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1
Ulvestad, Anders. "Consolidation Settlement of Suction Caissons". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bygg, anlegg og transport, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19504.
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Consolidation settlement analysis is an essential part of the design process for suction caissons. However it is a complex task since soil volume important for settlement analyses is directly affected by the installation process. Consolidation settlements have been found to be the critical design criterion in several subsea developments, adequate and correct analysis is therefore vital. The FEM code PLAXIS has been used to evaluate the reconsolidation process after completed installation of the suction caisson. Emphasize has been placed on studying the shear strength increase with time along the skirt walls. During consolidation dissipation of excess pore pressures result in higher effective stresses. Consequently the modeled undrained shear strength increases. However the increase is small compared to the expected increase in shear strength due to the set-up phenomenon. To account for the deviation an adjusted simulation procedure incorporating incremental increase of friction angle in the interface zones has been suggested. The results were found to be reasonable with respect to final consolidation settlements and development of mobilized shear strength with time.Adequate modeling of the changes in the interface zones adjacent to the caisson walls during consolidation is vital for correct prediction of long term settlements. Modeled undrained shear strength with time have huge impact on the analysis results due to different mobilization of the surrounding soil. Appropriate evaluation of soil structure interaction is essential to assess the reliability of the analysis. Taking into account changes of the soil volume important for settlement analysis is also vital. A simple physical model test has been performed. Due to delays and relatively short test period the results were inconclusive. However the importance of considering short term set-up effects has been underlined by recorded resistance and physical observations in the field.
2
Pinna, Rodney. "Buckling of suction caissons during installation". University of Western Australia. School of Civil Engineering, 2003. http://theses.library.uwa.edu.au/adt-WU2004.0008.
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Suction caissons are a foundation system for offshore structures which offer a number of advantages over traditional piled foundations. In particular, due to the method of installation used, they are well suited for deep-water applications. The suction caisson consists of an open ended cylindrical shell, which is installed below the seabed in a sequence which consists of two loading phases. The caisson is first installed part way under self weight, with the installation being completed by lowering the pressure within the cylinder and thus allowing the ambient water pressure to force the caisson into the ground. This thesis examines a number of structural issues which result from the form of the caisson — essentially a thin walled cylinder — and the interaction of the caisson with the surrounding soil during installation. To do this, variational analysis and nonlinear finite element analysis are employed to examine the buckling and collapse behaviour of these cylinders. In particular, two issues are considered; the influence of the open end, and the interaction between the cylinder and soil on the buckling and collapse loads. First, the behaviour of open ended cylinders is considered, where the boundary condition at the open end is allowed to vary continuously from completely free to pinned, by the use of a variable lateral spring. This lateral spring restraint may be considered to represent the intermediate restraint provided by a ring stiffener which is not fully effective. The effect of various combinations of boundary conditions is accounted for by the use of a multiplier on the lower bound to the buckling load of a cylinder with classical supports. The variable spring at the open end may also be considered to be an initial, simple representation of the effect of soil restraint on the buckling load. More complex representations of the soil restraint are also considered. A nondimensional factor is proposed to account for the influence of this spring on the buckling load. One combination of boundary conditions, where the upper end of the caisson is pinned, and the lower end free (referred to as a PF boundary condition), is found to have buckling and collapse behaviour which is unusual for cylindrical shells. Buckling loads for such shells are much lower than would be found for cylinders with more typical boundary conditions, and of similar dimensions. More unusually however, PF cylinders are shown to have positive postbuckling strength. The behaviour is found to be a result of the large flexibility which results from the low restraint provided by the PF boundary conditions. This is shown by continuously decreasing the flexibility of the cylinder, by increasing the axial restraint at the pinned end. It is shown that this results in a large increase in buckling load, and a return to more usual levels of imperfection sensitivity. In particular, with an intermediate level of axial restraint, buckling loads and imperfection sensitivity are intermediate between those of PF shells with no, and with full, axial restraint. Overall however, collapse loads for PF cylinders with no additional restraint are well below those of cylinders with stiffer boundary conditions, for equal geometries. Eigenvalue buckling of cylinders fully and partially embedded in an elastic material are examined, and two analytical solutions are proposed. One of these is an extension of a method previously proposed by Seide (1962), for core filled cylinders, to pin ended cylinders which have support from both a core and a surrounding material. The second method represents the elastic support as a two parameter foundation. While more approximate than the first method, this method allows for the examination of a wider range of boundary conditions, and of partial embedment. It is found that the buckling load of the shell/soil system decreases as the embedment ratio decreases. Collapse of fully and partially embedded cylinders is also examined, using nonlinear finite element analysis. The influence of plasticity in the soil is also considered. For cylinders with small imperfections, it is found that the collapse load shows a large increase over that of the same cylinder with no soil support. However, as the size of initial geometric imperfections increases, it is found that the collapse load rapidly approaches that of the unsupported cylinder. In particular, in weak soils the gain in strength over the unsupported shell may be minimal. The exception to this is again PF cylinders. As these have relatively low collapse loads, even very weak soils are able to offer an increase in collapse load over the unsupported case. Finally, a summary of these results is provided in the form of guidance for design of such structures.
3
Byrne, Byron Walter. "Investigations of suction caissons in dense sand". Thesis, University of Oxford, 2000. http://ora.ox.ac.uk/objects/uuid:64c30b2e-155c-4642-9115-5e2bf5667af5.
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Offshore structures are used in a variety of applications ranging from the traditional oil and gas extraction facilities to emerging renewable energy concepts. These structures must be secured to the seabed in an efficient and cost effective manner. A novel approach is to use shallow inverted buckets as foundations, installed by suction, in place of the more usual piles. These foundations lead to cost savings through reduction in materials and in time required for installation. It is necessary to determine how these foundations perform under typical offshore loading conditions so that design calculations may be developed. This thesis presents experimental data from a comprehensive series of investigations aimed at determining the important mechanisms to consider in the design of these shallow foundations for dense sand. Initially the long term loading behaviour (e.g. wind and current) was investigated by conducting three degree of freedom loading {V:M/2R:H} tests on a foundation embedded in dry sand. The results were interpreted through existing work-hardening plasticity theories. The analysis of the data has suggested a number of improved modelling features. Cyclic and transient tests, representing wave loading, were carried out on a foundation embedded in an oil saturated sand. The novel feature of the cyclic loading was that a 'pseudo-random' load history (based on the 'NewWave' theory) was used to represent realistic loading paths. Of particular interest was the tensile load capacity of the foundation. The results observed suggested that for tensile loading serviceability requirements rather than capacity may govern design. Under combined-load cyclic conditions the results indicated that conventional plasticity theory would not provide a sufficient description of response. A new theory, termed 'continuous hyperplasticity' was used, reproducing the results with impressive accuracy. Surprisingly, under the conditions investigated, loading rate was found to have a negligible effect on response.
4
Chen, Wen. "Uniaxial behaviour of suction caissons in soft deposits in deepwater". University of Western Australia. School of Civil and Resource Engineering, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0136.
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Suction caissons are a cost-effective alternative to traditional piles in deep to ultradeep waters. No design rule has been available on the axial capacity of suction caissons as part of the mooring system in soft sediments. In this research, a series of centrifuge tests were performed using instrumented model caissons, to investigate the axial capacity and radial stress changes around caissons during installation, consolidation and vertical pullout in normally consolidated, lightly overconsolidated and sensitive clays. Total pressure transducers instrumented on the caisson wall were calibrated for various conditions. The radial total stress acting on the external wall varied almost linearly during penetration and extraction of the caisson, with smaller gradients observed during post-consolidation pullout. Minimum difference was found in the penetration resistance and the radial total stress for caissons installed by jacking or by suction, suggesting that the mode of soil flow at the caisson tip is similar under these two types of installation. Observed soil heave showed that the soil particles at the caisson tip flow about evenly outside and inside the caisson during suction installation. Comparison was made between measurements and various theoretical predictions, on both the radial stress changes during caisson installation, and the radial effective stress after consolidation. Significant under-predictions on excess pore pressure changes, consolidation times and external shaft friction ratios were found for the NGI Method, based on the assumption that the caisson wall is accommodated entirely by inward motion of the clay during suction installation. Obvious over-predictions by the MTD approach were found in both stress changes and shaft capacity of the caissons. A simple form of cavity expansion method was found to give reasonable estimations of stress changes and post-consolidation external shaft friction. A model for predicting the penetration resistance of suction caissons in clay was evaluated. Upper and lower bound values of external shaft friction ratio during uplift loading after consolidation were derived. Uplift capacity of caissons under sustained loading and cyclic loading were investigated, revealing approximately 15 to 30% reduction of the capacity compared to that under monotonic loading. External shaft friction ratios and reverse end-bearing capacity factors were both found to be significantly lower than those under monotonic loading
5
McKenna, Janice Elizabeth. "Wave forces on caissons and breakwater crown walls". Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263464.
