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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

A relevância das unidades de conservação na proteção de espécies arbóreas ameaçadas de extinção da Mata Atlântica do Sudeste da Bahia / The relevance of conservation units for the protection of tree species threatened by extinction from Atlantic Forest of Southeast of Bahia

Santos, Renata dos 19 August 2018 (has links)
Orientadores: Carlos Roberto Espindola, Raquel Maria de Oliveira / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-19T20:03:13Z (GMT). No. of bitstreams: 1 Santos_Renatados_M.pdf: 6198017 bytes, checksum: 5aa39ecf5f645aa9039abd03fc2501d2 (MD5) Previous issue date: 2011 / Resumo: A Floresta Atlântica do sudeste da Bahia apresenta uma das maiores riquezas de espécies arbóreas por área do planeta, com uma significativa porcentagem endêmica. Essas espécies encontram-se altamente ameaçadas pelos elevados índices de desmatamento, fragmentação de habitat e corte seletivo decorrente na região. As Unidades de Conservação têm , dentre suas metas, proteger esses remanescentes florestais. O objetivo deste estudo foi avaliar a relevância da rede de Unidades de Conservação (UCs) no sudeste da Bahia na proteção das espécies dos remanescentes da Mata Atlântica desta região a partir da análise de ocorrência de 10 (dez) espécies arbóreas ameaçadas de extinção. Fez-se o uso de geotecnologias como os programas Arc Gis 9.2 e DIVA GIS 7.2 para elaboração dos mapas de ocorrências das espécies arbóreas e das Unidades de Conservação e da distribuição potencial das espécies arbóreas. As 10 (dez) espécies selecionadas são endêmicas da Mata Atlântica do sudeste da Bahia e com alto grau de ameaça, integrando a Lista Vermelha da IUCN e do Ministério do Meio Ambiente. O levantamento de dados e de registro de ocorrência das espécies contou com o banco de dados oriundo da CEPEC, compilação de listas de espécies de artigos e de plano de manejo de UCs, mais a realização de trabalhos de campo, tendo sido realizado também um levantamento de dados sobre as UCs encontradas na região. Os mapas de ocorrência das dez espécies arbóreas foram sobrepostos com os mapas das UCs, possibilitando verificar os registros de ocorrência de todas as espécies arbóreas. Para que as UCs possam cumprir todos os seus objetivos, políticas mais eficazes devem ser adotadas, bem como a participação mais direta de órgãos fiscalizadores na elaboração e aplicação dos seus Planos de Manejo, os quais devem ser mais efetivos, garantindo a conservação das espécies arbóreas, bem como de todo a gama de recursos naturais encontrados dentro dos limites das UCs. A distribuição potencial demonstrou áreas com maior probabilidade de ocorrência das espécies, onde deverão ser realizados outros estudos que possam fortalecer a indicação destas áreas para o estabelecimento e/ou ampliação ou de novas UCs / Abstract; The Atlantic Forest of Southeast of Bahia presents one of the greatest resources of tree species per area of the planet, with a significant endemic percentage. Those species are very threatened by the high rates of deforestation, habitat fragmentation, and selective logging in the region. The Conservation Units among other aims protect those forest remnants. The objective of this study was to evaluate the network relevance of Conservation Units (CUs) present in the southeast of Bahia for the species protection of Atlantic Forest remnants of this region from the analysis of occurrence of 10 species threatened by extinction. The use of geotechnologies was made as the programs Arc Gis 9.2 and DIVA GIS 7.2 to elaborate occurrence maps of tree species, the Conservation Units, and the potential distribution of tree species. About the selected species, 10 (ten) are endemics of Atlantic Forest from southeast of Bahia and with a high level of threats integrating the IUCN Red List and the Ministry of Environment. The data collection and record of the occurrence of the species counted with database of CEPEC, compilation of species lists of paper and management plan of CUs but studies in field. A collection data was also accomplished about CUs that were found in the region. The occurrence maps of the ten tree species were superimposed with maps of CUs, making possible to check the records of the occurrence of tree species. For CUs can meet all goals, more efficient policies must be adopted as the more direct participation of enforcement organs in the preparation and application of Management Plan, which must be effective ensuring the conservation of the tree species as well as all the range of natural resources found within the limits of CUs. The potential distribution has shown areas with more probability of species occurrence, where it must be accomplished other studies that can reinforce the indication of these areas to establish an expansion, and/or new Cus / Mestrado / Análise Ambiental e Dinâmica Territorial / Mestre em Geografia
42

