Dissertations / Theses on the topic 'Hardening Soil'

A constitutive model based on rate-independent elastoplasticity concepts is developed to simulate the behavior of geologic materials under arbitrary three-dimensional stress paths, stress reversals and cyclic loading. The model accounts for the various factors such as friction, stress path, stress history, induced anisotropy and initial anisotropy that influence the behavior of geologic materials. A hierarchical approach is adapted whereby models of progressively increasing sophistication are developed from a basic isotropic-hardening associative model. The influence of the above factors is captured by modifying the basic model for anisotropic (kinematic) hardening and deviation from normality (nonassociativeness). Both anisotropic hardening and deviation from normality are incorporated by introducing into the formulation a second order tensor whose evolution is governed by the level of induced anisotropy in the material. In the stress-space this formulation may be interpreted as a translating potential surface Q that moves in a fixed field of isotropic yield surfaces. The location of the translating surface in the stress-space, at any stage of the deformation, is given by the 'induced anisotropy' tensor. A measure to represent the level of induced anisotropy in the material is defined. The validity of this representation is investigated based on a series of special stress path tests in the cubical triaxial device on samples of Leighton Buzzard sand. The significant parameters of the models are defined and determined for three sands based on results of conventional laboratory test results. The model is verified with respect to laboratory multiaxial test data under various paths of loading, unloading, reloading and cyclic loading.

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.

Shallow foundations are extensively used to support structures of all sizes in order to safely transmit the structural load to the ground without exceeding the bearing capacity of the ground and causing excessive settlement. They are typically embedded up to a few meters into the soil profile. While designing foundations, two requirements need to be satisfied: complete failure of the foundation must be avoided with adequate margin of safety (bearing capacity) and relative settlement should be within limits that can be tolerated by superstructure. Foundation is that part of the structure which is in direct contact with soil and involves the footing and the ground influenced by the footing. The master thesis aims to back-calculate the load tests using advanced soil models in PLAXIS 2D in order to gather experience on soil behavior and constitutive models. For this, extensive study of literature with full-scale load tests was carried out. Both tests on clay and sand were the theme interest.To examine the plate-load tests, three case studies were selected. In this report, the load-settlement responses of vertically loaded footings placed on both sands and clay were analysed using the finite element method. The numerical analysis was performed using PLAXIS 2D. The soil profiles and parameters used in the analysis were based on either in situ tests or laboratory tests. The Hardening Soil model was used as a material model to analyse the soil behavior. Finally, the load-settlement curves obtained from finite element analysis were compared with those from plate-load tests and see whether they are well fitted.The first case study was on clay till from Sweden. In this case, the back-calculated results showed that c_ref^' = 11.45 to 14.45 kPa and ɸ = 300. The second case was in saprolitic soil from Portugal. In this case, c_ref^' = 8 to 13 kPa and ɸ = 370 to 380. The third case was on sand from USA. In this case, sand shows some varying behavior in stiffness. The stiffness from laboratory tests and back-calculated vary by a factor of 3 to 8. The angle of friction was from 360 to 390.

Lateral pressures on non-yielding walls due to surface strip loads were investigated considering the non-linear stress-strain behaviour of the soil by finite element analyses. Data obtained from the finite element analyses were used to train neural networks in order to obtain a solution to assess the total lateral thrust and its point of application on a non-yielding wall due to a strip load. A 2-layered backpropogation type neural network was used. An artificial neural network solution was obtained, as a function of six parameters including the shear strength parameters of the soil ( cohesion and angle of friction ). The effects of each input parameter on the lateral thrust and point of application were summarized and the results were compared with the conventional linear elastic solution.

The fascination of a leaning towers actually descends from to the interaction with the foundation soil, not so clearly deduced at first glimpse. Furthermore, initial defects and non-uniform foundations in a structure and a soil with a low stiffness, can led to long-term critical conditions. The maintenance of existing constructions is one of the fields of activity of Civil Engineering, in particular, Geotechnical Engineering plays a significant role in a number of relevant cases. The conservation of Heritage is one of the most challenging problems facing modern civilization. It involves a number of factors belonging to different fields (cultural, humanistic, technical and economical), joint by inextricable patterns. A convenient way to forecast this long term behavior, is to define a reliable response for the soil-foundation system. Strain-hardening plasticity models, developed in relation to the overall soil-footing system can provide such a relationship, but, in any case, it is rather difficult to validate these models. In this respect, a rather significant contribution comes from an experimental identification analysis, performed before the realization of the numerical model on Plaxis. The behaviour can be modelled in order to predict how large the deformations will be. This thesis investigates the effectiveness of such models, referring to the current state of the tower. The project being examined is located in central Bologna. The analysis focuses on the displacements, stresses and plasticity below the site. An analysis was carried out to investigate the significance of different parameters, of different material models and methods of analysis. 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.

