published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Geography and Geology / Master / Master of Philosophy

published_or_final_version / Earth Sciences / Master / Master of Science

The main objective of this thesis is to investigate the impact of microbial extracellular polymeric substances (EPS) on sediment stability and the related factors which influence “biogenic stabilisation” as a basis to the prediction of sediment erosion and transport. The ability to make direct and sensitive measurements of the physical properties of the biofilm is a critical demand to further understanding of the overall biostabilisation processes. Therefore, attention has been focused on developing a new technique, Magnetic Particle Induction (MagPI) for measuring the adhesive properties of the biofilm. MagPI determines the relative adhesive properties or “stickiness” of the test surface, whether a biofilm, a sediment or other submerged material. The technique may have future applications in physical, environmental and biomedical research. Newly developed Magnetic Particle Induction(MagPI) and traditional techniques Cohesive Strength Meter (CSM) for the determination of the adhesion/cohesion of the substratum were used to assess the biostabilisation capacity of aquatic microorganisms. Whilst these devices determine slightly different surface properties of the bed, they were found to complement each other, increasing the range of measurements that could be made and presented a strong correlation in the overlapping portion of the data. It is recognized that microorganisms inhabiting natural sediments significantly mediate the erosive response of the bed (“ecosystem engineers”) through the secretion of naturally adhesive organic material (EPS: extracellular polymeric substances). Interactions between main biofilm consortia microalgae, cyanobacteria and bacteria in terms of their individual contribution to the EPS pool and their relative functional contribution to substratum stabilisation were investigated. The overall stabilisation potential of the various assemblages was impressive, as compared to controls. The substratum stabilisation by estuarine microbial assemblages was due to the secreted EPS matrix, and both EPS quality (carbohydrates and proteins) and quantity (concentration) were important in determining stabilisation. Stabilisation was significantly higher for the bacterial assemblages than for axenic microalgal assemblages. The peak of engineering effect was significantly greater in the mixed assemblage as compared to the bacterial and axenic diatom culture. This work confirmed the important role of heterotrophic bacteria in “biostabilisation” and highlighted the interactions between autotrophic and heterotrophic biofilm components of the consortia. An additional approach, to investigate the impact of toxins on biostabilisation capacity of aquatic organism was performed on cultured bacterial and natural freshwater biofilm. The data suggest a different mode of triclosan (TCS) action ranging from suppressing metabolisms to bactericidal effects depending on the TCS concentration. The inhibitory effect of triclosanon bacterial and freshwater biofilms was confirmed. This information contributes to the conceptual understanding of the microbial sediment engineering that represents an important ecosystem function and service in aquatic habitats.

Call number: LD2668 .T4 1986 L39 / Master of Science / Agronomy

In recent history, C. jamaicense has been displaced by another native monocot, T. domingensis, predominantly resulting from increased phosphorous enrichment in the Everglades. This study aimed to elucidate these two species responses to low and high [Pi] in terms of allocation, photosynthate partitioning and growth. C. jamaicense growth was independent of Pi, while T. domingensis growth increased with [Pi]. Under high [Pi], allocation to younger T. domingensis shoots occurred, while C. jamaicense shoots retained more [Pi], while low [Pi] resulted in homogeneous allocation patterns for both species. Additionally, Pi deficiencies induced carbohydrate levels in older shoots of T. domingensis, while [Pi] had no effect on photosynthate partitioning patterns in C. jamaicense. ACP activity was induced by Pi deficiency in all T. domingensis shoots and increased with shoot age, while no effect was observed in C. jamaicense. Results indicate these two species differ in allocation strategies when [Pi] is altered. / by Brian Hill. / Vita. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Effect of cementitious stabilization on the stress-compressibility characteristics of three different South Florida organic soils were evaluated in this study. The objectives of the research were to (l) determine if the secondary compression characteristics of organic soils and peats can be stabilized with (a) cement only, (b) binary blends of cement/slag (C-S), cement/gypsum (C-G), and cement/cement-kiln-dust (C-CKD) and (c) ternary blend of cement-slag-gypsum in equal proportions; (ll) quantify the effectiveness of cementitious stabilization by evaluating the time-stress-compressibility (t-log σ'v - e) relationship in terms of the Cα / Cc ratio; and (lll) provide some guidelines for selecting optimum dosage of cementitious materials in deep mixing methods when organic soils and peats are encountered. It was concluded that cementitious mixes containing various waste materials is effective in controlling the secondary compression behavior of organic soils, and therefore should be considered in deep mixing methods as a sustainable practice. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

