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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Investigating the Need for Drainage Layers in Flexible Pavements

Masoud Seyed Mohammad Ghavami (6531011) 10 June 2019 (has links)
<p>Moisture can significantly affect flexible pavement performance. As such, it is crucial to remove moisture as quickly as possible from the pavements, mainly to avoid allowing moisture into the pavement subgrade. In the 1990s the Indiana Department of Transportation (INDOT) adopted an asphalt pavement drainage system consisting of an open-graded asphalt drainage layer connected to edge drains and collector pipes to remove moisture from the pavement system.</p> <p>Over the intervening two decades, asphalt pavement materials and designs have dramatically changed in Indiana, and the effectiveness of the pavements drainage system may have changed. Additionally, there are challenges involved in producing and placing open-graded asphalt drainage layers. They can potentially increase costs, and they tend to have lower strength than traditional dense-graded asphalt pavement layers. </p> <p>Given the potential difficulties, the overall objective of this research was to evaluate the effectiveness of the INDOT’s current flexible pavement drainage systems given the changes to pavement cross-sections and materials that have occurred since the open-graded drainage layer was adopted. Additionally, the effectiveness of the filter layer and edge drains were examined.</p><p><br>Laboratory experiments were performed to obtain the hydraulic properties of field-produced asphalt mixture specimens meeting INDOT’s current specifications. The results were used in finite element modeling of moisture flow through pavement sections. Modeling was also performed to investigate the rutting performance of the drainage layers under various traffic loads and subgrade moisture conditions in combination with typical Indiana subgrade soils. The modeling results were used to develop a design tool that can assist the pavement designer in more accurately assessing the need for pavement drainage systems in flexible pavements.<br></p>
52

Digitale Bildanalyse zur Messung fraktaler Eigenschaften der Bodenstruktur / Digital image analysis for measuring fractal properties of soil structure

Dathe, Annette 27 June 2001 (has links)
No description available.
53

Retenção e disponibilidade de água em solos de Santa Catarina: avaliação e geração de funções de pedotransferência / Water retention and availability in soils of Santa Catarina: Evaluation and generation of pedotransfer functions

