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[en] AN ANALYTICAL METHOD FOR THE HARMONIC ANALYSIS OF SATURATED REACTORS / [pt] UM MÉTODO ANALÍTICO PARA ANÁLISE HARMÔNICA DE REATORES SATURADOSMAURO SCHWANKE DA SILVA 19 January 2007 (has links)
[pt] Este trabalho consiste na apresentação de um método
analítico para a análise harmônica de reatores saturados
trifásicos quando usados no controle de tensão em
sistemas
de potência.
A este respeito é primeiramente discutida a necessidade
do
controle de tensão através da compensação de potência
reativa em sistemas de transmissão e distribuição e em
seguida são apresentados os vários tipos de
compensadores
existentes que satisfazem estas necessidades, dando-se
ênfase aos reatores trifásicos de núcleo de ferro
saturado.
Os núcleos dos reatores saturados são levados à completa
saturação para as tensões de operação causando,
naturalmente, o surgimento de correntes não senoidais
nos
enrolamentos. Duas soluções possíveis são apresentadas
para eliminação de harmônicos nas correntes de linha: o
uso de filtros e o cancelamento interno dos harmônicos
por
meio de arranjos adequados de enrolamentos em reatores
saturados trifásicos. Este trabalho desenvolve um método
analítico para análise harmônica de reatores saturados
em
que a eliminação ou redução dos harmônicos é feita
internamente.
São apresentadas em seguida as relações básicas do
métodos
de análise cujo objetivo é determinar as formas de onda
das correntes no enrolamentos e linhas, com tensão de
alimentação senoidal balanceada. O método é
completamente
geral e pode ser aplicado a reatores saturados com
qualquer número de núcleos e enrolamento.
Em seguida aplica-se o método previamente descrito a um
tipo particular de reator saturado, o Twin-tripler, e
desenvolve-se um programa em computador digital. Os
resultados obtidos são depois comparados com os
conhecidos
experimental. / [en] This work is concerned with the presentation of an
analytical method for the harmonic analysis of three-phase
saturated reactors when used for controlling voltage in
power systems.
The requirements for voltage control in transmission and
distribution systems through the demand for reactive power
are first discussed and the various types of existing
compensators which meet these requirements are presented.
Particular attention is devoted to three-phase iron-cored
saturated reactors.
The cores of ac self saturated reactors are drive well
into saturation at their operating voltages causing,
naturally, non-sinusoidal currents to appear in the
windings. Two possible approaches for the elimination of
harmonics in the line currents are presented: use of
filters and internal elimination of harmonics by means of
suitable winding arrangements in three-phase saturated
reactors. This work develops an analytical method for the
harmonic analysis of satures reactors in which the
harmonic elimination or reduction is achieved internally.
The basic relations of the analytical method, which has
the objective of determining the waveforms of the line and
winding currents with a balanced three-phase voltage
source, are then presented. The method is completely
general and can be aplied to saturated reactors of any
number of cores and windings.
The previously described method is then applied to a
particular type of saturated reactor, the Twin-tripler,
and a digital computer programme is developed. The
obtained results are then compared with those
experimentally Known.
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[pt] REATORES SATURADOS E SUA APLICAÇÃO EM SISTEMAS DE EXTRA ALTA TENSÃO / [en] SATURABLE REACTORS AND THEIR APPLICATIONS IN EXTRA HIGH VOLTAGE SYSTEMPEDRO MARTIN 18 July 2007 (has links)
[pt] O acentuado crescimento dos blocos de energia a serem
transportados de distantes fontes de geração aos centros
de carga indica a necessidade de variados estudos de
sistemas de extra alta tensão, levando em consideração a
inclusão de novos equipamentos com a finalidade de
obtenção de melhores resultados econômicos.
O presente trabalho apresenta um estudo dos reatores
saturados, seu comportamento e uma análise de suas
aplicações, de modo especial, em um sistema de extra alta
tensão. / [en] The progressive growth of energy blocks to be transmitted
from distant generation sources to load centers determines
the necessity of several extra high voltage systems
studies, taking in account the introdction of new
equipaments to get better economic results.
This work presents a sutdy of saturable reactors, their
behavior and an analysis of their applications,
specifically, in an extra high voltage system.