A questão central deste trabalho é demonstrar a viabilidade técnica e econômica da estabilização de solos com os cimentos pozolânicos de cinza de casca de arroz e de resíduo cerâmico. Para alcançar este objetivo o trabalho foi desenvolvido em duas etapas: a primeira referente ao desenvolvimento dos cimentos pozolânicos e a segunda referente à estabilização do solo propriamente dita. Em ambas as etapas adotou-se o critério da simplicidade e da possibilidade de utilização de equipamentos leves e de absorção de mão-de-obra não especializada. Os resultados técnicos e econômicos referentes ao cimento pozolânico de cinza de casca de arroz foram animadores; porém o mesmo não ocorreu com o cimento pozolânico de resíduo cerâmico que apresentou um desempenho em um patamar inferior. Quanto à estabilização de solos, os experimentos e a avaliação econômica efetuada mostram que a eficácia dos cimentos pozolânicos utilizados é limitada sendo difícil a obtenção de resultados comparáveis com o atualmente obtido com o cimento Portland. / The main scope of this work is to demonstrate the technical and economical viability of the soil stabilization with pozzolanic cements made from rice husk ash and waste bricks and tiles. In order to reach this objective the work has been developed in two stages: the first referes to the development of the pozzolanic cement and the second one referes to the soil stabilization. In both these stages the criteria that has been adopted was of the simplicity, of the use of light equipments and of non skilled labour. The technical and economical results referring to the rice husk ash pozzolanic cement were encouraging; but the same was not the case with the waste bricks and tiles pozzolanic cement that had an inferior performance. As regards the soil stabilization, the tests and the economical evaluation show that the efficiency of the pozzolanic cement is limited thus the results achieved are not as good as of the Portland cement.

O Estado do Maranhão possui uma rede de aproximadamente 55.000 km de estradas, em sua grande maioria com volumes diários médios inferiores a 400 veículos, e uma baixa densidade de rodovias pavimentadas (0,02 km/km²). Os recursos escassos das administrações públicas impossibilitam a realização de novas obras de pavimentação no Maranhão, em ritmo adequado para que alcance padrões similares aos dos Estados brasileiros mais desenvolvidos. A busca de alternativas de pavimentação ou de melhoria da trafegabilidade das estradas, empregando materiais disponíveis na região e técnicas que sejam introduzidas facilmente no meio técnico local, foi a motivação central do trabalho. O uso de solo local reduz consideravelmente os custos, por evitar grandes distâncias de transporte, porém muitos solos de ocorrência na região precisam de estabilização para o emprego em pavimentos. A estabilização destes solos por meio de emulsão asfáltica é uma das alternativas existentes e compõe o objetivo central da tese. Apesar de ser uma técnica utilizada no passado, há poucos trabalhos publicados e não se dispõe de uma norma brasileira que trate de um procedimento laboratorial, nem tampouco uma especificação de serviço que trate das técnicas executivas. Neste trabalho, realizouse um levantamento das ocorrências de solo na região da ilha de São Luis e a seleção de quatro solos para mistura com um tipo de emulsão apropriada para esta finalidade. Realizaram-se ensaios básicos de caracterização dos solos e da emulsão asfáltica, testando-se diversas porcentagens de emulsão e de umidade da mistura solo-emulsão. Compactaram-se e curaram-se corpos-de-prova em diferentes condições, de modo a identificar a melhor prática e os eventuais ganhos com o tempo e forma de cura em laboratório. Foram determinadas propriedades mecânicas destas misturas solo-emulsão de forma a qualificar os materiais e compará-los entre si e com os materiais de pavimentação usualmente empregados na região. Conceberam-se dois trechos experimentais, com acompanhamento técnico da execução da obra. Após solicitação ao tráfego, os trechos foram monitorados por meio de deflectometria e evolução das patologias. A pesquisa laboratorial e os trechos concebidos e avaliados possibilitaram a proposição de um procedimento laboratorial para a mistura solo-emulsão e de um método executivo para pavimentos, aplicáveis para a região estudada, mas que podem servir de base para estudos com outros solos e regiões, e melhoria da técnica. / The Brazilian State of Maranhão has a road network of 55,000-km, mainly with an average daily traffic lower than 400 vehicles and a low density of paved roads (0.02- km/km²). Limited Government funds inhibit new paving works, so the State of Maranhão cannot reach road patterns similar to those of other more developed States in Brazil. The search for a paving alternative or for the improvement on the road traffic conditions, using local materials available and procedures that can be easily introduced in the local technical environment, was the prior motivation in this work. The use of a local soil considerably reduces the amount spent on long hauls; however, many occurrence soils in this region need stabilization to be employed in paving works. The stabilization of these soils by asphalt emulsions is one of the current alternatives and is the main purpose of this thesis. Despite being a technique used in the past, there are a few papers published and there is neither a Brazilian standard for guiding laboratory tests nor a service specification concerning construction techniques. In this work, a soil occurrence survey was carried out in the region of São Luis Island and also the selection of four soils to be mixed with one type of emulsion appropriate to this purpose. Basic tests for characterizing the soils and the asphalt emulsion were made, testing several percentages of emulsion and moisture of the mixtures soil-emulsion. Samples were compacted and cured in different conditions, in order to identify the best practice and laboratory way of curing, as well as possible gains over time. Some mechanical properties of those soilemulsion mixtures were determined to qualify the materials and to make a comparison among them and also with paving materials usually employed in the region. Two trial sections were constructed, with technical monitoring of the whole process, including the construction work. After loading by the traffic, they were monitored by means of deflections and defects evolution. The laboratory research and the trial sections studied enabled the development of a proposition containing a laboratory procedure for the mixture soil-emulsion and a paving executive method, applicable to the studied region, but it can serve as a basis for studies of other soils and regions and for improving the technique.