Costa, André da 24 February 2012 (has links)
Made available in DSpace on 2016-12-08T15:50:03Z (GMT). No. of bitstreams: 1 PGMS12DA009.pdf: 7314998 bytes, checksum: 8e93659478a7813ba0b934959e229681 (MD5) Previous issue date: 2012-02-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Studies on the retention and availability of water are scarce for humid subtropical and temperate regions in the Southern Hemisphere. The objectives of this study were to evaluate, generate and validate some pedotransfer functions (PTFs) to estimate the retention and the availability of water in soils of Santa Catarina. Were sampled 44 profiles, in areas under different vegetal coverings, to determine the water retention at suctions from zero to 1.500 kPa, the particles size distribution (7 classes), the organic matter content, the bulck density and particle density of soil, the conductivity hydraulic, and the aggregate stability. Regarding the attributes, soils with finer texture and / or more organic matter retain higher water content, where the organic matter is the main attribute that governs the availability of water, mainly in the surface horizons. Some classes of sand, mainly very fine sand, fine and coarse fractions, have greater effects on water availability than the silt fraction. The soils with contrasting textural classes, with high contents of clay or sand, have the same content of water available, although the sand soils have very low field capacity. Increased water availability occurs in soils with textural class loam, with higher content of organic matter and the lower availability occurs in sand class soils. In relation to lithology, there is a higher retention in soils derived from igneous extrusive rocks of the Serra Geral Formation, metamorphic, intrusive igneous, and sedimentary with fine texture, and a lower retention in those derived from rocks or sedimentary deposits rich in quartz. Increased availability of water occurs in soils derived from siltstone and less in soils derived from granite and recent alluvial deposits. Regarding soil classes (suborders), the water retention is higher in Cambisols, Ferralsols and Nitosols, and lower in Quartzarenic Neosols. In relation the regions, the soils of the Midwest and West, Serrano Highlands and Valley of Itajaí have high water retention, the intermediary are the Eastern Sierra, and lower in the coast. Humic Cambisols and Entisols, located in the Serrano Highlands has increased availability of water, mainly because of high contents of organic matter. In relation to soil types in the normative instruction n. 2/2008 of the MAPA (BRAZIL, 2008), which classifies the soils as a function of clay and sand, it is observed that is not adequate to classify the soils of Santa Catarina in terms of availability of water, although, the hydraulic conductivity of the unsaturated soil is lower in Type 1 soils. In relation the pedotransfer functions of literature, they better estimate the retention than water availability and with greater precision by the functions originated from climate regions subtropical and for the subsurface horizons of the soil. Most functions evaluated underestimates the water retention, with greater deviations in soils with 20-60 % clay. About the functions generated for the soils of Santa Catarina, the estimation of retention and availability of water was better in those adjusted separately for surface and subsurface horizons. To estimate the water retention, the point PTFs must be used including data of the texture, organic matter and their interactions. To estimate the availability, the point PTFs should include the five classes of sand, silt, clay, organic matter, soil bulk density, soil particles density, total porosity and their interactions. The parametrics PTFs estimate properly the water retention curve for most of the textural classes of the soil, when data of texture, organic matter, soil bulk density, soil particles density, total porosity and their interactions are included as predictors. The class PTFs estimate properly the water retention curve for most of the soil textural classes of Santa Catarina / Estudos sobre a retenção e disponibilidade de água são escassos para as regiões de clima subtropical ou temperado úmido do hemisfério sul. Os objetivos deste estudo foram avaliar, gerar e validar funções de pedotransferência (FPTs) para estimar a retenção e a disponibilidade de água em solos de Santa Catarina. Foram amostrados 44 perfis, em áreas sob diferentes coberturas vegetais, para determinar a retenção de água nas sucções de zero até 1.500 kPa, a distribuição do tamanho de partículas (7 classes), o teor de matéria orgânica, a densidade do solo e de partículas, a condutividade hidráulica e a estabilidade de agregados. Em relação aos atributos, solos com textura mais fina e/ou com maior teor de MO retêm maior conteúdo de água, sendo a MO é o principal atributo que governa a disponibilidade de água, principalmente nos horizontes superficiais. Algumas classes de areia, principalmente as areias muito fina, fina e grossa, possuem maiores efeitos sobre disponibilidade de água do que a fração silte. Os solos com classes texturais contrastantes, com elevados teores de argila ou de areia, disponibilizam o mesmo conteúdo de água disponível, embora os arenosos tenham baixa capacidade de campo. Maior conteúdo de água disponível ocorre em solos das classes com textura franca e com maior teor de MO, enquanto que a menor disponibilidade ocorre em solos da classe areia. Em relação à litologia, ocorre uma maior retenção em solos derivados de rochas ígneas extrusivas da Formação Serra Geral, e de rochas metamórficas, ígneas intrusivas e sedimentares de textura fina, e menor nos derivados de rochas ou depósitos sedimentares ricos em quartzo. Maior disponibilidade de água ocorre em solos derivados de siltitos e o menor em solos derivados de granito e de depósitos aluvionares recentes. Em relação às classes de solos (subordens), a retenção de água é maior nos Cambissolos, Nitossolos e Latossolos e menor nos Neossolos Quartzarênicos. Em relação às regiões, os solos do Meio Oeste e Oeste, Planalto Serrano e Vale do Itajaí possuem elevada retenção de água, euquanto que, nos da Serra Leste é intermediária e os do Litoral é baixa. Os Cambissolos Húmicos e os Neossolos Litólicos, localizados no Planalto Serrano, têm maior disponibilidade de água, principalmente devido aos elevados teores de matéria orgânica. Em relação aos tipos de solos da instrução normativa n. 2/2008 do MAPA (BRASIL, 2008), que classifica os solos em função do teor de argila e areia, observa-se que a mesma não é adequada para classificar os solos catarinenses quanto a disponibilidade de água. Entretanto, a condutividade hidráulica não saturada é menor nos solos do Tipo 1. Em relação às funções de pedotransferência (FPTs) publicadas na literatura, elas estimam melhor a retenção do que a disponibilidade de água, com maior precisão pelas funções originadas de regiões de clima subtropical e para os horizontes subsuperficiais do solo. A maioria das funções avaliadas subestima a retenção de água, com erros maiores nos solos com 20 a 60% de argila. Quanto às funções geradas para os solos de Santa Catarina, as que melhor estimam a retenção e disponibilidade de água são aquelas ajustadas separadamente para os horizontes superficiais e subsuperficiais. Para estimar a retenção de água devem ser utilizadas as FPTs pontuais que incluem dados de textura, matéria orgânica do solo e suas interações. Para estimar a disponibilidade de água devem ser utilizadas as FPTs pontuais que utilizam as cinco classes de areia, silte, argila, matéria orgânica, densidade do solo e de partículas, porosidade total e suas interações. As FPTs paramétricas estimam adequadamente a curva de retenção de umidade do solo para a maioria das classes texturais, quando são incluídos dados de textura, matéria orgânica, densidade do solo e de partículas, porosidade total e suas interações como variáveis preditoras. As FPTs de classe estimam adequadamente a curva de retenção de água do solo para a maioria das classes texturais dos solos de Santa Catarina
54

