Submitted by Claudia Raffa (clau197018@gmail.com) on 2017-03-22T14:57:36Z No. of bitstreams: 1 Tese Claudia Raffa 21 03.pdf: 2202332 bytes, checksum: b806c8b15ab75c4ec5512c372c30981d (MD5) / Approved for entry into archive by Pamela Beltran Tonsa (pamela.tonsa@fgv.br) on 2017-03-22T15:13:08Z (GMT) No. of bitstreams: 1 Tese Claudia Raffa 21 03.pdf: 2202332 bytes, checksum: b806c8b15ab75c4ec5512c372c30981d (MD5) / Made available in DSpace on 2017-03-22T15:59:33Z (GMT). No. of bitstreams: 1 Tese Claudia Raffa 21 03.pdf: 2202332 bytes, checksum: b806c8b15ab75c4ec5512c372c30981d (MD5) Previous issue date: 2017-02-22 / This study aims to identify variables related to the internal environment (practice of resource management, structural characteristics of service rendering and processes) relevant to bed management in hospital organizations. One of the critical processes that hospitals have experienced is bed management. Therefore, it’s necessary to clearly identify the processes that interact with the occupation of the beds, and then to propose improvements. The research contemplates an exploratory and descriptive study, elaborated from the collection of data in sources of evidences that included interviews with managers and documentary analysis. This work used the Systematic Literature Review (SLR) based on the bibliographical research and theoretical discussion based on five cases of private hospitals, a mapping of a theoretical model that was used to guide the analysis of the data with the use of the content analysis method with NVivo 11 Pro software support. Thus, it was found that bed management involves strategic processes. For these management, knowledge is needed that go beyond administrative routines, justifying the need for staff training, as well as investment in infrastructure and personnel. In this study, it was confirmed that the most productive hospital was the one with the shortest average length of stay, the highest turnover rate and the lowest replacement interval index. It is concluded that in health the request of beds should be considered a strategic process, and should be redesigned, if necessary to guarantee support for the reach of organizational strategies. It’s considered that the management intends to seek the use of the available beds in their maximum capacity, with safety within the established criterion, with the objective of optimizing the waiting time for hospitalization and satisfaction of the internal and external clients of the hospital environment / Este trabalho objetiva identificar variáveis relacionadas ao ambiente interno (prática de gerenciamento de recursos, características estruturais da prestação de serviços e processos) relevantes no gerenciamento de leitos em organizações hospitalares. Um dos processos críticos que os hospitais têm vivenciado é o gerenciamento de leitos. Portanto, faz-se necessário identificar claramente os processos que interagem na ocupação dos leitos, para posteriormente, serem propostas melhorias. A pesquisa contempla um estudo exploratório e descritivo, elaborado a partir da coleta de dados em fontes de evidências que incluíram entrevistas com gestores de leitos e análise documental. Este trabalho utilizou a revisão sistemática da literatura (Systematic Literature Review – SLR) com base na pesquisa bibliográfica e discussão teórica baseada em cinco casos de hospitais particulares. A análise de dados foi norteada pelo uso do método da análise de conteúdo com o apoio do software NVivo 11 Pro. Como resultado, verificou-se que a gestão de leitos envolve processos estratégicos. Para sua gestão são necessários conhecimentos que vão além das rotinas administrativas, justificando a necessidade de capacitação da equipe, bem como o investimento em infraestrutura e pessoal. Nesta pesquisa identificou-se que melhores indicadores (menor tempo médio de permanência, maior índice de giro e menor índice de intervalo de substituição) estão associados a modernas práticas de gestão, bem como ao apoio da tecnologia. Conclui-se que na saúde a solicitação de leitos deve ser considerado um processo estratégico, devendo ser redesenhado, se necessário para garantir o suporte para o alcance das estratégias organizacionais. Considera-se que o gerenciamento visa buscar a utilização dos leitos disponíveis em sua capacidade máxima, com segurança dentro dos critérios estabelecidos, com objetivo de otimizar o tempo de espera para internação e satisfação dos clientes internos e externos do ambiente hospitalar.

