Les sols non saturés jouent un rôle important dans de nombreux domaines. En Génie Civil (stabilité des talus, fondations superficielles), en Ingénierie de l'environnement (transport de polluants par les eaux souterraines, enfouissement de déchets radioactifs), en Ingénierie des Réservoirs (subsidence suite aux pompages dans les champs pétroliers ou dans les nappes aquifères), etc. L'objet de la thèse est l'étude du comportement hydromécanique des sols fin non saturés, tels les limons et les argiles. Les phénomènes typiques du comportement de ces sols sont d'abord présentés avant d'aborder l'étude de leurs lois constitutives. Divers modèles sont passés en revue et un modèle unifié original est développé. Ensuite, une vaste gamme d'essais de laboratoire est analysée. Ils portent sur des sols saturés, quasi saturés et non saturés et concernent quatre matériaux: l'argile de Kruibeke, le limon de Gembloux, l'argile de Boom et la bentonite d'Almeria. Cette partie de la recherche conduit à une critique détaillée des procédures classiques d'essais de laboratoires sur les sols supposés saturés. Elle fournit également une base de données importante pour la calibration de la loi constitutive unifiée développée plus haut. Enfin, des simulations numériques, réalisées en aveugle, d'expériences n'ayant pas servi à la calibration permettent de valider ce modèle.

Orientador: Ricardo Alan Verdú Ramos / Banca: João Batista Campos Silva / Banca: Eduardo Mirko Valenzuela Turdera / Resumo: No presente trabalho avalia-se uma opção para o aproveitamento energético do biogás gerado numa estação de tratamento de esgoto urbano, com capacidade de tratar os rejeitos provenientes de uma cidade de 1.000.000 de habitantes, através da instalação de um sistema de cogeração de energia, usando tecnologias baseadas em um conjunto turbina a gás e turbina a vapor (Caso 1) ou motor a gás e turbina a vapor (Caso 2), para produção de eletricidade para consumo próprio e de vapor para secagem do lodo. São realizadas análises termodinâmicas e termoeconômicas das duas plantas de cogeração propostas definindo-se índices de desempenho, como eficiências, custos unitários de produção eletricidade, calor e lodo seco, em função dos equipamentos utilizados e custos envolvidos com a implantação, operação e manutenção. Por fim, são realizadas análises econômicas das plantas propostas para verificação da viabilidade da implantação, levando-se em conta as receitas obtidas com a comercialização de créditos de carbono e de lodo como biofertilizante, bem como a diferença de custo entre a eletricidade gerada e a atualmente comprada. Dos indicadores estabelecidos e dos resultados obtidos, pode-se concluir que o primeiro caso parece significativamente mais atrativo do que o segundo. / Abstract: In the present work an option for the deployment of biogas energy generated at a urban sewage treatment plant with capacity to process the effluents from a city of 1,000,000 inhabitants is studied, considering the installation of a cogeneration power system, using technologies based on a gas turbine and steam turbine set (Case 1) or a gas IC engine and steam turbine set (Case 2), for production of electricity for own consumption as well as steam for drying the sewage residual sludge. Thermoeconomic and thermodynamic analysis are performed for both cogeneration plants proposed, setting up performance indicators, such as efficiencies, unitary costs for production of electricity, heat and dry mud, depending on the equipment and costs involved with the deployment, operation and maintenance. Finally, an economic analysis of the plants proposed is developed for verifying the feasibility of implementation, taking into account the proceeds from the sales of carbon credits and mud as biofertilizer as well as the difference between the costs of electricity generated and currently purchased. From the settings established and results obtained, it can be concluded that the first case seems to be significantly more attractive than the second. / Mestre

