Tesi sul tema "Coulomb-Mohr"

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Capes
A deformação permanente é definida como o acúmulo de pequenas quantidades de deformação não recuperáveis resultante da aplicação das cargas dos veículos. A deformação permanente na camada de revestimento asfáltico pode ser oriunda por três mecanismos: deformação permanente por densificação, por uso e por fluência da mistura. Dado que as temperaturas de serviço da camada de revestimento estão em torno de 40 a 60 °C, a mistura asfáltica nesse intervalo de temperatura se comporta como um material sólido. Sendo assim, é razoável supor que os mecanismos de falha aplicáveis aos materiais sólidos sejam válidos para as misturas de asfálticas. Sendo o critério Mohr-Coulomb amplamente utilizado para descrever as características de cisalhamento de materiais sólidos, poderá ser utilizado para obtenção do ângulo de atrito interno da mistura, bem como o seu intercepto coesivo. Este trabalho teve como objetivo a determinação de ângulos de atrito internos de diferentes misturas asfálticas e sua influência no comportamento mecânico, em especifico, na resistência à deformação permanente destas misturas. Como forma de atingir o objetivo da pesquisa foi desenvolvido um programa experimental visando à avaliação das propriedades mecânicas relacionadas ao ângulo de atrito interno das misturas asfálticas com CAP 50/70 e E – 55/75. Foi possível executar análises em laboratório a partir da determinação de parâmetros de ruptura por cisalhamento, com o auxílio da teoria de Mohr-Coulomb, tendo como inferência o desempenho de misturas estudadas em campo. Verificou-se que, a cada acréscimo de 5% de partículas graúdas em uma faixa granulométrica, as misturas estudadas apresentaram, em geral, um ganho de 1° (Grau) no ângulo de atrito interno para cada faixa estudada. Entretanto, deve ser observado o limite de 30 a 35% de partículas graúdas para cada mistura. Pode-se concluir que: os parâmetros de ruptura por cisalhamento, ângulo de atrito interno e intercepto coesivo são fatores determinantes no desempenho a deformação permanente de misturas asfálticas. Para os ligantes utilizados os resultados indicaram que o acréscimo do ângulo de atrito interno resulta numa maior resistência a deformação permanente.
Permanent deformation is defined as the accumulation of small amounts of non-recoverable deformation resulting from the application of vehicle loads. The permanent deformation in the surface layer of asphalt pavements can come from three mechanisms: permanent deformation by densification, by use and by creep of the mixture. Since the service temperatures of the pavement surface layer are around 40 and 60 ºC, the asphalt mixture, in this temperature range, behaves as a solid material. Therefore, it is reasonable to assume that failure mechanisms applicable to solid materials are valid for asphalt mixtures. As the Mohr-Coulomb criterion is widely used to describe the shear characteristics of solid materials, it can be used to obtain the internal friction angle of the asphalt mixture as well as to estimate its cohesive intercept. This work had as objective to determine the internal angles of friction of different asphalt mixtures and their influence on the mechanical behavior, in particular, on the resistance to permanent deformation of these mixtures. In order to achieve the objective of this research, an experimental program was developed to evaluate the mechanical properties related to the internal angle of friction of asphalt mixtures with the 50/70 asphalt binder and the E 55/75 asphalt binder. It was possible to perform laboratory analyses from the determination of shear rupture parameters, supported by the Mohr-Coulomb's theory, inferred by the performance of mixtures studied in the field. It was verified that, at each increment of 5% of coarse particles in a particle size range, the studied mixtures presented, in general, a gain of 1° (degree) in the internal angle of friction for each size range studied. However, the limit of 30 to 35% of coarse particles should be observed for each mixture. It can be concluded that: the parameters of shear rupture, internal angle of friction and cohesive intercept are determining factors in the permanent deformation performance of asphalt mixtures. For the asphalt binders used, the results indicated that the increment of the internal angle of friction results in a greater resistance to permanent deformation.

L'objectif de ce travail est de comprendre l'influence des particules très fines sur le phénomène de ré-agglomération lors du broyage. Des billes de verre de taille 0 à 20 µm avec un pourcentage massique variant entre 0 à 1% sont ajoutées dans un tas granulaire de billes de verre de 200 à 300 µm dans un tambour tournant cylindrique de diamètre et longueur 10 cm. La présence des particules fines montre un effet ambivalent sur la stabilité du tas granulaire. Nous avons établi un diagramme de stabilité du milieu granulaire en fonction de la concentration de particules fines et cherché à quantifier l'effet des fines combiné avec d'autres paramètres (humidité relative et vitesse de rotation du tambour). La stabilité d'un tas granulaire dans un tambour tournant est déterminée par la mesure de son angle maximum de stabilité θm. Dans un premier temps, nous avons étudié l'évolution de cet angle à des vitesses de rotation différentes. Les expériences montrent qu'à faible concentration (< 0; 15%), le tas se déstabilise par avalanches lorsque le tambour tourne, θm diminue lorsqu'on augmente la quantité de fines. Quand la vitesse de rotation augmente, le mouvement du tas évolue du régime d'avalanche intermittent au régime d'écoulement continu. En revanche, lorsque la concentration des fines est supérieure à 0,15%, la déstabilisation du tas se traduit par un phénomène de stick-slip à la paroi du tambour, et la quantité de fines augmente la stabilité du tas. Ce comportement apparemment contradictoire est lié au fait que la localisation de la déstabilisation est modifiée. Dans le régime des faibles concentrations, les avalanches commencent à la surface du tas, et le remplissage de l'espace intermédiaire entre les grosses billes par les fines rend la surface de plus en plus lisse, ce qui déstabilise le tas. Par ailleurs, les fines induisent une augmentation de la cohésion du tas par la nucléation des ponts capillaires entre les grains. Ainsi, dans le régime des fortes concentrations, le tas granulaire se comporte comme un corps solide et la déstabilisation a lieu à l'interface tas-tambour. Nous avons également étudié l'influence de l'humidité relative sur la stabilité et montré que dans le régime de faible concentration de particules fines, la déstabilisation est indépendante de l'humidité. D'autre part dans le régime des hautes teneurs en fines, une humidité relative élevée induit une forte cohésion due à la condensation capillaire entre les grains et le tambour ce qui entraîne une augmentation de l'angle maximum de stabilité.