Une étude précise des écoulements gaz-particules poly-solides et réactifs rencontrés dans les lits fluidisés circulants (LFC) appliqués au procédé de Chemical Looping Combustion (CLC) est indispensable pour prédire un point de fonctionnement stable et comprendre l'influence de la réaction et de la polydispersion sur l'hydrodynamique des LFC. Dans ce but, des simulations avec le code NEPTUNE_CFD ont été confrontées aux expériences menées à l'Université Technologique de Compiègne par ALSTOM. Cette modélisation a été validée sur des LFC non réactifs mono-solides et poly-solides. L'influence des caractéristiques des particules et de la position des injecteurs sur l'entrainement de solide est étudiée. Un modèle de prise en compte de la production locale de gaz au cours de la réaction est présenté. L'étude locale de l'écoulement a permis de comprendre l'influence des collisions interparticulaire et de la production locale de gaz sur l'écoulement. Finalement, un point de fonctionnement a été proposé pour le pilote CLC en construction à Darmstadt. Ce travail a montré que NEPTUNE_CFD pouvait prédire l'hydrodynamique de LFC poly-solides à l'échelle du pilote industriel et participer au dimensionnement de centrales de types CLC. / This work deals with the development, validation and application of a model of Chemical Looping Combustion (CLC) in a circulating fluidized bed system. Chapter 1 is an introduction on Chemical Looping Combustion. It rst presents the most important utilizations of coal in the energy industry. Then, it shows that because of the CO2 capture policy, new technologies have been developed in the frame of post-combustion, pre-combustion and oxy-combustion. Then, the Chemical Looping Combustion technology is presented. It introduces multiple challenges: the choice of the Metal Oxide or the denition of the operating point for the fuel reactor. Finally, it shows that there are two specicities for CFD modeling: the influence of the collisions between particles of different species and the local production of gas in the reactor due to the gasication of coal particles. Chapter 2 outlines the CFD modeling approach: the Eulerian-Eulerian approach extended to flows involving different types of particles and coupled with the chemical reactions. Chapter 3 consists in the validation of the CFD model on mono-solid (monodisperse and poly-disperse) and poly-solid flows with the experimental results coming from an ALSTOM pilot plant based at the Universite Tchnologique de Compiegne (France). The relevance of modeling the polydispersity of a solid phase is shown and the influence of small particles in a CFB of large particles is characterized. This chapter shows that the pilot plant hydrodynamics can be predicted by an Eulerian-Eulerian approach. Chapter 4 consists in the validation of the CFD model on an extreme bi-solid CFB of particles of same density but whith a large particle diameter ratio. Moreover, the terminal settling velocity of the largest particles are twice bigger than the fluidization velocity: the hydrodynamics of the large particles are given by the hydrodynamics of the smallest. An experiment performed by Fabre (1995) showed that large particles can circulate through the bed in those operating conditions. Our simulations predicted a circulation of large particles, but underestimated it. It is shown that it can be due to mesh size eect. Finally, a simulation in a periodic box of this case was dened and allowed us to show the major influence of collisions between species. Chapter 5 presents the simulation of a hot reactive CLC pilot plant under construction in Darmstadt (Germany). The simulations account for the chemical reactions and describe its eect on the hydrodynamics. Different geometries and operating conditions are tested.

Cette thèse porte sur l’étude numérique de la dynamique des écoulements fluide-particules au sein des lits fluidisés denses. Le but de ces travaux est d’améliorer la compréhension des phénomènes qui s’y déroulent afin d’optimiser les performances des procédés industriels confrontés à ces écoulements diphasiques. En effet, la diversité des échelles de longueur et les différents types d’interaction fluide-solide et solide-solide rencontrées dans ce type de configuration rendent cette catégorie d’écoulement particulièrement complexe et intéressante à étudier. Le modèle développé à cet effet permet de suivre individuellement la trajectoire des particules et de traiter les collisions avec leurs voisines tandis que la phase fluide est décrite de façon localement moyennée. Dans ce mémoire, nous présentons tout d’abord les origines physiques du phénomène de fluidisation d’une population de particules et les grandeurs physiques qui le caractérisent. Puis nous détaillons le modèle Euler-Lagrange implémenté et présentons une série de tests de validation basés sur des résultats théoriques et des comparaisons à des résultats expérimentaux. Cet outil numérique est ensuite employé pour simuler et étudier des lits fluidisés comportant jusqu’à plusieurs dizaines de millions de particules. Enfin, nous comparons des simulations réalisées conjointement à l’échelle micro et avec le modèle développé au cours de cette thèse à l’échelle méso. / This thesis deals with numerical analysis of particulate flows within dense fluidized beds. The aim of this work is to improve phenomena understanding in such flows in order to optimize engineering processes design. Wide variety of length scales and various fluid-solid and solid-solid interactions makes complex and challenging this type of flows study. The present developed model permits individual particle tracking and handle particles collisions whereas fluid flow is space averaged. In this manuscript, we first present origins of fluidization phenomenon and describe the macroscopic quantities which characterize it. Then we introduce the Euler-Lagrange model we developed and detail its numerical implementation. Moreover, we present a bench of validation tests based both on theoretical results and experimental data comparison. This numerical tool is then used to simulate and study fluidized beds containing up to several tenth of millions particles. Finally, we compare simulations performed both at micro and meso scales, i.e. with the model developed during this thesis.

