Tesi sul tema "Submarine Pipeline"

Includes bibliography.
This thesis describes an experimental investigation into the hydrodynamic forces induced on a cylinder placed transversely to a steady stream. Various cylinder locations near the bed of a water flume were considered. The work relates to pipeline design. The various flow phenomena around a cylinder are theoretically analysed and an explanation of the phenomenon of lift provided. A thorough literature review was undertaken regarding the classical theory, as well as experimental and theoretical studies carried out on the subject. This revealed that theoretical studies are virtually non-existent. Measurements have been done in intermediate water depths with both smooth and rough beds. Two different methods, comprising very simple yet novel techniques, were utilised in a water flume 18 m long x 600 mm wide x 450 mm deep. The methods involved a unique pressure determination method as well as the direct measurement of hydrodynamic forces, using a "weighing" method. Very ' accurate flow velocities were measured using a unique differential manometer. Experiments were performed in the Reynolds number range 6 000 to 26 000, using 30 and 50 mm diameter cylinders. comprehensive tests on cylinder roughening were carried out in a flow region which had not been well researched regarding this aspect. Cylinder locations were varied from a gap-to-cylinder diameter ratio of zero to 2,67. Results revealed that the force coefficients are not appreciably affected by bed roughness. Cylinder roughening produced somewhat contradicting results for the two different cylinders used. The influence on the lift coefficient was inconclusive, but the "rougher" 30 mm cylinder produced a slightly higher drag coefficient. Although the lift force was predominantly away from the bed, a downward lift force was measured on a few occasions with the cylinder situated further than one cylinder diameter away from the bed. A possible explanation is offered for this and other unexpected results. Flow visualisation tests were performed to confirm certain features of the flow around the cylinder. These as well as all the other results have been related to published work.

Soil surrounding a submarine buried pipeline consolidates as ocean waves propagate over the seabed surface. Conventional models for the analysis of soil behaviour near the pipeline assume a two-dimensional interaction problem between waves, the seabed soil, and the structure. In other words, it is often considered that water waves travel normal to the orientation of pipeline. However, the real ocean environment is three-dimensional and waves approach the structure from various directions. It is therefore the key objective of the present research to study the seabed behaviour in the vicinity of marine pipelines from a three-dimensional point of view. A three-dimensional numerical model is developed based on the Finite Element Method to analyse the so-called momentary behaviour of soil under the wave loading. In this model, the pipeline is assumed to be rigid and anchored within a rigid impervious trench. A non-slip condition is considered to exist between the pipe and the surrounding soil. Quasi-static soil consolidation equations are then solved with the aid of the proposed FE model. In this analysis, the seabed behaviour is assumed to be linear elastic with the soil strains remaining small. The influence of wave obliquity on seabed responses, i.e. the pore pressure and soil stresses, are then studied. It is revealed that three-dimensional characteristics systematically affect the distribution of soil response around the circumference of the underwater pipeline. Numerical results suggest that the effect of wave obliquity on soil responses can be explained through the following two mechanisms: (i) geometry-based three-dimensional influences, and (ii) the formation of inversion nodes. Further, a parametric study is carried out to investigate the influence of soil, wave and pipeline properties on wave-associated pore pressure as well as principal effective and shear stresses within the porous bed, with the aid of proposed three-dimensional model. There is strong evidence in the literature that the failure of marine pipelines often stems from the instability of seabed soil close to this structure, rather than from construction deficiencies. The wave-induced seabed instability is either associated with the soil shear failure or the seabed liquefaction. Therefore, the developed three-dimensional FE model is used in this thesis to further investigate the instability of seabed soil in the presence of a pipeline. The widely-accepted criterion, which links the soil liquefaction to the wave-induced excess pressure is used herein to justify the seabed liquefaction. It should be pointed out that although the present analysis is only concerned with the momentary liquefaction of seabed soil, this study forms the basis for the three-dimensional analysis of liquefaction due to the residual mechanisms. The latter can be an important subject for future investigations. At the same time, a new concept is developed in this thesis to apply the dynamic component of soil stress angle to address the phenomenon of wave-associated soil shear failure. At this point, the influence of three-dimensionality on the potentials for seabed liquefaction and shear failure around the pipeline is investigated. Numerical simulations reveal that the wave obliquity may not notably affect the risk of liquefaction near the underwater pipeline. But, it significantly influences the potential for soil shear failure. Finally, the thesis proceeds to a parametric study on effects of wave, soil and pipeline characteristics on excess pore pressure and stress angle in the vicinity of the structure.

