in the field of China and Germany clearly demonstrated that the accordance between measured values and calculated values for water content using the simulation program PCSiWaPro® was very good. In addition, two kinds of stability analysis models (the Infinite Slope Model and the BISHOP’S Model, one kind of the limit equilibrium method), which were both developed from the old Mohr-Coulomb Model, have been improved with the additional consideration of root reinforcement in the upper layer of the slope and soil water in the earth slope. The Infinite Slope Model has been proved to be mainly applied for the surficial landslide; while the BISHOP’S Model is more responsible for the deeper slip landslide forecasting. Then based on the PCSiWaPro® simulation result of water content in the unsaturated slope in the earth bodies from two study sites, Fs (safety of factor) calculation for those earth slopes was derived providing a sufficient forecasting system for the slope-failure-flood. The results have been compared with the calculated Fs values from the old models (without consideration of the influence of water content change on the slope stability) to study how significantly water content increased the risk of slope landslides.

[pt] O presente trabalho apresenta a implementação computacional pelo método dos elementos finitos de procedimentos para análise de problemas de escavação e de fluxo permanente bidimensional, não confinado, para solos saturados. Tais procedimentos, particularmente indicados para investigação do comportamento mecânico/hidráulico de barragens de terra, vem completar o trabalho iniciado por Parra (1996) para análise do comportamento de barragens sob carregamentos estático e sísmico. Foram implementadas duas técnicas para simulação de escavações, obtendo-se, em ambas, resultados numéricos praticamente idênticos. O procedimento para análise de fluxo permanente foi baseado na proposição de Bathe e Khoshgoftarr (1979), a qual considera a situação de fluxo não-confinado como problema não linear, porém conservando a configuração original da malha de elementos finitos. Os resultados numéricos obtidos neste trabalho foram detalhadamente comparados com os valores publicados na literatura, numéricos ou analíticos, como forma de assegurar a confiabilidade das implementações computacionais. A previsão do comportamento da barragem de terra Macusani, a ser construída no Peru, foi estudada neste trabalho, nos aspectos referentes às fases de escavação, construção, primeiro enchimento do reservatório e determinação da superficie de infiltração de fluxo permanente. Os resultados assim obtidos podem ser eventualmente úteis no detalhamento do projeto final da obra. / [en] This work presents a computer implementation for finite element analysis of excavation problems and unconfined steady state flow through saturated soils. These computer routines are particularly useful for the study of earth dams and they were written with the aim to pursue the development of a numerical model (Parra, 1996) devised to investigate the behavior of earth dams under static and seismic loading. Two techniques were implemented for excavation simulations, with both yielding the some numerical results. For the unconfined fluid flow problem the technique proposed by Bathe and Khoshgoftaar (1979) was adopted, which recasts the problem in a non-linear form but keeps the same basic finite element mesh. The results computed in this research were compared with other analytical and numerical values published in the literature, in order to ensure, as much as possible, the feasibility and efficiency of the computer implementations. The behavior prediction of the Macusani earth dam, to be built in Peru, was also studied in this research, focusing on several aspects related to its planned construction: the excavation, the construction itself and the first reservoir filling. This results may eventually be useful for the final engineering design of the Macusani dam. / [es] El presente trabajo presenta la implementación computacional de procedimentos para análisis de problemas de excavación y de flujo permanente bidimensional, para suelos saturados utilizando el método de elementos finitos. Tales procedimentos, particularmente indicados para la investigación del comportamiento mecánico/hidráulico de represas, completa el trabajo iniciado por Parra(1996) para análisis del comportamiento de represas bajo sobrecarga estática y sísmica. Se implementaron dos técnicas para simulación de excavaciones, obteniendo, en ambas, resultados numéricos prácticamente idénticos. El procedimento para análisis de flujo permanente tubo como base la propuesta de Bathe y Khoshgoftarr (1979), que considera la situación de flujo no confinado como problema no lineal, pero conservando la configuración original de la malla de elementos finitos. Los resultados numéricos obtenidos em este trabajo fueron detalladamente comparados con los valores publicados en la literatura, numéricos o analíticos, para asegurar la confiabilidad de las implementaciones computacionales. La previsión del comportamiento de la represa de Macusani, que será construida en Perú, fue estudiada en este trabajo, especifícamente los aspectos vinculados a las fases de excavación, construcción y determinación de la superficie de infiltración de flujo permanente. Los resultados obtenidos pueden ser eventualmente útiles en el proyecto final de la obra.