Numerisk modellering av deformationer och portryck i en experimentdamm : Jämförelse mellan in-situmätningar och FE-simuleringar i PLAXIS 2D / Numerical modelling of deformations and pore pressures in an experimental embankment dam : Comparison between in-situ measurements and FE simulations in PLAXIS 2D

Sjödin, Adam January 2021 (has links)
Under hösten 2019 har Vattenfall Research &amp; Development byggt en experimentell jordfyllningsdamm i Älvkarleby med dimensionerna 20x15x4 meter. Delar av experimentdammen är konventionellt konstruerade och har installerats med geoteknisk utrustning som utgörs av bland annat inklinometrar och portrycksgivare. Andra delar av experimentdammen har byggts in med defekter som ska representera åldersrelaterade skador eller utförandefel vid konstruktion. Experimentdammen ger möjlighet att under realistiska och kontrollerade förhållanden studera det mekaniska beteendet i samband med fyllning av vatten och vidare drift med hjälp av den geotekniska instrumenteringen samt med stöd av numerisk modellering. I detta examensarbete, som utgör en del av Luleå tekniska universitets forskningsprojekt mot experimentdammen, har experimentdammens beteende i form av deformationer och portryck studerats under uppfyllnad och drift fram till sommaren 2021. Detta har utförts genom simuleringar i det finita elementprogrammet PLAXIS 2D 2019 för en tvärsektion av experimentdammen i plant-deformationstillstånd. Mätpunkterna i modellen har baserats på faktisk placering av den geotekniska instrumenteringen. Den finita elementmodellen av experimentdammen har konstruerats och fyllts med vatten enligt dokumentation från fält. En flödes-deformationsanalys, med den konstitutiva modellen Hardening Soil och den hydrauliska modellen van Genuchten, har tillämpats för att modellera den simultana utvecklingen av portryck och deformationer under uppfyllnad. Materialparametervärden för den finita elementmodelleringen har erhållits från Vattenfall R&amp;D, relevant litteratur och från fält- och laboratorieförsök. I fält har vattenvolymeterförsök utförts på tätkärnan och i laboratoriemiljö har modifierad proctorpackning, dränerade konventionella triaxialförsök, permeabilitetsförsök och övertryckskapillarimeterförsök utförts på tätkärnans material. Resultatet från övertryckskapillarimeterförsök har anpassats mot den hydrauliska modellen van Genuchten för att uppskatta en vattenbindningskurva som beskriver det icke-linjära förhållandet mellan jordens vatteninnehåll och porundertryck, det vill säga det omättade förhållandet. Vattenbindningskurvor för övriga materialzoner har uppskattats baserat på litteratur. Verktyget PLAXIS SoilTest har använts för att optimera materialparametervärden för tätkärnan mot resultat från utförda triaxialförsök. Materialparametrarna E50ref, Eoedref, Eurref, m, c, och ϕ har optimerats fram till brott i triaxial belastning. En känslighetsanalys har utförts för reduktion av filterzonernas och stödfyllningens styvhetsmoduler och deras inverkan på horisontella deformationer i dammkroppen under uppfyllnad. Känslighetsanalysen indikerar att finfiltrets styvhetsmoduler har störst inverkan och grovfiltrets styvhetsmoduler har minst inverkan på de horisontella deformationerna. Studiens resultat visar att magnituden av horisontella och vertikala deformationer kommer vara som störst i den övre delen av dammkroppen och uppgår där till 3,5 respektive 4,0 mm. Dammkroppens huvudsakliga rörelse kommer vara i nedströms riktning och det observerades hur en kontaktzon mellan uppströms filterzon och tätkärnan utgör en gräns för riktning av deformationer. Faktiskt uppmätta rörelser i installerade inklinometrar kunde inte jämföras mot deformationer i den finita elementmodellen eftersom författarens tolkning indikerar på att botten av inklinometrarna har rört på sig, och mätpunkterna i botten av modellen är fixerade. Modellen visar hur en fördröjd utveckling av vattenmättnad sker genom tätkärnan, där uppströms sida av tätkärnan reagerar snabbare på förändringar i vattennivå jämfört med nedströms sida av tätkärnan som uppvisar en fördröjd respons. Vid en sänkning av vattennivån observerades hur tätkärnan håller kvar vatten ovan portryckslinjen medan de grövre materialen dränerar i takt med vattennivåns sänkning. Utvecklingen av de simulerade portrycken i modellen under uppfyllnad och drift överensstämmer bra med de uppmätta portrycken i experimentdammen, när portrycken är positiva. Det observeras hur den finita elementmodellen överskattar negativa portryck (porundertryck). Portrycken i modellen når ett stadigt tillstånd ungefär 115 dagar efter att fyllningen av vatten påbörjats. Den finita elementmodellen lyckas att återge det teoretiska beteendet av jordfyllningsdammar under fyllning i form av huvudsakliga riktningar av deformationer och utveckling av vattenmättnad i tätkärnan. Denna studie bidrar till en djupare förståelse för experimentdammens, och i allmänhet jordfyllningsdammars, mekaniska beteende under uppfyllnad. Resultaten från den finita elementmodellen kan ur ett dammsäkerhetsperspektiv användas för erhålla indikationer på utvecklingen av deformationer, portryck och vattenmättnadsgrad i jordfyllningsdammar under uppfyllnad, och även under en tillfällig sänkning av vattennivån under den första fyllningen. Studien ger också indikationer på vilka materialparametrar som är viktiga vid numerisk modellering av