An investigation of the pH, organic matter content, and cation exchange properties of the soil of the 26-year-old rotation and continuously cropped plots at Blacksburg, Virginia was carried out. Individual soil samples were taken of the eight sub-plots which represent each plot. After the chemical work had been completed, the data obtained were analyzed statistically. As a result of this investigation, the following conclusions are considered worthy of mention: Fertilizer and cropping practices which tended to increase crop yields also tended to increase soil organic matter and cation exchange capacity. There was a significant, positive correlation between organic matter content and cation exchange capacity of the soil. The organic fraction seemed to be of greater importance than the mineral fraction in contributing to the cation exchange capacity of this soil. Superphosphate, rock phosphate, muriate of potash and farm manure had or no effect on soil reaction. Ammonium sulphate caused a reduction of the pH and exchangeable calcium and magnesium and an increase in exchangeable hydrogen. The application of this fertilizer decreased exchangeable calcium but had no influence on the pH. Of the total potassium applied as muriate of potash, an average of 15 percent remained as exchangeable potassium in the upper six inches of soil. Where farm manure was applied, exchangeable calcium, magnesium, potassium, and cation exchange capacity were increased significantly. Examination of the samples and crop yield data from the check plots indicated considerable soil variation. / Master of Science

Magister Scientiae (Integrated Water Resource Management) / River catchments in agricultural areas are strongly influenced by runoff from cultivated or grazed fields, and nutrient loading of these fields can result in large quantities of nitrates and phosphates being transported to rivers in surface runoff. In intensively farmed areas, nutrient loading is often so high that large quantities of nitrates and phosphates are transported to streams in surface runoff. Within these areas, strips of natural riparian vegetation and wetlands are critical in providing nutrient uptake functions that can reduce the load entering streams. A wetland can be a source, sink or transformer of nutrients, where fine sediments such as silt and clay have the ability to store and trap considerable amounts of phosphorus through adsorption and precipitation processes. Therefore, the determination of phosphorus adsorbed to fine sediment is important in understanding the role and value of wetlands in agricultural landscapes, and is the main focus of this study. The aim of the study is to evaluate an indicator-based approach, WET-EcoServices, to assess wetland sediment and phosphate trapping, through comparison with field survey data. The study focuses on spatial analysis and field survey of three Hydrogeomorphological (HGM) units classified for the Wiesdrift wetland on the Nuwejaars River, Cape Agulhas. The three HGM units are classified as: a floodplain wetland at the inlet of the system, a channelled valley-bottom wetland towards the middle part of the system and a floodplain wetland towards the outlet of the system. In-field observations were recorded for hydrogeomorphic and vegetation characteristics for each HGM Unit. AstroTurf mat sediment samples, grabbed channel bed and floodplain sediment samples were analysed for particle size and orthophosphate concentrations, while suspended sediment masses were recorded from three pairs of time-integrated sediment samplers located near the inlet, near the middle, and near the outlet of the wetland. Statistical analysis showed that orthophosphate concentrations are associated with fine sediment. Thus, the orthophosphate concentrations follow the distribution of silt on the Wiesdrift wetland. The dominant vegetation along transect 2, at which the highest concentrations of orthophosphate was found, is occupied by Typha capensis and Cyperus textilis. The percentage of fine sediment (silt) ranged between 0-37%, where the remaining percentage was sand. There was also a significant positive correlation between orthophosphate concentration and silt (Spearman’s rank-order correlation: rs = 0.692, N = 70, P < .001). The largest total sediment amount was found at Outlet 1 and Outlet 2 in the HGM unit 3 of the Wiesdrift wetland, with a value of 0.653 g. Overall, orthophosphate concentrations ranged between 0 mg/kg and 31320 mg/kg within the Wiesdrift wetland. WET-EcoServices determines an average score for phosphate trapping from on-site indicators such as hydrological zones, vegetation structure and soil texture/permeability. The dispersal of fine sediment and associated adsorbed phosphate is more complex than can be determined by a tool like WET-EcoServices because the tool captures the long-term mean conditions of a wetland system that determines the overall uptake of phosphates over extended time periods, thus future wetland assessments is recommended to take place over a longer period than this study. However, the field results of orthophosphate distribution are generally consistent with the findings from WET-EcoServices, further motivating for the use of the tool in wetland management applications.