Kartläggning av kvicklera med hjälp av flygresistivitetsmätningar / Mapping quick clay using airborne resistivity measurements

Jönsson, Clara, Larsson, Linn January 2017 (has links)
Purpose: One of the major soil problems that the construction industry may face is the presence of a certain type of highly sensitive marine clay, known as quick clay. The quick clay possesses properties that allow the clay to move from being relatively stable to on mechanical impact losing virtually all shear strength and act as a viscous mass. The majority of the Swedish, Norwegian and Canadian landslides, caused by quick clay, have caused significant consequences due to lack of bearing capacity of quick clay. In order to prevent these landslides knowledge about where there is quick clay is required. A large-scale mapping work has therefore been ongoing for a long time. The government has for some time been researching how to streamline mapping work and the result has shown a connection between quick clay attendance and increased resistivity. The purpose of this study is to develop a theoretical framework for areas with higher risk for presence of quick clay based on linking the resistivity to geotechnical properties. Method: The study has mainly applied quantitative data collection methods in the form of data analyzes combined with literature studies. Measurement data used in the study comprise of data collected through geotechnical and geophysical surveys. Literature studies have mainly been supported by reports from previous research in the field. Result: The result of the study points to a variety of geological factors that can give rise to increased risk of quick clay existence such as good permeability, artesian groundwater and uneven mountain subsidence etc. The study also shows a possible link between resistivity and sensitivity. Consequences: The study demonstrates the possibility of linking resistivity to the geotechnical property sensitivity to facilitate and streamline the mapping of quick clay through airborne resistivity measuring. Limitations: The study is limited to studying two research areas in south western Sweden, Strömstad and Lödöse. The study intends to examine the evidence from previous surveys and no further supplementary studies are conducted. The work is also delimited to study the geotechnical and geophysical properties of quick clay (in terms of resistivity). Chemical aspects are not taken into account. / Syfte: Ett av de större markproblem bygg- och anläggningsbranschen kan tvingas stå inför är förekomsten av en viss typ av högsensitiv havsavsatt lera, kallad kvicklera. Kvickleran besitter egenskaper som innebär att leran kan gå från relativt stabil till att vid mekanisk påverkan förlora praktiskt taget all sin skjuvhållfasthet och uppträder som en trögflytande massa. Majoriteten av de svenska, norska och kanadensiska lerskred som medfört betydande konsekvenser har varit ett resultat av kvicklerans bristande bärighet. För att förebygga dessa kvickleraskred krävs vetskap om var kvicklera förekommer. Ett omfattande kartläggningsarbete har därför pågått under en lång tid. Staten har under en tid bedrivit forskning för att effektivisera kartläggningsarbetet och resultatet har visat på ett samband mellan kvickleraförekomst och förhöjd resistivitet. Syftet med detta examensarbete är att ta fram ett teoretiskt ramverk för områden med större risk för förekomst av kvicklera baserat på att koppla samband mellan resistivitet och geotekniska egenskaper i form av vattenkvot, sensitivitet och densitet. Metod: I studien har i huvudsak kvantitativa datainsamlingsmetoder i form av dataanalyser tillämpats i kombination med litteraturstudier. Mätdatat som studien omfattar är insamlad via geotekniska och geofysiska undersökningar, litteraturstudierna har främst tagit stöd i rapporter från tidigare forskning inom området. Resultat: Resultatet pekar på en rad olika geologiska faktorer som kan ge upphov till ökad risk för kvickleraförekomst, exempelvis god permeabilitet, artesiskt grundvatten samt ojämn bergunderyta etc. Studien visar även på en möjlig koppling mellan resistivitet och sensitivitet. Konsekvenser: Studien visar på möjligheten att koppla resistivitet till den geotekniska egenskapen sensitivitet för att underlätta och effektivisera kartläggningen av kvicklera genom flygburna resistivitetsmätningar. Begränsningar: Uppsatsen begränsas till att studera två undersökningsområden i sydvästra Sverige, Strömstad och Lödöse. Studien avser granska underlag från tidigare utförda undersökningar och inga ytterligare kompletterande undersökningar har utförts. Arbetet avgränsas till att studera kvicklerans geotekniska egenskaper samt dess resistivitetsegenskaper. Arbetet tar således inte hänsyn till kemiska aspekter.
43