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Ropert, François. "Modélisation numérique du comportement hydraulique des caissons Jarlan". Compiègne, 1999. http://www.theses.fr/1999COMP1203.
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Parmi l'ensemble des ouvrages verticaux soumis à la houle, les caissons Jarlan représentent le type de structure le plus fréquemment construit en France au cours des trois dernières décennies. Ces ouvrages sont le siège de phénomènes hydrauliques complexes, ce qui rend leur dimensionnement particulièrement délicat, notamment sous l'influence des houles obliques. L'objet du présent travail est de proposer une modélisation, par la méthode des éléments finis, des phénomènes les plus pertinents, visant à déterminer à chaque instant l'allure du plan d'eau dans le voisinage immédiat de l'ensemble des parois compo-sant l'ouvrage, afin de pouvoir calculer dans une phase ultérieure, les efforts locaux et glo-baux s'exerçant sur la structure. Deux modèles numériques bidimensionnels verticaux et un modèle bidimen-sionnel horizontal ont été développés pour couvrir l'ensemble des phénomènes à traiter. Il s'agit de modèles stationnaires travaillant avec une houle monochromatique. Les phénomènes de perte de charge et de dissipation induites par la pré-sence des perforations sont prises en compte à travers leur influence globale, moyennée sur une période et quantifiée en termes de consommation de flux d'énergie. L'exploitation du modèle horizontal, qui est couplé à un modèle classique de Berkhoff a nécessité la formulation de nouvelles conditions aux limites pour les frontières ouvertes, notamment en raison du caractère multidirectionnel de la réflexion des ouvrages composés de caissons Jarlan. Les modèles numériques ont été validés sur la base de résultats obtenus lors d'essais en modèles réduits physiques, en particulier ceux de l'Université du Havre et ceux réalisés à la SOGREAH conçus précisément à cette fin.
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Supachawarote, Chairat. "Inclined load capacity of suction caisson in clay". University of Western Australia. School of Civil and Resource Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0188.
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This thesis investigates the capacity and failure mode of suction caissons under inclined loading. Parametric finite element analyses have been carried out to investigate the effects of caisson geometry, loading angle, padeye depth (i.e. load attachment point), soil profile and caisson-soil interface condition. Displacement-controlled analyses were carried out to determine the ultimate limit state of the suction caissons under inclined load and the results presented as interaction diagrams in VH load space. VH failure interaction diagrams are presented for both cases where the caisson-soil interface is fully-bonded and where a crack is allowed to form along the side of the caisson. An elliptical equation is fitted to the normalised VH failure interaction diagram to describe the general trend in the case where the caisson-soil interface is fully-bonded. Parametric study reveals that the failure envelope in the fully-bonded case could be scaled down (contracted failure envelope) to represent the holding capacity when a crack is allowed to form. A stronger effect of crack on the capacity was observed in the lightly overconsolidated soil, compared to the normally consolidated soil. The sensitivity of caisson capacity to the changes in load attachment position or loading angle was quantified based on the load-controlled analyses. It was found that, for caisson length to diameter ratios of up to 5, the optimal centreline loading depth (i.e. where the caisson translates with no rotation) is in the range 0.65L to 0.7L in normally consolidated soil, but becomes shallower for the lightly overconsolidated soil profile where the shear strength profile is more uniform. The reduction of holding capacity when the padeye position is shifted from the optimal location was also quantified for normally consolidated and lightly overconsolidated soil profiles at loading angle of 30 [degrees]. Upper bound analyses were carried out to augment the finite element study. Comparison of holding capacity and accompanying failure mechanisms obtained from the finite element and upper bound methods are made. It was found that the upper bound generally overpredicted the inclined load capacity obtained from the finite element analyses especially for the shorter caisson considered in this study. A correction factor is introduced to adjust the upper bound results for the optimal condition. Comparisons of non-optimal capacity were also made and showed that the agreement between the upper bound and finite element analyses are sensitive to the change in the centreline loading depth when the caisson-soil interface is fully bonded, but less so when a crack forms.
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Senders, Marc. "Suction caissons in sand as tripod foundations for offshore wind turbines". University of Western Australia. School of Civil and Resource Engineering, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0163.
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[Truncated abstract] The demand for offshore wind turbines is increasing in densely populated areas, such as Europe. These constructions are typically founded on a gravity foundation or a large 'mono pile'. Gravity foundations can only be used at locations where strong soils exist and water depths are limited. Costs associated with a 'mono pile' type foundation contribute to a very large percentage of the total investment costs. This research, therefore, focuses upon a different foundation for offshore wind turbines, namely suction caissons beneath a tripod. This foundation can be used in all kinds of soil types and is cheaper than the 'mono pile' foundation, both in the amount of steel used and installation costs. Cheaper foundations can contribute to a more competitive price for offshore wind energy in comparison with other energy resources. To date, there have been relatively few studies to investigate the behaviour of this type of foundation during the installation process and during operational and ultimate loading for seabed conditions comprising dense sand. Two types of investigations were performed during this research to determine the behaviour of suction caissons beneath a tripod. Firstly, an existing computer program was extended to predict the typical loading conditions for a tripod foundation. Secondly, centrifuge tests on small scale suction caissons were performed to investigate the behaviour during the installation and loading phases. The computer program developed helped to quantify the likely ranges of environmental loading on an offshore wind turbine. For a typical 3 MW wind turbine of 90 m height, the vertical load is low at around 7 MN. During storm conditions the horizontal hydrodynamic load can be in the order of 4 MN. During normal working conditions the horizontal aerodynamic loads can reach 0.4 MN, but can increase to 1.2 MN when the pitch system malfunctions and gusts reach 30 m/s. This aerodynamic load will result in a very large contribution to the overturning moment, due to the high action point of this load. When the wind turbine is placed on top of a tripod, these large moments are counteracted by a push-pull system. ... The development of differential pressure was found to depend on the soil permeability, the extraction speed and a consolidation effect. During cyclic loading no obvious signs of a decrease in resistance were observed. During very fast cyclic loading differential pressures developed, which could increase the drained frictional resistance by approximately 40%. All centrifuge tests results were used to develop methods to predict or back calculate the installation process of suction caissons in sand and layered soil, and the behaviour during tensile and cyclic loading. These methods all use the cone resistance as the main input parameter and predict the force (or required suction) as a function of time, for a given rate of pumping or uplift displacement, in addition to the variation of suction with penetration (or force with uplift displacement). These new methods provide a useful tool in designing a reliable foundation for offshore wind turbines consisting of a tripod arrangement of suction caissons embedded in dense sand.
9
Sgardeli, Christina G. (Georgia-Chrysouli C. ). "A finite element analysis of the pullout capacity of suction caissons in clay". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53111.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.Includes bibliographical references (leaves 90-92).
Suction caissons are increasingly becoming the foundation of choice for offshore structures in deep water. They are used extensively in Tension Leg Platforms and provide the most efficient foundations for many offshore wind turbine structures. One of their major advantages is the ability to withstand large uplift forces by mobilizing shear on their external and internal surface and by the suction forces induced in the enclosed soil plug. These suction forces can be relied upon for short-term loading, while the behaviour of the soil remains undrained, but are more questionable for the sustained loading induced by storms and loop currents. This study uses finite element analysis to investigate the uplift capacity of suction caissons under three loading conditions: a) short-term undrained loading, b) long-term drained loading and c) sustained loading for short and long periods of time. The study compares the capacity from 5 different geometries with length to diameter ratios, L/d = 0.5,0.65,1,2 and 3 under these three loading conditions. For the sustained loading case, a minimum time under which the load can be sustained is established for different load levels. The commercial finite element program Plaxis is used and a Mohr-Coulomb model is assumed for the soil. Comparisons are presented between the results of this study, the theoretical Mohr-Coulomb model predictions and other finite element analysis found in the research for undrained and drained loading.
by Christina G. Sgardeli.
M.Eng.
10
Seigneurin, Alain. "Instabilité de structures formées de plaques orthotropes (écrasement de caissons en carton ondulé)". Bordeaux 1, 1988. http://www.theses.fr/1988BOR10547.