The Understen-Märket trench is located in the Southern Quark and is the only deep-water connection between the Baltic Propper and the Gulf of Bothnia. Bathymetric mapping reveals a number of eroded channels and drift deposits exists on the seafloor, indicating that the area is heavily affected by current activity. Bottom current behavior in the area is not thoroughly understood, but generally in the BalticBasin, there is southward flowing fresh surface waters compensated by denser northward-flowing more saline bottom waters. The dominant direction of flow for bottom waters in the Southern Quark is northward. Northward speeds often exceed the threshold required to erode fine material on the seafloor. Using geophysical data and marine sediment cores, this study shows that current eroded channels and drift deposits in the Understen-Märket trench were initially formed in the late Holocene between 3 – 4kyr BP, during the transition from the Littorina to the Post Littorina stages of the Baltic Sea. Application of the sortable silt (SS) proxy for current sorting show three distinct regimes that closely match the assigned lithologic units (LU) based on core descriptions. Downcore grain size analysis of three marine sediment cores reveals a gradual boundary to sandy sediments that caps two of the cores recovered from an eroded channel. The third core was recovered from the drift deposit which mostly consists of silt. The progressive coarsening suggests that the current activity has increased during the late Holocene. A simplified model is presented that shows how moderate (20-50 m) shallowing of the sill, which has occurred in response to isostatic rebound between 8 and 4 kyr BP, could have generated the higher current speeds seen today. However, this should be explored using more advanced paleo-circulation models.

Silt fence is one of the most widely used perimeter control devices and is considered an industry standard for use in the control of sediment transport from construction sites. Numerous research studies have been conducted on the use of silt fence as a perimeter control, including a number of studies involving controlled laboratory flume tests and outdoor tests performed in the field on construction sites with actual monitored storm events. In field tests, due to the random and uncontrollable nature of real storm events and field conditions, studies have shown difficulty in evaluating silt fence performance. These field studies have shown the need for performance testing of silt fence in a more controlled environment, which can also simulate the actual use and performance in the field. This research, which is a continuation of ongoing research on silt fence fabrics at UCF Stormwater and Management Academy, was conducted in order to evaluate silt fence performance under simulated field conditions. Presented in this thesis are evaluation of two silt fence fabrics, a woven (ASR 1400) fabric and nonwoven (BSRF) fabric. Both fabrics were installed separately on a tilted test bed filled with a silty-sand soil and subjected to simulated rainfall. Previous field studies on the performance of silt fence fabrics have evaluated the turbidity and sediment removal efficiencies only after the rain event, with the assumption that the efficiency values represent the true overall performance of silt fence. The results of this study revealed that the turbidity and suspended sediment performance efficiencies of silt fence were significantly affected by the time of sampling. The performance efficiencies during rainfall remained less than 55 percent, however, after the rainfall event ended, the performance efficiencies increased over time, reaching performance efficiency upwards of 90 percent. The increase in efficiency after rainfall was due to the constant or decreasing ponding depth behind the silt fence, increased filtration due to fabric clogging, and sedimentation of suspended particles. The nonwoven fabric was found to achieve higher removal efficiencies and flow-through rates both during and after the rain event when compared with the woven fabric. However, over the entire test duration (during and after rainfall combined), the projected overall efficiencies of both fabrics were similar. The projected overall average turbidity performance efficiencies of the woven and nonwoven silt fence fabrics was 80 and 78 percent, respectively. Both fabric types also achieved comparable overall average suspended sediment concentration efficiencies of 79 percent. This result leads to the conclusion that silt fence performance in the field is dependent on three main processes: filtration efficiency occurring during the rain event, filtration and sedimentation efficiency occurring after the rainfall event, and flow-through rate of the silt fence fabrics. Decreases in the flow-through rate lead to increases in the overall efficiency. This thesis quantifies the different mechanisms by which these processes contribute to the overall efficiency of the silt fence system and shows how these processes are affected by different conditions such as the degree of embankment slope and rainfall intensity.