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[en] SATURATED REACTOR TYPE STATIC COMPENSATOR MODELLING AND ITS IMPLEMENTATION IN A DIGITAL TRANSIENT STABILITY PROGRAM / [pt] MODELAGEM DE COMPENSADORES ESTÁTICOS TIPO REATOR SATURADO E SUA IMPLEMENTAÇÃO NUM PROGRAMA DE ESTABILIDADE TRANSITÓRIAJOSE EDUARDO ONODA PESSANHA 16 January 2007 (has links)
[pt] Este trabalho envolve o desenvolvimento de um modelo de
compensador estático do tipo reator saturado e sua
implementação no programa de estabilidade transitória
TRANSTAB, implantado no computador CYBER 170-835 da
PUC/RJ.
O modelo é composto por bancos de capacitores fixos,
responsáveis pela geração de reativos, em paralelo com o
reator saturado, responsável pela absorção de reativos.
São obtidos em primeiro lugar as equações do modelo e, a
partir destas, elabora-se o diagrama de blocos a ser
implementado no programa.
Vários testes (simulações digitais) são realizados
utilizando sistemas de potência, sob condição de
distúrbio. Os resultados obtidos são então comparados
com outros da literatura e a partir daí se comprova a
validade do modelo desenvolvido.
Com a conclusão deste trabalho, o programa TRANSTAB
passa a dispor de dois tipos de compensadores estáticos:
Reator Saturado e Reator Controlado por Tiristores. / [en] The model comprises fixed capacitor banks, for the
generation of reactive power, in parallel with the
saturated reactor, for the absortion of reactive power.
The model equations are obtained in first place and from
them the block diagram is developed for implementation in
the program.
Tests are carried out (digital simulations) using power
systems under disturbance conditions. The results are then
compared with others from the literature to access the
validity of the model.
With the conclusion of this work the TRANSTAB program stay
with two types of static compensators: Saturated Reactor
Type and Thyristor Controled Reactor.
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[en] DEVELOPMENT OF A SERVO-CONTROLLED TRIAXIAL EQUIPAMENT AND EVALUATION OF MECHANICAL BEHAVIOUR OF A BIOTITE-GNEISS RESIDUAL SOIL / [pt] DESENVOLVIMENTO DE UM SISTEMA TRIAXIAL SERVO-CONTROLADO E AVALIAÇÃO DO COMPORTAMENTO MECÂNICO DE UM SOLO RESIDUAL DE BIOTITA GNAISSEGUILHERME ROBERTO SLONGO 06 April 2009 (has links)
[pt] A presente dissertação contemplou o estudo de propriedades mecânicas de um solo Residual Biotita Gnaisse do Alto Leblon (Município do Rio de Janeiro) e o desenvolvimento de um equipamento triaxial para ensaios não saturados. Para o estudo do comportamento mecânico foi desenvolvido um programa experimental que envolveu: (a) ensaios de caracterização física; (b) caracterização mineralógica através da difratometria de Raio-X, microscopia óptica e Microscopia Digital; (c) determinação de propriedades não saturadas através da curva característica determinada utilizando o método do papel filtro, porosimetria de mercúrio e análise digital de imagem; (d) parâmetro de resistência ao cisalhamento através de ensaios triaxiais convencionais e não convencionais com controle de trajetória de tensões na condição saturada; (e) análise dos Módulos Iniciais com a utilização de sensores para a medição de deformação externa e interna (Eletronível tipo Imperial College) e os efeitos das trajetórias de tensões sobre os Módulos Iniciais.
O equipamento Triaxial desenvolvido para ensaios na condição parcialmente saturada está equipado com um sistema de medição de variação de volume total do corpo de prova o qual está baseado no princípio de vasos comunicantes aliado a uma balança de precisão. Visando eliminar o efeito de dilatação, a câmara
triaxial foi desenvolvida utilizando o artifício da câmara dupla. O equipamento encontra-se montado, porém não houve a possibilidade de sua validação devido a atrasos no processo de importação de componentes referentes ao controle, aplicação de pressões e aquisição de dados. / [en] This dissertation presents a study of the mechanical properties of biotite
gneiss residual soil found at Alto Leblon, Rio de Janeiro, and the development of
a triaxial equipment for unsaturated soil testing. An experimental program has
been created to study the mechanical behaviour of soil. The methodology
proposed by this campaign is: (a) physical characterization tests; (b) mineralogical
characterization by X-Ray difratometry tests, optical microscopy and digital
microscopy analysis; (c) study of unsaturated properties based on its moisture
retention curve  which has been determined by using the filter paper method, the
mercury intrusion porosimetry test and digital image analysis; (d) by obtaining
shear strength parameter through conventional and unconventional triaxial tests
using stress paths controlled at a saturated condition and; (e) by analyzing the
Initial Modules using sensors to measure internal and external axial strain
(Imperial College electrolevel) and to study the stress paths effects on Initial
Modules. The triaxial equipment used in this research was specially developed for
the study of unsaturated soils. It includes a system for measuring the total volume
variation of the specimen. This system is based on the principle of communicating
vessels and is associated with a precision balance. The triaxial chamber has been
developed based upon the dual chamber principle to eliminate dilatation effects.