Master of Engineering (Research)
Soil surrounding a submarine buried pipeline consolidates as ocean waves propagate over the seabed surface. Conventional models for the analysis of soil behaviour near the pipeline assume a two-dimensional interaction problem between waves, the seabed soil, and the structure. In other words, it is often considered that water waves travel normal to the orientation of pipeline. However, the real ocean environment is three-dimensional and waves approach the structure from various directions. It is therefore the key objective of the present research to study the seabed behaviour in the vicinity of marine pipelines from a three-dimensional point of view. A three-dimensional numerical model is developed based on the Finite Element Method to analyse the so-called momentary behaviour of soil under the wave loading. In this model, the pipeline is assumed to be rigid and anchored within a rigid impervious trench. A non-slip condition is considered to exist between the pipe and the surrounding soil. Quasi-static soil consolidation equations are then solved with the aid of the proposed FE model. In this analysis, the seabed behaviour is assumed to be linear elastic with the soil strains remaining small. The influence of wave obliquity on seabed responses, i.e. the pore pressure and soil stresses, are then studied. It is revealed that three-dimensional characteristics systematically affect the distribution of soil response around the circumference of the underwater pipeline. Numerical results suggest that the effect of wave obliquity on soil responses can be explained through the following two mechanisms: (i) geometry-based three-dimensional influences, and (ii) the formation of inversion nodes. Further, a parametric study is carried out to investigate the influence of soil, wave and pipeline properties on wave-associated pore pressure as well as principal effective and shear stresses within the porous bed, with the aid of proposed three-dimensional model. There is strong evidence in the literature that the failure of marine pipelines often stems from the instability of seabed soil close to this structure, rather than from construction deficiencies. The wave-induced seabed instability is either associated with the soil shear failure or the seabed liquefaction. Therefore, the developed three-dimensional FE model is used in this thesis to further investigate the instability of seabed soil in the presence of a pipeline. The widely-accepted criterion, which links the soil liquefaction to the wave-induced excess pressure is used herein to justify the seabed liquefaction. It should be pointed out that although the present analysis is only concerned with the momentary liquefaction of seabed soil, this study forms the basis for the three-dimensional analysis of liquefaction due to the residual mechanisms. The latter can be an important subject for future investigations. At the same time, a new concept is developed in this thesis to apply the dynamic component of soil stress angle to address the phenomenon of wave-associated soil shear failure. At this point, the influence of three-dimensionality on the potentials for seabed liquefaction and shear failure around the pipeline is investigated. Numerical simulations reveal that the wave obliquity may not notably affect the risk of liquefaction near the underwater pipeline. But, it significantly influences the potential for soil shear failure. Finally, the thesis proceeds to a parametric study on effects of wave, soil and pipeline characteristics on excess pore pressure and stress angle in the vicinity of the structure.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
Neste trabalho são avaliadas as condições de estabilidade do subsolo marinho ao longo da rota de um duto rígido de aço revestido com concreto, de 10 de diâmetro, localizado na Bacia de Campos, RJ. Os dados geológicos e geotécnicos foram adquiridos a partir de um amplo levantamento geofísico e geotécnico realizado na diretriz do duto. Devido as adversidades à estabilidade do fundo marinho, várias análises vêm sendo realizadas de forma qualitativa e quantitativa. Atualmente, por questões ambientais e de segurança de obras de engenharia, busca-se uma avaliação mais quantitativa dos riscos geológicos associados à condição de estabilidade do fundo marinho, pois os escorregamentos de taludes representam o principal risco para estas estruturas. As análises de estabilidade foram feitas a partir da teoria do talude infinito, em metodologia aplicada por Nowacki et al. (2003) nos campos profundos de Mad Dog e Atlantis, no Golfo do México, e comparadas com os resultados encontrados a partir da formulação clássica do talude infinito. Uma integração de dados geotécnicos e geofísicos foi necessária, para que todos os parâmetros utilizados na metodologia pudessem ser obtidos. Os resultados indicaram dois pontos críticos ao longo da rota, ambos associados aos flancos do cânion Itapemirim, que apresentam gradientes altos. Foram realizados breves estudos com o objetivo de se avaliar a possibilidade de ocorrência de mecanismos disparadores (terremotos e ondas de tempestade) nesses pontos críticos mas os resultados descartaram esta possibilidade. Concluiu- se ainda que os dados geotécnicos utilizados neste trabalho não foram suficientes e de certo modo não apropriados para a análise de estabilidade de taludes. Uma nova campanha de ensaios geotécnicos de laboratório foi proposta para futuros estudos.
This research analyses stability conditions of marine sediments superficial layers of along a 10 in. diameter pipeline`s route, located at Campos Basin, RJ. The geological and geotechnical data were obtained during a wide geophysical and geotechnical survey along the pipeline`s route. Due to adversities to botton stability found in the marine environment, several qualitative and quantitative stability analysis have been made. Nowadays, because of environmental and safety issues, the researches are more focused on quantitative analysis of geohazards associated with the stability condition of the sea bottom, since slope slides represent the main risk for those structures. The stability analyses were based on the infinite slope theory. The methodology applied was the same used by Nowacki et al. (2003) at the deep fields of Mad Dog and Atlantis, in the Gulf of Mexico. The results were compared with the results from the classical formulation of the infinite slope. An integration of geotechnical and geophysical data was necessary, in order to obtain all the parameters used in the methodology. The results indicated two critical points along the route, both associated with the flanks of the Itapemirim Canyon, which have steep slopes. Brief studies were made to evaluate the importance of triggering mechanisms (earthquakes and storm waves) at these critical points but the results discard this possibility. It was also concluded that the geotechnical data used in this research were insufficient and in a certain way not appropriate for the slope stability analysis. A new geotechnical lab tests campaign was proposed for future studies.

The impact of a pipeline by a dropped object has been considered to consist of four distinct impact components: the dropped object, pipeline protection, the soil bed and the pipeline itself. The effect of these components as energy absorbers and the effect on system response has been investigated. Quasi-static and dynamic testing has been earned out to investigate the interaction between the various impact components. Quasi-static testing has been widely used to develop initial predictions, since closer observation of interaction is easier. The validity of applying these predictions to dynamic situations has been addressed using results from dynamic impact testing. The Dropped Object: Two areas have been investigated which address the dropped object within the impact system: the dropped object's impact profile and its deformability. Testing has been carried out to study the effect of typical loading profiles. Research has shown that the dropped object profile significantly effects the pipe response; a cone shaped indentor generates deformation with far less energy than either a wedge or a patch shape. The applicability of a method to predict the interaction between two deforming structures, using a method of shared energy, has been investigated for quasi-static and dynamic loading. During quasi-static testing it was found possible to predict a combined response using individual responses. During dynamic testing prediction was not possible, since inertia effects where found to dominate the response. The Concrete Protective Coating: A programme of work carried out has qualified the role of a pipeline protective coating and assessed the effect of four different types of concrete reinforcement. Summary Although the study has not been exhaustive, it is clear that reinforcements, which hold the concrete coating to the pipe, allow the coating to continue its protection. Fibres added to a concrete mix were found to reduce the damage to the pipe. However mesh reinforcements were found to hold the concrete together most effectively and provided the greatest added protection. The Soil Support: All foundations absorb some energy. Tests have been carried out to investigate the effect of a soil bed on the response of a laterally loaded pipeline. During dynamic tests on sand supported pipes it was noted that no energy was absorbed during the initial deformation, possibly corresponding to local indentation of the pipe wall. After this the sand was seen to react and absorbed a proportion of the energy, depending on the hammer's drop height. The energy absorbed by the soil continued to increase until an energy plateau was reached, after which the soil absorbed no further energy. It was noted that the displacement at which this energy plateau was reached increased as the drop height increased. Two possible causes of the energy plateau have been discussed. The first cause questioned an assumption that the pipe would deform as if on simple supports. The second possible cause suggested a change from dynamic to quasi-static response and investigated the relationship between acceleration, velocity and reaction force. Of the possible causes of the energy plateau, the most likely is thought to be soil related. Investigation into the Deformation of Locally Loaded Pipes: The investigation into pipeline deformation has been carried out using experimental, numerical and theoretical analysis methods. Quasi-static test results have been used to investigate four pipeline parameters and their influence on energy absorbed by the pipeline, (length, L, wall thickness, t, diameter, D and material yield stress, ay). This investigation led to an empirical equation, which brought all energy-displacement (E-8) curves on to a common curve, for a wide range of these variables. This empirical relationship has been developed to predict deformation, for the range of parameters investigated. Dynamic results obtained were normalised using these empirical equations and data was seen to fall into two broad groups, one group comprising seam welded pipe and one group comprising cold drawn pipe. Strain rate effects were proposed as the most likely cause of this bi-grouping. Limitations in the experimentally derived empirical relationship have been identified, resulting from an insufficient range of pipe samples tested.