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On etudie l'instabilite d'un caisson soumis a la compression en utilisant l'analyse lineaire au second ordre. La structure est supposee formee de quatre plaques, ce qui necessite une parfaite connaissance du type de liaison permettant leur assemblage. La principale modelisation decrite dans cette etude est basee sur la resolution des equations d'equilibre, etude classique qui permet une approche analytique du probleme. On n'a pu mener cette etude qu'en ayant prealablement effectue les essais mecaniques caracterisant le materiau constitutif (le carton ondule). Celui-ci est suppose dans une premiere approche homogene et orthotrope
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Seigneurin, Alain. "Instabilité de structures formées de plaques orthotropes écrasement de caissons en carton ondulé /". Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37618514k.
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El-Gharbawy, Sherif Lotfy. "The pullout capacity of suction caisson foundations /". Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Colmard, Christophe. "Etude des phénomènes induits par les digues partielles de type caissons fondés sur pieux". Le Havre, 1997. http://www.theses.fr/1997LEHA0003.
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La construction des digues en eau profonde pose de nombreux problèmes dont en particulier celui du volume considérable de matériaux nécessaires à la réalisation. Pour remédier a cette difficulté, un nouveau type d'ouvrage a fait son apparition. Il s'agit de caissons préfabriqués, flottants, remorques sur le site et fixes sur pieux. Ce type d'ouvrage, ne coupant que partiellement le port du large, ne se comporte pas comme une digue ordinaire et le phénomène caractérisant son fonctionnement est appelé mur d'eau fixe. De façon à mieux connaitre le phénomène, nous l'avons analyse sur modelé réduit et nous avons effectué une étude à la fois expérimentale et numérique au Laboratoire de Mécanique des Fluides et Génie Civil du Havre. Cette étude met en évidence les effets moyens du phénomène et l'évolution du système de façon instantanée. Les champs de vitesses nous ont permis d'offrir de nouvelles solutions optimisant le profil de la digue. La configuration bybop est montrée
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Semai, Jugurtha. "Formation de silicium poreux appliquée à la réalisation de caissons isolants dans le silicium". Thesis, Tours, 2010. http://www.theses.fr/2010TOUR4032/document.
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Le développement du marché des appareils de communication nomades, a nécessité l'intégration de composants passifs et actifs sur du silicium via des montages « hybrides ».Ceci a amené le LMP partenaire de l'entreprise STMicroelectronics à rechercher des solutions pour une intégration « monolithique ». Le silicium micro/mésoporeux est un candidat potentiel pour satisfaire les exigences de cette intégration. Ce travail traite de la réalisation de caissons profonds de silicium poreux sur silicium résistif de type P 30-50 Ω.cm et N 37-46Ω.cm. L'utilisation de l'acide acétique comme solvant industriellement compatible nous a permis de réaliser des structures micro/mésoporeuses. L'intégrité mécanique de nos échantillons a été étudiée via la mesure de la porosité en fonction de l'épaisseur. Ainsi des caissons poreux avec des épaisseurs de plus de 400 µm et 50 % de porosité ont été fabriqués.La réalisation d'une couche N⁺ sur du silicium type N 37-46 Ω.cm a permis la mise en œuvre de doubles couches composées d'une dizaine de micromètres de micro/mésoporeuse sur une couche de 200 µ.m de silicium macroporeux. Des changements importants ont été observés par addition d'une très faible quantité d'un tensioactif (triton X-I00®) a notre solution électrolytique et où des doubles couches ont été obtenues sur silicium type P 30-50 Ω.cmThe rapid expansion of wireless devices caused a tremendous demand of the development of active and passive devices integration on silicon via « hybrid » systems. The search of a« monolithic » integration has led the LMP in partnership with STMicroelectronics to focus on this topic. Micro/Mesoporous silicon is a good candidate to fulfill the requirements to achieve this purpose. The present work deals with the realization of thick porous silicon layers on low doped P type (30-50 Ω.cm) and N type Si (37-46 Ω.cm). The use of a particular solution based on HF-H₂O and acetic acid allowed the implementation of micro/mesoporous Si structures. The mechanical integrity is studied via the porosity and the PS layer thickness.Thus layers with a thickness up to 400 µm have been implemented with a porosity of 50 % on P Type Si samples. Double layers with micro/mesoporous layer of tenth micrometers on a macroporous layer stack up to 200 µm have been realized on N-Type Si samples via the realization of an N⁺ layer by phosphorous implantation. Important changes occurred when a tiny amount of surfactant (triton X-I00®) has been introduced into our organic electrolyte and allowed the implementation of double layers on P type Si
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De, Luca Ugo. "Le barotraumatisme pulmonaire dans la hernie diaphragmatique congénitale : étude expérimentale chez le mouton". Master's thesis, Université Laval, 1985. http://hdl.handle.net/20.500.11794/33648.
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Moras, Benoît Pierre. "Étude de l'effet d'échelle sur la déformation à rupture des aciers à hautes vitesses de déformation". Metz, 2000. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/2000/Moras.Benoit.SMZ0028.pdf.
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L'Institut fur reaktorsicherheit Forschungszentrum de Karlsruhe dispose de maquettes de couvercle de cuve de réacteur nucléaire sur lesquelles sont réalisées des simulations d'explosions. Afin d'extrapoler les résultats de ces expériences à des réacteurs de taille réelle, une bonne compréhension de l'effet d'échelle sur les caractéristiques mécaniques des matériaux constituant les cuves de réacteurs est nécessaire. Les principaux éléments des cuves de centrales nucléaires sont constitues d'aciers ferritique et austénitique. Dans le cadre de cette étude, ces aciers ont été testés à des vitesses de déformation allant de 0. 001/s à 200/s. Des éprouvettes axisymmetriques lisses et entaillées de trois diamètres 3, 9 et 30 millimètres ont été considérées. Les résultats d'essais obtenus ont montré que l'unique caractéristique des aciers affectée par la taille des éprouvettes était la déformation à rupture, les déformations à rupture mesurées sur les éprouvettes de grands diamètres étant plus faibles que celles mesurées sur les éprouvettes de diamètre plus petit. Une étude bibliographique étendue a été effectuée afin de trouver des idées d'approches permettant de traiter de l'effet d'échelle dans les matériaux ductiles et d'en identifier les origines possibles. A la vue des articles répertoriés, il est apparu que les inclusions présentent dans les métaux ductiles pouvaient être à l'origine de l'effet d'échelle observé, soit parce que le taux de croissance critique des inclusions suit une loi statistique, soit parce la taille des inclusions et leur espacement est indépendant de la taille structure considérée, soit parce que la croissance des inclusions dépendant de la distribution de la triaxialité des contraintes. Dans l'étude théorique effectué ici un modèle de rupture basé sur la triaxialité des contraintes et l'existence d'une dimension intrinsèque au processus de rupture a été testé, ce modèle s'est révélé inadapté pour traiter de l'effet d'échelle rencontré. D'autre part, il a été montré qu'un critère de rupture ductile uniquement basé sur la triaxialité des contraintes permettait de prédire de manière acceptable la rupture des éprouvettes testées. Finalement, il a été montré qu'une loi d'effet d'échelle en fonction puissance pouvait être utilisée pour traiter de l'effet d'échelle rencontré à la déformation à la rupture
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Tran, Manh Ngoc. "Installation of Suction Caissons in Dense Sand and the Influence of Silt and Cemented Layers". University of Sydney, 2006. http://hdl.handle.net/2123/4064.
