[pt] Nos projetos de locais de disposição de resíduos e na avaliação da contaminação do solo e da água subterrânea por substâncias químicas orgânicas e inorgânicas, é essencial que se conheça os mecanismos de transporte de contaminantes por estes meios. São dois os processos básicos no transporte de solutos: advecção e dispersão hidrodinâmica. Advecção é o processo através do qual a água subterrânea carrega consigo os solutos dissolvidos. A quantidade de soluto transportado depende de sua concentração na água subterrânea, do volume de água fluindo e da velocidade da água subterrânea. O mecanismo de dispersão hidrodinâmica engloba o mecanismo de dispersão mecânica e o transporte por difusão. A medida que o soluto se movimenta no meio poroso, o processo de dispersão age no sentido de diluir o soluto e reduzir sua concentração. A difusão é o processo através do qual as espécies moleculares e iônicas dissolvidas na água se movem devido a um gradiente de concentração, indo das áreas de maior para menor concentração, mesmo na ausência de fluxo de água subterrânea. O transporte difusivo através de um meio não saturado é mais complicado do que através de meios saturados. Neste caso os parâmetros de transporte podem variar no espaço e no tempo. Portanto, a determinação destes parâmetros no laboratório deve ser feito nas condições mais próximas possíveis das condições in situ. Os processos através dos quais as substâncias se movem através do solo podem ser expressos por modelos matemáticos. Eles se baseiam na integração da equação advectiva-dispersiva utilizando condições de contorno específicas para o sistema de interesse. Entretanto, sua aplicabilidade é limitada devido à falta de parâmetros experimentais confiáveis. Esta tese procura preencher o espaço entre os modelos numéricos e os estudos experimentais. Um novo difusímetro foi desenvolvido para medir o coeficiente de difusão em solos não saturados. O projeto combina o método do reservatório simple, proposto por Rowe et al. (1988), com a técnica de controle osmótico. Foram feitos ensaios com sucção variando entre 0 e 500 kPa. Os solutos utilizados foram cloreto de sódio e cloreto de potássio difundindo através de um amostra relativamente inerte, preparada em laboratório. Os resultados obtidos indicam que a nova técnica proposta funciona bem, sendo entretanto recomendado maiores desenvolvimentos no sistema de controle de sucção, através do uso de instrumentação mais precisa. / [en] In the design of waste disposal facilities and evaluation of groundwater and soil contamination by organic and inorganic species, it is essential a knowledge of the mechanisms of transport of the contaminants. There are two basic processes in the transport of solutes: advection and hydrodynamic dispersion.Advection is the process by which moving groundwater carries with it dissolved solutes. The amount of solute being transported depends on its concentration in the groundwater, on the volume of groundwater flowing, and on the groundwater velocity. The hydrodynamic dispersion mechanism involves mechanical dispersion and diffusion. As solutes are carried through porous media, the process of dispersion acts to dilute the solute and reduce its concentration. Diffusion, is the process by which both ionic and molecular species dissolved in water move from areas of higher concentration to areas of lower concentration, even in the absence of groundwater flow.Advective-diffusive transport through unsaturated media is somewhat more complicated than for saturated soils. In this case, the transport parameters may vary both in space and in time. Hence, the determination of such parameters in laboratory should be performed as close as possible to in situ conditions.The processes by which the substances move through porous media can be expressed through mathematical models. They are based on the integration of the advection-dispersion equation using specific boundary conditions for the system of interest. However, their applicability has been often limited due to the lack of reliable parameters obtained experimentally. This thesis seeks to fulfil the gap between numerical modelling and experimental studies. A new diffusimeter has been developed to measure the diffusion coefficient in unsaturated soils. It combines the single reservoir method, proposed by Rowe et al. (1988), with the osmotic control technique. Tests were performed under suction values ranging from 0 to 500kPa. Sodium chloride and potassium chloride were used as solutes diffusing through a compacted inert sample prepared in the laboratory. The results obtained indicated that the new proposed technique worked quite well, being however recommended an improvement in the system of suction control through the use of more precise instrumentation.