Clump weights come in several shapes, with a mass generally between 2 to 9 tons [5]. With extensive oshore development in the last decades, vast networks of pipelines are installed on the sea bottom. With both pipeline extension and trawl equipment development in mind, the need for designing pipelines able to resist forces from trawl gear interaction have emerged. A recommended practice for pipeline design, DNV-RP-F111, was established by DNV. In this master thesis, a brief introduction to trawl gear and recommended practices are given. The main objective of the master thesis is to reproduce model tests numerically and analyse the response from clump weight over-trawling pipelines. Evidence is sought to establish and dierentiate between the importance of various parameters, e.g free span height, pipeline diameter, and pipe end conditions. Several sensitivity studies were performed, with alterations in several parameters, e.g warp line angle alteration and clump weight wobbling. A full scale pipeline model was also analysed, investigating eects of exibility in pipelines and comparing the results with design loads. All analyses are performed in SIMLA, a special purpose non-linear nite element program. A general description of non-linear nite element method is included in the report. All input values used to model the dierent cases are presented in the master thesis. A good correspondence linking model test results and reproduced simulated models were generally achieved, with some deviations. The deviations are primarily found for low free spans, indicating that this discrepancy can be reduced by further development of the numerical model, e.g by introducing friction to the model. For the full scale pipeline model, design loads are evidently higher than vii viii the pull over force from the corresponding full scale simulation. When comparing design loads with pull over forces from simulated experimental test models, they are more closely related. For small diameter pipelines, a simulation in a full scale model, compared to the rigid model simulations, reduce the pull over forces signicantly. Sensitivity simulations indicate a connection between free span height, pipeline diameter and pull over force. For high free spans, the simulated pull over force increase with decreasing pipe diameter. For low free spans, the simulated pull over force decrease when decreasing the pipe diameter. Clump weight wobbling have in the master thesis been shown to reduce the pull over force. This is seen in the sensitivity analyses performed. Changing clump weight geometry can lead to signicant changes in results. An alteration of the warp line bracket was performed, extending the bracket with 4 cm. The eect was an reduction in the pull over force by approximately 10%, in all cases. A change in warp line angle was also performed, by increasing and then decreasing the angle with 20%. The eect was an reduction in pull over force by 10% and an increase in pull over force by approximately 10%, respectively. For further details regarding the results, see chapter 5.

A recent development in bottom trawling is the use of twin trawl equipment, where two trawl nets are towed side by side from a single vessel. This increases the catch rate and efficiently of the trawler. Governed by cost and catch optimization, the use of twin trawl systems are expected to become more popular in the future. Using two trawl nets will, in addition to trawl doors on each side, require a heavy clump weight in the middle to prevent the trawl nets lifting from the seabed. The largest clump weights can have a mass up to 9000 kg and can cause substantial load towed across subsea pipelines, and may in many cases be the governing design load with respect to external loads in pipeline design. The main objective in this thesis work was to simulate and investigate pull-over forces from clump weights on free spanning pipelines. All simulations were carried out in the computer software SIMLA. Six different small scale tests were simulated in order to verify the finite element model, a very good agreement was obtained. Design loads from trawl gear are generally implemented according to DNV-RP-F111. The calculation methods provided in this recommended practice are based on the same small scale tests which was made available to this thesis work for verification purposes. The validity range of DNV-RP-F111 reflects the range of the small scale tests i.e. only valid for rigid pipelines. The effect of increasing pipeline flexibility was investigated. Simulations were carried out for span heights 0.25m, 0.50m and 0.75m for a 12” pipeline. Two different pipeline models was applied, a 25 m rigid pipeline model with spring representing the lateral pipeline stiffness, and a 1000m pipeline model including realistic soil resistance. The major finding was that pull-over forces decrease for increasing pipeline flexibility. Compared to DNV-RP-F111 the obtained pull-over loads was found considerably lower, both in magnitude and duration. To avoid over-conservatism it is thus recommended that a design method accounting for pipeline flexibility should be developed and used in future pipeline designs. The effect of warp angle was simulated varying the warp line length from 2.5 to 3.5 times the water depth. The horizontal pull-over force was found to increase for increasing warp line length. Regarding clump weight design and towing configuration, simulations have shown that a forward clump weight center of gravity will reduce the pull-over loads. Applying a lower warp line attachment point resulted in a more uniform sliding motion of the clump weight during interference and pull-over loads was almost complete reduced to a case of initial impact. It is thus suggested that future clump weight design should reflect this to reduce interference loads on both trawl gear and subsea pipelines.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Diversos acidentes envolvendo dutos submarinos já aconteceram no Brasil como o do Gasoduto PCR-01/Lubnor e o da plataforma P-55 de 2,3 km no campo de Roncador, na Bacia de Campos. Esses acidentes ocorrem em muitos casos devido à flambagem, à fadiga, ao intenso processo corrosivo, à deficiência de projeto, a falta de manutenção dos mesmos. Os dutos submarinos representam uma alta porcentagem no custo total de uma unidade de extração de petróleo. Sua importância se torna vital para a extração de petróleo em águas territoriais brasileiras. Seu projeto estrutural é uma atividade que pode ser dividida em várias etapas que devem ser seguidas à risca para garantir a conformidade do mesmo com as normas nacionais e internacionais sua operação em um dos mais inóspitos cenários da natureza: o fundo do mar. Nesta situação, o duto fica sujeito a carregamentos extremos, tanto estáticos quanto dinâmicos. Por este motivo, ele é constituído de uma estrutura de camadas bastante complexa. O objetivo deste trabalho é a avaliação das condições de operação de dutos submarinos sujeitos à ação de ondas e correntes marinhas. Um estudo paramétrico em elementos finitos é realizado para compreender a influência das condições de contorno, diferentes comprimentos de vão livre do duto submarino e variações do tipo de solo na resposta dinâmica do duto submarino. È desenvolvida também uma solução analítica para o problema. As soluções numérica, analítica e as recomendações da norma são confrontadas e tiradas conclusões sobre os principais fatores a serem considerados pelos engenheiros envolvidos na construção de estruturas deste tipo.
Several accidents involving subsea pipelines have happened in Brazil as the pipeline PCR-01 / Lubnor and the P-55 platform 2.3 km in the Roncador field in the Campos Basin. These accidents occur in many cases due to buckling, fatigue, the intense corrosive process, design deficiency, lack of maintenance. The submarine pipelines represent a high percentage in the total cost of an oil extraction unit. Its importance becomes vital for the extraction of oil in Brazilian waters. Its structural design is an activity that can be divided into several steps that must be followed strictly to ensure its conformity with national and international standards operation in one of the harshest scenes of nature: the seabed. In this situation, the product is subject to extreme loads, both static and dynamic. For this reason, it consists of a complex layer structure. The objective of this study is the evaluation of the operating conditions of submarine pipelines subject to the action of waves and currents. A parametric study of finite element is performed to understand the influence of the boundary conditions, different span lengths of submarine pipeline and variations of soil type on the dynamic response of submarine pipeline. It is also developed an analytical solution to the problem. The numerical solutions, analytical and standard recommendations are compared and conclusions drawn on the main factors to be considered by the engineers involved in the construction of such structures.