Os processos de secagem de resíduos produzidos em estações de tratamento de água e esgoto por processos mecânicos podem gerar lodos com teores de sólidos de 20% a 30%, podendo estes variar de acordo com as características do lodo bem como da tecnologia de desidratação. Uma vez que os custos de transporte e disposição final têm aumentado de forma significativa para lodos produzidos em regiões metropolitanas, torna-se atrativo a sua redução mediante o aumento do teor de sólidos do lodo desidratado. Desta forma, este trabalho teve por objetivo avaliar o processo de pós-secagem de resíduos gerados em estações de tratamento de água (ETA) e esgoto (ETE) por processos naturais, tendo-se avaliado a influência das condições climáticas da cidade de São Paulo para diferentes estações do ano. O estudo foi realizado com dois tipos de leitos de secagem em escala piloto; leito coberto (LC) e leito aberto (LA), tendo os mesmos 1,80m2 de área e piso impermeabilizado. Os dados hidrometeorológicos foram obtidos mediante a operação de uma estação hidrometeorológica portátil que forneceu dados de temperatura do ar e do lodo, umidade relativa do ar, radiação solar global, velocidade do vento e precipitação. O lodo gerado nas estações de tratamento foram dispostos nos leitos de secagem em leiras com 30cm de altura, sendo revolvidos e realizadas análises de teor de sólidos do lodo três vezes por semana, o período de secagem de cada ciclo foi de 30 dias. Os teores de sólidos dos lodos obtidos nos ensaios com pós-secagem natural apresentaram resultados distintos para diferentes períodos do ano; durante o período do verão foi obtido lodo com teor de sólido final de 58% médio, enquanto, no período de inverno foi obtido lodo com teor de sólido final de 18% médio. Foi utilizado um modelo matemático para o processo de secagem do lodo utilizando os dados meteorológicos medidos, uma equação do balanço de calor foi aplicada para o volume de controle do leito de secagem do lodo considerando a transferência de calor por radiação, convecção, e evaporação. / The mechanical drying process of residuals produced in water and wastewater treatment plants can generate sludge with solids content of 20% to 30%. These values may vary according to the characteristics of the sludge and dehydration technology. The costs of sludge produced in metropolitan areas have increased significantly due to transportation and final disposal. Hence, it is to, becoming attractive to reduce the residue volume by increasing the solids content of the dewatered sludge. This study aimed to evaluate the process of post drying of residues generated in water wastewater treatment plants (WTP and WWTP) by natural processes, evaluating the influence seasonal variation of the weather in the São Paulo city. The study was conducted with two drying beds on a pilot scale; one being a cover unit (CU) and the other an uncover unit (UU). Both units have the same area of 1.80m2 and waterproof floor. The hydrometeorological data were obtained through the operation of a weather station installed close to the units that supplied data for temperature of the air and sludge, relative humidity, solar radiation, wind speed and precipitation. The sludge source in the treatment stations are arranged in the drying beds to ridges with 30cm height, the sludge was mixed and analyzed of solid content three times a week, the drying time of each cycle was 30 days. The solid content of the sludge obtained in tests with post drying by natural processes showed different results for different seasonal of the year and during the summer period was obtained sludge with solid content finale average of 58%, while in the winter was obtained sludge with solid content finale average of 18%. A mathematical model is developed for the process of drying of sludge, a heat-balance equation is applied for a control volume of sludge that takes into account the heat transfer by radiation, convection, and evaporation.