Lorsqu’il est soumis à une contrainte homogène, un matériau granulaire se déforme d’abord de manière homogène puis, passé un certain seuil, de manière hétérogène. Cependant, les mécanismes de plasticité sous-jacents à l’origine de ce comportement ne pas complètement compris. L’objectif de cette thèse est d’étudier l’organisation de la plasticité afin de comprendre la transition d’une déformation homogène vers une déformation hétérogène. Les expériences sont menées sur un matériau amorphe modèle constitué de billes de verre d’un diamètre moyen de l’ordre de la centaine de micromètres. Le matériau granulaire est soumis à un test biaxial en déformation plane et l’organisation de la plasticité est observée par spectroscopie de diffusion multiple de la lumière (DWS). Au cours d’une expérience de compression uni-axial, le champ de plasticité peut se décomposer en deux parties indépendantes et évoluant à des échelles de déformation différentes. Les orientations de ces deux structures sont déterminées quantitativement. On observe alors une partie lentement variable et moyennée dans le temps qui s’oriente selon un angle prédit par le modèle de Mohr-Coulomb ; ainsi qu’une partie fluctuante qui peut être décrite à partir de la théorie Eshelby décrivant la redistribution de la contrainte après un réarrangement plastic local dans un matériau amorphe. D’autre part, pour la première fois, des évènements plastiques ont pu être observés et caractérisés à l’intérieur des bandes de cisaillement. Une analogie qualitative avec la sismicité terrestre en est déduite
When a homogeneous stress is applied on a granular material, it first, shows a homogeneous strain and then, above a certain threshold, a heterogeneous strain. However, underlying plasticity mechanisms which trigger this behavior are not known very well. The aim of this thesis is to study how the plasticity organizes in order to understand the transition between a homogeneous strain towards a heterogeneous one. Experiments are carried out on a model amorphous medium consisting of an assembly of glass beads with an average diameter about one hundred microns. A biaxial compressive test in plan strain conditions is performed on the granular material and the organization of the plasticity is observed using the Diffusing Wave Spectroscopy (DWS) technique. During a unixial compression experiment, the plastic field can be decomposed in two components operating on two decoupled strain increment scales. The orientations of these two structures are determined quantitatively. As a result, we observe a slowly varying and coarse-grained part which concentrates along a macroscopic direction corresponding to the Mohr-Coulomb angle; and a fluctuating part that may be related to an Eshelby-like stress redistribution after a plastic rearrangement in an amorphous material. Otherwise, for the first time, we observe and characterize plastic events within shear bands. A qualitative analogy with earth seismicity is deduced

In dense cities, the interactions between all structures, from tall skyscrapers to complex underground tunnel systems, need to be carefully analysed as soon as a new project is considered. This is necessary because of the stress changes in the soil induced by each new construction. Demolishing a building could cause heave at the base of the excavation, deflections in supporting structures and settlements of the surroundings. The behaviour can be modelled in order to predict how large the deformations will be. This thesis investigates the effectiveness of such models. This is done through the application of a parameter sensitivity analysis on models created in Plaxis. The purpose of the analysis is to identify which factors cause discrepancies between the models and the actual displacements monitored on site. The project being examined is located in central London. The analysis focuses on the displacements of existing tunnels below the site caused by the demolition of two buildings. An analysis was carried out to investigate the significance of different parameters, of different material models and methods of analysis, of 3D effects and of inaccurate groundwater data. Ground investigations, laboratory tests and published data were the main sources used to collect reliable initial input parameters for the material models. A model was created in Plaxis 2D using the Mohr-Coulomb and the Hardening Soil with small-strain stiffness material models, using two types of undrained analysis. A model using the Mohr-Coulomb material model was created in Plaxis 3D as well. A sensitivity analysis was then carried out on the 2D models to identify which input parameters were most significant to the tunnel displacements. The results were compared to monitoring data and a back-analysis was carried out to produce more accurate results. The initial and adjusted input parameters were also tested on the 3D model. Finally, the groundwater level was altered. The results indicate that soil stiffness and effective cohesion are the most significant. Small-strain stiffness is shown to be especially important when analysing small tunnel deformation. The 3D model generally yielded more accurate results than the 2D model, while the groundwater level did not appear to affect the deformations.
I tätbebyggda städer bör samspelet mellan olika konstruktioner, från skyskrapor till tunnelsystem, analyseras noga så fort ett nytt projekt ska påbörjas. Detta är kritiskt på grund av den förändrade spänningsfördelning som uppstår i marken vid varje ny byggnation. Marken häver sig, stödmurar deformeras och den omkringliggande marken sätter sig när en byggnad rivs. Denna process kan modelleras för att uppskatta hur stora deformationerna kommer att bli. Det här examensarbetet utvärderar hur effektiv en sådan modell är. En känslighetsanalys utfördes på modeller skapade i Plaxis. Syftet med denna analys är att undersöka vilka faktorer som orsakar skillnader mellan modellerna och mätdata. Projektet ligger i centrala London och analysen fokuserar på tunneldeformationer orsakade av att två byggnader rivs. Tunnlarna befinner sig i ett lager av Londonlera under byggarbetsplatsen. En analys utfördes för att undersöka huruvida olika parameterar, olika materialmodeller och analysmetoder, 3D effekter och grundvattennivån påverkar tunnelförflyttningarna. Markundersökningar, labbtester och publicerad data användes som grund för att bestämma indatavärden. En 2D modell skapades i Plaxis genom att använda materialmodellerna Mohr-Coulomb och ”Hardening Soil with small-strain stiffness”. En Mohr-Coulomb modell skapades dessutom i Plaxis 3D. En känslighetsanalys utfördes sedan på 2D modellen för att identifiera vilka parametrar som påverkade tunnelförflyttningarna mest. Resultaten jämfördes med mätdata och viktiga parameterar ändrades för att ge bättre resultat. Inverkan av att ändra dessa värden undersöktes även i 3D modellen. Slutligen undersöktes påverkan av en förhöjd grundvattennivå. Resultaten antyder att jordens styvhet och den effektiva kohesionen har störst inverkan på resultaten. Styvheten vid små töjningar visar sig vara särskilt viktigt eftersom deformationerna år små. 3D modellen gav generellt sätt mer korrekta resultat än modellen i 2D. En högre grundvattennivå påverkade inte resultaten nämnvärt.

A nonlinear Mohr-Coulomb constitutive model with a strain dependent yield surface and non-associated flow was employed to study the plastic soil properties which affect the rate of surface fault rupture propagation in reverse events. These numerical simulations show a trend for soils with higher stiffness to have a higher rate of rupture propagation. Additionally the study shows the effects of strain softening and hardening on the rate of rupture propagation. Soils which strain harden exhibiting ductile behavior typically require more basal offset to rupture to the surface than soils which strain soften exhibiting brittle behavior. These results agree with our previous fault box studies, which showed that soils with higher near surface shear wave velocity were more likely to propagate rupture to the surface for a given reverse event. The numerical modeling allowed for a more comprehensive evaluation of material types and fault angles than the fault box, and provided confidence in these findings.

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CAPES
A presente dissertação analisa, em termos do comportamento carga-recalque, um banco de dados organizado por Wilson Cartaxo Soares (2011), de fundações em grupo de estacas e radier estaqueados, executados em solo arenoso de várias camadas da área litorânea de João Pessoa/PB, com 07 provas de carga, estáticas, em estacas do tipo Hollow Auger, construídas em escala real, com 300 mm de diâmetro e 4,5 m de comprimento. Os dados foram retroanalisados com o Método dos Elementos Finitos (MEF 3D), utilizando o programa CESAR-LCPC v4 (Cleo 3D versão 1.07). Na modelagem do comportamento tensão-deformação do solo foi utilizado o modelo constitutivo de Mohr-Coulomb. Os parâmetros geotécnicos iniciais utilizados em cada um desses modelos foram obtidos através de correlações a partir de valores de NSPT obtidos por SOARES (2011). Os resultados dessas simulações numéricas foram comparados com os resultados experimentais, medidos nas provas de carga. Definiu-se os parâmetros geotécnicos do solo a partir da retroanálise por meio da modelagem numérica para serem empregados em futuras simulações no maciço. Análises paramétricas são executadas com o intuito de obter um maior conhecimento do comportamento da fundação em radier estaqueado, usando o modelo elásticoplástico de Mohr-Coulomb. Isso ocorre mediante algumas alterações de sua configuração que inclui a espessura do radier, número, diâmetro, espaçamento e comprimento das estacas embutido no solo. Carga vertical central está sendo considerada para a análise paramétrica. O recalque máximo, recalque diferencial e distorção angular do radier diminuem, com o aumento da espessura do radier, do número, comprimento e diâmetro das estacas.