The equipment has been set up, but its validation was not possible due to a delay
in the importation process of control, pressure application and data acquisition
components.
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[en] NUMERICAL AND EXPERIMENTAL STUDY ON SATURATED AND NON-SATURATED SOIL PROBLEMS / [pt] ESTUDO NUMÉRICO E EXPERIMENTAL DE PROBLEMAS DE FLUXO SATURADO - NÃO SATURADO EM SOLOSMARLENE SUSY TAPIA MORALES 10 September 2008 (has links)
[pt] O estudo de fluxo saturado - não saturado em solos exige
o
conhecimento das funções de relação, como a curva
característica (q x h) e a curva de condutividade
hidráulica (K x h). Para determinar estas relações o
presente trabalho utiliza o modelo de van Genuchten-
Mualem, o qual está implementado numa ferramenta numérica
que permite a utilização da retroanálise como método
para determinação dos parâmetros do modelo. O principal
objetivo deste trabalho é a avaliação de um método que
permita a estimativa dos parâmetros do modelo de van
Genuchten-Mualem, a partir de dados coletados em campo ou
laboratório para, então, realizar-se a análise de fluxo
saturado - não saturado e a estimativa dos parametros de
van Genuchtem-Mualem. Finalmente, a as condições de fluxo
saturado - não saturado em duas encostas foram simuladas,
em duas e três dimensões, a fim de verificar a variação
de
fluxo nestes casos. / [en] The study of saturated and non saturated flow in soils
requires the knowledge of relation functions, as water
retention curve (q vs. h) and hydraulic conductivity curve
(K vs. h).In order to determine these relations, this
research uses van Genuchten-Mualem`s model, which is
implemented on a numerical based method. This tool allows
the inverse solution as a method to determine the
parameters of the model. The main objective of this
research is the evaluation of a method which allows the
estimative of the required parameters by the chosen
model, determined based on field or laboratory data, so
then, based on these parameters, saturated and non-
saturated flow analysis were carried out and the
estimative of parameters of van Genuchten-Mualem`s model.
Finally, saturated and non-saturated simulations were made
on two slopes. These simulations were followed by 2D and 3D
models, in order to verify the flow variation on these
cases.
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[es] ESTUDIO NUMÉRICO DE LA ESTIMACIÓN DE PARÁMETROS HIDRÁULICOS EN SUELOS PARCIALMENTE SATURADOS / [pt] ESTUDO NUMÉRICO DA ESTIMATIVA DE PARÂMETROS HIDRÁULICOS EM SOLOS PARCIALMENTE SATURADOS / [en] NUMERICAL ESTIMATION OF HYDRAULIC PARAMETERS IN PARTIALLY SATURATED SOILSRAQUEL QUADROS VELLOSO 30 July 2001 (has links)
[pt] A análise de fluxo em solos parcialmente saturados exige o
conhecimento das propriedades hidráulicas do solo: a curva
característica, q(y), e a curva de permeabilidade, k(y).
Entre os problemas geotécnicos que envolvem fluxo em meios
parcialmente saturados pode-se citar a instabilização de
encostas, muitas vezes associada a variações de sucção, e o
transporte de contaminantes, pois, freqüentemente, a fonte
contaminante está acima do nível d`água.
O principal objetivo deste trabalho é a implementação
numérica de um programa, baseado num código de elementos
finitos, para a realização da retroanálise de parâmetros de
fluxo em solos parcialmente saturados a partir de ensaios
de campo, e que forneça também informações sobre a
qualidade da estimativa obtida. O método de retroanálise
utilizado permite a determinação simultânea da curva
característica e da curva de permeabilidade a partir de
dados de fluxo transiente.