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Doctor of PhilosophySuction caissons have been used in the offshore industry in the last two decades as both temporary mooring anchorages and permanent foundation systems. Although there have been more than 500 suction caissons installed in various locations around the world,understanding of this concept is still limited. This thesis investigates the installation aspect of suction caissons, focusing on the installation in dense sand and layered soils, where sand is inter-bedded by silt and weakly cemented layers. The research was mainly experimental, at both normal gravity and elevated acceleration levels in a geotechnical centrifuge, with some numerical simulations to complement the experimental observations. This study firstly explored the suction caisson installation response in the laboratory at 1g. The influence and effect of different design parameters, which include caisson size and wall thickness, and operational parameters including pumping rate and the use of surcharge were investigated in dense silica sand. The sand heave inside the caisson formed during these installations was also recorded and compared between tests. The 1g study also investigated the possibility of installing suction caissons in layered sand-silt soil, where caissons were installed by both slow and rapid pumping. The heave formation in this case is also discussed. The mechanism of heave formation in dense sand and deformation of the silt layer was further investigated using a half-caisson model and the particle image velocimetry (PIV) technique. The installation response at prototype soil stress conditions was then investigated in a geotechnical centrifuge. The effects of caisson size, wall thickness, as well as surcharge were investigated in various types of sand, including silica sand, calcareous sand dredged from the North Rankin site in the North West Shelf (Australia), and mixed soil where silica sand was mixed with different contents of silica flour. Comparison with the 1g results was also made. The general trend for the suction pressure during installation in homogenous sand was identified. The installation in layered soil was also investigated in the centrifuge. The installation tests were performed in various sand-silt profiles, where the silt layers were on the surface and embedded within the sand. Comparison with the results in homogenous sand was made to explore the influence of the silt layer. Installations in calcareous sand with cemented layers were also conducted. The penetration mechanism through the cemented layer is discussed, and also compared with the penetration mechanism through the silt layer. Finite element modelling was performed to simulate key installation behaviour. In particular, it was applied to simulate the sand deformation observed in the PIV tests. The likely loosening range of the internal sand plug during suction installation in silica sand was estimated. By investigating the development of hydraulic gradient along the inner wall, the principle underlying the suction response for different combinations of selfweight and wall thickness was identified. FE modelling was also performed to explore the influence of the hydraulic blockage by the silt layer. This study found that the caissons could penetrate into all soils by suction installation. Among the key findings are the observations that the suction pressure increases with depth following a distinct pressure slope, corresponding to a critical hydraulic condition along the inner wall; and the installation was possible in both layered sand-silt and uncemented-cemented soils if sufficient pumping was available. While the caisson could penetrate the weakly cemented layers well with no notable adverse effects, problems were observed in the installation in layered sand-silt soil. These include piping failure in slow pumping rate installation at 1g, and the formation of extremely unstable soil heave during installation.
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Tran, Manh Ngoc. "Installation of Suction Caissons in Dense Sand and the Influence of Silt and Cemented Layers". Thesis, The University of Sydney, 2005. http://hdl.handle.net/2123/4064.
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Suction caissons have been used in the offshore industry in the last two decades as both temporary mooring anchorages and permanent foundation systems. Although there have been more than 500 suction caissons installed in various locations around the world,understanding of this concept is still limited. This thesis investigates the installation aspect of suction caissons, focusing on the installation in dense sand and layered soils, where sand is inter-bedded by silt and weakly cemented layers. The research was mainly experimental, at both normal gravity and elevated acceleration levels in a geotechnical centrifuge, with some numerical simulations to complement the experimental observations. This study firstly explored the suction caisson installation response in the laboratory at 1g. The influence and effect of different design parameters, which include caisson size and wall thickness, and operational parameters including pumping rate and the use of surcharge were investigated in dense silica sand. The sand heave inside the caisson formed during these installations was also recorded and compared between tests. The 1g study also investigated the possibility of installing suction caissons in layered sand-silt soil, where caissons were installed by both slow and rapid pumping. The heave formation in this case is also discussed. The mechanism of heave formation in dense sand and deformation of the silt layer was further investigated using a half-caisson model and the particle image velocimetry (PIV) technique. The installation response at prototype soil stress conditions was then investigated in a geotechnical centrifuge. The effects of caisson size, wall thickness, as well as surcharge were investigated in various types of sand, including silica sand, calcareous sand dredged from the North Rankin site in the North West Shelf (Australia), and mixed soil where silica sand was mixed with different contents of silica flour. Comparison with the 1g results was also made. The general trend for the suction pressure during installation in homogenous sand was identified. The installation in layered soil was also investigated in the centrifuge. The installation tests were performed in various sand-silt profiles, where the silt layers were on the surface and embedded within the sand. Comparison with the results in homogenous sand was made to explore the influence of the silt layer. Installations in calcareous sand with cemented layers were also conducted. The penetration mechanism through the cemented layer is discussed, and also compared with the penetration mechanism through the silt layer. Finite element modelling was performed to simulate key installation behaviour. In particular, it was applied to simulate the sand deformation observed in the PIV tests. The likely loosening range of the internal sand plug during suction installation in silica sand was estimated. By investigating the development of hydraulic gradient along the inner wall, the principle underlying the suction response for different combinations of selfweight and wall thickness was identified. FE modelling was also performed to explore the influence of the hydraulic blockage by the silt layer. This study found that the caissons could penetrate into all soils by suction installation. Among the key findings are the observations that the suction pressure increases with depth following a distinct pressure slope, corresponding to a critical hydraulic condition along the inner wall; and the installation was possible in both layered sand-silt and uncemented-cemented soils if sufficient pumping was available. While the caisson could penetrate the weakly cemented layers well with no notable adverse effects, problems were observed in the installation in layered sand-silt soil. These include piping failure in slow pumping rate installation at 1g, and the formation of extremely unstable soil heave during installation.
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Barge, David. "Etude de la faisabilité de caissons traversant dans le silicium pour application aux composants de puissance". Aix-Marseille 3, 2001. http://www.theses.fr/2001AIX30111.
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La diffusion de dopants dans le silicium, sur des profondeurs dépassant dix microns, est un procédé peu étudie en technologie nucro-éîèctroniquc, Celui ci est pourtant potentiellement utile pour l'élaboration de dispositifs de puissance aux propriétés électriques originales. Cette diffusion nécessite cependant la mise en oeuvre des recuits particulièrement longs ̂à des température très élevées. Les. Effets de ce type de traitement thermique sur les propriétôs'du silicium sont peu connus. Nous avons étudié Pimpact de ces recuits sur l'état de surface et les propriétés électriques du silicium orienté (100). Nous avons pu mettre alors en évidence une fortedégradation de la surface. Celle ci à pu être pu reliée à une dynamique de surface inattendue, dont nous avons pu rendre compte des effets sur la topographie de la face * (100) au moyen d'un modèle BCT. La dégradation des propriétés électriques du silicium, elte, a pu être reliée à la diffusion d p̂uretés, dont nous avons pu atténuer les effets ne procédant à une neutralisation appropriée de leur propriétés électriquesDiffusion of dopants in silicon in depths exceeding 10 micron is a process rarely studied micro-electromcs. This kind of process of some interest for the elaboration of specific power devices. However, to perform such diffusion, a long time si needed, even a high temperature, and the consequence of a this long annealing on the properties of silicon are almost unknown. We have studied the impact of these annealings on the surface state and the electric properties of (100) silicon. A strong perturbation of the surface state was shown. This degradation could be linked with an unsuspected surface dynamic, that can be explained with an adapted BCF model. The observed degradation of the electrical properties of the silicon could be linked with impurities diffusion during the annealing. We have shown that it was possible to reduce the effects of these impurities by an adequate gettering
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DEHU, PASCALE. "Utilisation du silicium poreux pour realiser des caissons diffuses en technologie des composants electroniques de puissance". Paris, CNAM, 1994. http://www.theses.fr/1994CNAM0187.
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Nous avons utilise la technologie du silicium poreux pour realiser des caissons d'isolement destines aux composants de puissance. Cette realisation a necessite le franchissement de trois etapes. La premiere est la formation de couches poreuses profondes obtenues par anodisation electrochimique du silicium en milieu acide fluorhydrique. Le procede que nous proposons a donne de tres bons resultats: homogeneite de la repartition des pores a la surface et dans l'epaisseur du substrat. On anodise une tranche de silicium n-, dans pratiquement toute son epaisseur (350m) en une quarantaine de minutes. La deuxieme etape est la localisation des zones poreuses. Nous avons montre les possibilites de masquage qu'offre le polysilicium, qu'il soit isole du substrat par une couche d'oxyde ou non. D'autre part, nous avons determine la structure du masque qui convient le mieux. Il est compose d'une couche de polysilicium deposee sur une epaisseur d'oxyde. Ce dernier doit etre totalement encapsule par le silicium polycristallin afin d'etre protege de la dissolution par l'acide. Enfin, c'est la diffusion qui a finalement ete realisee dans les zones poreuses localisees. Le procede que nous avons utilise permet d'obtenir des profondeurs de jonction variables. Il suffit d'ajuster la duree de la redistribution en fonction de la profondeur desiree. On diffuse ainsi des impuretes dopantes dans toute l'epaisseur d'une tranche en un temps relativement court
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Laval-Meunier, Fabien. "Etude des aérodontalgies chez le personnel navigant civil et militaire en France en 2010". Bordeaux 2, 2010. http://www.theses.fr/2010BOR20074.