Three-dimensional scour propagation along offshore pipelines is a major reason to pipeline failures in an offshore environment. Although the research on scour in both numerical and experimental aspect has been extensive over the last three decades, the focus of the investigation has been limited to the two-dimensional aspect. The knowledge on three-dimensional scour is still limited. This dissertation presents the results of an experimental investigation on threedimensional scour along offshore pipelines in (1) steady currents (2) waves only and (3) combined waves and current. The major emphasis of the investigation is to investigate the propagation of the scour hole along the pipeline after the initiation of scour. Physical experiments conducted were used to quantify the effects of various parameters on scour propagation velocities along the pipeline. The problem of monitoring real time scour below a pipeline was solved by using specifically developed conductivity scour probes. Effects of various parameters such as pipeline embedment depth, incoming flow Shields parameter, Keuglegan- Carpenter (KC) number and flow incident angle to the pipeline on scour propagation velocities along the pipeline were investigated. The investigations clearly reveal that scour propagation velocities generally increase with the increase of flow but decrease with the increase of the pipeline embedment depth. A general predictive formula for scour propagation velocities is proposed and validated against the experimental results. There are still some common issues related to pipeline scour that is lacking in the literature to date. One of these issues is the effects of Reynolds number on two-dimensional scour beneath pipelines. A numerical approach was adopted to investigate the Reynolds-number dependence of two-dimensional scour beneath offshore pipelines in steady currents. A novel wall function is proposed in calculating the suspended sediment transport rate in the model. The effects of Reynolds number were investigated by simulating the same undisturbed Shields parameters in both model and prototype but with different values of Reynolds number in two separate calculations. The results revealed that scour depths for prototype pipelines are about 10~15% smaller than those for model pipelines. The normalized time scales was found to be approximately the same, and the simulated scour profiles for the model pipelines agree well with the experimental results from an independent study. The backfilling of pipeline trenches is also an important issue to the design and management of offshore pipelines. A numerical model is developed to simulate the self-burial of a pipeline trench. Morphological evolutions of a pipeline trench under steady-current or oscillatory-flow conditions are simulated with/without a pipeline inside the trench. The two-dimensional Reynolds-averaged continuity and Navier-Stokes equations with the standard k-e turbulence closure, as well as the sediment transport equations, are solved using finite difference method in a curvilinear coordinate system. Different time-marching schemes are employed for the morphological computation under unidirectional and oscillatory conditions. It is found that vortex motions within the trench play an important role in the trench development.

Orientador: Sergio Nascimento Bordalo
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-08-14T18:41:08Z (GMT). No. of bitstreams: 1 Oliveira_RafaeldeCastro_M.pdf: 1603033 bytes, checksum: 5b19ae643a703f87aab5fd52d37d741a (MD5) Previous issue date: 2005
Resumo: A deposição de parafinas em dutos submarinos é um sério problema para a produção marítima de petróleo. Parafinas são substâncias orgânicas caracterizadas por longas cadeias de carbono e hidrogênio, formadas por ligações covalentes simples, apresentando peso molecular elevado, devido ao grande número de átomos de carbono. Parafinas precipitam-se de soluções oleosas devido a um decréscimo de temperatura, e com o tempo, a parafina sólida fora da solução líquida deposita-se nas paredes das tubulações obstruindo o fluxo e ocasionando o aumento de perda de carga por fricção nas linhas. Em conseqüência, ocorre diminuição da vazão dos fluidos e entupimento da seção do duto de produção, entre outros problemas. O presente trabalho visa estudar esse fenômeno na produção de petróleo no mar, onde existe um gradiente térmico ao longo do escoamento devido à elevada diferença de temperatura entre o reservatório e o fundo do oceano. Para esse fim, foi construído um aparato experimental que consiste em uma tubulação horizontal de 25,4 mm (1") de diâmetro e cerca de 13 metros de comprimento, imersa em um banho de água gelada. Medidas de gradiente de pressão e de temperatura são efetuadas ao longo da tubulação, de modo a estudar o efeito da presença de água no escoamento, em relação ao fluxo monofásico de óleo, na deposição de parafina e no aumento do gradiente de pressão.
Abstract: The paraffin deposition in submarine pipelines poses a serious problem for the offshore oil production. Paraffins are organic substances characterized by long chains of carbon and hydrogen, linked by simple covalent bonds, presenting high molecular weight, due to the large number of carbon atoms. Paraffins precipitate off oily solutions due to a temperature decrease, and with time, the solid paraffin out of the liquid solution deposits on the walls of the pipeline, obstructing the flow and causing an increase of the pressure drop along the lines. Consequently, a reduction of the flow rate occurs, as well as clogging of the cross section of the production duct, among others problems. The present work aims to study this phenomenon in the case of oil production at the sea, where a thermal gradient exists along the flowlines, due to high temperature difference between the petroleum reservoir and the bottom of the ocean. To this end, an experimental apparatus was built consisting of an horizontal pipeline about 13 meters long with a 25,4 mm (1 in) diameter, immersed in a chilly water bath. Measurements of temperature and pressure were taken along the length of the pipeline, to study the effect of the two-phase flow, in relation to the single-phase flow, on the paraffin deposition and on the increase of the pressure gradient.
Mestrado
Explotação
Mestre em Ciências e Engenharia de Petróleo

La mer Caspienne qui est devenue l’objet du droit international depuis le XVIIIe siècle n’a jamais connu un statut juridique précis. Cet espace dont la nature aquatique fait l’objet de divergence était dominé par l’URSS jusqu’en 1991. Cependant, à la suite de la disparition de l’URSS, la mer Caspienne - désormais entourée de cinq États riverains (Azerbaïdjan, Iran,Kazakhstan, Russie et Turkménistan) – a fait sa réapparition sur la scène internationale, surtout en raison de ses riches ressources naturelles. C’est précisément dans ces conditions que la question de la situation juridique de la mer Caspienne au regard du droit international s’est posée à la fin du XXe siècle. Il convient donc de former un régime juridique de la mer Caspienne adéquat et durable à long terme et de trouver des solutions pour le règlement desdifférends juridiques entre les États caspiens
The Caspian Sea which has become the object of international law since the eighteenth century has never had a clear legal status. This space of which the aquatic nature is not defined was dominated by the Soviet Union until 1991. However, following the collapse of the USSR, the Caspian Sea - now surrounded by five littoral States (Azerbaijan, Iran, Kazakhstan, Russia and Turkmenistan) - has re-emerged on the international scene, especially because of its rich natural resources. It is precisely in these circumstances that the question of legal status of the Caspian Sea under international law arose in the late twentieth century. Therefore, it is necessary to form an adequate and sustainable long-term legal regime of theCaspian Sea and to find solutions for the settlement of legal disputes between the Caspian States