[pt] Em uma barragem de terra homogênea responsável pelo abastecimento de água de um empreendimento privado, observou-se um processo inicial de carreamento de partículas finas próximo ao pé do talude de jusante, situação tida como um dos principais modos de falha de barragens. Embora esta anomalia tenha sido devidamente controlada na estrutura em estudo, este trabalho buscou encontrar as causas para a ocorrência detectada, visando aprofundar o conhecimento sobre o assunto. Para isso, investigou-se o histórico da estrutura, coletou-se amostras indeformadas próximo a região de interesse com a função de realizar ensaios de laboratório para caracterizar o solo no local, determinar os parâmetros físicos, aferir coeficientes de permeabilidade sob diferentes tensões efetivas e encontrar a sua curva característica (SWCC) através de ensaios de papelfiltro. Com os resultados dos ensaios, foram elaborados modelos computacionais sob diferentes cenários para investigar o comportamento dos gradientes hidráulicos. Foi empregado o software Plaxis LE para esta função. Avaliou-se se a adoção de parâmetros não saturados ou a consideração de análises tridimensionais promoveria alguma alteração no padrão de fluxo na estrutura em estudo, o que não ocorreu. Também foi considerado se a interação solo-atmosfera poderia gerar gradientes hidráulicos críticos através de ciclos de chuva e evaporação, mas também não houve resultados críticos. Ao variar o coeficiente de permeabilidade no corpo da barragem, observou-se que existe uma relação inversamente proporcional com o gradiente hidráulico. Desta forma, entende-se que a presença de solos orgânicos no pé do talude de jusante pode ter acarretado o processo de carreamento observado. / [en] In a homogeneous earthfill dam responsible for the water supply of a private company, an initial process of internal erosion was observed near the base of the downstream slope, which is listed as one of the main dam failures causes in the world. Although this problem has been correctly solved at the studied structure, this thesis aimed to find the causes for the detected anomaly in order to increase knowledge about this subject. To do so, the history of the structure was investigated, undisturbed samples were collected near the region of interest to carry out laboratory tests to characterize the soil, determine the physical parameters, measure permeability coefficients under different effective stresses and find its characteristic curve (SWCC) through filter paper tests. With the results of the tests, computational models were elaborated under different scenarios to investigate the behavior of hydraulic gradients. The software Plaxis LE was used in this work. It was evaluated whether the adoption of unsaturated parameters or 3D analysis would promote any change in the flow pattern in the studied structure, which did not occur. It was also considered whether the soil-atmosphere interaction could generate critical hydraulic gradients through rainfall and evaporation cycles, but there were no critical results either. Although, permeability seems to have a an inversely proportional relationship with hydraulic gradient. Thus, it is understood that the formation of organic soils at the toe of the downstream slope may have led to the observed internal erosion process.

[pt] A análise das condições de fluxo na barragem de Curuá-Una (Pará) tem como objetivo avaliar a viabilidade geotécnica quanto à elevação do nível de operação do reservatório. A Usina de Curuá-Una (operada pela REDE Celpa) é responsável pelo abastecimento elétrico de Santarém. No entanto, nos horários de grande consumo, a produção de energia tem se mostrado insuficiente. O alteamento do reservatório de Curuá-Una é uma alternativa para o aumento de geração energética. Curuá-Una destaca-se por ser fundada em terreno arenoso, solução poucas vezes utilizada no mundo. A barragem de terra é do tipo zonada, com altura máxima de 26m e comprimento de 600m. Os parâmetros geotécnicos necessários para as análises do presente trabalho foram obtidos em ensaios de laboratório, em informações referentes à construção e em dados de instrumentação durante a operação da barragem. As análises numéricas foram realizadas com o programa FLOW3D. A retroanálise do regime de fluxo, feita com base na piezometria, possibilitou a estimativa das permeabilidades dos diversos materiais. A partir destes dados foi possível simular as poropressões associadas a diferentes níveis do reservatório. Foram definidos três níveis de alerta (normal, atenção e emergência) referentes à segurança da barragem. As análises indicam que a barragem opera atualmente dentro do nível normal e que um alteamento de 1,5m do reservatório não afeta a condição de segurança. O aumento das subpressões na base da barragem foi também avaliado, com os resultados mostrando um incremento máximo de 5 por cento. / [en] The analysis of flow conditions in Curuá-Una Dam, State of Pará, has the objective of evaluating the geotechnical feasibility of raising the operation level of the reservoir. Curuá-Una Power Plant, operated by REDE Celpa, is responsible for the electric supply of Santarém city. However, in periods of peak consumption, the energy production has been insufficient. Raising of Curuá-Una reservoir is an attractive alternative for increasing energy production. Curuá-Una Dam is distinguished for being constructed on sandy alluvial soil, which is a solution rarely used in the world. The earth dam is zoned, with maximum height of 26m and crest length of 600m. The geotechnical parameters were obtained from laboratory tests, field instrumentation data and construction reports. The numerical analyses were carried out with FLOW3D program. A back-analysis of flow behavior was performed for evaluating permeability parameters, taking into account results from piezometers installed in the dam and in the foundation materials. These parameters were used to predict pore pressures associated to different reservoir levels. Three levels of alert conditions (normal, attention and emergency) referring to the safety of the dam have been defined. The analyses indicated that the dam is operating within normal levels and a 1.5m rising of the reservoir shall not affect dams safety. The uplift pressures, due to different reservoir levels, have also been evaluated, with results showing a maximum increment of 5 percent.