I samband med Förbifart Stockholm och Tvärförbindelse Södertörn förväntas en flaskhals skapas vid Vårbybron i södra Stockholm. För att förhindra överbelastning planeras en nybyggnation där pålgrundläggning med grävpålar föreslås. Markförhållanden är ovanliga i Stockholm, med över 100 meter ned till berg. Komplexa omständigheter i området gör det nödvändigt att analysera markrörelser som verkar på grundläggningen. Syftet med studien är att undersöka horisontella- och vertikala sättningar vid ett brolandfäste. Syftet är vidare att analysera vilken typ av numerisk konstitutiv modell som är lämplig med hänsyn till studiens specifika fall och område; Mohr-Coulomb (MC), Hardening Soil (HS) och Hardening Soil med small-strain stiffness (HSS). Slutligen ska jordparametrarnas väsentlighet avgöras i en parameterstudie. Sonderingsdata tillämpas i studien för att skapa en jordlagermodell i AutoCAD Civil 3D 2019 Metric och vidare simulering av sättningar i Plaxis 2D. Vid modellering av sättningar i förekommande geologi rekommenderas att en avancerad modell används, med fördel HSS. Däremot kräver mer avancerade modeller noggranna indata för tillförlitligt resultat och ytterligare tester för styvhetsparametrar bör utföras. I detta projekt kan dyrare tester tänkas sänka slutgiltig budget, eftersom underskattning av moduler i djupa och fast lagrade jordar baserade på konservativt valda moduler ger upphov till en dyrare konstruktion.
In conjunction with the opening of the Stockholm Bypass and Tvärförbindelse Södertörn, a bottleneck is expected at the bridge Vårbybron in southern Stockholm. To prevent traffic congestion, a new construction is planned where pile foundation consisting of bored piles is proposed. The ground conditions are unusual and not typical for Stockholm involving over 100 meters distance to rock. Complex circumstances in the area makes it complicated as well as necessary to analyze ground movements. The aim of the study is to investigate horizontal- and vertical settlements at a bridge abutment. The aim is further to analyze which type of numerical constitutive model that is appropriate with respect to the specific case and area; Mohr-Coulomb (MC), Hardening Soil (HS) and Hardening Soil with small-strain stiffness (HSS). Finally, the significance of the soil parameters is to be determined in a parameter analysis. Results from soundings are used to create a geological model in AutoCAD Civil 3D 2019 Metric. Furthermore, simulation of settlements in Plaxis 2D is performed. It is recommended to apply advanced models for this type of geology, advantageously HSS. However, more advanced models require accurate input data to obtain reliable results, and additional tests for stiffness parameters must be performed for accuracy in the results. In this project, more expensive tests can be thought of as lowering the final budget, as underestimation of modules in deep and stiff soils based on conservatively selected modules leads to an unnecessarily expensive construction.

La maintenance, la réparation et le renforcement de murs en maçonnerie par matériaux composites collés nécessitent le développement de méthodes et techniques d'évaluation de l'aptitude au service et de requalification tant pour leur restauration fonctionnelle que pour leur adaptation à de nouvelles contraintes (évolution du zonage sismique par exemple). Le présent travail de thèse a pour objectif de proposer un outil d'évaluation par calcul de l'état limite ultime de murs en maçonnerie, renforcés par composites collés, chargés dans leur plan.Les travaux effectués concernent la modélisation par homogénéisation de murs en maçonnerie et une campagne expérimentale de caractérisation du transfert de charge entre un renfort en tissu de fibres de carbone et un support en blocs creux de béton par le biais d'un joint de colle. Pour modéliser la résistance des murs maçonnés, nous proposons une loi élastique parfaitement plastique pour le comportement dans le plan d'une maçonnerie constituée de blocs liés par des joints de mortier. Le convexe de plasticité est obtenu par une technique d'homogénéisation périodique qui prend en compte la nature tridimensionnelle de la cellule de base. On obtient alors un convexe limité par plusieurs surfaces de charge. Un algorithme numérique original est ensuite proposé et programmé dans le logiciel aux Eléments Finis ABAQUS. Des simulations numériques utilisant le module développé sont présentées

Railways are one of the largest transportation networks in the world that play an important role in the mass transportation of both the passengers and freight. The speed of trains and as well as the axial load carrying capacity have been increasing significantly during the past few decades to keep in pace with the population and economy growth and to compete with other modes of transportation such as the road, air and water transportation system. Billions of dollars are spent annually for maintenance of rail tracks in the world. The efficient and optimum use of these funds is a challenging task that demands innovative and cutting edge technologies in railway engineering. The railway subgrade is an important part of railway foundation and should be capable of providing a suitable base supporting the ballast and subballast to accommodate the stresses due to traffic loads without failure or excessive deformation. The progressive shear failure is a well-known and age old challenging problem for railways over the world for centuries. The subgrade of railway track which typically constitutes of fine-grained material tends to fail through the accumulation of soil movements up- and sideward developing a path for the least resistance along which progressive shear failure occurs under repeated train-induced loads and due to the effects of climate factors. To-date, limited number of studies have addressed failure mechanism associated with the progressive shear failure, especially using the mechanics of unsaturated soils. In this thesis, a novel and first of its kind, Visual Basic program developed in AutoCAD environment based on Mohr-Coulomb failure criteria and unsaturated soil mechanics theory. This program is capable of taking account of the influence of matric suction and simulate progressive shear failure in the subgrade under moving train. Simulation results suggest several parameters that include stress distribution, matric suction, cohesion, coefficient of lateral earth pressure at rest, and coefficient of residual friction as well as the angle of internal friction have a significant effect on the progressive shear failure and the shape of failure planes in the subgrade. The progressive shear failure in subgrade can be reduced by increasing matric suction, cohesion, coefficient of lateral earth pressure at rest, and coefficient of residual friction as well as the angle of internal friction, and optimizing combination of these parameters. The simulation results suggest the progressive shear failure can be well simulated with the Mohr-Coulomb failure criteria. Several suggestions are made for railway subgrade construction and maintenance based on the results of this study.