Створено та науково обгрунтовано ефективність розширеної інженерної методики дослідження деформації і руйнування матеріалу морських трубопроводів при статичному та низькочастотному навантаженні з урахуванням впливів структури, масштабного фактору, концентрації напружень, частоти навантаження, асиметрії циклу напружень, агресивності середовища, а також комбінації цих впливів. Розроблено автоматизовану випробовувальну систему з ЕОМ та оригінальне програмне забезпечення для комплексних досліджень в кінетиці деформації, руйнування, електродного потенціалу матеріалу трубопроводу в робочих (технологічних) середовищах, а також сканованих поверхонь зламів, забезпечуючи імітацію умов навантаження елемента трубопроводу. Введено комплексне поняття про малоциклову та багатоциклову низькочастотну втому і корозійну втому морських трубопроводів, спираючись на ґрунтовний аналіз умов їх експлуатації та деформаційно-кінетичне трактування процесу. Побудовано повні криві низькочастотної втоми для сталі трубопроводу з різною структурою та зварного з’єднання. Вперше, в області низькочастотної (0,8 Гц) малоциклової втоми та корозійної втоми, виявлено аномальну деформаційну поведінку текстурованої сталі 20 та зварного з’єднання, яка проявляється у виникненні деформаційних піків. З метою подальшого розвитку теорії низькочастотної корозійної втоми, вперше кінетичні криві деформації та електродного потенціалу представлено в об’єднаному вигляді, а їх аналіз виконується комплексно з графічною інтерпретацією макробудови поверхні руйнування. Запропоновано способи прискореної оцінки корозійної витривалості основного металу та зварного з’єднання труб за прогнозованими ділянками кривих низькочастотної корозійної втоми, побудованими з використанням однієї або двох експериментальних точок. Вперше введено поняття про кінетичний цикл росту втомної (корозійно-втомної) тріщини. Показано, що тривалість кінетичного циклу є важливою характеристикою низькочастотної втоми, чутливою до величини σа та впливу середовища, Запропоновано методику визначення деформаційних областей низькочастотної втоми морських трубопроводів, а саме спонтанної, прогнозованої та безпечної деформації, і показано її ефективність у випадку, коли характеристики граничних станів є малочутливими до зміни структури трубної сталі.
Создана автоматизированная испытательная система с ЭВМ для комплексных исследований в кинетике деформации, разрушения, ЭП материала трубопровода при статическом и низкочастотном нагружении в рабочих (технологических) средах, используя разработанные конструкции образцов-моделей, изготовленных из стенки трубы. Предложены и определены в статике нестандартные характеристики упругости, пластичности, деформационного упрочнения, ползучести для объяснения поведения стали в конструкции трубопровода и уточнения расчетов. Построены полные кривые низкочастотной усталости для стали трубопровода с разной структурой и сварного соединения по результатам испытаний образцов-моделей с конструктивными концентраторами и без. Показана возможность оценки влияния среды на величину разрушающих циклических напряжений по площади долома образца-модели. В условиях низкочастотного нагружения подтверждена локализация коррозионных процессов в зоне сварного соединения около границы раздела фаз „основной металл - сварной шов”.
It is created automated test system with computer for complex studies of the deformation. fracture, electrode potential of pipeline steel under static and low frequency loading in technological environments. Full curves of low frequency fatigue and corrosion fatigue of texturated and not texturated steel and welded join of pipes was presented. The complex concepts of low cycle and high cycle low frequency fatigue and corrosion fatigue of sea pipelines was offered. For the first time, in the field of low frequency (0,8 Hz) fatigue and corrosion fatigue, is revealed anomalous deformation behaviour texturated steel 20 and welded join, which reveals itself in deformation peaks. For the first time kinetic curves of deformation and electrode potential are presented in united type for the reason deepened their analysis, which is executed in complex with graphic interpretation of fracture surfaces macrostructure.

Este trabalho busca avaliar o efeito da sobrepressão interna na avaliação crítica de engenharia (ECA) de dutos submersos sujeitos a flambagem lateral controlada, que essencialmente consiste na análise de carregamentos combinados associados a grandes deformações longitudinais. O objetivo principal é avaliar a viabilidade da adoção de corpos-de-prova SENT na avaliação da resistência à fratura em dutos sujeitos a esforços combinados utilizando procedimentos analíticos que incorporam do aumento das forças motrizes devido à sobrepressão interna. Este estudo apresenta uma revisão sobre os procedimentos de ECA utilizados em dutos submersos e sobre o efeito da pressão interna na capacidade de deformação de dutos. Os procedimentos adotados atualmente e procedimentos alternativos são discutidos e implementados em um problema prático envolvendo diferentes razões de diâmetros por espessuras, expoentes de encruamento, níveis de sobrepressão e deformação longitudinal. Alguns casos selecionados são comparados com soluções elasto-plásticas de J, e.g. EPRI. Os resultados apresentados fornecem uma boa compreensão sobre as vantagens e limitações de cada procedimento, incluindo a possibilidade de estender sua aplicação além do limite normativo de 0,4% de deformação longitudinal.
This work aims to evaluate the effect of internal overpressure on the engineering critical assessment (ECA) of submarine pipelines subjected to controlled lateral buckling, which essentially consists of the analysis of combined loading with large longitudinal strains at the buckle crown. The main goal is to evaluate the feasibility of using SENT specimens to characterize the fracture resistance in the assessments of pipelines subjected to combined loadings using analytical procedures that takes into account the increase of crack driving force due to internal overpressure. This study presents a revision about ECA procedures used in submarine pipelines and about the effect of biaxial stresses their tensile strain capacity. Both standard and alternative procedures are discussed and implemented in a practical problem involving different diameter to thickness ratios, hardening exponents, levels of internal pressure and longitudinal strain. Some selected cases are compared with full elastic-plastic J solutions, e.g. EPRI. The results provide useful insights regarding the advantage and limitations of each procedure, including the possibilities to extend their applicability beyond the standard limit of 0,4% of longitudinal strain.