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En médecine aéronautique, on regroupe sous le terme de dysbarisme l’ensemble des troubles physiopathologiques répondants à l’effet de la diminution de la pression barométrique sur les gaz contenus dans l’organisme. Le terme de barodontalgie se rapporte à une douleur au niveau de la sphère ORL relative à un changement de pression atmosphérique. Les aérodontalgies désignent quant à elles des douleurs dentaires se déclenchent au cours du vol. Elles furent étudiées pour la première fois durant les années quarante et la seconde guerre mondiale. Pourtant, à l’heure actuelle, aucun consensus concernant la physiopathologie exacte des aérodontalgies n’existe. Il semblerait que les aérodontalgies soient d’origine multifactorielle. La dernière partie de notre travail comporte une étude réalisée sur 1184 navigants et montre que malgré les progrès technologiques accomplis en aviation et en dentisterie, les aérodontalgies sont bien présentent en 2010. Le chirurgien-dentiste du personnel navigant devra donc être très attentif à la qualité des soins réalisés sur ces patients. Il devra s’attacher à éradiquer toutes sources possibles d’aérodontalgies lors d’examens de prévention (panoramiques dentaire, rétro-alvéolaires, tests de vitalité pulpaire). Il devra tout mettre en œuvre pour que les traitements ne soient pas la cause de nouvelles douleurs dentaires au cours des volsIn aeronautical medicine, all the physiopathological effects due to the decrease in the barometric pressure of gases contained in the body are gathered under the term dysbarism. Pain is the O. R. L. Sphere caused by any change in pressure is called barodontalgia. As for aerodontalgia, it refers to dental pain that starts to occur during flight. It has been studied for the first time during the Forties and the Second World War. However, at present, there is not yet any consensus on the exact physiopathology of aerodontalgia. It seems that the latter might be multifactorial. The last part of our work consist of a study made on 1184 crew members. It shows that despite all the technological progresses in aviation and dentistry, aerodontalgia is still present in 2010. The dental surgeon treating patients who are crew members has to be very careful regarding treatment quality. He will to eradicate all possible sources of aerodontalgia during preventive examination (by using for instance dental panoramic X-rays, retroalveolar X-rays, pulp vitality tests). He must also use all possible means so that the dental treatment does not trigger any new dental pain during flight
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Zhou, Hongjie. "Numerical study of geotechnical penetration problems for offshore applications". University of Western Australia. Centre for Offshore Foundation Systems, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0239.
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The research carried out in this thesis has concentrated on the application of numerical solutions to geotechnical penetration problems in offshore engineering. Several important issues closely relevant to deep-water oil and gas developments were investigated, covering installation of suction caisson foundations, interpretation of fullflow penetrometers and shallow penetration of a cylindrical object (submarine pipeline or T-bar), all in clayey sediments such as are often encountered in deep-water sites. These problems are commonly characterised by large vertical movements of structural elements relative to the seabed. A large deformation finite element method was adopted and further developed to simulate these challenging problems, referred to as Remeshing and Interpolation Technique with Small Strain. In this approach, a sequence of small strain Lagrangian increments, remeshing and interpolation of stresses and material properties are repeated until the required displacement has been reached. This technique is able to model relative motion between the penetrating objects and the soil, which is critical for evaluating soil heave inside the caissons, the effect of penetration-induced remoulding on the resistance of full-flow penetrometers, and influence of soil surface heave on the embedment of pipelines. '...' Simple expressions were presented allowing the resistance factors for the T-bar and ball penetrometers to be expressed as a function of the rate and strain-softening parameters. By considering average strength conditions during penetration and extraction of these full-flow penetrometers, an approximate expression was derived that allowed estimation of the hypothetical resistance factor with no strain-softening, and hence an initial estimate of the stain-rate dependency of the soil. Further simulations of cyclic penetration tests showed that a cyclic range of three diameters of the penetrometers was sufficient to avoid overlap of the failure mechanism at the extremes and mid-point of the cyclic range. The ball had higher resistance factors compared with the T-bar, but with similar cyclic resistance degradation curves, which could be fitted accurately by simple expressions consistent with the strain-softening soil model adopted. Based on the curve fitting, more accurate equations were proposed to deduce the resistance factor with no strain-softening, compared with that suggested previously based on the resistances measured in the first cycle of penetration and extraction. The strain-rate dependency was similar in intact or post-cyclic soil for a given rate parameter. The resistance factor for the post-cyclic condition was higher than that for the initial conditions, to some degree depending upon soil sensitivity and brittleness parameter. For the shallow penetration of a cylindrical object, the penetration resistance profile observed from centrifuge model tests was very well captured by the numerical simulation. The mechanism of shear band shedding was reproduced by the numerical technique, although the frequency of the shear band generation and the exact shape of the heave profile were not correctly captured, which were limited by the simple strainsoftening soil model adopted.
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Varun. "A Simplified Model for Lateral Response of Caisson Foundations". Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14016.
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Caisson or pier foundations are encountered as part of the foundation system of tall structures such as bridges, transmission towers, heliostats, etc, and correspond to rigid blocks of length-to-diameter (D/B) ratio on the order of D/B = 2-6. As a result of their geometry and stiffness characteristics, the mechanisms of load transfer from the superstructure to the surrounding soil and their kinematic response to seismic wave propagation are governed by a complex stress distribution at the pier-soil interface, which cannot be adequately represented by means of simplified Winkler models for shallow foundations or flexible piles. Continuum model solutions, such as 3D finite elements (FE) cannot be employed frequently in practice for the design of non-critical facilities due to the cost and effort associated with these analyses. The objective of this work is to develop a Winkler-type model for the analysis of transversely-loaded caissons, which approximately accounts for all the main soil resistance mechanisms mobilized, while retaining the advantages of simplified methodologies for design at intermediate levels of target accuracy. Investigation of the governing load-transfer mechanisms and development of complex spring functions is formulated on the basis of 3D FE simulations. Initially, the soil-structure stiffness matrix is computed by subjecting the pier to transverse static and dynamic loading at the top, and numerically estimating the response. Complex frequency-dependent functions are next developed for the spring constants by equating the stiffness matrix terms to the analytical expressions developed for the four-spring model. Sensitivity analyses are conducted for optimization of the truncated numerical domain size, finite element size and far-field dynamic boundary conditions to avoid spurious wave reflections. Simulations are next conducted to evaluate the transient response of the foundation subjected to vertically propagating shear waves, and results are compared to the response predicted by means of the 4-spring model. Finally, the applicability of the method is assessed for soil profiles with depth-varying properties. While the methodology developed is applicable for linear elastic media with no material damping, the expressions of complex spring functions may be extended to include hysteretic damping, nonlinear soil behavior and soil-foundation interface separation, as shown in the conclusions.
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Marianne, Dit Cassou Pierre-Jean. "Les indications de l'oxygénothérapie hyperbare ; rapportées à l'activité des caissons du centre hospitalier sud Réunion de 1982 à novembre 1998". Bordeaux 2, 1999. http://www.theses.fr/1999BOR2M064.
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Masurel, Gérard. "Contribution à l'étude du rôle physiopathologique des bulles générées chez l'animal et chez l'homme par un séjour en atmosphère hyperbare". Lyon 1, 1987. http://www.theses.fr/1987LYO10017.
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Stapelfeldt, Marc [Verfasser]. "The influence of the drainage regime on the installation and the response to vertical cyclic loading of suction caissons / Marc Stapelfeldt". Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2021. http://d-nb.info/1226854575/34.
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Balestra, Costantino. "Is the patency of the cardiac foramen ovale a risk factor for disbaric pathologies: contribution to diving research and fostering diving safety". Doctoral thesis, Universite Libre de Bruxelles, 2003. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/241291.
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Blatteau, Jean-Éric. "Contribution à l'étude des noyaux gazeux pour la prévention des accidents de désaturation". Aix-Marseille 2, 2006. http://www.theses.fr/2006AIX20699.
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Simonet, Laurence. "Effet des hétérogénéités sur le Pouvoir Thermoélectrique de l'acier de cuve". Lyon, INSA, 2006. http://theses.insa-lyon.fr/publication/2006ISAL0123/these.pdf.