mekaniskt beteende i jordfyllningsdammar. / During the autumn of 2019, Vattenfall Research &amp; Development constructed an experimental embankment dam in Älvkarleby with the dimensions 20x15x4 metres. Parts of the experimental dam are conventionally constructed and have been equipped with geotechnical instrumentation which consist of, among other things, inclinometers and pore pressure transducers. Other parts of the experimental dam have built in defects to represent age-related damages or execution errors during construction. The experimental embankment dam provides the opportunity to, under realistic and controlled conditions, study the mechanical behaviour during filling of water and operation by means of the geotechnical instrumentation and the use of numerical modelling. In this master’s thesis, which forms part of Luleå University of Technology’s research project towards the experimental dam, the behaviour of the experimental dam in terms of deformations and pore pressures have been studied during filling and operation until the summer of 2021. This has been performed by simulations in the finite element program PLAXIS 2D 2019 for a cross section of the experimental dam under plane-strain conditions. Measuring points in the model have been based on the actual location of the geotechnical instrumentation. The finite element model of the experimental dam has been constructed and filled according to documentation from field. A fully-coupled flow deformation analysis, with the constitutive model Hardening Soil and hydraulic model van Genuchten, has been utilised to model the simultaneous development of pore pressure and deformations during filling. Values of material parameters for the finite element modelling have been received from Vattenfall R&amp;D, relevant literature and from field- and laboratory tests. In the field, balloon tests have been performed on the core material. In laboratory environment, modified proctor compaction tests, drained conventional triaxial tests, permeability tests and pressure plate tests have been performed on the core material. Results from the pressure plate tests have been adapted to the hydraulic model van Genuchten to estimate a soil-water characteristic curve in order to describe the non-linear relation between the water content and suction in the soil, i.e. unsaturated conditions. Soil-water characteristic curves for the other material zones have been estimated based on literature. The tool PLAXIS SoilTest has been used to optimise material parameter values of the core against the results from conducted triaxial tests. The material parameters E50ref, Eoedref, Eurref, m, c, and ϕ have been optimised until failure in triaxial loading. A sensitivity analysis has been carried out, by reducing stiffness moduli of the filter zones and the shoulder material, to investigate the influence on horizontal deformations in the dam body during filling. The sensitivity analysis indicates that the stiffness moduli of the fine filter have the largest impact and the stiffness moduli of the coarse filter have the least impact on the horizontal deformations. The results of the study show that the magnitude of horizontal and vertical deformations will be largest in the upper part of the dam body and amounts to 3.5 and 4.0 mm, respectively. The main movement of the dam body will be in the downstream direction and it was observed how a contact zone between the upstream filter zone and the core forms a boundary for direction of deformations. Actual measured movements in the installed inclinometers could not be compared to deformations in the finite element model because the author’s interpretation indicates that the bottom of the inclinometers have moved, and the measuring points at the bottom of the model are fixed. The model shows how a delayed development of saturation occur through the core, where the upstream side of the core responds more quickly to changes in water level compared with the downstream side of the core which show a delayed response. At a lowering of the water level, it was observed how the core retains water above the phreatic line while the coarser materials drain as the water level decreases. Development of the simulated pore pressures in the model during filling and operation corresponds well with the measured pore pressures in the experimental dam, when the pore pressures are positive. It is observed how the finite element model overestimates negative pore pressures (suction). The pore pressures in the model reaches a steady state approximately 115 days after filling of water started. The finite element model succeeds in reproducing the theoretical behaviour of embankment dams during filling in terms of main directions of deformations and development of saturation in the core. This study contributes to a deeper understanding of the experimental dam, and in general mechanical behaviour of embankment dams during filling. The results from the finite element model can be used from a dam safety perspective to obtain indications on the development of deformations, pore pressures and degree of saturation in embankment dams during filling, and also for a temporary lowering of the water level during the first filling. The study also provides indications of which material parameters that are of importance in numerical modelling of mechanical behaviour in embankment dams.
55