Os estudos sobre rios em leitos fluviais rochosos têm servido de base para o entendimento da evolução das paisagens que se inserem. A análise mais detalhada das litologias que compõem estes leitos fluviais, se tornam desta forma, imprescindíveis para o entendimento da evolução das morfologias resultantes da interação, entre os processos fluviais e a resistência erosiva imposta pela rocha. A presente pesquisa visou obter a resposta geomorfológica de canais com leito predominantemente rochoso, sobre duas unidades litológicas da Formação Serra Geral nível superior. A primeira de origem vulcânica básica, é composta pelos Basaltos Hipoialinos e a segunda de composição ácida, é formada pelos Riodacitos. Partiu-se da análise da estruturação física de cada litologia pertencente a estas unidades e das fragilidades inerentes a cada uma, em relação aos processos fluviais mais atuantes sobre os leitos fluviais de três cursos principais e de seus principais afluentes. Utilizou-se do modelo de regressão denominado, relação declive-área (S = ks A-) para as análises das variações de declividade e de concavidade dos perfis dos rios a fim de compreender quais os principais controles que determinam a modificação dos ajustamentos morfológicos. Foi observado que as duas unidades litológicas apresentam alta erodibilidade frente a potência de escoamento. Primeiro porque o intemperismo generalizado prepara ambas as rochas para os principais processos fluviais identificados: abrasão/macro abrasão e arrancamento. Estes processos atuam mais intensamente sobre o fraturamento rochoso, que mesmo distinto entre as duas litologias (Hipoialinos = ~50 m/m2; Riodacitos = ~9 m/m2) permitem a erosão efetiva dos leitos fluviais. Segundo que, a interferência tectônica altera a dispersão dos dados da relação declive-área integral dos canais fluviais (R2), mascarando as tendências de ajustamento das declividades dos perfis longitudinais. Os valores de ajustamento da potência do escoamento, sobre a resistência erosiva das rochas, só pôde ser vislumbrados, a partir da análise dos índices de concavidade () e de declividade (ks), de acordo com os segmentos discretizados dos perfis longitudinais em domínios homogêneos, de cada litologia pertencente ao leito fluvial. A separação dos limiares superiores que representam os trechos de maior declividade, em relação aos limiares inferiores, que representam os trechos de menor declividade relativa, também foi necessária para a compreensão das tendências de ajuste morfológico pela potência do escoamento. / Studies about rivers in rocky riverbeds have served as a basis for understanding the evolution of the landscapes that are inserted. The more detailed analysis of the lithologies that composes these riverbeds are thus essential for the understanding of the evolution of the resulting morphologies from the interaction between the river processes and the erosive resistance imposed by the rocks of the riverbeds. The present research aimed at obtaining the geomorphological response of channels with rock layer, on two lithological units of the Serra Geral Formation, upper level. The first one of basic volcanic origin, is composed of basalts and the second of acid composition, is formed by rhyodacites. The starting point was the analysis of the physical structure of each lithology belonging to these units and of the inherent weaknesses in each one, in relation to the fluvial processes most active on the river layers of three main courses and their main tributaries. The regression model called the slope-area ratio (S = ks A-) was used for the analyzes of the slope and concavity variations of the river profiles in order to understand the main controls that determine the modification of the morphological adjustments. It was observed that the two lithological units present high erodibility against the flow power. First, because the general weathering prepares both rocks for the main fluvial processes identified: abrasion / macro abrasion and pulling out. These fluvial processes act more intensely on the rocky fracture, which, even distinguished between the two lithologies (basalts = 50 m / m2; rhyodacites = 9 m / m2), allows for the effective erosion of the riverbeds. Second, tectonic interference alters the data dispersion of the slope-area integral relation of the fluvial channels (R2), masking the adjustment tendencies of the slope longitudinal profiles. The values of the adjustment of the river profiles could only be glimpsed, according to the indices of concavity () and slope (ks), according to the discretized segments of the longitudinal profiles, in homogeneous domains, of each lithology belonging to the riverbed. The separation of the upper thresholds that represent the sections of greater slope, in relation to the lower thresholds, which represent the sections of smaller relative slope, was also necessary to understand the morphological adjustment tendencies of the profile slopes.