O programa desenvolvido foi utilizado para determinar os
parâmetros de fluxo de um ensaio realizado no campo
experimental II da PUC - Rio. Com base na análise dos
resultados obtidos neste ensaio e na análise de
sensibilidade foi proposto um ensaio de configuração mais
simples que pode fornecer resultados satisfatórios na
determinação das propriedades hidráulicas de solos
parcialmente saturados. / [en] Flow analysis in partially saturated soils requires the
determination of soil hydraulic properties: its
characteristic curve, q(y), and its permeability curve k
(y). The instabilization of slopes, often associated with
suction variations, and the transport of contaminants, where
the source of contaminants is often above water leve, are
some of the geotechnical problems involving flows in
partially saturated media.
The main objective of this work is the numerical
implementation of a program, based on finite element
coding, for the back analysis of flow parameters in
partially saturated soils, based on field experiments,
capable of providing information on the quality of the
estimates obtained.
The back analysis method used here allows the simultaneous
determination of the characteristic and permeability curves
from transient flow data.
The program was used to determine flow parameters of a
field experiment conducted in Experimental Field II (PUC-
Rio). A simpler configuration test is proposed based on the
analysis of the results obtained in this field experiment
and on a sensitivity analysis. This test may provide
satisfactory results in the determination of hydraulic
properties of partially saturated soils. / [es] El análisis de flujo en suelos parcialmente saturados exige el conocimiento de las propiedades
hidráulicas del suelo: la curva característica, q(y), y la curva de permeabilidade, k(y). Entre los
problemas geotécnicos que consideran flujos en medios parcialmente saturados se puede citar la
inestabilidad de pendientes, muchas veces asociada a la variaciones de succión; y el transporte de
contaminantes, ya que frecuentemente la fuente contaminante está encima del nível de agua. El
principal objetivo de este trabajo es la implementación numérica de un programa, basado en un
código de elementos finitos, para la realización del retroanálisis de parámetros de flujo en suelos
parcialmente saturados a partir de ensayos de campo, y que brinde también informaciones sobre la
calidad de la estimatición obtenida. El método de retroanálisis utilizado permite la determinación
simultánea de la curva característica y de la curva de permeabilidad a partir de datos de flujo
transitorio. El programa desarrollado fue utilizado para determinar los parámetros de flujo de un
ensayo realizado en el campo experimental II de la PUC - Rio. Analizando los resultados obtenidos
en este ensayo y el análisis de sensibilidad, se propone un ensayo de configuración más simple que
puede dar resultados satisfactorios en la determinación de las propiedades hidráulicas de suelos
parcialmente saturados.
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Dynamique des écoulements dans les aquifères calcaires de bas plateaux : de l'identification à la quantification des types de circulation. Exemple des formations triasiques et jurassiques dans le nord-est de la France / Flow dynamics in the limestone aquifers of low plateaus : from identification to quantification of the types of circulation : example of Triassic and Jurassic formations in the North-East of FranceFister, Vincent 07 December 2012 (has links)
L'hétérogénéité spatiale est un trait caractéristique des aquifères calcaires. Conditionnée par le karst et ses morphologies, cette hétérogénéité explique la fréquente sous-exploitation des réserves de ces hydrosystèmes mais également le degré lacunaire de connaissance de leurs fonctionnements. Nous avons voulu, dans cette recherche, approfondir cette connaissance en scrutant le fonctionnement des aquifères calcaires qui arment les bas plateaux du Nord-Est de la France. Trois de ces bas plateaux ont été retenus, ceux du Dogger et de l'Oxfordien (Jurassique) et celui du Muschelkalk (Trias). Afin de comprendre comment s'organisent les écoulements sur et dans ces trois systèmes, notre démarche s'articule autour de deux principaux axes ; le premier concerne l'identification des modalités de l'écoulement et le second est consacré à leur quantification. En pratique, la connaissance des modalités de circulation a été recherchée à travers l'étude des différents paramètres structurels (géologique, tectonique, karstique) et conjoncturels (précipitation, évapotranspiration) qui interagissent dans le cycle de l'eau. Nous montrons que la variété de fonctionnements hydrologiques observés, à l'échelle du domaine d'étude, est conditionnée principalement par les paramètres structurels ; l'hétérogénéité lithologique, notamment, apparaît comme une clef fonctionnelle déterminante, d'une part, par l'existence d'une multiplicité de nappes d'eau et d'autre part, par son rôle dans la karstogenèse. Les morphologies du karst s'observent principalement sur les secteurs de