Under hösten 2019 har Vattenfall Research & 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&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 & 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&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.

Diplomová práce představuje vytvoření softwarového 2D MKP modelu přehrady Slezská Harta v České Republice za pomoci softwaru PLAXIS 2D. V úvodu práce je analýza vodní nádrže, vytvořené jako zásobárna vody a protipovodňové dílo. Analýza sleduje geomorfologii, geologii, konstrukci tělesa hráze, použité materiály a metody, a stávající monitorovací zařízení. Pro pochopení tvorby 2D MKP modelu jsou předloženy a definované metody použitých analýz - metoda konečných prvků, analýza prosakování, materiálové modely, citlivostná analýza. Následně byla definována tvorba struktury modelu - určení posloupnosti použitých analýz, definování vstupních dat a mezních podmínek a tvorba kalibračního segmentu. V závěrečné části práce je analýza dosažených výstupů rozsáhlého testování modelu, jejich korelace s reálnými naměřenými hodnotami a celkové shrnutí přínosu vytvořeného modelu pro jeho využití při předpovídání chování přehrady v extrémních případech.

La presente ricerca illustra uno studio numerico sul comportamento di un muro di sostegno in terra rinforzata, basato sull'uso di un approccio agli elementi finiti in combinazione con due diversi modelli costitutivi di tipo elastoplastico, caratterizzati da un diverso grado di complessità. Le analisi proposte sono state svolte allo scopo di studiare l'influenza di alcuni parametri progettuali significativi, quali la lunghezza e la spaziatura verticale degli elementi di rinforzo, sulle prestazioni complessive della struttura di sostegno soggetta a carichi statici e sismici.

In this study settlement behaviour of Kü
rtü
n dam, which is the first concrete faced rockfill dam in Turkey, is investigated. Two dimensional plane strain finite element analyses are carried out in order to determine the total stresses and displacements during construction and reservoir filling conditions. Hardening soil model is used in order to represent the non-linear, inelastic and stress dependent behaviour of rockfill material. Material model parameters are selected mainly referring to the previous studies on the dams consisting of similar materials. Calculated stresses and settlements are compared with the observed values and in general, they were found to be in good agreement for the construction stages. It is seen that, due to the relatively narrow valley and steep abutment slopes, arching is a significant parameter as far as the stresses and settlements are concerned. For the reservoir impounding condition, calculated settlements were found to be slightly larger than the observed values, which may indicate that during the reservoir impounding, the rockfill embankment behaves in a stiffer manner as compared to that of during construction stages.

In this study, settlement and seepage behavior of Muratli Dam, which is the first asphalt faced rockfill dam in Turkey, is investigated for the &ldquo
end of construction&rdquo
and &ldquo
reservoir impoundment&rdquo
loading conditions. Two dimensional plane strain finite element analyses are carried out in order to determine the total stresses, displacements and pore water pressures. Hardening soil model is used in order to represent the non-linear, inelastic and stress dependent behavior of rockfill material. Material model parameters are selected mainly referring to the previous studies on the dams consisting of similar materials and then back analyses are done to find the best fit. Calculated stresses, displacements and pore water pressures are compared with the observed values for both end of construction and reservoir filling conditions.

The focus of this thesis is to deal with reverse engineering of high-rise building settlements. This is modeled via the finite element method performed in the Plaxis 3D program. In the first part of this thesis, a calibration of input parameters of an appropriate material model – Hardening soil – is conducted. This calibration is a result of oedometric test data which were obtained within a geotechnical survey. An influence of soils over consolidation affecting calibration and the material model choice is described. Final values of reference stiffness parameters are used in a mathematical model of the focused area. This model is created for one half of the high-rise building plan, including vestibule. The high-rise building is founded in a foundation pit. The foundations of this building consist of raft foundation and piles of jet grouting. In the model, there are also changes in pore pressure during an excavation of foundation pit included. The functional model is used for parametric analyses, namely examining cases of object´s foundations and the possible influence of foundation pit´s symmetry on the object´s settlement. All the calculated processes in the object´s settlements are then compared to data obtained from geotechnical monitoring of the structure.

In this study, a set of rules is established, which when implemented in the modeling of dilatant soils, within the framework of associative plasticity, enables very successful shear and dilatancy predictions. The proposed approach is based on a number of principles, the most important of which are: (1) The plasticity model must have a loading surface that hardens kinematically, and a failure surface that is perfectly plastic. (2) Experimental evidence shows that uniformly deformed sand samples dilate with a constant rate when they reach their ultimate strength value, while critical state is only achieved at very large strains. There is a unique point A on the loading surface that corresponds to the experimentally observed dilatation rate. The hardening rule must, therefore, ensure that the stress point approaches A as it approaches the failure surface. These principles are implemented in a plasticity model and compared to numerous published monotonic and cyclic tests, with varied stress paths, performed on a true triaxial apparatus. The agreement between experimental data and theoretical predictions is excellent.