Esta dissertação apresenta em primeira etapa o trabalho desenvolvido para averiguar a adequação dos modelos reológicos de Mohr-Coulomb e de Endurecimento de solo, para representar as deformações e distorções que ocorrem no sistema soloestrutura, quando do processo de escavação de valas escoradas. Além disto, em uma segunda etapa fazem-se estimativas de previsão de danos causados em edificações, em decorrência das escavações de uma vala escorada da linha 1 do Metropolitano de São Paulo (Metrô S.P.). A primeira e a segunda etapa foram feitas através de 810 simulações numéricas, em elementos finitos utilizando-se o software PLAXIS, associadas a retroanálise por processo direto do módulo de deformabilidade a 50% da tensão de ruptura dos solos utilizando-se para isto o processo direto. Apresenta-se também uma síntese da formação e dos tipos de solos que constituem a bacia sedimentar de São Paulo, onde se localiza a seção experimental nº1 objeto de estudo desta dissertação. Faz-se uma breve revisão bibliográfica a respeito das técnicas de retroanálise. Apresentam-se critérios para escolha de intervalos de parâmetros geotécnicos que representem o sistema solo-estrutura no processo de escavação. Foram feitas análises paramétricas para determinar os parâmetros geotécnicos que mais influenciam o sistema solo-estrutura. Comparam-se os modelos constitutivos de Mohr-Coulomb e de endurecimento na previsão das deformações. Por fim, faz-se a previsão do nível de danos causados pelas escavações da vala, a um edifício hipotético
This dissertation presents, in a first part, the work done to verify how appropriate are the Mohr-Coulomb and hardening soil constitutive models to represent the strains and the distortions associated with escavations of braced wall process. In the second part, estimates are made of the damages in constructions due to the braced excavations of line one of Sao Paulo Subway (Metrô S.P.). In the two phases, 810 numeric simulations were made, in finite elements using the software PLAXIS, associated the back analysis for direct process. It is presented a synthesis of the formation and the types of soils that constitute the basin of the sediments of the city of São Paulo, where is located the section experimental nº1, object of study of this dissertation. It is presented an short bibliographical revision regarding the back analysis techniques. Criteria for choice of intervals of parameters geotechnical that represent the system soil-structure in the excavation process are presented. Parametric analyses are made to determine which the parameters have larger influence in the behavior of the system soil-structure. The behavior of the soil-structure system is simulated using the Mohr-Coulomb and hardening soil constitutive models. The Mohr-Coulomb and hardening soil constitutive models are compared in the forecast of the deformations. Finally, it is made the forecast of the level of damages to a hypothetical building caused by the braced excavations

Structures like transmission towers, tele-communication masts, dry-docks, tall chimneys, tunnels and burried pipelines under water etc are subjected to considerable uplift forces. The net effect of external loading on the foundations of these structures results in forces that try to pull the foundations out of the ground. Anchors are usually provided to resist such uplift forces. Earlier theoretical research of anchor behavior has focused on elastic response and ultimate pullout capacity. Many investigators have proposed techniques for determining the collapse load of anchors. Essentially the approaches involve the use of limit equilibrium concepts, with some assumptions regarding the shape of the failure surface and/or the influence of the soil above the anchor. The possible effect of dilatency and initial stress state are not considered in these methods. A number of investigators have used the results of small size model anchors to understand the behavior and extrapolated the results for predicting the behavior of large sized anchors. This has lead to unsatisfactory results. It has been clearly shown by Dickin (1989) that the failure displacements and load displacement curve patterns are very different for small and large sized anchors, i.e. they are not just proportional to the size of the anchor. Critical pullout load and the load displacement behavior are required for the complete analysis of anchor foundations. Though, many theories have been proposed to predict the uplift capacity within the limits of accuracy required at engineering level, at present no simple rational method is available for computing deformations. In the present investigation attempts have been made to analyze the load deformation behavior of large size strip anchors in sands, clays and layered soils using two-dimensional explicit finite difference program FLAG (Fast Lagrangian Analysis of Continua), well suited for geomaterials, by assuming soil to be a Mohr-Coulomb material in the case of sands and modified Cam-clay material in the case of clays. It is now well understood that the shearing resistance of a granular soil mass is derived from two factors frictional resistance and the dilatency of the soil. So the peak friction angle can be divided in to two components critical friction angle Фcv and dilation angle Ψ. Critical friction angle is the true friction angle as a result of frictional resistance at interparticle level when the soil is shearing at constant volume. If Фcv for a given soil remains constant, the value of Ψ has to increase with the increase in initial density of soil packing. The dilatency of a soil mass gradually decreases with continued shearing from its initial high value to zero after very large shear strains, when the soil finally reaches a constant, steady volume at critical states. Correspondingly the observed friction angle Ф reduces from its peak value to Фcv at a very large strain. In earlier days, clays used to be characterized by the strength parameters c and Ф. often, under undrained conditions, Ф would be even considered zero. But in the recent developments, it is understood that all the strength of clays is frictional. There is nothing like cohesion. The part of shear strength, which appears to be independent of normal stress, is shown to be the effect of over-consolidation and the resulting dilation. Thus although Cam-clay model uses zero cohesion for all clays, it reflects this component of strength through over-consolidation and in a more realistic way. Hence, it is appropriate to consider the pre-consolidation pressure as parameter in the analysis. More specifically, the various aspects covered in this investigation are as follows. Chapter 1 provides the general introduction. In chapter 2, the existing literature for the analysis of anchors for both experimental and analytical investigations on the pullout capacity of anchors in homogeneous and layered soils and the load deformation behavior of anchors under pullout are briefly reviewed. Chapter 3 deals with the features and the implementation of the two-dimensional explicit finite difference program, Fast Lagrangian Analysis of Continua (FLAC) and the constitutive modeling of soils. It discusses the background and implementation of Strain softening / hardening model. This model is based on the Mohr- Coulomb model with non-associated shear and associated tension flow rules. In this model the cohesion, friction, dilation and tensile strength may harden or soften after the onset of the plastic yield. Further the critical state concepts and implementation of the modified Cam-clay model have been discussed. Cam-clay model originally developed for clays reflects the hydrostatic pressure or density dependent hardening material response. Chapter 4 focuses on the analysis of load deformation behavior of large size anchors in granular soils. Two-dimensional explicit finite difference program (FLAC) is used for the simulations and the soil is modeled as a Mohr-Coulomb strain softening/hardening material In this chapter a series of simulations have been carried out on large size anchor plates, with parametric variation. By analyzing these results, a generalized load deformation relationship for different sizes of anchors and different types of soil have been proposed. The results are presented in the form of influence/design charts which can be used in hand calculations to obtain an estimate of anchor capacity and deformation for a wide range of soil types and size of anchors. Chapter 5 deals with the analysis of the drained and undrained behavior of large size horizontal strip anchors in clays using modified Cam-clay model. Earlier investigators have studied the undrained behavior of anchor plates in clays, but no studies are reported in literature for the drained behavior of anchors in clays. Further it is not clear whether, drained or undrained condition will be critical for an anchor. In this chapter the drained and undrained behavior of large size anchor plates in both normally consolidated and over-consolidated states have been made. It has been found that the undrained pullout capacity of an anchor in a soil of normally consolidated state will always be more than the drained capacity. This is contrast to the usual understanding that undrained behavior is more critical than the drained behavior. In Chapter 6 an attempt has been made to analyze the behavior of large size anchors in two layered sands and in conditions where backfill material has a higher or lower strength than the native soil, for different shape of excavations. Soil is assumed to be a Mohr-coulomb strain softening/hardening material. In Chapter 7 the entire investigation covered in earlier chapters has been synthesized and some specific conclusions have been highlighted.