Využití presiometrických zkoušek pro stanovení tvaru mobilizačních křivek vrtaných pilot v metodě přenosových funkcí / Utilization of pressuremeter tests for determination of load-transfer curves

Bírošík, Matej January 2022 (has links)
The thesis is divided into seven parts. The first part is theoretical and consists of description of load-transfer method and its principal, description of load-transfer curves used for following inverse analysis and method for determining shaft friction in ß method. In the second part, there is an explanation of the determination of Ménard pressuremeter modulus from pressuremeter tests. The third part consists of the pressuremeter tests analysis and description of evaluating process of the pressuremeter modulus for different types of subsoil. In the fourth part states parametric study of load-transfer curves compiled on the basis of the pressuremeter tests, where we display an impact of input parameters on a load-settlement curves. The fifth part contains inverse analysis of pile load tests, which are set in similar geological conditions. Summary of used input parameters for individual load-transfer curves states in the sixth part. These parameters are responsible of achieving the best match of predicted and measured load-settlement curves. The last part is devoted to the thesis conclusion, which is the determination of parameters as inputs to the shape of load-transfer curves for bored piles with utilization of the pressuremeter tests.
44

Numerical modelling of high-speed railway transition zone

Norberg, Karl January 2022 (has links)
Transition zones are changes in the track structure, detected by an abrupt deviationin track stiffness and/or differential settlements. One inevitable transition zone is thebridge approach. This study has investigated in this transition zone, adapted for highspeed,ballastless track. The aim was to observe the general behaviour of the transitionzone including its critical components, and to compare different measures, transitionconstructions, to manage with the eventual problems. A base model, called Nullmodel,was developed using the 3D finite element method to evaluate the behaviour of thetransition zone. Based on the Nullmodel, six comparative models have been created,including different types of transition constructions within the substructure. New forthis study is that it investigates the overall behaviour of the transition zone, and alsothe substitution of subballast in combination with approach blocks.For the general behaviour of the transition zone, the results have shown that theballastless track does not behave as a traditional ballasted track. Furthermore,the direction of travel affects the magnitude of different dynamical parameters.Comparing different transition constructions, replacing the subballast with ahydraulically bonded layer in combination with an approach block with cementbounded granular material is found to be the best alternative. Finally, the invertedapproach block is found to be an equally good, or better, mitigative measure incomparison with the regular approach block.
45

Análisis comparativo de la resistencia de suelos cohesivos usando los ensayos de penetración estándar, corte directo y triaxial en la urbanización Sol Naciente, provincia y distrito de Jaén - Cajamarca

Hurtado Guevara, Tobias Moises January 2024 (has links)
La tesis presentada se enfoca en un estudio experimental que busca establecer correlaciones entre tres ensayos realizados en suelo cohesivo: Ensayo de Penetración Estándar (SPT), Corte Directo y Triaxial. Las pruebas se realizaron en un terreno de 3 hectáreas denominado AA.HH. Sol naciente, llegando hasta una profundidad de 3.50 metros debido a características geotécnicas del suelo. A continuación, llevaron a cabo un estudio sobre las propiedades físicas del suelo utilizando varias pruebas estándar, incluyendo granulometría, límites de Atterberg, contenido de humedad y gravedad específica. Con base en la recopilación de datos existentes y las correlaciones de los ensayos, que fueron un total de 7 pruebas de cada ensayo en el terreno, con la ayuda de equipos y operadores locales. El propósito final del estudio es proponer correlaciones entre los resultados obtenidos de los tres tipos de ensayos. Esta investigación proporciona un aporte significativo al campo de la geotecnia y la ingeniería civil, ya que los hallazgos podrían mejorar el entendimiento de las propiedades del suelo y permitir cálculos más precisos en cuanto a resistencia y comportamiento del suelo bajo diversas condiciones de carga y presión. En última instancia, estos resultados pueden aumentar la seguridad y estabilidad de las construcciones futuras en estos suelos, proporcionando un enfoque más sólidoy fiable para el análisis de suelos y la planificación de proyectos de construcción. / The presented thesis focuses on an experimental study aiming to establish correlations among three tests performed on cohesive soil: Standard Penetration Test (SPT), Direct Shear, and Triaxial. The tests were carried out on a 3-hectare land plot called AA.HH. Sol Naciente, reaching a depth of 3.50 meters due to the soil's geotechnical characteristics. Subsequently, they conducted a study on the soil's physical properties using various standard tests, including particle size distribution, Atterberg limits, moisture content, and specific gravity. Based on the existing data compilation and the tests' correlations, a total of 7 tests of each were performed on the field, with the assistance of local equipment and operators. The final purpose of the study is to propose correlations among the results obtained from the three types of tests. This research provides a significant contribution to the field of geotechnical and civil engineering, as the findings could enhance the understanding of soil properties and allow more precise calculations regarding soil strength and behavior under various load and pressure conditions. Ultimately,these results may increase the safety and stability of future constructions on these soils, providing a more robust and reliable approach for soil analysis and construction project planning.
46