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

La presente tesis tiene como finalidad establecer criterios de influencia entre parámetros geotécnicos y profundidad de excavaciones en suelos gravosos, mediante la aplicación de un software de elementos finitos. Para ello, se tomó como referencia a 5 estudios geotécnicos desarrollados en Lima Metropolitana (Santa Anita, San Isidro, Miraflores y San Luis), en donde se emplearon diversos ensayos con el fin de obtener parámetros necesarios para su modelación. Por ejemplo, gracias a estos estudios, se determinaron rangos a los parámetros geotécnicos (Ángulo de fricción, Cohesión y Peso Específico) que serán considerados en la modelación de los casos de estudio. De acuerdo con estos estudios, el Ángulo de Fricción oscila entre 25° y 46°; la Cohesión entre 10 kPa y 84 kPa; mientras que el Peso Específico tiene un rango de 18 kN/m3 a 24 kN/m3. Las excavaciones que serán evaluadas durante la presente investigación serán de 8m, 12m y 16m de profundidad y contarán también con rangos para el Módulo de Elasticidad (E50) y el Coeficiente de carga y descarga (Eur) necesarios para analizar el comportamiento físico del suelo. Los resultados obtenidos luego de emplear el Modelo Constitutivo Hardening Soil, fue que conforme van incrementado los Ángulos de fricción del suelo y el Módulo de Elasticidad (E50), los desplazamientos van disminuyendo poco a poco (estamos hablando de una relación inversamente proporcional). Asimismo, existe una relación directamente proporcional entre la profundidad de excavación, el módulo de elasticidad y los desplazamientos del suelo considerando un sistema de reforzamiento anclado.
The purpose of this thesis is to establish criteria of influence between geotechnical parameters and depth of excavations in burdensome soils, through the application of finite element software. For this, 5 geotechnical studies developed in Metropolitan Lima (Santa Anita, San Isidro, Miraflores and San Luis) were taken as a reference, where various tests were used in order to obtain parameters necessary for their modeling. For example, thanks to these studies, ranges were determined for the geotechnical parameters (Angle of friction, Cohesion and Specific Weight) that will be considered in the modeling of the case studies. According to these studies, the Angle of Friction ranges from 25 ° to 46 °; Cohesion between 10 kPa and 84 kPa; while the Specific Weight has a range from 18 kN / m3 to 24 kN / m3. The excavations that will be evaluated during this investigation will be 8m, 12m and 16m deep and will also have ranges for the Modulus of Elasticity (E50) and the Coefficient of loading and unloading (Eur) necessary to analyze the physical behavior of the soil. The results obtained after using the Hardening Soil Constitutive Model were that as the friction Angles of the soil and the Modulus of Elasticity (E50) increase, the displacements gradually decrease (we are talking about an inversely proportional relationship). Likewise, there is a directly proportional relationship between excavation depth, modulus of elasticity and soil displacements considering an anchored reinforcement system.
Tesis