contact lithostratigraphique et nous avons pu établir, à travers une répartition spatiale des phénomènes du karst (en surface et en souterrain), que ces trois plateaux sont majoritairement déconnectés du karst et dominés par des processus de circulation lents, de l'infiltration à la vidange aquifère. Afin d'apporter des éléments de quantification sur les circulations, une analyse hydroclimatique et géochimique d'exutoires de petites dimensions a été ensuite menée. C'est ainsi qu'une petite dizaine de sources et de bassins versants, localisés dans des contextes physiographiques variés, ont fait l'objet de suivis sur plusieurs cycles hydrologiques. L'analyse nous a permis de préciser les caractères hydrodynamiques de deux grands types de comportement observés au sein des bas plateaux étudiés : le comportement fissural et le comportement karstique. Le comportement fissural se manifeste, à l'échelle annuelle, par un filtrage important des précipitations par les systèmes (forte inertie des valeurs de débits et de conductivités électriques) et également par de lents processus de mise en charge à l'échelle des évènements de crue. Le comportement karstique, quant à lui, est attesté, à l'échelle annuelle, par des pluies moyennement filtrées par les systèmes mais aussi par des variations hydrogéochimiques accusées lors des sollicitations pluviométriques majeures, en lien avec la transmissivité importante de ces milieux / The spatial heterogeneity is a feature of limestone aquifers. Conditioned by the karst and its morphologies, this heterogeneity explains the frequent under-exploitation of these hydrosystem reserves but it also explains the incomplete degree of knowledge of their functionings. In this research we wanted to deepen this knowledge by scrutinizing the functioning of the limestone aquifers which arm the low plateaus of the North-East of France. Three of these low plateaus held our attention, those of Dogger and Oxfordian (Jurassic) and the one of Muschelkalk (Triassic). In order to understand how the flows on and into these three systems are organized, our approach focuses on two main axes ; the first one concerns the identification of the modes of flow and the second one is devoted to quantification. In practice, the knowledge of the flow modes was investigated through the study of various structural parameters (geology, tectonics, karst) and conjunctural parameters (precipitation, evapotranspiration) interacting the water cycle. We show that the variety of hydrological functionings which are observed, on the scale of the study area, is mainly dependent on the structural parameters ; the lithological heterogeneity, in particular, appears as a determining functional key, on the one hand, by the existence of a multiplicity of groundwater and on the other hand, by its role in the karstogenesis. The morphologies of the karst are primarily obvious on the areas of lithostratigraphic contact and we were able to establish, through a spatial distribution of karst phenomena (on and underground), that these three plateaus are mainly disconnected from the karst and run by slow-flow processes, from infiltration to ground water discharge. In order to provide some quantifications of the circulations, a hydroclimatic and geochemical analysis of small outlets was then conducted. Thus a dozen springs and catchments, located in various physiographic settings have been surveyed for several water years. The analysis allowed us to specify the hydrodynamic characteristics of two types of behavior observed in the low plateaus we studied: the fissural behavior and the karstic behavior. The fissural behavior appears, on an annual scale, through a significant rainfall filtering of the systems (high inertia of the values of discharges and electrical conductivities) and also by slow charging processes when flood events occur. The karst behavior, meanwhile, is evidenced on an annual scale, by a moderately rainy filtering of the systems but also by hydrogeochemical variations accused during major rainfall solicitations in connection with the important transmissivity of these environments
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Two Dimensional Numerical Modelling Of Variably Saturated FlowsMuthineni, Srinivas 01 1900 (has links)
The prediction of moisture and contaminant transport through unsaturated soil to ground water is becoming increasingly important in the fields of hydrology, agriculture and environmental engineering. Computer aided simulation techniques enables one to conduct a series of systematic numerical experiments to analyze flow phenomenon in subsurface hydrology under various physical and chemical processes. The flow movement depends upon medium characteristics, initial and boundary conditions, which reflect, physical processes occurring below the ground. To understand the effects of physical process an efficient and accurate model is needed. Thus the model developed must be able to handle varied initial and boundary conditions. In this regard, infiltration into a very dry soil becomes a very important problem of study.