Stratigraphic successions of sedimentary rocks represent an important repository for signals pertaining to the history and evolution of Earth. Whereas the specific processes reflected by the stratigraphic record differ with respect to a given depositional environment, deposits in deep-marine settings, particularly passive margins, provide a unique, long-term record of paleoclimate, paleoceanography, and tectonics affecting the basin in question. Whereas deep-marine strata may be used to answer myriad of questions regarding the evolution and development of Earth systems, this dissertation narrowly targets two distinct aspects of sedimentation in deep-sea settings. The first two chapters focus on the utility of sortable silt in reconstructing bottom-current intensity linked to major shifts in climate. First, the relationship of sortable silt to flow velocity was tested under controlled conditions in a flow-through flume. This chapter investigates the correlation of sortable silt metrics across several experimental parameters, which is found here to dispute longstanding assumptions that multiple metrics must correlate to infer sediment sorting by deep currents. Additionally, the results are compared to calibrations from natural settings, where the correlation between the two datasets is remarkably similar, validating the relationship of sortable silt with current velocity in the deep ocean. Chapter two leverages sortable silt to investigate the long-term evolution of the Deep Western Boundary Current in the North Atlantic, targeting contourite drifts offshore Newfoundland to investigate the Eocene-Oligocene Transition (EOT), the most recent global greenhouse-to-icehouse transition. Results suggest that the Deep Western Boundary Current intensified gradually from 35-26 Ma, not abruptly at the EOT, and change consistent with deepening of the Greenland-Scotland Ridge and enhanced overflow of deep water into the North Atlantic. Chapter three utilizes detrital zircon U-Pb dating to characterize source-to-sink pathways and linkages during the rift-to-drift transition, in the Early Cretaceous, along the U.S. mid-Atlantic passive margin. This work shows that onshore and offshore system segments were initially disconnected, and progressively integrated over the course of ~45 Myr. Taken together, this work demonstrates a focused yet powerful example of how deep-marine sedimentary systems can be leveraged to robustly model major changes throughout Earth history. / Doctor of Philosophy / Sediments and sedimentary rocks deposited in the deep ocean house long-term signals pertaining to important Earth processes and properties. The nature of a given deposit, for example, can be the direct result of climatic conditions or tectonic development in adjacent mountainous and coastal environments. While the range of questions that can be answered using the sedimentary record is vast, this dissertation narrowly focuses on 1) how deep-ocean currents change over long periods of time, and 2) how onshore and offshore depositional environments correlate during the early phases of supercontinent break-up. To address the reconstruction of deep-ocean currents, laboratory experiments were performed to test how the sortable silt proxy – the 10-63 um fraction of a deposit – correlates with current velocity, the first controlled test of the proxy since its inception by paleoceanographers nearly three decades ago. Sortable silt is then applied to sediments of Eocene-Oligocene age, recovered from contourites offshore Newfoundland, Canada, to assess the long-term behavior of the Deep Western Boundary Current in the North Atlantic across the Eocene-Oligocene Transition (EOT). While the EOT, a major global cooling that occurred ~33.7 Ma, is well-studied with respect to Antarctica and its surrounding ocean basins, little is known about the paleoceanographic response of the North Atlantic. Grain-size records show a gradual increase in sortable silt before, during, and after the EOT, through entirety of the 9 Myr record. This trend is interpreted to reflect a long-term invigoration of the Deep Western Boundary Current in North Atlantic, likely due to progressive deepening of the Greenland-Scotland Ridge. The final chapter leverages detrital zircon U-Pb geochronology to compare sediment provenance of Early Cretaceous fluvial sandstones with coeval, distal turbidite sands. Results suggest that coastal rivers were fed by a single source terrane during the earliest Cretaceous, disconnected from the regional catchment feeding the submarine fan. By the Aptian-Albian, coastal rivers share a detrital zircon signature with turbidite strata, suggesting that rivers were progressively integrated into the sediment-routing system feeding the offshore margin.