Le développement de l’urbanisme privilégie de plus en plus souvent la solution souterraine. Le creusement d’environ 200km de tunnels est prévu dans les dix prochaines années en France seulement, en milieu urbain dense.L’excavation d’une cavité dans un terrain engendre des mouvements dans le massif. Le front de taille se déplace généralement instantanément vers l’excavation. A ce déplacement d’extrusion s’ajoute la convergence des parois du tunnel. A faible profondeur, ces mouvements risquent de se propager jusqu'à la surface du terrain constituant une cuvette de tassement qui peut conduire à des désordres importants voire de nature accidentelle (tassements différentiels, développement de fontis, effondrement de constructions, etc.). Plusieurs paramètres influencent la qualité des simulations et la prévision des déplacements induits par le creusement d’un tunnel. Le choix d’une loi de comportement est primordiale pour la modélisation des tunnels qui dépend de la réponse du sol en termes de déformations. La prédiction des déplacements engendrés requière un modèle de comportement du sol rigoureux qui puisse simuler le plus fidèlement possible la réponse du sol.Cette thèse propose un modèle de comportement adapté à la simulation du creusement de tunnel avec un mécanisme d’écrouissage déviatorique dans le cadre de la théorie de l’état critique. Ce modèle reproduit de manière satisfaisante la réponse non linéaire du sol à l’échelle des essais de laboratoire et présente une alternative sécuritaire pour les simulations à l’échelle de la structure.L’effet de l’influence de plusieurs paramètres sur la simulation des tunnels est étudié à travers des simulations 2D et 3D avec différentes configurations et en considérant le couplage hydromécanique. Le modèle proposé est aussi utilisé pour la reproduction de mesures in-situ d’une section de tunnel du Grand Paris
Tunnels construction is increasingly favored as a sustainable transportation and infrastructure development system. 200km are going to be excavated only in France in the next ten years in dense urban areas.During tunnel excavation, ground movements must be controlled and well predicted to avoid any damage on existing buildings. The tunnel face moves typically instantly toward the excavation. The tunnel wall convergence is added to theface extrusion. These movements may spread to the surface of shallow tunnels leading to significant disturbances or accidental damage (differential settlement, cave-in occurrence, buildings collapse, etc.).Different parameters influence the quality of tunnels simulation and induced displacements prediction. The quality of those predictions closely depends on the choice of soil constitutive model. In this context, some widely used soil models in engineering practice not only fail to reproduce some characteristics of soil behavior on the constitutive level but also lead to shallower settlement.This PhD thesis proposes an enhanced critical state model incorporating deviatoric and volumetric hardening mechanisms adapted for tunneling simulations. This model satisfactorily reproduces the nonlinear soil response to laboratory tests and enables a more conservative tunneling design.The impact of other modeling choices is studied through 2D and 3D tunneling simulations in different configurations with the proposed soil model. Furthermore, comparison with measurements obtained from a tunnel section of the Grand Paris Project highlight the performance of the proposed model in simulating tunneling induced displacement

The soil response under cyclic loading conditions is of interest for a number of geotechnical structure such as road pavements, tank foundations and offshore structures. When a geotechnical structure is subjected to cyclic loading, permanent settlements and rotations are accumulated affecting the serviceability of the structure. In the last years, a number of modelling strategies have been proposed to quantify the strain accumulation of soils under cyclic loading; however, most of the models are valid only for limited loading and drainage conditions, and they generally employ complex constitutive formulations. In this thesis, a new constitutive model, the Memory Surface Hardening model, which accounts for the effects of cyclic loading on the soil response, is proposed. The primary aim of this research is to develop a simple set of equations which can accurately predict the cyclic mechanical response of granular soils under generalised loading and density conditions. The modelling strategy is developed in an existing critical state - bounding surface - state parameter - elasto-plastic framework. A new surface, the memory surface, is introduced to track the experienced stress history. In the experiments available in the literature, it is observed that the soil response is highly affected by the experienced loading states. The memory surface evolution responds to two rules: the yield surface is always enclosed by the memory surface; the memory surface expands or contracts following the experienced plastic strains. The last rule is the key to reproduce the typical features observed experimentally for granular soils subjected to cyclic loading. Whenever the soil experiences contractive volumetric strains, the memory surface expands; on the contrary, when the soil experiences dilative plastic volumetric strains, the memory surface contracts. The plastic soil stiffness is affected by the size of the memory surface. The evolution of the memory surface can be interpreted as a representation of the evolution of the soil fabric when the soil is subjected to cyclic loading conditions. The model is developed by maintaining the same hardening rules for any loading conditions, minimising the number of implemented rules and employing a limited number of constitutive parameters. The model is proposed for both the triaxial and the multiaxial stress space. The model has been validated for different types of granular soils under different loading conditions, drained and undrained conditions. The evolution of model surfaces for different loading conditions is presented in the simulations and the occurring mechanisms are widely described.

In first part of the thesis are proposed four variants of retaining structures for deep excavation of cut-and-cover tunnel part. It is nailed slope, pile wall, nailed slope in combination with pile wall and soldier pile wall. For those structures is in following part carried out an economic analysis and the most cost effective variant is chosen. Chosen structure is further analyzed in next part. This analysis is carried out with finite element method in software PLAXIS. As a material model is chosen Hardening Soil model and input parameters were determined by empiric formulas from literature. Behavior of neogene clays, in which is the structure designed, is considered as undrained, by type Undrained A. In the last part of the thesis is described technological procedure of construction this retaining structure.