A engenharia geotécnica frequentemente tem limitações de caráter econômico e ambiental. É por isso que a técnica de melhoramento das propriedades do solo pode se tornar uma alternativa de solução em diversos casos, como na construção de bases de pavimentos, camada de suporte em fundações superficiais, revestimento de canais e na proteção de taludes em barragens. Este trabalho faz parte de uma dissertação de mestrado que tem por objetivo avaliar a influência do teor de umidade de compactação, peso específico aparente seco e teor de agente cimentante na durabilidade, rigidez e resistência de um solo fino artificialmente cimentado. Para isso foram realizados ensaios de compressão simples após ciclos de molhagem e secagem, ensaios de perda de massa, rigidez inicial e ensaios de compressão triaxial. Os resultados mostraram que quanto maior o teor de cimento, o peso específico aparente seco e o teor de umidade para os teores estudados (17%, 20%, e 23%), maior é a resistência e menor é a queda da rigidez inicial após ciclos de molhagem e secagem, assim também menor é a perda de massa, mostrando um melhor desempenho quanto à durabilidade. Verificou-se que a metodologia apresentada por Consoli (2014) é válida para a previsão de parâmetros de resistência ao cisalhamento de solos com diferentes teores de umidade. / Geotechnical engineering often has limitations of economic and environmental natures, which is why the ground improvement technique can become an alternative solution in many cases, as in pavement base layers, support layers under shallow foundations, canal coating and in slope protection of earth dams. This work is part of a M.Sc. dissertation, which aims to assess the influence of the moisture content, porosity and cement content on durability, initial stiffness and strength of an artificially cemented fine-grained soil. A number of unconfined compression tests were carried out after wetting and drying cycles, together with weight loss and initial shear stiffness tests. Triaxial compression tests were also done. The results show that as higher the amount of cement, porosity and moisture content for the studied concentrations (17%, 20% and 23%), the greater is the resistance and lower is the drop of initial stiffness after wetting and drying cycles, as well as smaller the weight loss, showing a better performance in terms of durability. It was verified that, the methodology presented by Consoli (2014) is valid for predicting soil shear strength parameters with different moisture contents.