Most of the earlier numerical models developed are concentrated on the development of an efficient algorithm or the modelling of a particular process which govern the flow in unsaturated or saturated-unsaturated homogeneous medium. Not much work has been done on the analysis of variably saturated flow in layered soil medium. Models to simulate unsaturated flow through dry soils, especially through layered soils with varied boundary conditions are very limited. Further, not much studies have been reported in the literature on the prediction of seepage face development and the phreatic surface movement in variably saturated media with layering. These aspects are very important in determining the flow field and the discharge from the domain. A detailed literature review covering above aspects has been made and is reported in this thesis.
In the present work, two dimensional numerical models to predict the movement of wetting front in unsaturated domain and the movement of the phreatic surface in homogeneous and layered porous media under various initial and boundary conditions are developed based on finite difference and finite volume techniques. These models can handle flow in both rectangular flow domains and radial flow domains. The initial condition settings include the handling of very dry soil medium without any transformation of the governing equation, handling of infiltration and constant head conditions at the boundaries under steady state as well as transient scenarios. The models are also able to handle various soil moisture characteristics which depict the nonlinear behaviour between hydraulic conductivity, moisture content and pressure head in a soil media.
A mixed form of the governing partial differential equation is used in the present study as it leads to better mass conservation. The finite difference model uses a central difference approximation for the space derivatives and an Eulerian backward difference approximation for the time derivative. The fully implicit formulation is solved iteratively using Strongly Implicit Procedure after making Picard approximation for the highly nonlinear coefficients. The process of infiltration into an initially dry soil leads to the development of a steep wetting front. As the finite volume technique is naturally an upwind method, it is expected to play a positive role in modelling such processes accurately. Hence, a finite volume model is also developed by approximating the convective part using a MUSCL approach and a fully implicit central difference method for the diffusive part of the governing equation.
The models developed are validated using both experimental data and numerical solutions for problems reported in the literature. The validation problems cover a wide range of physical scenarios such as: infiltration into a very dry soil, infiltration into a dry soil column with gravity drainage, development of water table mound, steady state drainage in a sand filled wedge shaped tank with seepage face development and transient seepage face development in a rectangular domain. Five test problems are used for the validation of the models. The developed models perform very well for the test problems considered, indicating the models' capability in handling such situations. The results obtained by using the present models for simulating flow through highly unsaturated (very dry) soils show that the models perform very well when compared with models which use transformation techniques to handle such problems. The performance of the present models in comparison with the experimental data and numerical models available in the literature show the suitability of the present models in handling such situations.
The present models are also used to analyse various types of unsaturated flow problems with varying initial and boundary conditions. The boundary conditions considered are no flow and /or free flow conditions along the left, right and bottom boundaries with infiltration condition along a part of the top boundary. For the various cases considered in the present study, infiltration rate varies from 5 cm/day to 50cm/day through an initially very dry soil of -15000 cm pressure head in homogeneous and layered soils. Different types of soil media considered vary from sandy loam, loam and clay with horizontal and vertical layering of these soils. A total number of 14 cases are analysed. The results are discussed in terms of pressure head variation in the flow domain along with moisture redistribution for all the cases under consideration. It is observed from these studies that the infiltration rate play an important role on the wetting front movement through layered soils depending on the type of layering and the boundary conditions considered. The soil properties of various layers affect the movement of wetting front by changing the direction of movement. Even though the wetting front movement is predominantly vertical, there is a tendency for the wetting front to move in the horizontal direction as it moves from a coarse soil to fine soil. It is also observed that the vertical layering of soils with different hydraulic conductivity helps in redirecting the flow towards the bottom boundary through the neighboring coarser layers.
As finite volume method is more suitable for simulating sharp fronts, it is expected to perform better than finite difference method for simulating infiltration into very dry soils. So, a comparison is made between the performance of these two models by using the above test problems. It is observed from these studies that the performance of both the models are same except that the finite volume method takes much more CPU time than the finite difference model. Considering the type of problems tested, it is observed that for modelling unsaturated and saturated-unsaturated flows, finite difference method is better in comparison to finite volume method. It may be due to the predominant diffusive characteristics of the governing equation even while modelling flow through very dry soils.