abstract: Laterally-loaded short rigid drilled shaft foundations are the primary foundation used within the electric power transmission line industry. Performance of these laterally loaded foundations is dependent on modulus of the subsurface, which is directly measured by the Pressuremeter (PMT). The PMT test provides the lateral shear modulus at intermediate strains, an equivalent elastic modulus for lateral loading, which mimics the reaction of transmission line foundations within the elastic range of motion. The PMT test, however, is expensive to conduct and rarely performed. Correlations of PMT to blow counts and other index properties have been developed but these correlations have high variability and may result in unconservative foundation design. Variability in correlations is due, in part, because difference of the direction of the applied load and strain level between the correlated properties and the PMT. The geophysical shear wave velocity (S-wave velocity) as measured through refraction microtremor (ReMi) methods can be used as a measure of the small strain, shear modulus in the lateral direction. In theory, the intermediate strain modulus of the PMT is proportional to the small strain modulus of S-wave velocity. A correlation between intermediate strain and low strain moduli is developed here, based on geophysical surveys conducted at fourteen previous PMT testing locations throughout the Sonoran Desert of central Arizona. Additionally, seasonal variability in S-wave velocity of unsaturated soils is explored and impacts are identified for the use of the PMT correlation in transmission line foundation design. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2018

abstract: Urbanization and infrastructure development often brings dramatic changes in the surface and groundwater regimes. These changes in moisture content may be particularly problematic when subsurface soils are moisture sensitive such as expansive soils. Residential foundations such as slab-on ground may be built on unsaturated expansive soils and therefore have to resist the deformations associated with change in moisture content (matric suction) in the soil. The problem is more pronounced in arid and semi arid regions with drying periods followed by wet season resulting in large changes in soil suction. Moisture content change causes volume change in expansive soil which causes serious damage to the structures. In order to mitigate these ill effects various mitigation are adopted. The most commonly adopted method in the US is the removal and replacement of upper soils in the profile. The remove and replace method, although heavily used, is not well understood with regard to its impact on the depth of soil wetting or near-surface differential soil movements. In this study the effectiveness of the remove and replace method is studied. A parametric study is done with various removal and replacement materials used and analyzed to obtain the optimal replacement depths and best material. The depth of wetting and heave caused in expansive soil profile under climatic conditions and common irrigation scenarios are studied for arid regions. Soil suction changes and associated soil deformations are analyzed using finite element codes for unsaturated flow and stress/deformation, SVFlux and SVSolid, respectively. The effectiveness and fundamental mechanisms at play in mitigation of expansive soils for remove and replace methods are studied, and include (1) its role in reducing the depth and degree of wetting, and (2) its effect in reducing the overall heave potential, and (3) the effectiveness of this method in pushing the seat of movement deeper within the soil profile to reduce differential soil surface movements. Various non-expansive replacement layers and different surface flux boundary conditions are analyzed, and the concept of optimal depth and soil is introduced. General observations are made concerning the efficacy of remove and replace as a mitigation method. / Dissertation/Thesis / Ph.D. Civil and Environmental Engineering 2013