Análisis comparativo de estabilidad de taludes mediante las ecuaciones de equilibrio límite: método de morgenstern-price, spencer, sarma

Becerra Carrillo, Edgar Alonso January 2024 (has links)
Esta investigación tiene por finalidad Comparar las ecuaciones de equilibrio limite Morgenstern-Price, Spencer, Sarma aplicado a la estabilidad del talud del cerro Chalpón, distrito de Motupe y buscar una solución de estabilización del talud, el factor de seguridad del talud se obtendrá mediante el modelado en el software Slide, los datos que el software necesita son el perfil topográfico del talud, la cohesión, ángulo de fricción y peso específico de los materiales que lo conforman, para encontrar estos datos se debe hacer algunos ensayos de laboratorio cómo el ensayo de corte, el ensayo de peso específico y el ensayo de compresión de la roca. Se clasifico el macizo rocoso mediante índices de Bieniawski (R.M.R) con índices desde 47% hasta 63% mientras índice de calidad “Q” (Q de Barton) oscilo entre 0.325 a 2.375. Se elaboró 6 perfiles y cada perfil con 3 escenarios, de los cuales 4 perfiles tuvieron un factor de seguridad menor a 1.3, y se optó por las soluciones de estabilidad para el perfil “B” usar material de relleno (afirmado), para el perfil “C” se consideró 7 micropilotes de 5 m con diámetro de 13 cm distribuidos cada 1.5 m transversal y en el eje longitudinal estás distribuido cada 1 m, para perfil de “D” también necesita un muro de contención, y se debe rellenar como se muestra en el detalle con afirmado de las mismas características que el perfil C, para el perfil E se necesita 9 micropilotes de 13 cm de diámetro y 4 m de longitud y en el eje longitudinal estás distribuido cada 1 m, todos los micro pilotes serán clavados perpendicular al terreno. La solución beneficiará a que no haya deslizamientos de rocas ni de terrenos, lo que hará mantener su forma del cerro, evitando así el movimiento de tierra o escombros debido a deslizamientos. / The purpose of this research is to compare the equations of limit equilibrium Morgenstern-Price, Spencer, Sarma applied to the stability of the slope of Chalpon hill, district of Motupe and to look for a solution of slope stabilization, the safety factor of the slope will be obtained by modeling in the Slide software, The data that the software needs are the topographic profile of the slope, the cohesion, friction angle and specific weight of the materials that conform it, to find these data some laboratory tests must be done how the shear test, the specific weight test and the rock compression test. The rock massif was classified by means of Bieniawski indexes (R.M.R) with indexes from 47% to 63% while quality index "Q" (Barton's Q) ranged between 0.325 to 2.375. Six profiles were elaborated and each profile with three scenarios, of which four profiles had a safety factor lower than 1.3, and stability solutions were chosen for profile "B" using backfill material, for profile "C" 7 micropiles of 5 m with a diameter of 13 cm were considered, distributed every 1.5 m transversely and in the axis of the profile "C". 5 m transverse and in the longitudinal axis you are distributed every 1 m, for profile "D" also needs a retaining wall, and should be filled as shown in the detail with affirmed of the same characteristics as profile C, for profile E is needed 9 micropiles of 13 cm in diameter and 4 m in length and in the longitudinal axis you are distributed every 1 m, all micro piles will be nailed perpendicular to the ground. The solution will benefit that there will be no sliding of rocks or land, which will maintain the shape of the hill, thus avoiding the movement of earth or debris due to landslides.
47