Proper estimation of the seepage height is an important aspect in finding the discharge through the porous medium. It is observed from the literature that the use of a saturated flow model in such situations can lead to an underestimation of the discharge through the porous medium. This effect is more important when dealing with small dimension problems. It is also observed that various parameters which govern the moisture movement through saturated-unsaturated regions affect proper estimation of the seepage face height and there by discharge. Various factors like effect of boundary conditions, type of soil layering, problem dimension and aspect ratio on seepage face development and the associated phreatic surface formation is studied in the present work. It is seen from the present study that the seepage face development is more in rectangular flow domain than in radial flow domain for both homogeneous and layered soils. It is also seen that the seepage face development in rectangular problems are more sensitive than radial flow problems for various factors considered. The seepage height is also influenced by the tail water level. It is seen from the present study that as the tail water level increases the seepage face reduces with no seepage face development for some of the cases studied. This influence is relatively less for radial flow problems. As the length of the domain increases the seepage height decreases. It is seen that for different cases with same horizontal dimension, as the height of the domain increases the seepage face height also increases. This phenomenon is observed for both homogeneous and layered soil medium. The influence of the aspect ratio, which is the ratio of the length to height of the domain indicate that as the aspect ratio increases the seepage height decreases. The type of the soil layering is observed to have a very strong influence on the seepage face development. The study for understanding the effect of soil layering on the development of seepage face and phreatic surface suggest that as the coarseness of the material increases, the phreatic surface become flatter and its steepness increases with the fineness of the soil.
The present model is also used for studying the transient phreatic surface movement and the seepage face development. This is studied for homogeneous and layered rectangular soil medium. The present study is used to understand the effect of specific storage on the phreatic surface movement and the seepage face development. The studies indicate that the influence of specific storage on the seepage face development is insignificant in homogeneous soils with only very little effect in the early time for longer domains. It is also observed that the influence of the specific storage is significant in the case of layered soils. This effect depends on the type of layering and the problem dimension and is observed to have influence for relatively longer period. This observation suggests the importance of specific storage on transient seepage face development. When the specific storage effect is considered the drainage of the soil become faster resulting in a faster decline of the phreatic surface with time. The influence of specific storage is also studied considering the problem dimension effect. It is seen that as the aspect ratio increases, the effect of specific storage on the phreatic surface development decreases. The studies with change in the upstream boundary condition from a constant head to a no flow condition indicate that the effect of specific storage has no significant influence on the phreatic surface development for both homogeneous and layered soils.
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[en] A NUMERICAL AND EXPERIMENTAL PROCEDURE STUDY FOR USE IN THE MONITORED INFILTRATION TEST / [pt] UM ESTUDO DE PROCEDIMENTOS NUMÉRICOS E EXPERIMENTAIS PARA USO NO ENSAIO DE INFILTRAÇÃO MONITORADAFELIPE ALVES ROSA 22 March 2018 (has links)
[pt] A determinação dos parâmetros hidráulicos não saturados em laboratório nem sempre representa efetivamente as situações observadas em campo, principalmente devido ao erro causado pelo efeito de escala. Nesse sentido, inúmeros ensaios de campo vêm sendo desenvolvidos, fazendo o uso de medidas de carga de pressão no tempo, para a determinação das propriedades hidráulicas não saturadas. No presente estudo, foi utilizado o ensaio de campo proposto por Velloso (2000), denominado Ensaio de Infiltração Monitorada (EIM). Neste ensaio é mantida uma carga constante, utilizando um permeâmetro tipo Gueplh, sendo monitorada, com o auxílio de um tensiômetro, a variação da sucção ocasionada pela frente de infiltração. Quando a variação da sucção no solo torna-se constante e próxima a zero, o ensaio atingiu, portanto, a condição de fluxo permanente, podendo-se assim finalizar o teste. Os parâmetros do solo e os respectivos parâmetros do modelo de Van Genuchten (1980), os quais descrevem a curva de saturação versus o potencial mátrico, são obtidos matematicamente, através da resolução do problema inverso. Nesse sentido, o objetivo principal do presente trabalho é realizar uma avaliação detalhada dos procedimentos numéricos e experimentais para uso no Ensaio de Infiltração Monitorada (EIM), seguindo as diretrizes e recomendações apontadas nos estudos anteriormente realizados. Desta forma, buscou-se um melhor entendimento do EIM, e para isto, foram realizadas: análises comparativas com resultados de ensaio de laboratório do tipo papel filtro; foi adicionado o monitoramento de umidade de solo durante o EIM; e foram utilizados diferentes métodos de estimativa de parâmetros. Os ensaios apresentados no presente estudo foram realizados em cinco áreas do Estado do Rio de Janeiro. / [en] The determination of unsaturated hydraulic parameters in laboratory tests is not always represents as observed on the field, especially because of the presence of errors caused by the scale factor. So, several field tests have been developed using suction measures with time for a determination of the unsaturated hydraulic properties. This research aims to use the field test proposed by Velloso (2000), called Monitored Infiltration Test (EIM) to determine the Soil Water Characteristic Curve. In this test the constant head is maintained, using a constant head permeameter and, at the same time, monitoring a variation of the suction caused by the infiltration front with a tensiometer. When a variation of the suction in the soil becomes constant and close to zero, then, the test reached a condition of permanent flow, being possible to finalize the procedure. In addition, the soil water characteristic curve (SWCC) and the respective Van Genuchten parameters, that describes a saturation curve versus the matric potential, are obtained mathematically by solving the inverse problem. In this context, the main objective of this research is to develop a detailed evaluation of the numerical and experimental procedures to use it in the Monitored Infiltration Test (EIM), following the guidelines and recommendations pointed out in previous studies in the area. Moreover, was sought a better understanding of EIM, and for this, comparative analyzes were performed with laboratory test results of the filter paper type. In addition, it was added the soil moisture monitoring during the EIM. Finally, was used many optimization methods for parameter estimation. The tests developed and presented in this research, were performed in five areas around the State of Rio de Janeiro.