Made available in DSpace on 2017-07-21T19:26:02Z (GMT). No. of bitstreams: 1 Wellington Claiton Leite.pdf: 6655134 bytes, checksum: dd7dca4808ad414d8d2bb3427c5baa97 (MD5) Previous issue date: 2012-03-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The Rietveld Method (RM) is a tool commonly used in the study of polycrystalline material.This method coupled with data from X-ray disraction (XRD) has been shown to be esective in the qualitative and quantitative study of various samples. In the literature there are several computer programs that perform the algorithm of the method, however, each program has implemented diferent functions its the data, including the profile function. One issue to be considered in the refinements MR structures are proposed for the XRD pattern, appropriate structural models are desirable for the correct description of the total difraction pattern, more realistically describing the study sample. With regard to the quality of settings, using indices of disagreements (index R), these are used to evaluate the quality of the final refinement as well as their convergence. However,its strong dependence on the quality of equipment used and the characteristics of sample preparation, these become the major indexes (index S) doubtful about the quality of refinement. The objective of this study was to compare the results of the refinement program GSAS and DBWS, from these results to compare the crystal structure of the adjustments made by the two programs and structural adequacy of the samples studied. And also propose a new way of assessing the quality of refinement, independent of data collection for soil samples. Samples were characterized from silt (particle size between 2-20 cm) of a Dystrophic Red Latosol submitted to management systems: conventional tillage (CT), no-tillage (NT) and minimum tillage (MT). The XRD revealed the presence of the minerals gibbsite, quartz, kaolinite, halloysite, goethite, anatase, hematite, muscovite and vermiculite. For quantification by RM phase, the programs agree to the majority phase. In DBWS was not possible to refine the structures completely, the rates of disagreement values converged to unsatisfactory. The profile function used in this program, failed to adjust the enlargements of peaks of phases at low concentration and presents a good fit of the majority phases. In GSAS, it was possible to refine all variables. For the GSAS refinement of the levels of disagreement were compared to R indices generated by DBWS in GSAS these indices were more satisfactory. From this information the diference curve was analyzed, it was found that it follows a Gaussian distribution. The mean and fwhm of the Gaussian distribution, were used as parameters for evaluating the quality of refinement. The technique of X-ray fluorescence indicated the presence of oxides of Al, Si, Fe, Ti, K, Mg, Mn, P, Ca and Na in order of decreasing oncentration. Calculations performed concentration of oxides showed that among the results of the GSAS and DBWS compared with XRF show that the GSAS presents the results more similar than FRX. A tool used in the statistical analysis of multivariate data is the Principal Components Analysis, it is able to check the degree of correlation between samples, using this technique was verified that the samples differ due to their chemical composition. / O Método de Rietveld (MR) é uma ferramenta comumente utilizada no estudo de materiais policristalinos. Esse método aliado aos dados de difração de raios X (DRX), temse mostrado eficaz no estudo qualitativo e quantitativo de diversos tipos de amostras.Existem na literatura diversos programas computacionais que executam o algoritmo do método, no entanto, cada programa possui implementado diferentes funções de ajustes dos dados, entre elas, a função de perfil. Uma questão a ser levada em consideração em refinamentos pelo MR são as estruturas propostas para o padrão de DRX, modelos estruturais adequados são desejáveis para a descrição correta do padrão total de difração e de forma mais realística a amostra estudada. No que se refere à qualidade dos ajustes,utiliza-se índices de discordâncias (Índices R), esses são utilizados para avaliar a qualidade final do refinamento bem como sua convergência. Entretanto, sua forte dependência com a qualidade do equipamento utilizado e de características de preparação da amostra, tornam o principal desses índices (Índice S) duvidoso quanto a qualidade do refinamento. O Objetivo desse trabalho foi comparar os resultados do refinamento dos programas DBWS e GSAS, a partir desses resultados comparar os ajustes da estrutura cristalina realizada pelo dois programas e a adequação estrutural dessa as amostras estudadas. E também propor uma nova forma de análise da qualidade do refinamento, independente das condições de coleta de dados, para amostras de solo. Foram caracterizadas amostras da fração silte (partículas de tamanho entre 2-20 cm) de um Latossolo Vermelho distrófico, submetido aos sistemas de manejos: Plantio Convencional (PC), Plantio Direto (PD) e Preparo Minímo (PM). A DRX revelou a presença dos minerais Gibbsita, Quartzo, Caulinita, Haloisita, Goethita, Anatásio, Hematita, Muscovita e Vermiculita. Para quantificcação de fases pelo MR, os programas concordam para as fases majoritárias. No DBWS não foi possível refinar as estruturas por completo, os índices de discordância convergiram para valores insatisfatórios. Com a função de perfill utilizada neste programa, não se conseguiu ajustar os alargamentos de picos de fases em baixa concentração, porém apresentou um bom ajuste das fases majoritárias. No GSAS, foi possível refiar todas as variáveis. Para o refinamento do GSAS os índices de discordância R foram comparados aos índices gerados pelo DBWS, no GSAS esses índices foram mais satisfatórios. A partir dessas informações a curva de diferença foi analisada, verificou-se que a mesma segue uma distribuição Gaussiana.A média e a fwhm dessa, serviram como parâmetros para avaliar a qualidade do refinamento. A técnica de Fluorescência de Raios X indicou a presença dos óxidos de Al,Si, Fe, Ti, K, Mg, Mn, P, Ca e Na citado aqui em ordem decrescente de concentração. Cálculos realizados para a concentração dos óxidos mostraram que entre os resultados do DBWS e do GSAS quando comparados a FRX, mostram que o GSAS apresenta os resultados mais similares da FRX. Uma ferramenta utilizada dentro do estudo estatístico de dados multivariados é a Analise das Componentes Principais, ela capacita a verificação do grau de correlações entre as amostras, utilizando-se dessa técnica foi possível verificar que as amostras diferem entre si devido a sua composição química.

Although silt and clay mixtures were mostly considered to be resistant to cyclic loading due to cohesional components of their shear strength, ground failure case histories compiled from fine grained soil profiles after recent earthquakes (e.g. 1994 Northridge, 1999 Adapazari, 1999 Chi-Chi) revealed that the responses of low plasticity silt and clay mixtures are also critical under cyclic loading. Consequently, understanding the cyclic response of these soils has become a recent challenge in geotechnical earthquake engineering practice. While most of the current attention focuses on the assessment of liquefaction susceptibility of fine-grained soils, it is believed that cyclic strain and strength assessments of silt and clay mixtures need to be also studied as part of complementary critical research components. Inspired by these gaps, a comprehensive laboratory testing program was designed. As part of the laboratory testing program 64 stress-controlled cyclic triaxial tests, 59 static strain-controlled consolidated undrained triaxial tests, 17 oedometer, 196 soil classification tests including sieve analyses, hydrometer, and consistency tests were performed. Additionally 116 cyclic triaxial test results were compiled from available literature. Based on this data probability-based semi-empirical models were developed to assess liquefaction susceptibility and cyclic-induced shear strength loss, cyclically-induced maximum shear, post-cyclic volumetric and residual shear strains of silt and clay mixtures. Performance comparisons of the proposed model alternatives were studied, and it is shown that the proposed models follow an unbiased trend and produce superior predictions of the observed laboratory test response. Superiority of the proposed alternative models was proven by relatively smaller model errors (residuals).

The results from an experimental study on the dynamic properties of sand with nonplastic silt are presented. Combined resonant column and torsional shear equipment is used to evaluate the effects of confining pressure, shearing strain, frequency, and number of cycles of loading on the dynamic properties of silty sand. The goal of this study is to determine if relationships in the literature for sands and gravels are accurate for predicting the shear modulus and material damping characteristics of soil with nonplastic fines or if the incorporation of a fines content parameter improves predictions. This goal was primarily accomplished by reconstituting and testing samples of an alluvial deposit from Dillon Dam, Dillon, Colorado according to predetermined gradation curves with variable amounts of non-plastic fines. Among the findings of this investigation are: (1) soil parameters such as Cu and D50 can be related to dynamic properties of soils with up to 25% fines, (2) the effects of non-plastic fines on the small-strain dynamic properties of soils are not very pronounced for soils with less than 25% fines, and (3) an increase in the amount of non-plastic fines in uniform soils or soils with more than 25% fines generally results in lower values of small-strain shear modulus, higher values of small-strain material damping, and more linear G/Gmax - log([gamma]) and D - log([gamma]) curves. The effect of non-contacting, larger granular particles in a finer soil matrix is also investigated along with the impact of removing larger particles from laboratory samples. / text