Abstract This thesis discusses strengthening foundations of historic buildings by means of pretested, end-jacked, steel piles; pretested, end-jacked drilled spiral steel piles, as well as the geotechnical and structural design of strip foundations using ultimate limit state methods. Strengthening the foundations of historic buildings is a field of engineering where every site is more or less different from another. The variation of the substructure, foundation, and soil circumstances make every case unique. Preserving heritage buildings by preventing structural decay requires know-how and suitable strengthening methods. Drilled spiral piles and jacked piles were employed as strengthening methods for St. John’s Church of Tartu, because of the sinking and uneven settlement of the building. The strengthening work at St. John’s Church was challenging due to the risk of collapse of this historic church. Underpinning with jacked piles is a preferred method for strengthening historic foundations and where drilled spiral piles were employed, the author of this thesis developed special equipment. The strengthening method employed for the tower complies with the anastylosis principle by preserving the authenticity of the structures. Old block stones are visible upon the floating piled rafts. The empty space was left to give archaeologists and engineers a chance to study the realized work “in situ” in the future. The foundation of the tower was underpinned step by step with end-jacked piles and a concrete raft poured step by step. The weight of the tower is 5 500 tons and it rests on four pillars. Every pillar rests on its own floating piled raft. This thesis proves that by means of lower and upper bound theorems a floating, piled strip-foundation can be designed geotechnically and structurally using one method based on ultimate limit state (ULS) and serviceability limit state (SLS). The method takes the following into account as geotechnical requirements: total settlement and angular distortions; and as structural requirements; admissible plastic rotations, end moments due to displacement angle, as well as control of cracking. The chosen piling methods were suitable for St. John’s Church, and the installed piles work well in addition to the old foundations. The functionality of the strengthening techniques has been verified by test piling. Furthermore, every drilled spiral pile was preloaded twice and end-jacked for soil hardening
Tiivistelmä Tämä tutkimus käsittelee historiallisten rakennusten perustusten vahvistamista esikuormitetuilla teräksisillä puristuspaaluilla ja esikuormitetuilla, loppupuristetuilla spiraaliporapaaluilla. Tutkimus sisältää myös pitkänomaisen anturaperustuksen mitoitusmenetelmän, joka huomioi sekä murtorajatilan että käyttörajatilan vaatimukset. Historiallisten rakennusten perustusten vahvistaminen on insinööritieteen osa-alue, missä jokainen työmaa on oma, ainutlaatuinen kohteensa johtuen erilaisista maaperäolosuhteista, perustuksista ja rakenteista. Rakennuksen luonteen säilyttäminen edellyttää insinööriltä monialaista kykyä ja tietoa sopivista vahvistamismenetelmistä. Spiraaliporapaaluja ja puristuspaaluja käytettiin Johanneksen kirkon (Jaani Kirik) perustusten vahvistamisessa rakennuksen epätasaisen painumisen ja sortumisvaaran vuoksi. Perustusten vahvistamista puristuspaaluilla pidetään yleisesti parhaana menetelmänä historiallisille rakennuksille. Tämän tutkimustyön tekijä suunnitteli erikoiskaluston työtä varten kehitetylle kierrepaalulle. Anastylosis periaatteen mukaisesti käytetyssä tornin vahvistamismenetelmässä säilytettiin rakenteiden autenttisuus. Vanhat kivilatomukset ovat osittain näkyvissä. Niiden välissä oleva tyhjä tila antaa arkeologeille ja insinööreille mahdollisuuden tutustua suoritettuun työhön. Tornin perustukset vahvistettiin vaiheittain paaluilla sekä valetulla betonilaatalla. Torni painaa 5 500 tonnia ja se on neljän pilarin varassa. Jokaisella pilarilla on erillinen kelluva paalutettu laattaperustus. Tässä työssä on osoitettu, että plastisuusteorian ala- ja ylärajalauseiden avulla myötäävän kitkamaan ja myötäävän paalutuksen varaan perustettu pitkänomainen anturaperustus voidaan mitoittaa geo- ja rakenneteknisesti murto- ja käyttörajatilassa samalla menetelmällä. Menetelmä sisältää geoteknisinä vaatimuksina anturan pohjapaineen, kokonaispainuman ja kulmakiertymän (= epätasaisen painumisen) määrittämisen, rakenteellisina vaatimuksina plastisoituvien kohtien riittävän muodonmuutoskyvyn, kenttä- ja tukimomenttien, epätasaisen painumisen aiheuttamien pakkomomenttien sekä halkeamatarkastelun määrittämisen. Spiraaliporapaalujen toiminnallisuus varmistettiin koepaaluilla. Maanlujittumista varten jokainen spiraaliporapaalu koestettiin kahdella esikuormituksella ja loppupuristuksilla