Contribution à la formulation symétrique du couplage équations intégrales - éléments finis : application à la géotechnique / Contributing to the symmetric formulation of the coupling integral equations - finite elements : application to the geotechnics

Nguyen, Minh Tuan 17 September 2010 (has links)
Un des outils numériques les plus utilisés en ingénierie est la méthode des éléments finis, qui peut être mise en o euvre grâce à l'utilisation de nombreux codes de calcul. Toutefois, une difficulté apparaît lors de l'utilisation de la méthode des éléments finis, spécialement en géotechnique, lorsque la structure étudiée est en interaction avec un domaine de dimensions infinies. L'usage courant en ingénierie est alors de réaliser les calculs sur des domaines bornés, mais la définition de la frontière de tels domaines bornés pose de sérieux problèmes. Pour traiter convenablement les problèmes comportant des frontières à l'infini, l'utilisation d'éléments discrets "infinis" est maintenant souvent délaissée au profit de la méthode des équations intégrales ou "méthode des éléments de frontière" qui permet de résoudre un système d'équations aux dérivées partielles linéaire dans un domaine infini en ne maillant que la frontière du domaine à distance finie. La mise en oeuvre du couplage entre la méthode des éléments finis et la méthode des éléments de frontière apparaît donc comme particulièrement intéressante car elle permet de bénéficier de la flexibilité des codes de calcul par éléments finis tout en permettant de représenter les domaines infinis à l'aide de la méthode des éléments de frontière. La méthode est basée sur la construction de la "matrice de raideur" du domaine infini grâce à l'utilisation de la méthode des équations intégrales. Il suffit alors d'assembler la matrice de raideur du domaine infini avec la matrice de raideur du domaine fini représenté par éléments finis. L'utilisation de la méthode la plus simple de traitement des équations intégrales, dite méthode de « collocation » conduit à une matrice de raideur non-symétrique. Par ailleurs, la méthode dite «Singular Galerkin» conduit à une formulation symétrique, mais au prix du calcul d'intégrales hypersingulières. La thèse porte sur une nouvelle formulation permettant d'obtenir une matrice de raideur symétrique sans intégrales hypersingulières, dans le cas de problèmes plans. Quelques applications numériques sont abordées pour des problèmes courants rencontrés en géotechnique / One of the most used numerical tools in engineering is the finite element method, which can be implemented through the use of many computer codes. However, a difficulty arises when using the finite element method, especially in geotechnical engineering, where the structure is studied in interaction with a field of infinite dimensions. The commonly used in engineering is then performming the calculations on bounded domains, but the definition of the border of the domain also poses serious problems. To properly solve the problems which have the boundary at infinity, the use of discrete elements "infinite" is now often neglected in favor of the integral equations method or "boundary element method", which allows to solve a linear partial differential equations system in an infinite domain by the discretization of the only boundary of the domain at finite distance. The implementation of coupling between the finite element method and boundary element method is therefore particularly interesting because it allows to benefit the flexibility of computer codes by the finite element method, while the infinite domains is represented by the help of the integral equations method. It is sufficient to assemble the stiffness matrix of infinite domain with the stiffness matrix of finite domain represented by finite elements. Using the simplest method of treatment of integral equations, known as method of "collocation" leads to a non-symmetric stiffness matrix. Furthermore, a method known “Galerkin Singular” leads to a symmetric formulation, but it is at the cost of computing hypersingular integrals. The thesis focuses on a new formulation to obtain a symmetric stiffness matrix without full hypersingular, in the case of plane problems. Some numerical applications are discussed for common problems encountered in geotechnical engineering
48

Comparative Deterministic and Probabilistic Modeling in Geotechnics: Applications to Stabilization of Organic Soils, Determination of Unknown Foundations for Bridge Scour, and One-Dimensional Diffusion Processes