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En condition normale de fonctionnement, la cuve des Réacteurs à Eau Pressurisée (REP) est soumise à un vieillissement induit par l’irradiation. Afin de suivre l’évolution des caractéristiques de l’acier en service, EDF a lancé un programme de surveillance qui consiste à effectuer des essais mécaniques sur des éprouvettes vieillies en réacteur. Les résultats de ces essais présentent l’inconvénient d’être affectés par la présence d’hétérogénéités au sein de l’acier. En effet, du fait de son mode de fabrication, l’acier de cuve présente des zones ségrégées. Aussi, EDF a lancé un programme de mesures de Pouvoir Thermoélectrique (PTE) sur les éprouvettes de résilience du programme de surveillance, pour compléter les essais mécaniques et aider à leur interprétation. Actuellement, ces mesures sont difficilement exploitables car elles incluent à la fois l’effet de l’irradiation et l’effet des hétérogénéités métallurgiques. L’objectif de la thèse a consisté à évaluer l’effet des hétérogénéités sur le PTE de l’acier de cuve non irradié. Pour cela, un modèle numérique a été développé permettant de calculer le PTE d’une structure composite. Nous avons vu que le modèle était pertinent pour mettre en évidence l’effet des hétérogénéités sur le PTE de l’acier de cuve, qui est assimilé à un composite « matrice »/« ségrégation ». Le modèle nous a également permis de mettre en évidence l’influence de différents paramètres sur la mesure de PTE. Nous avons notamment montré que les conditions de mesure ont un effet majeur sur la valeur de PTE obtenue (influence de la pression de contact, de la position de l’éprouvette sur l’appareil, de l’emplacement des hétérogénéités métallurgiques,…)In service working conditions, the vessel of the Pressurized Water Reactors (PWR) undergoes an ageing due to irradiation. In order to follow the evolution of the mechanical characteristics of the steel in service, EDF launched a surveillance program which consists to carry out mechanical tests on samples aged in reactor. However, the results of these tests have the disadvantage to be affected by the presence of heterogeneities within the steel. Indeed, because of its manufacturing process, the steel contains segregated areas. Thus, EDF launched Thermoelectric Power Measurements (TEP) on the resilience samples of the surveillance program, to complete the mechanical tests and to help with their interpretation. However, these measurements are today difficult to analyse because they include at the same time the effect of the irradiation and the effect of the metallurgical heterogeneities. The aim of this work consisted in evaluating the effect of the heterogeneities on the TEP of the non-irradiated vessel steel. For that, a numerical model was developed which allows to calculate the TEP of a composite structure. We have shown that the model is pertinent to highlight the effect of the heterogeneities on the TEP of the vessel steel, which is considered like a “matrix”/“segregation” composite. The model allowed us to put emphasis on the influence of different parameters on the TEP measurement. We have thus showed that the measurements conditions have an important effect on the obtained TEP value (influence of the applied pressure, the position of the sample on the device, the site of the metallurgical heterogeneities,…)
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Aachboun, Said. "Etude de la gravure profonde du silicium à très basse température : application à la réalisation de caissons d'isolation pour la microélectronique de puissance". Orléans, 2000. http://www.theses.fr/2000ORLE2025.
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Ce travail étudie le développement d'un procédé spécifique de gravure profonde du silicium par plasma afin de démontrer la faisabilité d'une nouvelle approche pour réaliser des caissons d'isolation destinés aux composants de puissances intégrésThis work presents the study of a specific deep silicon etching process using plasma technology in order to demonstrate the feasibility of a new approach to achieve isolation of integrated power devices
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DUCAFFY, PHILIPPE. "Accidents de decompression dans la pratique de la plongee en scaphandre autonome sur l'ile de la reunion : activite de l'unite d'hyperbarie de l'hopital de saint-pierre entre 1989 et 1992". Lyon 1, 1993. http://www.theses.fr/1993LYO1M160.
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Boussuges, Alain. "Maladie de décompression : modifications hématologiques et détection des bulles circulantes". Aix-Marseille 2, 1998. http://theses.univ-amu.fr.lama.univ-amu.fr/1998AIX20669.pdf.
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L'amélioration de la compréhension de la physiopathologie de l'accident de décompression passe par une meilleure analyse des phénomènes de sursaturation/désaturation et de leurs conséquences circulatoires et biologiques. Nous avons étudié les paramètres de plongée modifiant la production de bulles circulantes. Chez le plongeur en apnée, il ne nous a pas été possible de dépister de bulles circulantes après des plongées profondes et répétées. Chez le plongeur en scaphandre autonome, nous avons observé que la diminution de la vitesse de remontée se traduisait par une diminution de la production de bulles circulantes. Au cours de ces travaux, nous avons été confrontés à des difficultés d'étude par le Doppler continu chez certains sujets. Nous avons donc élaboré une nouvelle méthodologie de détection des bulles circulantes associant l'imagerie échographique hi-dimensionnelle et l'exploration par Doppler pulsé du flux artériel pulmonaire. Une étude comparative avec la méthode traditionnelle par Doppler continu nous a permis de vérifier ses performances. Cette méthode de détection peut être proposée en réanimation chez le sujet suspect d'embolie gazeuse iatrogène. L'étude des phénomènes aéro-emboliques ne peut résumer la maladie de la décompression. Nos études cliniques nous ont permis d'élaborer un indice de gravité qui permettra la comparaison de groupes d'accidentés. Cette étude souligne la difficulté d'appréciation individuelle de la sévérité d'un accident d'après le seul examen clinique initial. La mesure de l'hématocrite pourrait être un indice d'alerte supplémentaire en raison de l'existence d'une corrélation entre élévation de l'hématocrite et sévérité de l'accident. L'activation de la coagulation est par contre rare en pathologie humaine. Elle n'a été observée, dans notre étude, qu'en présence d'une atteinte neurologique et ne semble pas corrélée avec la gravité. Cette étude soulève de nouvelles interrogations sur la physiopathologie de l'accident chez l'hommeBetter knowledge of the nitrogen supersaturation and desaturation phenomenoms together with their circulatory and biological consequences would be necessary for a better analysis of the physiopathology of the decompression illness (DCI). In this aim, we studied some parameters which could modify the production of nitrogen circulating bubbles, as an indice of nitrogen supersaturation. We demonstrated a lower circulating bubbles grade, following SCUBA dive with a lower ascent rate. We did not detect circulating bubbles after repeated and deep breath-hold living in underwater fishing divers. During those experimentations, continuous Doppler with blind positionning of the transducer appeared limited because of poor signal quality, in some subjects. In consequence, we developped a new method for the detection of circulating bubbles, which associates two-dimensionnal (2D) echocardiography and pulsed Doppler guided by 2D echocardiography. We performed a comparative study with the traditionnal continuous Doppler and we validated its performance. We think that this method for the detection of venous gas bubbles can also be proposed to critically ill patients suspected of iatrogenic venous gas embolism. Nitrogen supersaturation and desaturation phenomens may not resume DCI. We retrospectively analysed the clinical manifestations of an important population of patients victims of neurological decompression illness and we elaborated a gravity score of neurological DCI, which is necessary to allow comparaison of cohorts of patients. This first study underligned the difficulty to appreciate the individual severity with the only initial clinical signs. The venous haematocrit level may be another biological indice of severity as we demonstrated a correlation between an high haematocrit level and persistent neurological sequelae. At the contrary, we did not found any association between the severity of an accident and the activation of the coagulation
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Stale, Liva. "Development and application of framework of suitability assessment for onshore wind farm foundations". Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-318872.
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A framework for evaluating different wind turbine foundations has been proposed and applied in six hypothetical case studies located in three sites in different locations throughout Sweden.The framework is based on decision making method PROMETHEE II and consists of nine criteria covering financial, environmental and technical aspects of wind turbine foundations. The foundation has been evaluated from two different stakeholder perspectives – civil designers and financial advisors. Application of this framework has shown that an existing commonly used wind turbine foundation type is not the most favourable alternative, whilst a new market entrant – prefabricated foundation – shows promising results. Using PROMETHEE II it became evident that in any given case, a prefabricated foundation is ranked as the most or a close second to most suitable type of foundation. Gravity caissons ranked as the least favourable option in almost all, except one, case. Comparing these three alternatives prefabricated foundation showed greater economic feasibility, lower impact on environment and technologically more applicable than other alternatives with very few existing drawbacks.
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Capriolo, Malásquez Luca Giovanni, i Roca José Luis Pacheco. "Propuesta de un Documento Técnico con los Criterios Generales para el Uso de Caissons en Puentes mediante un Análisis de los Estudios Básicos y Juicio de Expertos en la Zona Norte del Perú". Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2020. http://hdl.handle.net/10757/653965.
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Caisson; Documento Técnico; Estudios Básicos; Pre-Diseño; Construcción.