Les marais de l'Ouest ont été gagnés sur les sédiments fluvio-marins par poldérisation débutée dès le moyen âge. Les aménagements hydrauliques avaient, initialement, des objectifs sanitaires et d'élevage. A partir des endiguements, ils ont divisé les territoires en marais mouillés et marais desséchés. Depuis les années 1970 le développement des cultures intensives de céréales a nécessité un rabaissement complémentaire de la nappe par drainage en partie pour augmenter la désalinisation de surface et limiter l’engorgement des sols. Néanmoins, ces territoires restent caractérisés par des nappes proches de la surface. En conséquence les profils hydriques vont être gouvernés par les conditions météorologiques y compris l'évapotranspiration, la pluviométrie, mais également par les remontées capillaires issues d'une nappe salée. D'autre par la nature argileuse des sols et ses propriétés de retrait conditionnent énormément le fonctionnement hydrodynamique et les évolutions de structure.La première partie du travail a été de suivre les évolutions des profils hydriques et de salinité en parcelles non drainées (prairies) et en parcelles drainées (Maïs, Blé, Tournesol). Ces suivis ont été complétés par les mesures des niveaux de nappes et par des mesures tensiométriques via des bougies poreuses implantées à différentes profondeurs. L'objectif final a été de calculer et modéliser les profils de réserve utile (RU) et de RU "résiduelle" utilisable par les plantes. Dans ces systèmes alimentés par les remontées capillaires, le réseau racinaire puise l'eau dans la zone non saturée de surface (vadose) puis dans la zone saturée sous-jacente. La teneur en eau caractéristique de l'interface zone non saturée - zone saturée a été déterminée par analogie entre les chemins d'état de la matrice argileuse le long de sa courbe de retrait et du sol le long de sa courbe de compaction. Les profils de RU résiduelle utilisable par les plantes ont été calculés à partir des profils de teneurs en eau puis comparés aux profils de RU obtenus via les données de station météorologique. Ces profils de RU résiduelle ont pu être écrits sous forme d'équation polynomiale du second degré puis modélisés. Dans cet environnement alimenté par les remontées capillaires, ces profils de RU résiduelles peuvent être modélisés à partir d'un paramètre facilement mesurable en surface qui prend en compte la structure du sol et les conditions météorologique : soit la teneur en eau à 10 cm de profondeur. Cette modélisation reste suffisamment réaliste pour être utilisée comme un outil prédictif face à la pédodiversité et/ou les rendements de culture.A ce travail s'ajoute deux études préliminaires : - les mesures des conductivités thermiques effectives de ces sols par la méthode du fil chaud et leurs modélisations dans les systèmes biphasés : eau - argile et air - argile, mais également pour les systèmes triphasés non saturés : eau - air - argile. Les perspectives sont la modélisation des transferts thermiques et hydriques dans le sol à partir de la surface, - et l'élaboration d'un protocole d'imprégnation-polymérisation des sols argileux humides par des résines de type HEMA. Cette imprégnation permet d'envisager la confection de lames minces dans le matériau argileux induré avec conservation de sa structure initiale humide. Les perspectives sont la pétrographie quantitative à l'interface racine - sol le long de profils verticaux dans les environnements argileux à degrés de saturation et structure évolutives
The coastal marshlands are territories generally reclaimed on primary fluvio-marine sediments. They result from hydraulic managements and/or polderization which may date from the Middle Ages. Historically these hydraulic managements were built for goals of wholesomeness, breeding and farming. They isolate two territories: the dried marshes and the wet marshes. For the intensive cereal crops the slow drying caused by land reclamation was recently improved by the drainage, in part for increase the depth of desalinization and decrease waterlogging. Nevertheless, these territories remain characterized by shallow ground water of initial salt water. Consequently, the hydric profiles are governed by the meteoric conditions including the Evapotranspiration, the rainfall, but also the capillarity rises from the salt groundwater. Moreover, the clay dominated nature of the soils and their drastic shrinkage properties govern the hydrodynamic functioning and the soil structure behavior.The first part of the work was the monitoring of the water content and salinity profiles in drained cereal crops and in undrained grasslands. These measurements have been completed by the ground water level and tensiometric monitoring. The final goal was the calculation and modeling of the available water capacity (AWC) and plant available water (PAW) profiles. In these systems mainly supplied by the capillarity rises, the root network gets water in the subsurface vadose zone and then in the deeper saturated groundwater zone. The water content characteristic of the interface between the vadose and saturated zone was determined by comparison between the clay material state paths along its shrinkage curve and along its compaction curve. The PAW profiles were calculated from the water content profiles and then compared to the AWC profiles. The PAW profiles have been equated as polynomial second degree equations. In these shallow groundwater environments the PAW profiles have been modeled taking into account an easy measurable surface parameter which includes the soil structure behavior and the meteoric conditions: i.e. the water content measured at 10 cm depth. The PAW modelling remains sufficiently realistic to be used as a tool for farming management. Two preliminary studies were added to this work: - the measurement of effective thermal conductivity of the clayey soils by the transient hot wire method, and the modeling of the effective thermal conductivity of biphasic air-clay and water-clay media, but also triphasic unsaturated air-water-clay media. The prospect is the modeling of thermal and hydric transfer from the surface to the depth. - and the elaboration of a protocol of impregnation - hardening for wet clay dominated soils by HEMA resins. This impregnation allows the making of thin sections in these clay materials with conservation of their initial wet structures. The prospective is the quantitative petrography at the root - clay matrix interface along vertical profiles in clayey soils at different degrees of saturation and different structures