De nombreuses failles à faible pendage (pendage inférieur à 30°) ont été décrites en domaine continental extensif depuis leur mise en évidence dans la province des Basin and Range (USA). Bien que les observations de terrain suggèrent, dans plusieurs régions, que le jeu d'une faille se produit à faible pendage dans la croûte cassante (Apennins, Italie ; Basin and Range, USA; Alpes orientales), l'activité sismique liée à ces failles est presque inexistante et est en accord avec les angles de blocage des failles prédits par la mécanique andersonienne associée à la loi de Byerlee. L'étude des Metamorphic Core Complex et de l'exhumation de détachements dans les Cyclades permet d'obtenir un modèle figé de la croûte continentale en extension. Le Metamorphic Core Complex qui affleure sur l'île de Mykonos se caractérise par une intrusion granitique (laccolite) dans le dôme migmatitique, recoupé à son sommet par un système de détachements composé de deux branches. La branche inférieure ductile du détachement met en contact la Nappe Supérieure Cycladique, constituée de métabasites, et le laccolite. La branche supérieure cataclastique du détachement juxtapose une unité sédimentaire molassique sur la Nappe Supérieure Cycladique ou directement sur le laccolite. Le détachement cataclastique conditionne la sédimentation syn-tectonique dans les bassins. Associée au réseau de veines contemporain du jeu du détachement, la déformation dans l'unité sédimentaire montre que le détachement cataclastique de Mykonos a été actif à faible pendage et à faible profondeur, au moins au cours des derniers incréments de déformation. La synthèse des données collectées sur les îles d'Andros, de Tinos et de Mykonos montre que les détachements nord-cyladiques peuvent être considérés à différents stades d'évolution comme une seule et unique structure d'échelle crustale (le Système de Détachement Nord-Cycladique) pouvant accommoder l'extension régionale et l'exhumation des roches de l'unité inférieure. L'étude de l'Anisotropie de la Susceptibilité Magnétique (ASM) dans le laccolite, couplée aux observations de terrain, a permis de mettre en évidence une rotation de l'unité inférieure du détachement de Mykonos autour d'un axe vertical, compatible avec les données paléomagnétiques disponibles dans la littérature. Afin de réconcilier observations de terrain et mécanique des roches, nous proposons un nouveau modèle de réactivation de failles en considérant la faille comme une fine couche déformable plastiquement, contrairement au modèle classique suggérant une dislocation avec des propriétés frictionnelles. Notre modèle permet alors d'inclure les variations volumiques de la zone de faille au cours du cisaillement, et notamment, de prendre en compte des coefficients de dilatation faibles voir négatifs (faille compactante), souvent observés en laboratoire ou sur le terrain. Notre modèle permet, en particulier, de déterminer les quantités de déformation plastique que peuvent accommoder ces failles au cours du cisaillement avant leur blocage. Les angles de blocage obtenus dans notre modèle varient peu par rapport au modèle classique de réactivation de faille, qui apparaît comme un cas particulier de notre modèle. La réactivation d'une faille à faible pendage en extension est alors possible complètement ou partiellement et peut être associée à la formation de veines et de failles normales dans l'encaissant. La réactivation est alors favorisée lorsqu'il s'agit d'une faille compactante et se produit en régime durcissant, suggérant ainsi un comportement asismique de la faille.

Un des modes de rupture redouté des barrages est le cisaillement autour des discontinuités rocheuses du massif de fondation ou de l’interface de fondation roc-béton. Afin d’évaluer la résistance au cisaillement de ces discontinuités, les guides professionnels préconisent la réalisation d’essais de cisaillement et l’utilisation du critère de rupture de Mohr-Coulomb. Une telle démarche permet alors d’obtenir une valeur de cohésion apparente que les guides professionnels suggèrent cependant de négliger dans les calculs de stabilité, privant alors l’ouvrage d’un paramètre de résistance. Issu d’une collaboration entre l’Université de Sherbrooke, INRAE et Hydro-Québec, ce projet à pour objectif d’améliorer l’état des connaissances sur le comportement au cisaillement des discontinuités rocheuses en : i) déterminant expérimentalement les facteurs d’influence et ii) développant un modèle mécanique de comportement au cisaillement des discontinuités rocheuses prenant en compte l’effet de la rugosité.110 essais de cisaillement direct ont été menés afin d’évaluer les effets sur le cisaillement des discontinuités rocheuses de : la rugosité, l’endommagement, l’emboîtement, la contrainte normale, l’effet des propriétés mécaniques du matériau ou du type de contact. Les résultats montrent que la rugosité et l’emboîtement semblent être les deux facteurs d’influence les plus importants. Par la suite des lois empiriques reliant le comportement mécanique au cisaillement d’une discontinuité rocheuse à sa rugosité ont été développées. Ce modèle a ensuite été extrapolé à l’échelle d’un ouvrage et de son massif de fondation à l’aide d’une modélisation numérique aux éléments discrets
Dams are subject to scheduled inspections to assess their stability. Indeed, shearing phenomena can occur around rock-rock joints inside the rock foundation mass or at the rock-concrete foundation contact. Professional guidelines recommend to perform direct experimental shear tests and to use the Mohr-Coulomb failure criterion to assess the shear strength of these discontinuities. Such a process allows getting an apparent cohesion value from the experimental data. However, for safety reasons, professional standards suggest, that the apparent cohesion should be taken as null. This practice is conservative and motivated by the lack of knowledge about the rock joint shear behavior and failure mechanisms. This PhD project, in collaboration with Université de Sherbrooke, INRAE and Hydro-Québec aims to : i) evaluate through an extensive experimental protocol the factors influencing the rock joint shear behavior and ii) develop a mechanical numerical model that takes into account the effect of roughness on the joints shear behavior. 110 direct shear tests were performed to assess the effect on the shear behavior of roughness, damaging, interlocking, normal load, material mechanical properties or contact. In this study, it appears that the roughness and the interlocking are the two main factors of influence. Empirical relationships between the joint shear mechanical behavior and its roughness were developed. Used with a Mohr-Coulomb mechanical model, it appeared that these relations were suitable to assess the joint shear mechanical behavior. Then, the model was exported to a case study: a dam and its rock mass foundation were modeled with discrete elements methods

Cette thèse traite le problème de la stabilité des ouvrages souterrains creusés en terrain meuble à faible profondeur. La stabilité de ce type d'ouvrages est normalement étudiée en utilisant des méthodes justifiées par l'expérience mais dont les hypothèses ne sont pas toutes cohérentes au plan mécanique. L'application systématique du calcul à la rupture et de l'analyse limite fournit des encadrements pour les chargements conduisant à la rupture d'un système donné. Le mémoire décrit la mise en oeuvre numérique d'une forme régularisée de l'approche cinématique de l'analyse limite pour l'étude de la stabilité des ouvrages souterrains. La résistance des sols est modélisée par des critères de Tresca, de Tresca tronqué en traction et de Mohr-Coulomb en conditions bidimensionnelles, et par des critères de Tresca et de Mohr-Coulomb pour les calculs tridimensionnels. Les calculs reproduisent les modes de rupture observés dans les travaux souterrains et sur modèles. Les charges limites calculées sont voisines des valeurs expérimentales.