Yousefpour, Negin 16 December 2013 (has links)
This study presents different aspects on the use of deterministic methods including Artificial Neural Networks (ANNs), and linear and nonlinear regression, as well as probabilistic methods including Bayesian inference and Monte Carlo methods to develop reliable solutions for challenging problems in geotechnics. This study addresses the theoretical and computational advantages and limitations of these methods in application to: 1) prediction of the stiffness and strength of stabilized organic soils, 2) determination of unknown foundations for bridges vulnerable to scour, and 3) uncertainty quantification for one-dimensional diffusion processes. ANNs were successfully implemented in this study to develop nonlinear models for the mechanical properties of stabilized organic soils. ANN models were able to learn from the training examples and then generalize the trend to make predictions for the stiffness and strength of stabilized organic soils. A stepwise parameter selection and a sensitivity analysis method were implemented to identify the most relevant factors for the prediction of the stiffness and strength. Also, the variations of the stiffness and strength with respect to each factor were investigated. A deterministic and a probabilistic approach were proposed to evaluate the characteristics of unknown foundations of bridges subjected to scour. The proposed methods were successfully implemented and validated by collecting data for bridges in the Bryan District. ANN models were developed and trained using the database of bridges to predict the foundation type and embedment depth. The probabilistic Bayesian approach generated probability distributions for the foundation and soil characteristics and was able to capture the uncertainty in the predictions. The parametric and numerical uncertainties in the one-dimensional diffusion process were evaluated under varying observation conditions. The inverse problem was solved using Bayesian inference formulated by both the analytical and numerical solutions of the ordinary differential equation of diffusion. The numerical uncertainty was evaluated by comparing the mean and standard deviation of the posterior realizations of the process corresponding to the analytical and numerical solutions of the forward problem. It was shown that higher correlation in the structure of the observations increased both parametric and numerical uncertainties, whereas increasing the number of data dramatically decreased the uncertainties in the diffusion process.
49

Comportement sous chargement cyclique des massifs de sol renforcés par inclusions rigides : expérimentations en laboratoire et modélisation numérique / Behaviour under cyclic load of soils improved by rigid piles : experimentations and numerical modelling.

Houda, Moustafa 22 January 2016 (has links)
Une des méthodes les plus populaires et largement utilisée pour l’amélioration des sols compressibles est la technique d'inclusions rigides verticales qui constitue une alternative intéressante aux techniques plus traditionnelles telles que le pré-chargement, la mise en place de drains verticaux, le remplacement du sol en place, etc.Le Projet National ASIRI (Amélioration du Sol par Inclusions Rigides) a permis d’apporter des réponses sur le comportement de cette technique de renforcement et d’établir des recommandations de dimensionnement et de réalisation. Celui-ci comprend un volet expérimental (expérimentations en vraie grandeur, modèles physiques réduits à 1g, études en chambre d’étalonnage) et un volet numérique. Cependant, les recommandations publiées par ASIRI sont limitées aux cas de chargement monotone. Pourtant, différents cas de structures sous chargement cyclique sont couramment rencontrés dans la pratique: chargement des vagues sur les structures offshore, force du vent, charge sismique, la charge de trafic, remplissage et vidange de réservoirs, chargement et déchargement des zones de stockage… Cela nécessite alors de comprendre le comportement sous chargement cyclique et/ou dynamique de ces ouvrages.Ce travail de thèse constitue une contribution à la compréhension du comportement de ce type d’ouvrage, et s’intéresse plus particulièrement à la modélisation des mécanismes qui se développent dans le matelas de transfert de charge lors d’un chargement cyclique vertical quasi-statique. Il se fait suivant deux approches complémentaires : Expérimentale : par des essais sur un nouveau modèle physique réduit tridimensionnel à 1g et à l’échelle 1/10ème, Numérique : par la modélisation numérique tridimensionnelle en milieu continu utilisant le logiciel FLAC3D.Dans un premier temps, le travail expérimental réalisé nous a permis d’étudier le comportement de cette technique de renforcement sous chargement monotone et cyclique mettant en œuvre la méthode de corrélations d’images. La modélisation physique réalisée nous a permis d’étudier l’influence de l’épaisseur de la plateforme de transfert de charge granulaire et des conditions aux limites (cas remblai/cas dallage).Dans un deuxième temps, les résultats expérimentaux nous ont servi comme une base de données pour la validation d’un modèle numérique en milieu continu. La première étape de la modélisation numérique consiste à valider un modèle numérique à la même échelle réduite du modèle physique. La validation de l’approche de modélisation numérique à échelle réduite nous a permis, dans une deuxième étape, de réaliser une étude paramétrique afin de déterminer l’influence des différents paramètres sur le comportement du système. / One of the most popular and widely used methods for soft soil improvement is the reinforcement using vertical rigid inclusions. It constitutes an interesting alternative to the other traditional techniques such as preloading, vertical drains, replacing soil etc...The national French project ASIRI (Amélioration du Sol par Inclusions Rigides) allowed to provide answers about the behavior of this technique and to establish recommendations for design and construction. It included an experimental part (full-scale, 1g physical model experiments and calibration chamber studies) and a numerical part. However, the recommendations established by ASIRI are limited to the case of monotonic loading. Yet, various cases of structures under cyclic loading are commonly encountered in practice: waves loading on offshore structures, wind strength, seismic load, traffic load, filling and emptying of tanks, loading and unloading of storage areas... This then requires the understanding of the behavior of this technique under cyclic and/or dynamic loading.The work done in this thesis constitutes a contribution to understanding the behavior of this type of structures, and is particularly interested in modeling the mechanisms that develop in the load transfer mattress under a quasi-static vertical cyclic loading . Two complementary approaches have been followed: Experimental: by performing experimental tests using a new 1g tridimensional physical model with a scale factor of 1/10, Numerical: by performing numerical tridimensional simulations in a continuous media using the software FLAC3D.At first, the experimental work has allowed us to study the behavior of this reinforcement technique under monotonic and cyclic loading implementing the digital image correlation method. A parametric study performed with the physical modeling allowed us to study the influence of the granular load transfer platform (LTP) and the boundary conditions (presence of a rigid slab at the surface of the LTP).Secondly, the experimental results have served as a database for the validation of a numerical model in continuous medium. The first step of the numerical modeling is to validate a numerical model at the same reduced scale of the physical model. The validation of the numerical modeling approach at the reduced scale allowed us in a second step to perform a parametric study in order to determine the influence of different parameters on the behavior of the system.
50