State-of-the-art SiGe BiCMOS technologies leverage the maturity of deep-submicron silicon CMOS processing with bandgap-engineered SiGe HBTs in a single platform that is suitable for a wide variety of high performance and highly-integrated applications (e.g., system-on-chip (SOC), system-in-package (SiP)). Due to their bandgap-engineered base, SiGe HBTs are also naturally suited for cryogenic electronics and have the potential to replace the costly de facto technologies of choice (e.g., Gallium-Arsenide (GaAs) and Indium-Phosphide (InP)) in many cryogenic applications such as radio astronomy. This work investigates the response of mixed-signal circuits (both RF and analog circuits) when operating in extreme environments, in particular, at cryogenic temperatures and in radiation-rich environments. The ultimate goal of this work is to attempt to fill the existing gap in knowledge on the cryogenic and radiation response (both single event transients (SETs) and total ionization dose (TID)) of specific RF and analog circuit blocks (i.e., RF switches and voltage references). The design approach for different RF switch topologies and voltage references circuits are presented. Standalone Field Effect Transistors (FET) and SiGe HBTs test structures were also characterized and the results are provided to aid in the analysis and understanding of the underlying mechanisms that impact the circuits' response. Radiation mitigation strategies to counterbalance the damaging effects are investigated. A comprehensive study on the impact of cryogenic temperatures on the RF linearity of SiGe HBTs fabricated in a new 4th-generation, 90 nm SiGe BiCMOS technology is also presented.

碩士
國立臺灣科技大學
營建工程系
101
Numerical analysis has become the important tool to assist geotechnical engineering project or case. Some of soil model are provided in numerical software. Hardening Soil model is advance soil model which become more widely used. Selecting the reliable parameter is a key to perform numerical simulation, thus laboratory testing such as triaxial test and oedometer test are applied to investigate the soil stiffness parameter. In addition to triaxial test and oedometer test, developing a reliable reconstitution soil method is a key to produce reliable soil sample. Designing and performing reconstituted soil test is the first step to obtain reliable soil sample prior to triaxial test, oedometer test and bender element test. Based on the water content test, the new design of consolidometer (reconstituted soil) to produce undisturbed soil is quite reliable. A series of triaxial tests such as CK0U_AC, CIU_AC, CIU_AD, CK0U_AE, CIU_AE and oedometer test were conducted to evaluate the stiffness parameter such as initial Young’s Modulus (E0), secant Young’s Modulus (E50), oedometer Young’s Modulus (E50), and initial Shear Modulus (G0). Finally, In order to verify the testing results, this study performed numerical simulation which is included back analysis of stress strain curve and parametric study of initial shear modulus (G0) and shear strain (