Ce mémoire est consacré à l'interaction sol/structure avec l'accent mis sur les effets locaux à l'interface entre le sol et la structure et sur le problème d'interface avec le logiciel éléments finis. Le travail reprend le code de calcul Gefdyn et l'enrichit de quelques modules. Des éléments de structure, poutres et plaques épaisses, ont été développés et intégrés dans Gefdyn. Ces éléments utilisent une formulation nouvelle et sont spécialement adaptés aux besoins de l'ingénieur. Des tests en statique et dynamique montrent leur précision numérique. Pour l'interaction sol/structure des approches différentes, nécessitant plus ou moins de développement, sont proposées. Dans l'approche implantée dans Gefdyn, l'interaction entre structures composées de poutres et plaques et le sol est traité au niveau local de l'interface, prenant en compte des effets de frottement et de décollement. La performance des développements a été vérifiée dans des applications numériques, par comparaison soit aux solutions analytiques, soit aux calculs d'un mur de soutènement par l'Eurocode 8. Afin d'améliorer la communication entre l'utilisateur et le code Gefdyn une interface graphique a été développée qui permet de définir rapidement les paramètres de calcul. Cet interface gère les erreurs d'utilisation et met à disposition des outils de préparation des données et d'évaluation des résultats

Foundations on unbearable and yielding subsoil require such actions as to achieve both desired bearing capacity and limited settlement. Issue is presented at foundation the circular tank in saturated fine-grained soils, circular tank in Klobouky u Brna in particular. Comparison analysis is performed for alternative methods (shallow foundation, vibro stone columns, deep soil mixing, pile foundation). Differential and total settlement, time-depending analysis and baseplate stress state (bending moment, shear force) are assessed for each alternative. Pile foundation provides the best results regarding total and differential settlement, but baseplate is also under high puncture shear stress. Vibro stone columns seem suitable due to time-depending analysis of settlement, on the other hand settlement reductions are not just as good. Deep soil mixing provides satisfactory alternative for both pile foundation and vibro stone columns. Under such circumstances shallow foundation is not suitable.

Dans le cadre de cette thèse, on étudie le comportement mécanique de panneaux sandwich métalliques avec une âme à architecture gaufrée. Ces structures fournissent une alternative économiquement avantageuse aux nids d'abeilles hexagonaux car leur production de masse est réalisable par emboutissage progressif de tôles planes. Les différentes géométries possibles de la structure gaufrée sont limitées par des risques de rupture lors de la fabrication. Ainsi, l'étude de l'optimisation de la capacité portante des panneaux sandwich à âme gaufrée est contrainte par la rupture ductile du matériau de base. Le choix d'un modèle de rupture ductile approprié pour prédire le comportement à rupture du matériau de base joue donc un rôle central dans cette recherche. La première partie de cette thèse est entièrement consacrée aux évaluations expérimentale et numérique des capacités prédictives de deux versions du modèle de rupture de Mohr-Coulomb; l'une étant la version originale, l'autre intégrant un indicateur d'endommagement. En limitant notre attention aux contraintes planes induites par la traction uni-axiale et équi-biaxiale dans la tôle d'acier doux, on réalise des essais de rupture sur des éprouvettes entaillées et des essais de poinçonnement à l'aide d'un poinçon circulaire afin d'identifier les paramètres du modèle de rupture. Un test de Hasek et un essai d'emboutissage d'une structure gaufrée sont utilisés afin d'évaluer les capacités prédictives des deux modèles de rupture. Le modèle avec indicateur d'endommagement utilisant une fonction poids dépendant de l'état de contrainte prédit l'apparition de la rupture lors de l'essai d'emboutissage avec la meilleure précision. Dans la deuxième partie de cette thèse, pour l'étude de la fabrication de la structure gaufrée, on utilise le modèle de Mohr-Coulomb avec indicateur d'endommagement pour déterminer la profondeur d'emboutissage maximale en fonction de la géométrie de l'outil de mise en forme. Le comportement en grandes déformations est décrit par un modèle de plasticité quadratique avec écrouissage isotrope et une loi d'écoulement non associée. Des cartes de sensibilité aux principaux paramètres sont développées : rigidité au cisaillement de la partie cœur, résistance au cisaillement, résistance au délaminage et au flambement élastique des peaux en fonction de la géométrie de la structure cœur. Une méthode d'optimisation des performances des panneaux sandwich à âme gaufrée est développée pour les panneaux rectangulaires sur appuis simples soumis à un chargement latéral uniforme. Les résultats des expériences de flexion quatre points montrent que les panneaux sandwichs optimisés offrent des plus grandes résistance et rigidité (pour un moindre poids) que des panneaux avec une partie cœur en mousse de polyéthylène de haute densité. La dernière partie de cette thèse se concentre sur l'étude de la résistance à la perforation des panneaux sandwich métalliques à âme gaufrée. L'effet des paramètres décrivant la géométrie de la structure cœur et le l'influence du matériau constituant les peaux est étudié. On s'intéresse en particulier à un acier doux, un acier " dual-phase " DP780 et un acier martensitique à très haute résistance. Un nouveau modèle utilisant un indicateur d'endommagement avec une fonction poids basée sur le critère de Hosford est utilisé pour modéliser la réponse à la rupture de ces matériaux. Une étude paramétrique de la résistance à la perforation des panneaux sandwich pour différentes tailles de cellule élémentaire de la partie cœur est réalisée à l'aide d'un modèle éléments finis. La résistance à la perforation diminue avec la taille de la cellule et avec la hauteur de la partie cœur. Ainsi, le panneau sandwich le plus mince offre une résistance supérieure à la perforation. Des essais sont réalisés qui confirment ce résultat important.

The thesis deals with the back analysis of the instrumentated embankment on the subsoil, improved by prefabricated vertical drains. The first part is devoted to the theory of consolidation calculation. Furthermore, the author deals with a parametric study of the analytical calculation of prefabricated drains and the comparsion of the analytical and numerical solution. The last and the largest part of the work is a back analysis of the embankment which was built as a part of the subsoil improvement near the Suez Canal in Egypt by Keller GmbH.

Dredging activities at Ports and Harbors are inevitable for the safe navigation of ships and vessels. Dredged material may range from very fine and contaminated sediments to sand and gravels. While, granular dredged material can be directly utilized in civil engineering applications, fine sediments may require further treatment before use. In geotechnical context, fine sediments are characterized by low shear strength and high compressibility. However, these unfavorable properties do not rule out the suitability of these fine dredged sediments for use in geotechnical construction, such as, road embankment, building foundation or as structural backfill in land reclamation. Mass stabilization solidification provides a comprehensive technology for amending fine sediments at high initial water content, resulting into construction materials of improved strength and reduced compressibility. The ultimate in-situ soil behavior types, stiffness and strength properties of stabilized mass depend on various factors such as binders, mixing equipment, curing temperature, in-situ boundary conditions and mostly important the applied preloading weight during the period of curing. However, despite improved mechanical properties for geotechnical applications, the performance of treated materials becomes susceptible to repeated freeze-thaw cycles. Understanding geotechnical design process, which includes evaluation of material properties, loading condition and selection of appropriate constitutive model, is an important task for settlement and stability analysis of structures founded on stabilized mass. The selection of suitable material model is vital for successful finite element analysis. Nevertheless, among all existing constitutive soil models, none of them can capture all aspects of soil behavior. Therefore, the meaningful and quantifiable predictions of field behaviors are possible only if, undisturbed samples or in-situ tests are used for determination of mechanical properties, and the predictive capacity of selected constitutive model comes from the comparison with field observations In the present research work, utilization of cone penetration test (CPT) data for evaluating the mechanical properties of stabilized dredged sediments for geotechnical design and analysis was presented. A large-scale field test at the Port of Gävle was utilized as a case study, to verify the simulated settlement of preloaded stabilized dredged sediments. The stabilized mass–soil classification behavior type was studied utilizing CPT classification charts. Computation of the primary consolidation settlement due to preloading weight were carried out in PLAXIS 2D geotechnical software and verified against field measurements. A suggestion to protect the stabilized mass against severe weather condition was discussed.
Godkänd; 2013; 20130409 (makusa); Tillkännagivande licentiatseminarium 2013-04-25 Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Gregory Paul Makusa Ämne: Geoteknik/Soil Mechanics and Foundation Engineering Uppsats: Mechanical Properties of Stabilized Dredged Sediments for Sustainable Geotechnical Structures Examinator: Professor Sven Knutsson, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Civ.ing. Forskningsdirektör Göran Holm, Statens Geotekniska Institut, Linköping Tid: Torsdag den 16 maj 2013 kl 10.00 Plats: F1031, Luleå tekniska universitet