O método INTERMED é um instrumento que classifica a complexidade biopsicossocial de pacientes em diversos níveis de assistência, qualifica o cuidado e melhora a comunicação interprofissional. Ele permite avaliar a complexidade do paciente através da investigação de quatro domínios: biológico, psicológico, social e sistema de saúde. Promove o cuidado integrado com foco no paciente e viabiliza práticas de gestão da clínica e de leitos hospitalares. O objetivo principal desta pesquisa foi realizar a tradução, adaptação transcultural e validação do método INTERMED para realidade hospitalar brasileira. Os objetivos secundários foram avaliar a consistência interna do método, estudar a interface dos resultados do INTERMED com dados sociodemográficos e verificar sua contribuição no gerenciamento de leitos hospitalares e gestão da clínica. O instrumento foi aplicado a um total de 300 pacientes, com mais de 5 dias de internação hospitalar, com idade >=a 21 anos e média de idade de 57,8 anos, sendo que 58,3% eram do sexo masculino. Esta amostra foi coletada entre setembro e dezembro de 2011 em três hospitais da cidade de São Paulo, a saber, um privado (A), um de ensino (B) e um público(C). A validação e adaptação transcultural ocorreram em cinco fases: tradução, síntese, retrotradução, avaliação e validação por um comitê de juízes e pré-teste. A validação da tradução pelo comitê de juízes foi realizada pelo Índice de Validade de Conteúdo e a consistência interna do instrumento foi avaliada pelo coeficiente alpha de Crombach. A estrutura do documento foi estudada pelo Coeficiente de Correlação de Spearman e a validade preditiva para tempo de internação, pela relação entre a pontuação total do score do INTERMED e o tempo de hospitalização dos pacientes. A validação da tradução foi de 94,2% de equivalência semântica, 94,3% equivalência idiomática e 86,6% de equivalência cultural entre o instrumento original e o traduzido. No pré-teste, obteve-se acima de 90% de compreensão em todos os itens do INTERMED. Os scores médios obtidos com o INTERMED foram de 15,20e 21 nas instituições A,B e C respectivamente. Isto significa, pela classificação, do instrumento, que nas três instituições os pacientes não eram complexos (<21 pontos). A consistência interna e precisão do instrumento foram consideradas boa para as três instituições. As correlações entre os domínios do instrumento foram positivas e significantes em sua maioria. Em relação à validade preditiva, tempos maiores de internação foram observados em pacientes com escores maiores. Os dados encontrados sugerem que para além da gravidade biológica, o tempo de internação pode estar relacionado aos aspectos psicológicos, sociais ou do sistema de saúde, como a espera para realização de procedimentos. A versão brasileira do INTERMED possui equivalência com o instrumento original; é confiável, uma vez que os itens do instrumento relacionam-se e são complementares entre si; é válida, pois é capaz de medir o objeto ao qual se propõe. Assim, recomenda-se sua incorporação como uma ferramenta de apoio a gestão de leitos e ao cuidado integral do paciente. / The INTERMED method is an instrument that classifies the biopsychosocial complexity of patients under various levels of healthcare. It also qualifies care and improves interprofessional communication. It also allows us to evaluate patient\'s complexity by means of the investigation of four domains: biological, psychological, social and healthcare. Apart from that, it promotes integrated care by focusing on the patient and by enabling clinical management practices and the availability of hospital beds. The main objective of this research was to translate, transculturally adapt and validate the INTERMED method to the Brazilian health system reality. As a secondary objective, INTERMED aimed at evaluating the internal consistency of the method by studying the interface of the INTERMED results along with sociodemographic data and by verifying its contribution to the availability of hospital beds and clinical management. That instrument was applied to a total of 300 inpatients who had been at hospital for more than 5 days. All of them were 21 years old or more and the average age was 57,8 years old, being 58,3% male patients. That sample was collected between September and December 2011 at three hospitals in São Paulo, being one private (A), one university hospital (B) and one public hospital (C). The validation and transcultural adaptation occurred on five stages: translation, synthesis, back-translation, evaluation and validation by a committee of judges and pre-test. The validation of the translation by the committee of judges was carried out by using the Content Validity Index and the internal consistency of the instrument was evaluated by the alpha Crombach coefficient. The structure of the document was studied by using the Spearman correlation coefficient and the predictive validity for length of stay was evaluated by the ratio between the INTERMED total score and the patients\' length of stay. The validation of the translation reached 94,2% of semantic equivalence, 94,3% of language equivalence and 86,6% of cultural equivalence when the original and the translated document were compared. During pre-test phase, more than 50% of comprehension was achieved in all INTERMED items. The average scores achieved by INTERMED were 15, 20 and 21 at institutions A, B and C, respectively. It means that according to the classification of the instrument at the three institutions patients were not considered complex (< 21 points). The internal consistency and the accuracy of the instrument were regarded as good for the three institutions. In general, the correlation among the domains of the instrument were positive and significant. As regards the predictive validity, longer lengths of stay were observed in patients with higher scores. The data found suggest that besides the biological seriousness, the length of stay may be related to psychological or social aspects or even to the health system in which the time patients wait for procedures may be long. The Brazilian version of INTERMED is equivalent to the original; it is reliable, since its items relate to each other and are complementary among themselves; it is valid, on the grounds that it is able to measure the object it is intended to. Having said that, its use is recommendable as a tool to support the patient\'s integrated care management as well as the availability of hospital beds.