Dissertação de Mestrado Integrado em Engenharia Civil apresentada à Faculdade de Ciências e Tecnologia
O projeto da maioria das obras geotécnicas requer, para além da verificação da segurança em relação a diferentes estados limites últimos, a estimativa dos movimentos associados à sua construção. O recurso à via numérica é o modo mais eficiente de o fazer, exigindo, no entanto, a sua aplicação uma escolha criteriosa do modelo constitutivo a empregar.Um modelo constitutivo de uso cada vez mais generalizado em solos compactos ou rijos é o Hardening Soil Model, implementado no programa de cálculo automático Plaxis, que, associando algumas das vantagens dos modelos mais simples com as dos mais elaborados e complexos, consegue ser parametrizado com base em ensaios de emprego corrente e reproduzir algumas das principais características do comportamento mecânico dos solos interessados pelas obras.O objetivo desta dissertação é então o de verificar a aptidão do Hardening Soil Model em reproduzir convenientemente a resposta de um solo a carregamentos com diferentes trajetórias de tensões, servindo-nos do caso particular das “Areolas da Estefânia”, formação miocénica que constitui grande parte do subsolo da região de Lisboa.Na primeira parte da dissertação, recorrendo à bibliografia especializada e a alguns resultados de um estudo paramétrico realizado, aborda-se os principais aspetos referentes aos modelos constitutivos dos solos, com especial ênfase no modelo de Mohr-Coulomb, sem dúvida o modelo ainda hoje de longe mais utilizado, e no Hardening Soil Model, e faz-se uma análise comparativa do desempenho destes dois modelos na reprodução de diferentes trajetórias de tensões.Na segunda parte da dissertação, recorrendo-se a alguns resultados de ensaios laboratoriais realizados em amostras colhidas na formação das “Areolas da Estefânia” publicados na bibliografia, começa-se por definir os parâmetros caracterizadores do Hardening Soil Model e verifica-se a aptidão do modelo para reproduzir os resultados experimentais obtidos nos diversos tipos de ensaios e com diferentes trajetórias de tensões.Por fim, são apresentadas as principais conclusões do trabalho e são propostos alguns estudos a serem desenvolvidos no futuro no âmbito da temática abordada.
The design of most geotechnical works requires besides to the verification of safety in relation to different final limit states, the estimation of the movements associated with their construction. The use of numerical models are the most efficient way of doing this, but its application requires a careful choice of the constitutive model to be used.A constitutive model of general use in compact or hard soils is the Hardening Soil Model, implemented in the automatic calculation program Plaxis, which, combining some of the advantages of the simplest models with others more elaborate and complex, can be parameterized with Based on current employment tests and reproduce some of the main characteristics of the mechanical behavior of the soils interested in the works.The objective of this dissertation is to verify the ability of the Hardening Soil Model to reproduce the soil response to different stress trajectories, using the particular case of the "Areolas da Estefânia", a myocene formation that constitutes a large part of the subsoil of the Lisbon region.In the first part of the dissertation, using the specialized bibliography and some results of a parametric study, are exposed the main aspects of the constitutive models of the soils, with special emphasis on the Mohr-Coulomb model, the most used model nowadays, and the Hardening Soil Model, and is elaborated a comparative analysis of the performance of these two models in the reproduction of different trajectories of tensions.In the second part of the dissertation, using some results of laboratory tests carried out on samples collected in the "Areolas da Estefânia" formation published in the bibliography, it begins by defining the characterizing parameters of the Hardening Soil Model and verify the suitability of the Model to reproduce the experimental results obtained in the different types of tests and with different stress trajectories.Finally, the main conclusions of the paper are presented and some studies are proposed to be developed in the future in the scope of the subject.

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.

碩士
國立高雄應用科技大學
土木工程與防災科技研究所
104
Considering fasten development of urban area in Taiwan, a need of use of underground space is increased so deep excavation is recognized as an important technology for this matter. In this study, a deep excavation in loose to medium dense sand occasionally with thin clay is selected for research background. For selection of parameters and constitutive model of soils, no matter with what parameters chosen, Dao(2015) indicated that it is not possible to have a reason surface settlement trough induced by deep excavation using Mohr-Coulomb(MC) model in numerical analysis. Thus, an advanced Hardening Soil (HS) model is used in this study and the relationship between SPT- N (N) and soil modulus which can be adopted as a reference for further simulation. However, due to varieties in operating personnel and equipment, etc., these factors might lead to uncertainties of SPT- N value. Therefore, an equation concluded by Hsung et al. (2016) takes ground depth as a factor for interpretation of soil modulus. In addition, definitions of related soil modulus in HS model are also explored and suggested. For 3- dimensional analysis, it is recommended that model parameter E50 = 2000N (Unit in kPa) shall be adopted and elastic modulus of soil (E) = 1.5E50 if only elastic modulus of soil (E) is available. Further, considering output from this study, it is recommended that so called “Plane Strain Ratio, PSR” is not affected significantly by using different constitutive models of soil once an excavation is conducted in similar ground condition. Finally, combining with geotechnical engineering and geographic information system (GIS), it can visualize colorful and easily understand an area influenced by a deep excavation. Settlement contour can be automatically generated from output of geotechnical analysis and mapped on neighborhood environment. As a result of that, safety of adjacent structures can be evaluated by settlement contours and the judgement can be made afterwards. Necessary structure protection measures can be prepared in advanced if necessary herein.

碩士
國立高雄應用科技大學
土木工程與防災科技研究所
105
Development of technology and population in urban area globally are growing very fast. The role of deep excavation thus becomes essential in the aspect of expansion of underground space, no matter for high-rise building and underground infrastructure etc.. That’s also the reason that analyses and construction method of deep excavations are important. Dao (2015) indicated that simple elastic perfect- plastic model can’t provide a good prediction of ground surface settlement. Wu (2016) used “Hardening Soil (HS)” model which has additional consideration in soil stiffness under stress- relief condition for simulation and further approved that use of HS model could perform better. However, the model predicts soil heaves at the place near the excavation which is not consistent with reality. Therefore, an advanced “Hardening Soil-Small Strain (HSS)” model is used instead to conduct 3- dimensional analyses using software PLAXIS 2D & 3D for evaluation of displacements induced by excavations in loose to medium dense sand. Key contributions of this study include determination of key input parameters of HSS model, ground settlement pattern, advantage of the model and also effectiveness of various protection measures in deep excavations in loose to medium dense sand.

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

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