Em muitas partes do mundo, engenheiros geotécnicos freqüentemente lidam com solos não saturados, e o desempenho de obras nestes solos depende de suas características mecânicas, como a resistência ao cisalhamento. A determinação experimental da resistência de solos não saturados pode ser feita em laboratório utilizando técnicas que permitem controle ou medida da sucção, sendo uma delas o ensaio de compressão triaxial com teor de umidade constante. Neste contexto, essa pesquisa analisa a resistência ao cisalhamento de um solo arenoso compactado não saturado por meio de ensaios de compressão triaxial. Ensaios do tipo adensado-drenado e adensado-não drenado foram realizados com solo saturado, enquanto ensaios com teor de umidade constante foram realizados para caracterizar o comportamento do solo não saturado. Os resultados dos ensaios com solo saturado foram combinados e forneceram uma envoltória de resistência comum em termos de tensões efetivas. Para o solo não saturado, as curvas tensão-deformação foram representadas pela diferença de tensões principais e por esta normalizada por algumas das variáveis de estado de tensão do solo. Tais curvas se assemelham a curvas típicas de um material plástico, com exceção das obtidas para a menor tensão confinante, nas quais se observou a ocorrência de picos de resistência. Já a sucção apresentou um comportamento comum a todos os ensaios, com redução inicial seguida de estabilização. As diferentes representações da curva tensão-deformação permitiram definir superfícies planares de resistência no espaço tensão x sucção x resistência, nas quais foram observadas pequenas variações nos valores de coesão efetiva e ângulo de atrito com relação à sucção. Apesar do bom ajuste destas envoltórias planares, os resultados mostraram alguma não-linearidade. Por fim, testaram-se os métodos de Khalili e Khabbaz (1998) e Vilar (2007) de previsão da resistência ao cisalhamento de solos não saturados. / In many parts of the world, geotechnical engineers frequently deal with unsaturated soils, and the performance of constructions on such soils depends on their mechanical characteristics, and among them, the shear strength. The unsaturated soil shear strength can be experimentally determined by using techniques which allow soil suction control or measurement and one of the available techniques is the constant water content triaxial compression test. In this context, this research analyzes the shear strength of an unsaturated compacted sandy soil using triaxial compression tests. Consolidated-drained and consolidated-undrained triaxial compression tests were performed with the saturated soil, while constant water content triaxial compression tests were performed to characterize the unsaturated soil behavior. Results of tests with saturated soil were gathered and yielded a common shear strength envelope in terms of effective stress. Regarding the unsaturated soil, the stress-strain curves were represented by the deviator stress and the deviator stress normalized by some stress state variables of the soil. Such curves were similar to typical curves of a plastic material, except for those obtained for the lower confining pressure, in which peak of stress were observed. Suction development during shearing presented a common behavior to all the tests, with initial reduction followed by stabilization. The different representations of stress-strain curves allowed defining shear strength planar surfaces on stress x suction x strength space, which showed small variations of effective cohesion and angle related to suction. Despite of the good adjustment of these planar shear strength envelopes, the results showed some non-linearity. Finally, the methods proposed by Khalili and Khabbaz (1998) and Vilar (2007) for predicting the shear strength of unsaturated soils were tested.

Para a determinação do comportamento de um solo não saturado, é necessária a identificação da sua curva característica, que representa a capacidade de armazenamento de água pelo solo em função do valor de sucção imposto. Quando este solo é submetido a algum processo de contaminação, a sua estrutura interna pode ser alterada por processos físico-químicos, modificando, por conseqüência, o seu comportamento. Esta dissertação propõe uma metodologia de ensaio para a determinação de curvas características de sucção total em um solo artificialmente contaminado com diferentes teores de óleo diesel. O programa experimental proposto consiste basicamente na realização do método do papel filtro, através da técnica sem contato entre a amostra e o papel, com algumas modificações em relação às metodologias anteriormente descritas na literatura geotécnica. Foram também executados ensaios para controle e quantificação da evaporação do contaminante ao longo do tempo, e sua possível