In recent decades, the rapid development of intelligent vehicle and 3D scanning tecnologies has led to a growing interest in applications based on 3D point data processing, with many applications such as augmented reality or robot manipulation and obstacle avoidance, scene understanding, robot navigation, tracking and assistive technology among others, requiring an accurate solution for the 3D pose of the recognized objects. Thus object recognition is becoming an important topic in computer vision, where machine vision and robotics techniques are becoming key players. In this thesis work, the main objective is to develop a semantic mapping method by integrating a 3D object recognition pipeline with a feature-based SLAM system, in order to assist autonomous underwater interventions in the near future. To this end, the work proposed in this paper targets three axes. First, it aims to compare the performance of 3D global descriptors within the state of the art, focusing on those based on point clouds and targeted at real-time object recognition applications. For this purpose, we selected a set of test objects representative of Inspection, Maintenance and Repair (IMR) applications and whose shape is usually known a priori. Their CAD models were used to: 1) create a data base of synthetic object views used as a priori knowledge, and 2) simulate the point clouds that would be gathered during the scanning under realistic conditions, with added noise and varying resolution. Extensive experiments were performed with both virtual scans and real data collected with an AUV equipped with a fast laser scanner developed at our research centre. The second goal of our work was to use a real-time laser scanner mounted on an AUV to detect, identify, and locate objects in the robot’s environment, with the aim of allowing an intervention Autonomous Underwater Vehicle (I-AUV) to know what manipulation actions could be performed on each object. This goal was tackled by the design and development of a 3D object recognition method for uncolored point clouds (laser scans) using point features. The algorithm uses a database of partial views of the objects stored as point clouds. The recognition pipeline includes 5 stages: 1) Plane segmentation, 2) Pipe detection, 3) Semantic Object-segmentation, 4) Feature-based Object Recognition and 5) Bayesian estimation. To apply Bayesian estimation, it is necessary to track objects across scans. For this purpose, the Inter-distance Joint Compatibility Branch and Bound (IJCBB) data association algorithm was proposed based on the distances between objects. The performance of the method was tested using a dataset of the inspection of a pipe infrastructure made of PVC objects connected by pipes. The structure is representative of those commonly used by the offshore industry. Experimental results show that Bayesian estimation improves the recognition performance with respect to the case where only the descriptor is used. The inclusion of semantic information about object pipe connectivity further improves recognition performance. The final goal of the thesis, consists of integrating the 3D object recognition system with a feature-based SLAM system to implement a semantic map providing the robot with information about the location and the type of objects in its surroundings. The SLAM improved both the accuracy and reliability of pose estimates of the robot and the objects. This is especially important in challenging scenarios where significant changes in viewpoint and appearance arise
A les darreres dècades, el ràpid desenvolupament de vehicles intel·ligents i de les tecnologies d’escaneig 3D han contribuït a augmentar l’interès en les aplicacions basades en processament de núvols de punts 3D, amb aplicacions com la realitat augmentada, la manipulació robòtica, l’evasió d’obstacles, la comprensió d’escenes, la navegació robòtica, el seguiment d’objectes i la tecnologia d’assistència, etc., que requereixen una soluci´o precisa de la posició 3D i l’orientació d’un objecte. Per tant, el reconeixement d’objectes s’està convertint en un tema, on la visió per computador i les tècniques robòtiques esdevenen protagonistes clau. En aquest treball de tesi, l’objectiu principal és desenvolupar un mètode per a la construcció de mapes semàntic mitjançant la integració d’una cadena de processament per al reconeixement d’objectes 3D, amb un sistema de SLAM basat en característiques, amb l’objectiu d’ajudar a les futures intervencions submarines. Per això, el treball proposat en aquesta tesi es divideix en tres eixos principals. El primer té com a objectiu comparar el rendiment de descriptors globals d’última generació, centrant-se en els basats en núvols de punts 3D i destinats a aplicacions de reconeixement d’objectes en temps real. Per a aquest objectiu, s’ha seleccionat un conjunt d’objectes de prova representatius d’aplicacions d’inspecció, manteniment i reparació (IMR), la forma dels quals es coneix a priori. Els seus models CAD s’han utilitzat per a: 1) crear una base de dades amb les vistes sintètiques dels objectes, i 2) simular els núvols de punts que adquiriria, en condicions realistes, un escàner làser incloent soroll sintètic i simulant diferents resolucions. S’han dut a terme experiments tant a partir d’escaneigs virtuals com de dades reals recopilades amb un AUV equipat amb un escàner làser de temps real desenvolupat al nostre centre de recerca. El segon objectiu del nostre treball va consistir en utilitzar aquest escàner làser, muntat a un AUV per detectar, reconèixer i localitzar objectes a l’entorn del robot, per tal de permetre, a un Vehicle Submarí Autònoms d’Intervenció (IAUV), saber quines accions de manipulació podria fer amb cada objecte. Aquest objectiu es va abordar amb el disseny i el desenvolupament d’un mètode de reconeixement d’objectes 3D en núvols de punts incolors (escanejos làser) utilitzant descriptors dels punts 3D. L’algorisme utilitza una base de dades de vistes parcials dels objectes emmagatzemats en forma de núvols de punts. El procés de reconeixement consta de 5 passos: 1) Segmentació de plànols, 2) Detecció de canonades, 3) Segmentació semàntica d’objectes, 4) Reconeixement d’objectes a partir dels descriptors de punts 3D i 5) Estimació bayesiana. Per aplicar l’estimació bayesiana, cal ser capaços de fer un seguiment dels objectes en escanejos successius. Per fer-ho, s’ha proposat l’algorisme Inter-distance Joint-Compatibility Branch and Bound (IJCBB) d’associació de dades basada en les distancies entre objectes dins del núvol de punts. El rendiment del mètode es va avaluar fent servir dades experimentals relatives a la inspecció d’una infraestructura composta de canonades interconnectades per objectes de PVC. L’estructura ´es representativa de les comunament utilitzades per la indústria offshore. Els resultats experimentals mostren que l’estimació bayesiana millora el rendiment del reconeixement en comparació de l’ús ´únic del descriptor. La inclusió d’informació semàntica sobre la connectivitat d’objectes a canonades millora encara més el rendiment del reconeixement. L’objectiu final de la tesi va abordar la integració del sistema de reconeixement d’objectes 3D basat en descriptors amb un sistema de SLAM basat en característiques, per implementar un mapa semàntic que proporciona al robot informació sobre la ubicació i el tipus d’objectes a l’entorn. La utilització de tècniques de SLAM ha millorat la precisió i la fiabilitat de les estimacions de la postura del robot i els objectes. Això és especialment important en escenaris difícils on es produeixen canvis significatius de perspectiva i aparença
Programa de Doctorat en Tecnologia