O estudo dos fatores intervenientes, micro e macropropriedades dos lodos de estação de tratamento de água (ETA), no desaguamento por sistemas naturais, com uso de leito de drenagem, constituiu o principal foco desta pesquisa. Assim, ensaios de desaguamento por leito de drenagem foram realizados com amostras de lodos de sulfato de alumínio e de cloreto de polialumínio (PA\'CL\') e monitoramento das variáveis climáticas. Os resultados comprovaram o desempenho do leito de drenagem para redução de volume, da ordem de 80% e 90% para os lodos de PA\'CL\' e sulfato de alumínio e teor de sólidos final respectivamente de 30 a 90%, sem consumo de energia. Na fase de drenagem, independente do tipo e volume de lodo aplicado, a vazão de drenagem foi maior quanto menor o valor da taxa de aplicação de sólidos - TAS (Kg/\'M POT.2\') (fração volumétrica de partículas). As variáveis analisadas, teor de sólidos, distribuição de tamanho de partículas, morfologia e composição das partículas entre outros, na massa de lodo bruto e desaguado indicaram diferentes mecanismos de secagem e conseqüente influencia na velocidade de secagem. O uso do fluxo de massa de água evaporada revelou-se adequado para avaliar a fase de secagem. O estudo das micro e macropropriedades do lodo mostram-se decisivos para balisarem pesquisas de desenvolvimento dos sistemas de desaguamento e de reúso dos lodos de ETAs. / The study of involved factors, micro and macroproperties of sludge from water treatment plants (WTP) in dewatering by natural systems with the use of draining beds is the main focus of this research. For this purpose, dewatering assays by draining beds were done with samples from aluminium sulphate and polyaluminium chloride (PA\'CL\') sludge, and monitoring of the climatic variables along the experiments. The results proved the performance of the draining beds in reducing the volume, ranging from 80 to 90% for the sludges from PA\'CL\' and aluminium sulphate and the final rate of solids from 30 to 90%, without consuming the energy. In dewatering phase, independently of the type and volume of the applied sludge, the bigger the flow of dewatering the lesser the value of the applied rate of solids (TAS, Kg/\'M POT.2\', volumetric fraction of particles). The analised variables, solid rates, distribution of the height of the particles, morphology, and composition of the particles among others, in the mass of the brute and dewatered sludge indicated different mechanisms of drying and consequently influence in the rate of drying. The use of the flow of mass of humidity revealed adequate to evaluate the drying phase. The studies of micro and macroproperties of the sludge were decisive to conduct researches of development of dewatering systems and reusing of the sludges from WTP´s.