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[en] EVALUATION OF HYDRAULIC PROPERTIES OF UNSATURATED TROPICAL SOILS / [pt] AVALIAÇÃO DE PROPRIEDADES HIDRÁULICAS DE SOLOS TROPICAIS NÃO SATURADOSMONICA PRISCILLA HERNANDEZ MONCADA 07 October 2008 (has links)
[pt] O presente trabalho de pesquisa teve dois objetivos
principais. O primeiro foi obter um índice geotécnico que
permita avaliar o grau de intemperismo dos
solos residuais. Para isto foram analisados dados
correspondentes a perfis de alteração de Gnaisse
característicos do município do Rio de Janeiro e executou-se
a caracterização completa de um perfil específico de
alteração de Gnaisse Facoidal. O segundo objetivo foi a
determinação experimental das propriedades
hidráulicas de solos tropicais não saturados. Como parte
deste objetivo foram desenvolvidos novos instrumentos e
modificados equipamentos existentes. A
determinação da curva característica de sucção foi efetuada
em seis solos residuais e em dois solos sedimentares. Na
obtenção das curvas de retenção foram utilizadas as técnicas
de translação de eixos, papel filtro e umidade relativa.
Esta curva foi também definida a partir de resultados de
ensaios de porosimetria de mercúrio. Avaliou-se a
aplicabilidade dos modelos disponíveis na literatura no
ajuste dos dados experimentais. A função de permeabilidade
foi determinada em dois solos, um residual e um sedimentar,
utilizando um permeâmetro de parede
flexível com sucção controlada. Análises numéricas,
efetuadas para avaliar o comportamento do equipamento
utilizado, possibilitaram a definição de uma
metodologia otimizada de interpretação dos resultados. A
aplicabilidade dos modelos disponíveis na literatura na
obtenção da função de permeabilidade foi
analisada, tendo-se verificado a necessidade de introdução
de mudanças nestas formulações para se conseguir reproduzir
as medidas diretas efetuadas. / [en] The present research work had two main objectives. The
first was to obtain a geotechnical index for measuring the
weathering degree of gneissic residual
soils. For that it were analyzed data corresponding to
typical weathering profiles
found in the municipality of Rio de Janeiro and executed a
complete
characterization of a specific weathering profile of
facoidal gneiss. The second
objective was to determine, experimentally, the hydraulic
properties of tropical
unsaturated soils. As part of that new instruments were
developed and existing
equipments were modified. Moisture retention curves were
determined for six
residual soils and two sedimentary ones. The axis-
translation technique, the filter
paper method and the relative humidity one were employed to
obtain such curves.
Data from mercury intrusion porosimetry tests were also
used to define these
curves. The applicability of models available in literature
to adjust the obtained
experimental data was evaluated. The hydraulic conductivity
function was
determined for two soils, one residual and one sedimentary.
A suction controlled,
flexible wall permeameter set up was used for that.
Numerical modeling was
implemented to evaluate the performance of the experimental
set up. This
provided means for an optimized interpretation of the
testing results. The
applicability of models available in the literature to
obtain the permeability
functions was evaluated, being found the need to introduce
changes in their
formulation in order to be able to reproduce the obtained
experimental data.
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