Keywords: Caisson; Technical Document; Basic Studies; Pre-Design; BuildingLa presente investigación busca proponer un documento técnico que contemple los criterios necesarios a tomar en cuenta en el pre-diseño y construcción de caissons en puentes. La realización de un análisis de estudios básicos de diferentes proyectos de puentes con cimentación con caissons y una validación de la investigación bajo la metodología de juicio de expertos permitieron plantear diferentes criterios y recomendaciones que permitan decidir las características de los caissons a implementar y que a su vez procuren disminuir los riesgos en el proceso constructivo de caissons abiertos y neumáticos. Dicho documento técnico nace de la necesidad de complementar y ordenar la información existente en manuales y normas nacionales para definir el uso de caissons. En el año 2017, muchos puentes colapsaron debido a los fuertes niveles de socavación producidos por las grandes avenidas provocadas por el Fenómeno del Niño. Estos puentes fallaron porque no contaban con la cimentación adecuada para soportar las circunstancias ya descritas y por eso, es que es importante la correcta definición de la cimentación a utilizar. En cuanto al contenido del documento técnico, se pueden observar criterios de definición según el nivel de socavación y según el tipo de suelo. Por ejemplo, si nuestro proyecto se ve afectado por una socavación total de más de dos metros, se recomienda utilizar caissons, de lo contrario, bastaría una cimentación superficial. Por otro lado, también se plantean medidas para mejorar o solucionar problemas durante la construcción como el control de la nivelación en el hundimiento mediante equipos apropiados para evitar desplomes y acciones que nos permitan recuperar la verticalidad de la estructura. Finalmente, se concluyó que los estudios básicos son imprescindibles como punto de partida para evaluar los criterios de pre-diseño y definir el tipo de caisson a utilizar según el tipo de suelo, sus características y las de la superestructura a recibir. Además, se tiene que considerar que este tipo de infraestructura requiere mano de obra calificada.
The present investigation seeks to propose a technical document that contemplates the necessary criteria to be taken into account in the pre-design and construction of caissons in bridges. The realization of an analysis of basic studies of different bridge projects with foundations with caissons and a validation of the research under the expert judgment methodology allowed to propose different criteria and recommendations that allow to decide the characteristics of the caissons to be implemented and that try to reduce the risks in the construction process of open and pneumatic caissons. This technical document arises from the need for scarcity of information in manuals and national standards to define the use of caissons. In the year 2017, many bridges collapsed due to the strong levels of scour caused by the great floods caused by the El Niño Phenomenon. These bridges failed because they did not have the adequate foundation to withstand the circumstances already described and that is why the correct definition of the foundation to be used is important. Regarding the content of the technical document, you can observe definition criteria according to the level of scour and according to the type of soil. For example, if our project is affected by a total scour of more than two meters, it is recommended to use caissons, otherwise a surface foundation would suffice. On the other hand, measures are also proposed to improve or solve problems during construction such as the control of leveling in the subsidence by means of appropriate equipment to avoid crashes and actions that allow us to recover the verticality of the structure. Finally, it was concluded that the basic studies are essential as a starting point to evaluate the pre-design criteria and define the type of caisson to be used according to the type of soil, its characteristics and those of the superstructure to be received. In addition, it must be considered that this type of infrastructure requires skilled labor.
Tesis
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Thérène-Fenoglio, Marie-Catherine. "Effets neurochimiques de l'oxygène hyperbare : lipoperoxydation de différents organes périphériques et centraux, et étude de l'évolution dynamique d'acides aminés extracellulaires par microdialyse intramédullaire". Aix-Marseille 2, 1999. http://theses.univ-amu.fr.lama.univ-amu.fr/1999AIX20676.pdf.
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Ce travail constitue une approche neurochimique de la toxicité de l'oxygène qui se traduit, dans sa forme aiguë, par une crise convulsive de type épileptique. Par ailleurs l'oxygène hyperbare constitue un moyen thérapeutique des accidents médullaires de décompression et améliore généralement le pronostic fonctionnel. La similitude des lésions observées lors de ces accidents avec des lésions d'ischémie, suggère des mécanismes neurochimiques communs qui sont explorés dans notre travail, soit par une approche endogène, soit par une approche dynamique par microdialyse intramédullaire chez le rat. Dans l'approche endogène, l'oxygène pur administré 2 h à 350 kPa ne provoque pas de variation de matériel TBA-réactif (index de lipoperoxydation) ni d'acide urique (index du stress oxydatif) au niveau de la moelle lombaire. En approche dynamique, sous les mêmes conditions, la glycine augmente pendant le séjour hyperoxique, corrigeant ainsi une élévation de glutamate constatée pendant la phase de compression mais aussi au cours de la décompression. La crise convulsive induite par une exposition à 600 kPa d'oxygène est précédée par des libérations générales, ponctuelles et répétées de l'ensemble des acides aminés (AA). Ces variations plus limitées qu'au cours de la crise elle-même constituent des éléments prodromiques de la crise. Sur une moelle ischémiée par clampage aortique, une exposition de 2 h à 350 kPa puis de 30 min à 600 kPa d'oxygène entraîne une augmentation en plateau pendant le séjour hyperoxique de glutamate et de glycine, alors que des élévations de taurine paraissent sensibles aux transitions de pO2 et signent une activité inhibitrice de la glie. Au cours d'expositions hyperoxiques hyperbares d'oxygène sur une moelle saine, on observe une libération massive de l'ensemble des AA au moment de la décompression. Ce phénomène pourrait être lié à une levée brutale de la vasoconstriction réflexe initialement induite par la forte pO2, générant ainsi une hyperoxie relative et "paradoxale".
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Souquière, Luc. "Accidents neurologiques de désaturation et foramen ovale perméable : à propos de 9 plongeurs de la marine nationale de 1987 à 1998". Bordeaux 2, 1999. http://www.theses.fr/1999BOR2M042.
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Czerniak, Erik. "Le sauvetage des équipages des sous-marins naufragés en pression". Bordeaux 2, 1999. http://www.theses.fr/1999BOR2M100.
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Bernigaud, Emmanuel. "Rôle du stress oxydatif dans la maladie de décompression : étude expérimentale chez le lapin". Bordeaux 2, 1995. http://www.theses.fr/1995BOR2M132.
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Pavageau, Ellen-Mary. "Modélisation de la corrosion du côté secondaire des tubes de générateurs de vapeur de centrales à réacteur à eau sous pression : application à la corrosion sous contrainte de l’alliage 600". Grenoble INPG, 2001. http://www.theses.fr/2001INPG0151.
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Les tubes en alliage 600 mill-annealed (MA) présentent de la corrosion dans les zones confinées du côté secondaire des générateurs de vapeur des centrales à réacteur à eau pressurisée. Il est possible qu’à terme, les tubes plus récents en alliage 600 traité thermiquement (TT) présentent également de la corrosion. Nous proposons une modélisation empirique et statistique afin de prévoir le comportement en corrosion des tubes en alliage 600 MA et TT, basée sur des essais de corrosion sous contrainte de longue durée dans des milieux confinés type : le milieu soude et le milieu sulfate. La modélisation en milieu soude montre que la corrosion sous contrainte de l’alliage 600 se produit selon trois stades successifs : une période d’incubation, un stade de propagation lente puis un stade de propagation rapide. Nous prévoyons de manière satisfaisante les localisations et orientations de fissures observées sur site ainsi que le risque faible de passage en régime rapide. De plus, nous mettons en évidence un risque de corrosion de ces tubes, significativement plus faible pour les tubes en alliage 600 TT que pour ceux en alliage 600 MA. Le modèle en milieu de sulfate, établi par « réparation » de plan d’expériences, met en évidence des interactions significatives entre paramètres, non prévisibles à priori. Il décrit de manière satisfaisante le comportement en corrosion du côté secondaire des tubes de générateurs de vapeur. L’effet bénéfique du traitement thermique sur la résistance à la corrosionStress corrosion cracking (SCC) occurs in flow-restricted areas on the secondary side of Mill Annealed (MA) Alloy 600 steam generator tubes of pressurized water reactors. More recent Thermally Treated (TT) Alloy 600 tubes could some day also suffer from corrosion. Our work consists in modelling the phenomenon empirically and statistically to predict the behaviour of Alloy 600 tubes toward corrosion. The environments formed in the flow-restricted areas are poorly known but chemical analyses during shutdowns show they could resemble sodium hydroxide or sulphate environments. Therefore, our modelling is based on SCC laboratory test in these two typical environments. The modelling in sodium hydroxide environments shows SCC involves three steps: incubation, slow propagation and rapid propagation. The tubes behaviour is well predicted in terms of location and orientation of cracks as well as little risk of having rapid propagation. Finally, the application to TT Alloy 600 tubes gives a smaller risk of SCC than for MA Alloy 600 tubes. The modelling in sulphate environments, established by use of the technique of « repair » of design of experiments, evidences interactions of model parameters. This modelling satisfactorily describes the secondary side corrosion of steam generator tubes. Moreover, the beneficial effect of the thermal treatment on Alloy 600 SCC resistance seems confirmed
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Salgado, Francisco Manuel Goncalves Alves. "Analysis procedures for caisson-retained island type structures". Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30845.