Liquefaction is a phenomenon in which soil loses a large percentage of its shear resistance due to increased pore water pressure and flows like a liquid. Undrained cyclic loading conditions during earthquakes cause liquefaction of soils, which can lead to catastrophic failures such as bearing capacity failures, slope failures and lateral spreads. The concepts and mechanisms of liquefaction were studied extensively by many researchers. Though the factors affecting the liquefaction response of soils during earthquakes are well documented in literature, there are still some gray areas in understanding the individual and combined effects of factors like frequency, gradation, fines content and surcharge pressure on the initiation of liquefaction. The objective of this thesis is to study the influence of ground motion, soil and site parameters on the initiation of liquefaction in saturated sand beds through laboratory shaking table model tests and numerical studies. Shaking table tests are carried out using a uniaxial shaking table on sand beds of 600 mm thickness. The initiation of liquefaction was observed and identified by measuring the pore water pressure developed during the sinusoidal cyclic loading. Free field liquefaction studies are carried out on sand beds to study the influence of ground motion parameters, namely, input acceleration and frequency of shaking on liquefaction. These studies revealed that acceleration is one of the important parameters that can affect the initiation of liquefaction in sands. Increase in acceleration reduces the liquefaction resistance of sand and a small increase in acceleration can trigger liquefaction. Frequency of shaking did not affect the initiation of liquefaction at lower frequencies but a threshold frequency which triggered instant increase in the excess pore pressures is observed. Liquefaction caused slight initial amplification followed by de-amplification of accelerations due to the stiffness reduction in soils during liquefaction, the effect being more pronounced in the top layers of the sand bed. Pore water pressure ratios during dynamic loading decreased with depth below the surface of the sand bed due to the low initial effective vertical stress and upward transmission of pore pressure during undrained loading. Shaking table tests are carried out to study the influence of soil parameters such as relative density, thickness of dry overlying sand layer and gradation. Relative density of sand can influence the liquefaction potential of sand to a great extent, about 10% increase in relative density bringing down the probability of liquefaction by about 50%. With the increase in height of dry overlying sand layer, liquefaction potential has decreased nonlinearly. Change in grain size altered the pattern of liquefaction and pore pressure development and it is observed that the liquefaction in finer sands is influenced by the frequency of shaking to a larger extent. Surcharge pressure from building loads increased the liquefaction potential and heavier structures got liquefied at lower pore water pressure ratios. Significant post-liquefaction de-amplification was observed in sand beds with surcharge pressure. Parametric numerical analyses are carried out using finite difference program FLAC (Fast Lagrangian Analysis of Continua) with FINN model to measure pore water pressures in the sand bed. Results from numerical analyses with change in the acceleration, surcharge pressure and thickness of dry overlying layer agreed well with the experimental results. However, effect of frequency in numerical studies did not match with the experimental observations, because of the inherent boundary effects in the experimental models. Results from this thesis provided important insights into the development of pore water pressures in sand beds during cyclic loading events, apart from enhancing the understanding towards the effect of various ground motion, site and soil parameters on the initiation of liquefaction in sand beds.

Les Invertébrés de l’épifaune vagile présents dans les herbiers de Magnoliophytes marins ont un rôle essentiel dans le transfert d’énergie des producteurs primaires vers les niveaux trophiques supérieurs. L’objectif de ce travail a été d’analyser la relation entre la complexité de l’herbier et la structure des communautés de l’épifaune vagile, et d’étudier le rôle de ce compartiment dans le fonctionnement des réseaux trophiques des herbiers à Thalassia testudinum. Deux sites d’herbiers ont été comparés, l’un proche de la mangrove côtière et l’autre près de la barrière récifale, au cours de deux saisons. L’utilisation de différentes sources trophiques par les Invertébrés a été montrée en utilisant les méthodes des isotopes stables du carbone et de l’azote et de la composition en acides gras. L’herbier côtier, qui présente une structure complexe du fait de ses longues feuilles, de sa litière abondante et de sa forte charge en épiphytes, abrite une faune abondante et diversifiée de Crustacés. La préférence alimentaire de ces Invertébrés pour les micro-algues et les fines particules détritiques favorise la contribution du biofilm au réseau trophique de l’herbier côtier. L’herbier du large, moins complexe, abrite une communauté d’Invertébrés dominée par les Gastéropodes Cerithiidae. La limitation de la disponibilité en nourriture existant dans cet herbier explique la contribution plus élevée de la litière et des feuilles vivantes de Thalassia au réseau trophique par rapport à l’herbier côtier. Le couplage de l’analyse des isotopes stables à celle des contenus stomacaux réalisé sur les poissons a montré le rôle essentiel des Crevettes en tant que proies. L’herbier côtier, qui présente des ressources en nourriture plus abondantes et diversifiées, assure mieux son rôle de « nurserie » pour les juvéniles de poissons que l’herbier du large. / In seagrass beds, vagile epifauna plays a major role in the energy transfer from primary producers to higher trophic levels. The main aim of the work was to examine the relationship between the seagrass complexity and the vagile epifauna community structure, and to study the role of this compartment within the food web of Thalassia testudinum seagrass beds. Two seagrass sites were compared, one near the coastal mangrove and another one near the barrier reef, during two seasons. Trophic resources used by primary consumers were assessed by combining stable isotopes analysis and fatty acid compositions. The coastal seagrass bed is complex due to its long leaves and its great biomass of litter and epiphytes. It shelters a great abundance and diversity of Crustaceans. The feeding preference of them for micro-algae and detrital particles promotes biofilm contribution to food web of the coastal seagrass bed. The seagrass bed located seawards, lesser complex, harbors an Invertebrate community dominated by the Gastropods Cerithiidae. The reduced food availability in that seagrass bed explains the higher contribution of litter and Thalassia leaves to that food web compared to the coastal seagrass bed. By coupling stable isotopes and stomach contents analyses, it was possible to highlight the major role of shrimps in the feeding diet of fishes. The coastal seagrass bed, where the trophic resources are more abundant and diverse, better plays its role of nursery for juveniles fishes than the seaward seagrass bed.