Orientador: Celso Kazuyuki Morooka
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências
Made available in DSpace on 2018-08-27T09:36:46Z (GMT). No. of bitstreams: 1 Santos_MarcusViniciusFranchidos_M.pdf: 2250280 bytes, checksum: 714679541259e76068e17573b7fb74b1 (MD5) Previous issue date: 2015
Resumo: Vibrações Induzidas por Vórtices em dutos com vãos livres sujeitos a corrente marítima é um problema presente na indústria offshore. Embora significativos esforços tenham sido feitos para entender este complicado problema de interação fluido estrutura, a modelagem numérica para cálculo é ainda um grande desafio. O presente trabalho tem como objetivo principal caracterizar o comportamento dinâmico dos dutos em vãos livres sob os efeitos do fenômeno da vibração induzida por vórtices (VIV). A disponibilidade de diversos programas de cálculo de VIV para estruturas offshore esbeltas facilita a avaliação da vida útil dessas estruturas e reduz o custo de projetos. No entanto, um bom domínio das metodologias adotadas por programas utilizados na indústria e a consciência das limitações correspondentes a diferentes técnicas são fundamentais para que o analista faça uso adequado dessas ferramentas computacionais. Neste sentido, este trabalho faz uma revisão dos diferentes modelos para estimar as forças de VIV devidas à corrente marinha. Para isto, diferentes programas de computador foram utilizados para calcular as vibrações na direção transversal de incidência de corrente, provocadas pelo desprendimento de vórtices em um duto com vão livre. As simulações do comportamento dinâmico da parcela em vão livre do duto foram realizadas utilizando três abordagens, respectivamente: modelos hidrodinâmicos de força de VIV semi-empíricos, no domínio da frequência; modelos hidrodinâmicos de força de VIV semi-empíricos, baseados nos coeficientes de sustentação e número de Strouhal, no domínio do tempo e um modelo hidrodinâmico de wakeoscillator, no domínio do tempo. Os resultados das simulações são analisados através de comparações com dados experimentais. Além disso, as limitações da cada modelo são discutidas
Abstract: Vortex induced vibration (VIV) of free span pipeline subjecting to ocean current is a present problem in the offshore industry. Although significant efforts have done to understand this complicated fluid structure interaction problem, the numerical modeling and predicting is still a big challenge. The primary objective of this work is to characterize the dynamic behavior of pipelines with free span under the effects of the Vortex-Induced Vibration (VIV) phenomenon. Different models to estimate VIV forces due to sea current are discussed. For this purpose, different computer programs were used to predict vibrations in the transverse direction of the current incidence direction, caused by the vortex shedding in a free span of the pipeline. Simulations of the dynamic behavior of a free span portion of the pipeline were carried out by two approaches, respectively: semi-empirical hydrodynamic VIV force model, in frequency domain and, semi-empirical VIV force model based on the lift coefficient and Strouhal number, in time domain and a wake oscillator in time domain. Simulations results are analyzed through comparisons with experimental data and also limitations of the each model are discussed
Mestrado
Explotação
Mestre em Ciências e Engenharia de Petróleo

Este projeto tem o objetivo de apresentar o estudo dos arames da armadura de tração que são empregados no transporte de óleo, gás e umbilicais hidráulicos na indústria petrolífera. Este estudo foi desenvolvido sob a necessidade de melhor ancoragem dos arames da armadura de tração de modo a garantir que, mesmo após a ruptura do arame dentro do conector não haverá o escorregamento do mesmo provocando a queda do duto flexível. Assim sendo, foi estabelecido o estudo de aderência da interface dos arames da armadura de tração dos dutos flexíveis. Com os ensaios concluídos se estudou um novo procedimento para o melhoramento de aderência mecânica dos arames com a resina epóxi. Após os ensaios de aderência e adesão concluídos foi realizado ensaio de tração em cada arame da armadura de tração sob sua montagem no conector de extremidade para verificação de carregamento que chegam nos ganchos dos arames da armadura de tração. Os estudos realizados no conector de extremidade de 2,5 demonstram que os ganchos dos arames da armadura de tração são de grande importância para a integridade estrutural do duto flexível, visto que o cone de resina formado dentro do conector não está em contato com toda a área dos arames das armaduras de tração.
This project aims to present the study of tensile armor wires usually employed in the transport of oil, gas and hydraulic umbilicals in the petroleum industry. This study was developed as a need for better anchoring of the tensile armor wires in order to guarantee that even after the rupture of the wire within the connector it will not slip causing the fall of the flexible riser. Thus was established the adhesion study of the interface of the tensile armor wires of the flexible risers. After the end of the tests a new procedure for improving mechanical adhesion between the wires and the epoxy resin was studied. After the end of the adhesion tests tensile test was performed on each wire of the tensile armor under its mounting on the end fitting for checking the loading that reaches the hook of the armor wires. The trials performed in the 2.5end fitting show that the tensile armor wire hooks are of great importance for the structural integrity of the flexible riser, as there is no contact between the resin cone formed within the end fitting and the tensile armor wires area.

Yes
This paper presents the results of laboratory experiments and numerical simulations to investigate the effect of different piggyback pipeline configuration on the morphology of local seabed scour subject to steady currents. Piggyback pipeline configuration investigated includes the commonly used piggyback pipeline, namely a small pipe attached on the top of large pipe and new form of piggyback pipeline proposed in this study in which a small pipe is attached to the large pipe on the upstream and downstream side, respectively. Pressure gradient, drag coefficient, lift coefficient and scour extent around pipelines are measured and analyzed for a range of pipelines and current conditions. Results show that the vortex strength downstream of the commonly used piggyback pipeline is larger than that for a single as well as the new piggyback pipeline under the same condition. This new type piggyback pipeline can effectively reduce the depth and width of the scour hole. In particular, when the ratio of the small pipe diameter over the large pipe diameter is greater than 0.3, little scour under this new type piggyback pipeline occurs for the test conditions. The bed topography downstream of the pipe has also been altered to favor the backfill.
National Natural Science Foundation of China (No. 51279189).

碩士
國立臺灣科技大學
自動化及控制研究所
103
Taiwan region relies on imports for its petroleum demands. Because issues such as depth of immersion, docking, steering, fire prevention, and water pollution must be taken into account when crude carriers enter the port, offshore tanker unloading equipment is used. Therefore, all crude carriers are equipped with sea dumping equipment. Oil is transported to the oil tank near the shore through the submarine pipeline and then is sent to the refinery plant to cut down transportation costs. By using the submarine pipeline to transport oil, the tonnage of crude carriers, required depth, submarine pipeline length, and pipeline diameter can be increased. However, literature survey indicates that the issues are rarely discussed concerning the submarine pipeline path layout optimization. Therefore, the Ant Colony Optimization (ACO) was adopted in this study to discuss the optimal path planning of submarine pipelines. First, the map was given five different weights depending on the seabed contours to represent the slope of the terrain. Then, the hexagonal unit interval method was adopted to design the map and reduce the wear and tear of the pipeline bend. Secondly, the ACO (using one set of heuristic functions) and multi-objective ACO (using two sets of heuristic functions) were adopted to achieve optimal path selection based on the weight distribution and the shortest distance settings in the map. In addition, an effectiveness evaluation of nearby seas of oil stations was conducted to obtain a better path compared to the original offshore oil station location setting, thereby facilitating future pipeline layout selection. The simulation results show that the multi-objective ACO is superior to the ACO, and with iteration, the optimal path of submarine pipeline layout can be found.