absorção pelo papel filtro utilizado. Além disso, foram realizados ensaios para a caracterização física, mineralógica e química do solo, antes e após a adição do óleo, com o intuito de constatar as alterações causadas pela contaminação. O material estudado é constituído por sedimentos coluvionares provenientes de arenito da Formação Botucatu, sendo que sua curva característica, sem contaminação, já foi determinada em um estudo anterior, através do método do papel filtro com contato. Para possibilitar comparações entre estes resultados, foram medidos também alguns pontos em amostras não contaminadas, através da técnica proposta nesta dissertação. Estes apresentaram uma satisfatória concordância em relação à curva anteriormente ajustada. Na análise das curvas características do solo contaminado com 2%, 5%, 10% e 15% de óleo diesel, constatou-se a permanência do formato bimodal, sugerindo que a microestrutura e a macroestrutura continuam influenciando na entrada e saída de água do meio. Entretanto, foram identificadas alterações na forma da curva e na extensão dos patamares resultantes, em relação à curva característica sem contaminação, assim como as diferentes localizações dos valores de entrada de ar. Foi verificado que, conforme o aumento do teor de contaminante, há uma gradual tendência ao formato unimodal da curva característica, induzindo a um comportamento de solo tipicamente granular. Este fato foi comprovado nos resultados de microscopia eletrônica, onde se verifica que, com teores menores de óleo, a estrutura do solo encontra-se mais fechada e, à medida que este teor aumenta, a estrutura torna-se mais porosa. Os tempos de equalização para o método de ensaio proposto variaram entre 7 e 30 dias, conforme o nível de sucção da amostra. A avaliação da histerese revelou que, com o aumento do teor de contaminante, há uma pequena redução deste fenômeno. Além disso, os ensaios complementares comprovaram a existência de uma pequena porcentagem de evaporação do óleo diesel, assim como a absorção do mesmo pelo papel filtro, que se apresentou praticamente nula. / The unsaturated soil behavior can be determined through its soil-water characteristic curve, which represents the capacity of the soil to store water when submitted to different suction levels. When this soil is contaminated, its internal structure can be modified according to physical and chemical processes, thus changing the initial behavior. This dissertation proposes a test methodology to determine the total-suction soil-water characteristic curves of a contaminated soil at different diesel oil contents. The experimental program consisted of using the filter-paper method without contact between the sample and the paper, but with some modifications in relation to previously studied techniques. Some control tests were also carried out to check oil evaporation and its absortion by the filter paper. Besides, the samples were submitted to physical, mineralogical and chemical characterization, before and after contamination, to verify the possible changes. The studied material is a colluvium soil, constituted basically by sandstone, from the Botucatu Formation. This soil was previously studied by the filter-paper method with contact, and its soil water characteristic curve without contamination was already known. To compare the results, the proposed test methodology was also performed with non contaminated samples, showing a satisfactory agreement with the initial curve. The soil-water characteristic curves of this soil with a diesel oil content of 2%, 5%, 10% and 15% showed a "saddle" shape, indicating that both the microstructure and the macrostructure were influenced by the entrance and exit of water through the soil. However, the shape of the curve and the extent of its plateau changed according to the level of contamination. Increasing the oil content, the curve tends to a unimodal shape, with a behavior similar to granular soils. This statement was proved by the microstruture photographs, which showed an increase of sample porosity due to the increase of oil content. The time required to reach suction equilibrium during the tests varied between 7 to 30 days, according to the initial water content of the samples. The observed hysteresis had a small reduction with the increase of oil content. The control tests proved that oil evaporation and its absortion by the filter paper were insignificant in the whole test program.