À l'interface bentho-pélagique, les herbiers marins présentent une multitude de rôles écosystémiques. Historiquement, les scientifiques et décideurs de La Réunion se sont focalisés sur l'écosystème récifal. Néanmoins, des prairies monospécifiques à Syringodium isoetifolium sont présentes de manière pérenne (3 hectares) au sein du complexe récifal de l'Ermitage / La Saline (côte ouest). L'objectif principal de cette étude était d'apporter les premières données sur l'écologie de ces herbiers marins. Ainsi, une approche pluridisciplinaire a été développée : 1. L'étude de la dynamique spatiale du paysage herbier sur 65 ans (dès 1950), et à l'échelle saisonnière (2013-2015) qui a permis de définir le rôle majeur des forçages hydrodynamiques et de l'eutrophisation. 2. L'analyse de la productivité de l'écosystème herbier et sa réponse métabolique face à des apports nutritifs, révèle des bilans métaboliques opposés (autotrophie/hétérotrophie) en fonction des conditions environnementales, ainsi qu'un rôle de tampon sur les flux de nutriments. 3. Des analyses isotopiques (δ13C et δ15N) ont permis d'identifier les sources de matière entrant dans l'écosystème et alimentant les réseaux trophiques associés aux herbiers. L'étude a permis d'établir un lien trophique entre Holothuria leucospilota et les herbiers marins ainsi qu'un rôle essentiel dans le maintien des populations de poisson herbivores récifaux. 4. Des enquêtes locales ont révélé une méconnaissance de cet écosystème malgré leur potentiel économique et écologique. À la lumière de ces travaux de thèse, la prise en considération des herbiers marins dans la gestion du milieu marin réunionnais est nécessaire. / Located at the benthos-pelagos interface, seagrass beds have many ecosystemic roles such as coastal protection or biodiversity. Historically, scientists and decision-makers at Reunion Island have been focusing on reef ecosystems. However, for several decades, monospecific (Syringodium isoetifolium) seagrass beds have been observed (3 hectares – 2013) within Ermitage / La Saline reef (West coast). The main objective of this study was to give the first data on seagrass ecology at Reunion Island. Therefore, a multi-disciplinary study was developed. First, seascape ecology of seagrasses is analyzed at decadal (since 1950) and seasonal scales (2013-2015). Physical settings (swell) and eutrophication were driving factors on the spatial dynamics of seagrass beds. Second, seagrass community metabolism and response to nutrient loads (nitrate and phosphate) show variations in metabolic budget (autotrophy to heterotrophy) and make seagrass beds a nutrient sink following the environmental conditions. Third, stable isotope analysis (δ13C and δ15N) identified sources of particulate matter entering the ecosystem and fueling food webs. The trophic roles of seagrass beds are assessed for echinoderm and herbivorous fish communities. This study highlighted a trophic link between seagrass and Holothuria leucospilota, and proved some species to be heavily dependent on seagrass ecosystem (Leptoscarus vaigiensis, Siganus sutor). Finally, interviews showed a lack of knowledge about this ecosystem despite crucial economic and ecologic roles. Considering their major functions, seagrass beds have to be considered in future management of the coastal marine systems at Reunion Island.