Yes
Local scour around submarine pipelines can affect the stability of the pipeline. The accurate estimation of the scour around submarine pipelines has been a hot topic of research among marine engineers. This paper presents results from a numerical study of clear-water scour depth below a submarine pipeline for a range of the steady flow conditions. The flow field around the pipeline under scour equilibrium condition is numerically simulated by solving the Reynolds-Averaged Navier-Stokes (RANS) equations with the standard k-ε turbulence closure. The flow discharge through the scour hole for various flow conditions is investigated. The results are used to establish the relationship between the flow discharge and the maximum scour depth. Incorporated with the Colebrook-White equation, the bed shear stress is obtained and an iterative method is proposed to predict the scour depth around the submarine pipeline. The calculated scour depths using the present method agree well with the laboratory measurements, with the average absolute relative error being smaller than that using previous methods, indicating that the proposed method can be used to predict the clear-water scour around the submarine pipeline with satisfactory accuracy.
National Nature Science Fund of China (Grant No.50879084, 51279189), the Open Fund from the State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University (SKHL1302),China Scholarship Council, Public Projects of Zhejiang Province (2016C33095) and the Natural Science Fund of Zhejiang Province (LQ16E090004).

碩士
國立臺灣科技大學
自動化及控制研究所
103
Submarine pipeline is the main access route for transporting imported crude oil from the offshore oil dump station to the oil tank near the shore. In this study, the particle swarm optimization (PSO) and the self-learning particle swarm optimization (SLPSO) were used to obtain the optimal submarine pipeline layout planning considering the facts including the changes in the subsea terrain, pipeline flow, and pipeline lengths. PSO is one of the most efficient tools for solving global optimization. Literatures have shown that when particles in the PSO make a subsequent selection, the same strategy is used. That is, only one learning model is used. Under this situation, due to social and cognitive model constraints, particles are likely to fall into local optimal solutions and thus be unable to process excessively complex problems. In order to resolve this problem, the self-learning algorithm was applied in this study. This algorithm divides learning strategies into four types to adapt to different environments, thus enabling each particle to choose a corresponding learning strategy based on their varied adaptation values. In general, the best solution for engineering applications related to optimum path planning, i.e., the shortest path. In other words, it refers to the path requiring the lowest cost. However, in actual engineering applications, the degree of engineering difficulty and costs that arise based on different terrain conditions should be taken into consideration. Based on the viewpoint in this study, the shortest path does not represent the path with the lowest costs. Hence, the shortest path does not necessarily represent the path with the lowest cost. The SLPSO with different construction cost weights was applied in this thesis to solve submarine pipeline layout planning. The simulation results in this study show that the SLPSO can derive the optimal solution more efficiently and more accurately compared to the PSO.

碩士
中原大學
土木工程研究所
107
Through the events of the 2004 South Asia tsunami and the 2011 northeastern tsunami in Japan, the problems of the liquefaction, erosion or structural damage caused by the tsunami through the nearshore were discovered. The engineering community''s knowledge of the interaction between tsunami, seabed and structures is still limited. The purpose of this study is to establish a numerical model to analyze the variation of the pore water pressure and the force of the pipeline caused by a solitary wave through the fully buried submarine pipeline. 　　In this study, a finite element method was used to establish a two-dimensional numerical model to solve the problem of the Biot equation describing the porous elastic bed. The model provides a solution to the displacement of the porous elastic bed and the variation of the pore water pressure. After the model is established, it is verified by simulating a one-dimensional consolidation problem, and the results show the correctness of this mode. By means of numerical simulation, the effects of solitary wave amplitude, Young''s modulus of the soil and permeability coefficient on the pore water pressure and seepage force are discussed. The numerical results can be used as a reference for future marine engineering applications. 　　In the simulation of solitary waves passing through fully buried submarine pipelines, numerical results indicate that the smaller the permeability coefficient in dense sandy bed the greater the vertical force acting on the pipeline, and the smaller the permeability coefficient in loose sand bed the smaller the vertical force acting on the pipeline. When the permeability coefficient is large, the smaller the Young''s modulus the more obvious the influence of the vertical force on the pipeline, and when the permeability coefficient is small, the larger the Young''s modulus the more obvious the influence of the vertical force on the pipeline.

Yes
This paper presents the results from laboratory experiments to investigate the protection of scour around submarine pipelines under unidirectional flow using a rubber plate placed underneath the pipes. The pressure difference on the two sides of the pipeline is the driving force to initiate the movement of sediment particles and can be obtained by force balance analysis. Experiments covering a wide range of incoming flow velocity, pipe diameter and plate length show that there exists a critical pressure difference over which the movement of sediment and, thus, scour takes place. Analysis of the experimental results demonstrates that this critical pressure difference is related to the pressure difference of the axial points between upstream and downstream of the pipe, which can be easily determined. This critical pressure difference is used to develop an empirical formula for estimating the critical length of the rubber plate, over which the sediment movement and scour will not take place. Good agreement between the experiments and calculated critical plate length using the proposed formula is obtained.
National High-Tech Research and Development program of China (863 Program, Grant No.2008AA09Z309), National Nature Science Fund of China (Grant No.50879084, 51279071 and 51279189), the Open Funding from the State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University (SKLH-OF-1306)

碩士
國立中興大學
土木工程學系所
97
The purpose of submarine water pipeline project is to build the pipeline underneath the seabed, for water running directly in between lands. Most submarine water pipeline project is built originally for the transportation of oil and natural gas under the sea. Since 1960s the development of mentioned technique is moderately established with 40 years experience. Although submarine water pipeline is rare case to apply, and this technique has not been standardized in accordance with the design of seabed water pipe domestically, yet the general design and planning is identical with the seabed oil pipe. This thesis is the overview of the related part of seabed water pipe project, and discussion for the failure causes of repair and reinforcement of seabed pipe in Kinmen and Leiyu. Furthermore, to adopt the result of under water technology association R.O.C “Study of the design and construction technology of undersea pipeline 2”，and in comparison of specifications from following organization，Ex:DNV(Det Norske Veritas)、BSI (British Standards Institution) 、API (American Petroleum Institute) and submarine pipeline project harbor association Japan, in addition to analyze the program of repair, the research of this thesis also provide the reference of related project design in the future.