碩士
國立臺灣科技大學
營建工程技術學系
82
In order to understand the stress behavior of vertically loaded piles in sand, the study used a finite difference program-FLAC as a tool to write the analysis program. The Q-S curve, Q-D curve t-z curve, q-z curve as well as f-D curve were studied and were compar edwith the test results. By using the Mohr- Coulomb model for soil elements, it is found that the square element is the best for these cases, and the assymetric model is bettr than the plain model. The boundary effect distances are then four times of pile diameter from the bottom of the pile tip and sixteen times of pile diameter form the side of the shaft. The Poesson''s fatio of pile shaft has little influence on the stress behavior of piles. Once using FLAC and following the rules describde above, one can prdeict the stress behavior of piles with any size of diameter and length in sand when the settlement of the pile top is less than ten percent of the pile diameter. However, the estimation fo pile top settlement will be a little bit conservative when it is larger than ten percent of the pile diameter.

Dissertação de Mestrado Integrado em Engenharia Civil apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra.
As fundações superficiais distribuem cargas estruturais sobre grandes áreas de solo ou rocha perto da superfície, diminuindo a intensidade das cargas aplicadas para níveis admissíveis para solos de fundação. O projeto de uma fundação superficial deve compreender normas básicas de segurança e utilidade funcional. No que diz respeito ao seu dimensionamento, as tensões de contacto não devem exceder a capacidade de carga do solo e é essencial manter o controlo sobre os assentamentos. Para simular o comportamento de uma fundação superficial pode recorrer-se ao ensaio de carga em placa, que tem como objetivo submeter o terreno a solicitações da mesma natureza como forma de previsão. A presente dissertação consiste na análise numérica de ensaios de carga em placa realizados no Laboratório de Geotecnia do DEC-FCTUC recorrendo ao programa de elementos finitos Plaxis. Os modelos numéricos foram concebidos para representar um tanque de altura de 1,5m e área da base de 1,0x1,5m, preenchido com solo arenoso submetido a um carregamento de uma placa circular com 300mm de diâmetro. Com vista a melhorar o comportamento da fundação superficial, estes modelos físicos têm a particularidade de terem sido reforçados através de uma saia estrutural fixada nos bordos da placa. Estudos indicam que, incorporando este novo tipo de reforço na fundação, há redução de assentamentos no solo e aumento da capacidade de carga da mesma. Realizou-se uma análise paramétrica de modo a avaliar a influência do comprimento da saia e da compacidade da areia no comportamento da fundação. Foi também estudada a influência do modelo elástico perfeitamente plástico, Mohr-Coulomb, de um modelo mais complexo nomeadamente o Hardening Soil. e da interface solo/fundação na relação carga/assentamento deste tipo de fundações.
Shallow foundations distribute structural load over large areas of near-surface soil or rock, decreasing the intensity of the applied loads to permissible levels for the foundation soils. The project of a shallow foundation must comprise basic safety functional utility standards. Regarding their design, the stresses can’t exceed the bearing capacity of the soil and, which is essential settlement control. To simulate the behavior of a shallow foundation a plate load test can be used, which has the goal of submitting the terrain to solicitations of the same nature as forecasting measure. The present thesis consists on the numerical modeling of experimental plate load test performed in the Geotechnical Laboratory of DEC-FCTUC, using the finite element program Plaxis. The numerical models were designed to simulate a tank with 1,5 m of height and a floor area of a 1,0x1,5m, filled with sand and submitted to a load of a circular plate with 300mm of diameter. To improve the behavior of a shallow foundation, these models have been reinforced with a structural skirt fixed to the edges. Several studies reported that using this type of reinforcement reduces the soil settlements and increases the bearing capacity of foundation. These simulations allowed the analysis of the influence of the skirt depth and the soil relative density, as well as different soil/foundation interface strength reduction factors using the elastic perfectly plastic model, as named as Mohr-Coulomb model, and a more complex model, the Hardening Soil model.

Dissertação de Mestrado Integrado em Engenharia Civil apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra
A Estação de Metropolitano do Terreiro do Paço representa uma das maiores obras geotécnicas alguma vez levadas a cabo em Portugal. Trata-se de uma escavação escorada de profundidade e extensão bastante consideráveis, construída a céu aberto num maciço terroso com elevada deformabilidade e fracas propriedades resistentes. A sua localização, na proximidade do Rio Tejo e de edificado de inestimável valor patrimonial, aliada às características dos solos interessados, fazem dela um excelente case study, não só pela dificuldade que está associada a realizar escavações nestas condições, mas também pela impreterivelmente necessária minimização da magnitude dos assentamentos induzidos à superfície. Deste modo, a primeira parte da presente dissertação é dedicada a uma detalhada descrição acerca dos principais condicionantes ao projeto e da solução adotada para a obra em estudo. Esta análise é acompanhada de uma extensa análise paramétrica em termos de tensões totais, levada a cabo no programa de elementos finitos PLAXIS, na qual se fazem variar aspetos como o pré-esforço aplicado, a rigidez da cortina de contenção, o seu encastramento no sobstrato e a espessura da laje de jet grouting usada como suporte provisório da escavação, de forma a avaliar a sua preponderância no comportamento da obra. Seguidamente, apresentam-se e comentam-se os resultados da modelação, quer usando o modelo elástico perfeitamente plástico, disponível no referido software como Mohr Coulomb Model, quer usando modelos mais elaborados, nomeadamente o Soft Soil Model e o Hardening Soil Model, a fim de aferir acerca da sua adequabilidade para a modelação da obra em estudo.
The Terreiro do Paço Metropolitan Station, is one of the major geotechnical works ever performed in Portugal. It consists of a cut-and-cover braced excavation, with considerable depth and length, executed in highly deformable grounds and low resistant properties. Its location, very close to Tagus river and to historic buildings, in addition to the difficult geotechnical scenery, turns it into an excellent case study, not only because of the difficulty of excavating in such conditions, but also because minimizing the induced settlements at the surface is one of the main concerns. The main purpose of this work is to perform a detailed analysis to the project of the retaining structure and to its on-site observed behaviour, which is complemented by parametric numerical analysis using the finite element programme PLAXIS, in order to evaluate which are the most important factors to the global performance of the excavation. Secondly, a new series of numerical simulations is carried out, using not only the elastic perfectly plastic model that, in the mentioned software, is named as Mohr Coulomb Model, but also more complex models, as the Soft Soil Model and the Hardening Soil Model. These approaches are important in order to evaluate the suitability of these advanced models for predicting the excavation behaviour

Mechanical properties of marine sediment near Koper and numerical modelling of a deep excavation Engineering geological conditions near the port Koper in southwestern Slovenia forces geotechnical experts and civil engineers to solve problems in foundation various types of objects and purpose of the practice since the fifties of last century, when it began an intensive development of infrastructure of the port. The results of series of geological and geotechnical surveys, monitoring, and long experience with foundation in the local geology shows that it is almost always the 3rd geotechnical category, or foundation of complex structures in difficult geological conditions below the water table. The entire area belongs to Alpine-Dinaric tectonic area. The rock foundation is composed of complexes of flysch sediments Eocene age at which mounted files of recent marine sediments in the area widely submerged river valley fluvial sands and gravels. From the geotechnical point of view it is interesting site, where most buildings were based on a layer of soft marine sediments, where it is through the creation of special methods implemented in the establishment of deep-level endurable layers of gravel and sand of the river Rižana or at the level footingwall flysch. Set of marine sediments near the port Koper,...