Pedotransferové funkce pro odhad vlhkostních retenčních křivek středně těžkých půd jižní Moravy / Pedotransfer functions for estimation of moisture retention curves of medium-heavy soils of South Moravia

Gavlasová, Iva January 2014 (has links)
The most important characteristics of each soil is its hydro-physical properties, which include retention curve. Retention curve expresses the relationship between humidity and pressure head. It is course affected by many factors such as grain size and mineralogical composition, humus content, structure and bulk density of dry soil. This thesis deals with direct and indirect determination of one of the basic hydraulic characteristics of the soil, soil moisture retention curve. For laboratory determination of moisture retention curves were used for sand tank and pressure instruments. Measured body retention curves were optimized RETC program.For indirect determination of retention curves were used Pedotransfer function by Wösten et . al .(1998 ) , derived from the European soils and under HYPRES Šútora and Štekauerová (2000). As in the project Wösten et al . (1998), PTF were processed for arable land in the area. The accuracy of both models PTF was assessed by the correlation coefficient R and standard error RMSE. Simple models PTF provide estimates of retention curves with sufficient accuracy for practical use in the locality.
56

Stanovení hydraulických charakteristik půdy ve vybrané lokalitě / Determination of soil hydraulic characteristics in the selected location

Stoklásková, Adéla January 2012 (has links)
This thesis deals with direct and indirect determination of soil hydraulic characteristics (retention curve and hydraulic conductivity) in the locality of Bohaté Málkovice. For laboratory determination of soil moisture retention curve is used sand tank and pressure relief device. For the indirect determination of soil hydraulic characteristics is used computer software Rosetta, which includes 5 models of pedotransfer functions. For estimatiton of retention curves are applied previously derived pedotransfer function (continuous parametric PTF and point PTF).

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