Ce mémoire de thèse est consacré à l'étude expérimentale du comportement hydromécanique d'un lœss naturel non saturé effondrable provenant d'un site proche de la ville de Bapaume (nord de la France) dans une zone où des problèmes de tassement le long de la ligne nord du TGV ont été attribués à l'effondrement du lœss, du fait d'infiltrations d'eau. Un nouvel appareil triaxial permettant de mesurer localement l'ensemble des caractéristiques du loess non saturé (déformation, teneur en eau et succion) a été développé. La courbe de rétention d'eau, déterminée à l'aide d'un tensiomètre de haute capacité et de la méthode du papier filtre a fait l'objet d'une attention particulière : elle présente autour de la teneur naturelle une zone sans hystérésis bordée par deux boucles d'hystérésis des côtés secs et humides. L'analyse de la courbe de rétention et du phénomène d'hystérésis a été approfondie grâce à une étude microstructurale réalisée à l'aide de la porosimétrie au mercure et de la microscopie électronique à balayage. Une structure assez complexe composée d'un arrangement métastable de grains de limon secs (probablement liés par la recristallisation du calcaire) et d'une phase argileuse répartie de façon hétérogène a été mise en évidence. L'étude du comportement hydromécanique a compris une investigation de l'effondrement à partir de faibles valeurs de contraintes proches de la contrainte in-situ, à l'aide d'essais oedométriques à taux de déformation constant avec mesures de succion. Le maximum d'effondrement et une dépendance fonction de la vitesse de chargement ont été identifiés. Une campagne d'essais triaxiaux à différentes teneurs en eau constantes avec mesure de succion a permis de déterminer l'allure de la limite élastique du limon naturel dans un diagramme p/q, ainsi que ses variations avec la teneur en eau et la succion et confirmer l'écrouissage en succion / The hydromechanical behaviour of an unsaturated natural loess from Northern France has been studied. Collapse-on-wetting phenomena under constant external load are observed in the in-situ conditions, related to some stability problems detected on the loess foundations of the high speed train line that links Paris to Brussels. A new triaxial apparatus with complete local monitoring of unsaturated properties (strains, water content and suction) of this loess has been developed. The water retention curve of loess, obtained by using an in-house constructed high capacity tensiometer and the filter paper method, shows a special behaviour, with a non-hysteresis zone detected around the natural hydric state bordered by two hysteresis loops at the dry and wet sides of the curve. Further analysis of the water retention curve and of the hysteresis phenomena were conducted by means of a microstructure study made by mercury intrusion porosimetry and scanning electron microscope observations. The complex structure of loess is highlighted, composed by a metastable arrangement of dry silt grains (possibly related to carbonate re-crystallisation) and a heterogeneously distributed clay fraction. The hydromechanical behaviour study includes the evaluation of the collapse sensibility of loess at stress states close to the in-situ one, by a series of suction-monitored oedometer tests performed at different constant strain rates (CSR tests). A maximum of collapse and a time-dependent behaviour of loess were observed. A triaxial testing programme at different water contents with suction measurement, allowed to obtain the yield surface of loess in a q/p diagram, and the water content and suction evolution upon loading and to confirm the suction hardening in this material

In the early years of the 20th century the first tailing dams were constructed, the upstream tailing dam being the first type. Before this the tailings were disposed in the nearest stream or river. This caused legal issues between farmers and the mining companies, which ended the random discharge of the tailings. During the 20th century many tailing dams collapsed raising questions whether the technology is sufficient and safe. The known failures are just a fraction of the actual number since not all failures are documented. If a tailing dam were to break the consequenses could be fatal not only on impact but longterm, affecting many generations to come. This paper analyses an active tailing dam in China using the software COMSOL 3.4. The main aspects are the seepage, stability and pollution transport of the unsaturated upstream tailing dam. The results indicate that the dam at this point in time is stable, based on the aspects studied, the inputdata and models that were created.