Tese de doutoramento em Construção Metálica e Mista, apresentada ao Departamento de Engenharia Civil da Faculdade de Ciências e Tecnologia da Universidade de Coimbra
In the last few years it was registered an increase in the exploitation of renewable energies, namely wind energy, due to the increasing concern about the environmental problems related with the global warming. The forecast of the official entities is to increase the exploitation of the wind energy of around 61% in the European Union territory until 2020, with the implementation of newer structures for wind turbines. The same trend is followed worldwide with an increase of around 47% in the cumulative wind power installations in the same period. The technological development of wind energy converters (WEC) make it possible to increase the power and consequently the rotor diameter of horizontal axis wind turbines (HAWT). The main hypothesis to carry out this improvement is based on the premises of the increase in height of the wind towers to allow the exploitation of stronger and more stable wind shear profiles therefore increasing the power production and the efficiency of the wind turbine. Therefore higher towers and more efficient and cost effective foundations are required for the new generation of wind energy exploitation. The increase in the height of the currently used tubular steel towers is possible given that the main problem that arises with the increase of diameter of the tube can be solved. Indeed, the transportation requirements with a maximum diameter of about 4.5 meters possible in public roads remains a major problem, allied with increase of fatigue loads in the flange connections and increase in the foundations dimensions. The work presented in this thesis has been developed in the scope of two European projects (HISTWIN and HISTWIN2) where the issues related to new type of connections in tubular towers, allowing for modularization and easier transportation, and to the improvement of foundations were studied. The behaviour of the current tubular steel towers is presented based on a monitoring of a full functional steel tubular tower. Stresses, dynamic displacements, vibrations and vibration frequencies are presented and the estimation of a fatigue spectra based on the vertical stresses on the shell was obtained. The feasibility of the production and assembly of a newer geometry for the towers is presented. The new geometry is composed by longitudinal bolted shear connection (modular segments) to allow the transportation and by friction connections to connect the segments together. Both these sets of connections withdraw the need of welding in and promotes the use of bolts allowing for improvements in the fatigue resistance. One requirement of the friction connections is the need of use of bolts that allow the tightening only from the inner side of the tower. Some solutions are available in the market and the behaviour of one of them was analysed in a long term monitoring. The improvement proposed for the foundation system focus on the reinforcement of the shallow foundations using micropiles to improve the overturning resistance, bearing capacity and foundation stiffness. The behaviour of the micropiles to be used in this solution is studied in detail, based on experimental laboratory tests and the subsequent calibration of a 2D numerical model to implement a procedure to allow the estimation of the micropile behaviour under monotonic and cyclic loading. Recommendations on the use of grouting techniques such as IRS and IGU are made in order to increase the grout-to-soil bond strength and the micropile resistance. Finally, based on LCA and LCC analysis, the micropiles have been proven to be an environmentally friendly and economical solution for all sets of case studies under consideration.
Nos últimos anos tem-se verificado um acréscimo na exploração de energias renováveis, nomeadamente na energia eólica, devido ao crescente aumento das preocupações com os problemas ambientais relacionados com o aquecimento global. As entidades oficiais preveem um crescimento da exploração de energias eólicas de cerca de 61% no território da União Europeia até 2020 com implementação de novas estruturas de suporte para torres eólicas. A mesma tendência é observada um pouco por todo o mundo com um acréscimo de cerca de 47% no acumulado de instalações de produção de energia eólica para o mesmo período. O desenvolvimento tecnológico dos geradores de energia eólica tornou possível o aumento da potência e consequentemente do diâmetro do rotor nas turbinas eólicas de eixo horizontal. A principal alternativa para levar a cabo este melhoramento é baseada na premissa do aumento em altura das torres eólicas para permitir a exploração de perfis de vento mais fortes e mais estáveis aumentando consequentemente a produção de energia e a eficiência da turbina. Apesar das torres mais altas serem mais eficientes e economicamente vantajosas, torna-se necessária a definição de novas tipologias de fundações para esta nova vaga de exploração de energia eólica. O aumento da altura das atuais torres eólicas tubulares metálicas é possível visto poder ser resolvido o problema inerente ao aumento do diâmetro das torres. O diâmetro máximo transportável de 4.5 metros em estradas públicas apresenta-se de facto como um problema importante, aliado ao aumento das cargas de fadiga nas ligações em flange e ao aumento das dimensões das fundações. O trabalho apresentado foi desenvolvido no âmbito de dois projetos de investigação Europeus (HISTWIN e HISTWIN2) nos quais foram abordados os aspetos relacionados com a nova tipologia de ligações em torres metálicas tubulares que permite uma modularização da estrutura e um transporte mais fácil e com o melhoramento das fundações. O comportamento das torres eólicas tubulares é apresentado com base na monitorização de uma torre eólica tubular em funcionamento. São apresentados esforços, deslocamentos dinâmicos, vibrações e frequências bem como a estimativa de um espectro de fadiga tendo como base os esforços verticais na casca. É apresentada a viabilidade da produção e montagem da nova tipologia para as torres. A nova geometria é composta por ligações ao corte aparafusadas longitudinais (segmentos modulares) para permitir o transporte e ligações de atrito para unir os segmentos entre si. Ambos os conjuntos de ligação removem qualquer necessidade de recurso a soldaduras e promovem o uso de parafusos conduzindo portanto a melhoramentos na resistência à fadiga. Um requisito das ligações de atrito é a necessidade de recurso a parafusos que permitam o aperto apenas pelo interior da torre. Existem no mercado algumas soluções disponíveis e o comportamento de uma delas foi analisado com uma monitorização de longa duração. O melhoramento proposto para o sistema de fundação assenta no reforço das fundações diretas com recurso a microestacas para melhorar a resistência ao derrube, capacidade de carga e rigidez da fundação. O comportamento de microestacas a utilizar nesta solução é avaliado em detalhe, com recurso a ensaios laboratoriais e subsequente calibração de um modelo numérico 2D para implementar um procedimento que permita a estimativa do comportamento das microestacas sujeitas a cargas monotónicas e cíclicas. São feitas recomendações para o uso de técnicas de injeção dos tipos IRS e IGU para permitir o aumento da resistência da interface solo-calda e da própria microestacas. Por fim, e tendo como base uma análise LCA e LCC, mostrou-se que as microestacas são uma solução de reforço de fundações eficiente, quer ecológica quer ambientalmente, para todas as tipologias abordadas.
Fundação para a Ciência e Tecnologia