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This thesis is concerned with the analysis of large offshore gravity structures used for oil exploration and recovery in the Beaufort Sea. Because of the high ice loads and the water depths involved, these structures comprise a large steel box infilled with a sand core for stability. One such structure was subjected to severe ice loading in April 1986 causing portions of the sand core to liquefy and bring the structure to a near failure condition. This structure was heavily monitored and thus serves as a case study against which the proposed analysis procedure can be checked.
The behaviour of these soil-structure systems is highly complex depending upon the characteristics of the soil, the structural elements and the soil-structure interface. In this thesis a three-dimensional Finite Element computer program with soil, interface and structural elements is developed.
Emphasis is placed on the three-dimensional stress-strain constitutive law both in terms of its ability to model observed laboratory response as well as the determination of the constitutive law parameters from in situ testing.
The results obtained in terms of displacement, acceleration and zones of liquefaction by the analysis were then compared with the field measurements obtained during the April 1986 ice load event. The good agreement obtained between predicted and observed response is a validation of the proposed procedure.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Hesari, Saeed Aroni. "A multilevel superelement substructuring for boxlike caisson analysis". Thesis, University of Ottawa (Canada), 1994. http://hdl.handle.net/10393/6540.
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A multilevel superelement substructuring approach for linear-static analysis of rectangular boxlike caissons is developed. The structure is considered as an assemblage of superelements in three substructural levels. These are panel, layer, and caisson superelements. Each superelement substructure is derived by applying the principle of static condensation. Rectangular 9-node flat shell elements, which are composed of membrane stress and Mindlin plate bending elements, are assembled together to make the stiffness and load matrices of each panel substructure. Every panel substructure is condensed to a panel superelement. Then all of them in a layer are assembled together and condensed to layer superelement. Finally, the later superelement(s) are assembled and condensed to yield to caisson superelement. After the assembling process, equilibrium equations are solved for the caisson superelement. Then a multilevel recovery process, with an inverse sequence of assembling one, gives the internal degrees of freedom for caisson, layer, and panel superelements, respectively. Finding all displacements, one can finally compute internal forces for every individual flat shell element. This special purpose superelement substructure method provides considerable efficiency in practical analysis and design of boxlike caissons. Based on this approach, a computer program is developed which takes the most advantage from the repetition of similar individual elements and panels. Several numerical examples are solved indicating good agreement with other analytical or numerical methods and proper convergency for design purposes.
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Bame, Abda Berisso. "New Method of Sinking Caisson Tunnel in Soft Soil". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bygg, anlegg og transport, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23298.
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Sinking a caisson tunnel in soft soil is new idea and this new concept could be an alternative method of tunneling in soft soil. The aim of this study is to evaluate geotechnical feasibility of sinking the caisson tunnel to the desired depth at the selected soil profile along tunnel alignment. This caisson tunneling method is proposed to reduce the use of temporary works such as propping of sheet pile walls and increase the ease and speed of construction. Besides, it reduces the disturbance on the nearby structures due to vibration.
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CIANCIMINO, ANDREA. "Performance of caisson foundations subjected to flood-induced scour". Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2924992.
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Dumas, Laurent. "L'apnée sportive : physiopathologie et prise en charge thérapeutique". Bordeaux 2, 2000. http://www.theses.fr/2000BOR2P079.
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Cotter, Oliver. "Installation of suction caisson foundations for offshore renewable energy structures". Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534163.
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Dekker, Marijn Johannes. "The Modelling of Suction Caisson Foundations for Multi-Footed Structures". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-27161.
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Suction caissons are a type of offshore foundation that allow for fast and noise-free installation and decommissioning of offshore structures. They have been used for 20 years in the oil and gas industry and are also becoming more common in the offshore wind sector as a promising way to cost reduction. SPT is a leading contractor for the installation of both single anchor piles and foundations on multiple caissons. The suction caissons are installed by applying a differential pressure between the inner and outer sides of the caissons, which pushes the caissons into the soil. When a platform is founded on multiple suction caissons, the way the wind and wave loads are transferred through the structure and various caissons into the soil will depend on the stiffness of both the platform and the caissons. The design of the substructure and suction caissons should thus be combined to include the effects of soil-structure interaction. This is currently done by modelling the suction caisson foundations as a set of linear-elastic springs attached to the substructure. These springs are however not able to capture the non-linear behaviour that is often characteristic for soils. A method has been developed to model the suction caisson foundations using non-linear springs. The characteristics of the springs are determined using FEM calculations with a nonlinear soil model in the geotechnical software PLAXIS. The springs are then implemented in a structural model of the substructure and the multiple foundations in the structural software SACS. The resulting loads on and displacements of the suction caisson foundations for a test load case have been compared to results from a complete FE model and a model that uses linear-elastic springs. The comparison has shown that the developed model gives results that match well with the results from the full FE model. The linear-elastic model on the other hand gives results that deviate significantly for high loads.When the stresses in the soil increase the soil will behave softer, leading to an increase of the displacements of the suction caissons for high loads. The substructure will help decrease large differences between the displacements of the suction caissons, resulting in a more even load distribution over the foundations and thus smaller design loads for the suction caissons. This allows for smaller suction caissons and savings of material and costs. The model with nonlinear springs is able to predict this behaviour of the soil and the substructure accurately and can be used to make a more efficient design of suction caisson foundations.
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MACCARINI, FABIANA. "Behaviour of vertical caisson breakwaters under wave-induced cyclic loading". Doctoral thesis, La Sapienza, 2005. http://hdl.handle.net/11573/917026.
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Sharma, Partha Pratim. "Ultimate capacity of suction caisson in normally and lightly overconsolidated clays". Thesis, Texas A&M University, 2005. http://hdl.handle.net/1969.1/2460.
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Petroleum exploration and production in recent years have moved into increasingly deeper water off the continental shelf. Some of these facilities are anchored in water depths in excess of 1000 meters. Exploration and production in deep water present new technological challenges where traditional fixed platforms have given way to floating structures. Today suction caissons are the most commonly used anchorage system for permanent offshore oil production facility. The objective of this study is to numerically predict the ultimate capacity of suction caissons in normally consolidated and lightly overconsolidated clays. Representative soil profile from the Gulf of Mexico and the North Sea are taken and analyzed for suction caissons with length over diameter ratios of 2, 4, 6 & 8. Normalized failure load interaction diagrams are generated for each of the cases. The location of optimum attachment point is also reported for each of the cases. General purpose finite element computer program ABAQUS is used for the numerical prediction. The finite element study is carried out with three-dimensional models using hybrid elements. A simplified elastic perfectly plastic model with von-Mises yield criterion is used for the study. The saturated clay is treated as an incompressible material. Results of the study compares well with existing simplified method for estimating load capacity of suction caisson anchors.
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Cox, James A. "Long-term serviceability behaviour of suction caisson supported offshore wind turbines". Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680352.
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Suction caissons have recently been considered as an alternative to monopile foundations for offshore wind turbines and met masts. By their nature, such structures have stringent limit states imposed on their design dictating the first modal frequency and the allowable structural rotations. The aim of this thesis is to assess how cyclic loading will affect the long-term serviceability behaviour of such an offshore structure. The behaviour of such a representative caisson system was assessed through the use of a series of scale model tests conducted in dry sand, replicating a fully drained prototype condition. These tests were designed to record the foundation stiffness, its evolution under cyclic loading, how the system accumulates rotation with loading cycles and the dynamic properties of a caisson system. This was conducted at a number of scales under single-g and multi-g conditions. Considering all of the experimentally obtained data it was possible to analyse and provide a prediction as to the long-term behaviour of such an offshore structure. It was discovered that the foundation stiffness was highly dependent on the strain level and under the application of cyclic loading the stiffness would tend to increase in a logarithmic manner. In addition it was found that when subjected to a cyclic load a caisson system will accumulate rotation in accordance with a power relationship. Finally the dynamic properties were found to closely match pre-existing formulations describing a simple dynamic system. Considering these results it was possible to produce an analytical model to describe the evolution of serviceability of a caisson founded offshore structure. Latterly this model was applied to a series of representative cyclic loading test to examine the validity of the complete model.
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Bédard, Diane. "Modélisation stochastique des caisses de retraite". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ32581.pdf.
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