Imagerie du module de cisaillement in situ du sol par méthodes d’ondes de surface et essais géotechniques : caractérisation des petites aux grandes déformations / Soil in situ shear modulus imagery by surface wave methods and geotechnical tests : characterization of small to big strains

Çami, Kastriot 29 May 2017 (has links)
Les projets géotechniques deviennent de plus en plus complexes et il s’avère alors nécessaire de caractériser de manière complète le comportement du sol dans les différentes plages de déformations sollicitées par le projet. Cependant les moyens mis en place lors de ces études sont souvent limités à quelques essais ponctuels lesquels ne donnent pour la plupart qu’une information liée à la résistance du terrain. Afin de caractériser de manière complète le comportement du sol avec la déformation, ce travail expose une étude détaillée de l’évolution du module de cisaillement avec la déformation en utilisant les méthodes d’ondes de surface, les essais géotechniques de laboratoire de mécanique des sols et les essais géotechniques in situ au pressiomètre. Des essais plus sophistiqués tels que l’essai à la colonne résonnante étau triaxial cyclique ont été aussi utilisés dans ce cadre. Le programme expérimental a permis de déterminer que le comportement du sol est non linéaire avec la déformation. Les observations réalisées ont permis de pouvoir proposer une démarche de caractérisation du comportement du sol en cas de disposition d’une information partielle. Ce mémoire de thèse présente une synthèse des données collectées par différents types d’essais in situ et en laboratoire qui ont permis de décrire l’évolution du module de cisaillement dans les différentes plages de déformations / The difficulty of dealing with complex geotechnical projects implies the necessity to determine adequately soil’s behaviour with strain’s increase. The information provided for these geotechnical studies mostly concerns soil’s in situ resistance and it is only punctual. In order to fully characterize soil’s behaviour with strains, this work exposes a detailed study of the shear modulus evolution with increasing strain by using surface waves methods, geotechnical laboratory tests such as soil mechanics tests and geotechnical in situ tests such as pressure meter test. More sophisticated tests such as resonant column test and cyclic triaxial test have been also used for this purpose. The experimental program described soil behaviour as being nonlinear. This observed behaviour permitted to propose an approach of characterizing the behaviour of soil incase if the needed information is only partial. This thesis manuscript presents a data synthesis of different types of in situ and laboratory tests which allowed describing soil shear modulus evolution for different ranges of deformation

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