京都大学 / 0048 / 新制・課程博士 / 博士(地球環境学) / 甲第22678号 / 地環博第199号 / 新制||地環||39(附属図書館) / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)教授 勝見 武, 教授 三村 衛, 准教授 高井 敦史 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DFAM

Changes in climatic regimes and land use have led to increases in wildfire activities around the world. Wildfires are now happening more frequently, at higher altitudes, and higher severities. Adverse impacts of wildfires can last years after the fire has been contained through post-fire geohazards, such as shallow landslides. Post-wildfire shallow landslides are often mobilized by rainfall and due to fire-induced changes in soil and land cover properties and near-surface processes. This study aims to develop a physics-based framework to evaluate the stability of burned hillslopes against rainfall-triggered shallow landslides. A coupled hydromechanical infiltration model is developed by employing a closed-form solution of the Richards equation. The model is integrated into an infinite slope stability analysis to capture the effect of temporal changes in the pressure head profile of an unsaturated vegetated slope on its stability. The proposed model considers the antecedent condition of soil and vegetation cover, the time-varying nature of rainfall intensity, and wildfire-induced changes in soil properties, root reinforcement, transpiration rate, and canopy interception. The efficacy of the proposed framework is illustrated through modeling a case study in the Las Lomas watershed in California, USA. The watershed was a part of a larger area that was burned in the San Gabriel Complex Fire (consisting of two separate fires, the Fish Fire and the Reservoir Fire) in 2016. Three years later, during a heavy rainstorm in January 2019, the affected area, including the Las Lomas watershed, experienced widespread landslides. The proposed framework is then integrated into a geographic information system (GIS) to generate a susceptibility map of post-wildfire rainfall-triggered shallow landslides. The applicability of the proposed framework at a regional scale is tested for the entire area affected by the San Gabriel Complex Fire to model the observed shallow landslides within the boundaries of the Fish Fire and the Reservoir Fire. The findings of this study can be used to warn the community of post-wildfire shallow landslides activities.

[pt] A estabilidade de encostas constituídas por solos residuais não saturados sofre grande influência das variações das condições de fluxo locais, uma vez que, em muitos casos, grande parte de sua resistência ao cisalhamento é conferida pela coesão aparente acarretada pelo fenômeno de sucção. Sabendo disso, o presente trabalho avaliou, através de análises de estabilidade e de fluxo realizadas em modelos bi e tridimensionais, a possibilidade de se criar um modelo onde o resultado final de estabilidade independa da distribuição de sucção inicial. As análises e modelagens de fluxo e estabilidade foram executadas com auxílio dos softwares SVDesigner, SVSlope e SVFlux-GE integrantes do pacote SVoffice, desenvolvido pela SoilVision. Buscou-se quantificar a influência da distribuição da sucção inicial nos casos estudados. Os parâmetros de solo utilizados como dados de entrada nos modelos derivaram de estudos desenvolvidos por de Oliveira (2013) sobre os mecanismos de ruptura de movimentos de massa que ocorreram em Nova Friburgo durante o megadesastre que ocorreu na Região Serrana do Rio de Janeiro em 2011, e os dados climáticos advieram de registros contemporâneos e pretéritos ao evento. Nos modelos 2D foi possível, ao se considerar aproximadamente oito meses de dados climáticos, que diferentes condições iniciais de sucção homogêneas convergissem para um resultado único de estabilidade. Nas modelagens também foi observado que o comportamento do fluxo diferiu entre os modelos 2D e 3D o que teve um significativo impacto em suas análises de estabilidade. / [en] The stability of slopes consisting of unsaturated residual soils is strongly influenced by variations in local flow conditions, since in many cases much of their shear strength is conferred by the apparent cohesion caused by the suction phenomenon. With this in mind, the present study evaluated the possibility of creating a model where the final stability result is independent of the initial suction distribution through stability and flow analyzes performed in two and three-dimensional models. Flow and stability analyzes and modeling were performed using the SVDesigner, SVSlope and SVFlux-GE software components of the SVoffice package developed by SoilVision. It was tried to quantify the influence of the initial suction distribution in the cases studied. The soil parameters used as input data in the models were derived from studies developed by de Oliveira (2013) on the mechanisms of rupture of the mass movements that occurred in Nova Friburgo during the disaster that occurred in the Serrana Region of Rio de Janeiro in 2011, and the climatic data came from records in the region during and before the event. In the 2D models, it was possible, considering approximately eight months of climatic data, that different initial homogeneous suction conditions converged to a single stability result. It was also observed that the flow behavior differed between the 2D and 3D models, which had a significant impact on their stability analyzes.