Dissertations / Theses on the topic 'Hardening Soil Model'

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.

This dissertation is on the geotechnical aspects of the completed Bangkok MRT Blue Line Project and its extension which is currently under design. There were 18 cut and cover subway stations and nearly 22 km of tunnels constructed by the use of earth pressure balanced shield tunnel boring machines. The soil profile model up to depths of 60 to 65 m consists of seven layers: Weathered Crust and Backfill Material; Very Soft to Soft Bangkok Clay; Medium Stiff Clay; Stiff to Hard Clay; Medium Dense to Very Dense Sand; Very Stiff to Hard Clay; and Very Dense Sand. The strength and deformation characteristics of the Bangkok subsoils are determined from laboratory tests (mainly oedometer and triaxial tests) and in-situ field tests (such as vane tests and pressuremeter tests). Additionally, the small strain behaviour is also investigated using Bender element tests in the laboratory and cross hole seismic tests in the field. The soil parameters needed for the deformation analyses are determined for the Mohr Coulomb Model, Soft Soil Model, Hardening Soil Model, and the Hardening Soil Model with Small Strain Stiffness.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
Full Text

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.

Coode Island Silt (CIS) is one of the predominant geological units in Melbourne, Australia. Having high compressibility and low shear strength, CIS is considered a problematic soft soil that challenges the construction of infrastructure in the region. To tackle such challenges, one practical approach is the application of ground improvement techniques such as in situ soil mixing. This PhD study focuses on the application of Cutter Soil Mixing (CSM) for the construction of excavation retaining walls in CIS. Although cement is widely used in most CSM projects, this study investigates the suitability of different lime types available in the Australian market as a potential alternative to cement for the stabilisation of CIS. To investigate the effect of lime stabilisation, a comprehensive geotechnical characterisation of untreated and lime treated CIS is performed. Four different lime types are used: agricultural lime, quicklime, hydrated lime and slag lime. Based on the results obtained from strength tests, slag lime was found to be the most effective among the four types that were tested. The optimum slag lime to CIS ratio is then found for the construction of retaining walls in CIS. Having the geotechnical characterisation of untreated and treated CIS from the laboratory experiments, a series of two-dimensional and three-dimensional finite element method (FEM) analyses were conducted to investigate the applicability and reliability of the selected mixing ratio for the construction of CSM excavation retaining walls in CIS. A nonlinear constitutive soil model was employed, calibrated and verified to be used in FEM analyses to investigate both the stability factor of safety and excavation-induced deformations. The results obtained for both undrained and fully coupled flow deformation analyses prove that CSM panels can be constructed by mixing slag lime and CIS to act as retaining walls to allow for deep excavation in CIS.
Doctor of Philosophy

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.

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.

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

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.

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.

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.

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

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.

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

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.

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

Tese de doutoramento em Engenharia Civil
Alternative binders based on the alkaline activation technology have been strongly investigated over the last decades as a potential replacement for Portland Cement. However, little research has been devoted to the shear behaviour of soft soils stabilised with those type of binders and their numerical modelling using constitutive models. This PhD thesis aims to deepen the knowledge in this area through the characterisation of the short- and long-term shear behaviour of soft soils stabilised with alkali-activated binders and the numerical modelling of the stress-strain behaviour of these geomaterials using a advanced constitutive model. In this context, triaxial tests were undertaken, after 28 and 90 curing days, in both a sandy lean clay and clay with high water content at reconstituted and stabilised states using alkali-activated blast furnace slags. The impact of the stress-history, represented by the overconsolidation ratio, and stress-state, represented by the initial mean effective stress, were investigated. Oedometer and isotropic consolidation tests were also undertaken. Scanning electron microscopy with energy dispersive spectroscopy, x-ray powder diffraction and leachate analyses were carried out to investigate the nature of the binding phases formed and the risk of contamination of soils. The results were used to calibrate an advanced kinematic hardening constitutive model proposed by Rouainia and Muir Wood, 2000 for natural clays. It was the first attempt of using this constitutive model in artificially cemented soils. Additionally, the opportunity to be integrated within a research project related to the application of alkali-activated industrial wastes in situ allowed me to be deeply involved in constructing a full-scale prototype of a (sub)base layer stabilised with alkali-activated binders and conventional binders. Big challenges arose, including the definition of a construction methodology, equipment selection, on-site handling of distinct materials, quality control techniques, among others. The in situ performance of the stabilised geomaterials was assessed through falling weight deflectometer tests, plate load field tests and unconfined compressive strength tests after 36 and 90 days. For each layer, it was estimated the financial cost of the construction and the equivalent CO2 emissions. The work showed the feasibility of the on-site application of alkali-activated binders in the stabilisation of soil layers in the context of transport infrastructures.
Os ligantes alcalinos têm sido fortemente investigados nas últimas décadas como um potencial substituto do cimento Portland. Contudo, o comportamento ao corte de solos estabilizados com este tipo de ligantes é ainda uma área pouco explorada atualmente, juntamente com o uso de modelos constitutivos. A presente tese de doutoramento visa aprofundar o conhecimento existente nesta área, através da caracterização do comportamento ao corte de solos moles estabilizados com ligantes alcalinos a curto e longo prazo e a modelação numérica do comportamento tensão-extensão desses geomateriais utilizando um modelo constitutivo avançado. Nesse contexto, foram realizados ensaios triaxiais, ensaios edométricos e de consolidação isotrópica, numa argila magra arenosa e numa argila com alto teor em água, ambos no estado reconstituído e estabilizado com escórias de alto-forno ativadas por álcalis, aos 28 e 90 dias de cura. O impacto do grau de sobreconsolidação, representado pela razão de sobreconsolidação, e do estado de tensão in situ, representado pela tensão média efetiva inicial, foram investigados no comportamento ao corte desses geomateriais. Foram realizadas análises de microscopia eletrônica de varrimento com espectroscopia de energia dispersiva e difração de raios-X e testes de lixiviados para investigar a natureza dos géis formados e o risco de contaminação dos solos. Os resultados foram utilizados na calibração de um modelo constitutivo de endurecimento cinemático proposto por Rouainia and Muir Wood, 2000 para argilas naturais que, até ao momento, não tinha sido utilizado em solos artificialmente cimentados. Adicionalmente, a oportunidade de estar integrada num projeto de investigação relacionado com a construção à escala real de uma camada de (sub)base estabilizada com ligantes alcalinos e ligantes convencionais possibilitou-me enveredar por esta temática. Grandes desafios foram encontrados do longo deste projeto, entre os quais, a definição de uma metodologia de construção, a seleção de equipamentos, manuseio dos materiais in situ, definição dos ensaios de controle de qualidade, etc. O desempenho in situ dos geomateriais estabilizados foi avaliado através de ensaios de capacidade de carga com defletómetro de impacto, ensaios de carga em placa e de compressão uniaxial aos 36 e 90 dias. Para cada camada foram também estimados os custos financeiros de construção e as emissões de CO2 equivalentes. Este projeto mostrou a viabilidade de utilização local dos ligantes alcalinos para a estabilização de camadas de solo no contexto das infraestruturas de transporte.
Fundação para a Ciência e a Tecnologia (FCT)
This research work was co-financed by the European Social Fund (FSE) through the Northern Regional Operational Program