The Experts below are selected from a list of 1437 Experts worldwide ranked by ideXlab platform
Lizhong Wang - One of the best experts on this subject based on the ideXlab platform.
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Single Buoyancy Load to Trigger Lateral Buckles in Pipelines on a Soft Seabed
Journal of Engineering Mechanics, 2015Co-Authors: Ruowei Shi, Lizhong WangAbstract:AbstractFor exposed subsea pipelines, lateral buckles are usually artificially triggered as an accommodation technique to release thermal expansion by providing temporary flotation with controlled spacing. With the given Buoyancy Load, the pipeline will be uplifted initially and will then buckle laterally under a certain thermally induced axial Load, which is called the bifurcation Load. Previous studies have analyzed this problem and modeled the uplifted pipeline as a fixed-fixed end beam, assuming the lateral seabed stiffness is infinite. However, the lateral seabed stiffness is usually low because the seabed is formed from soft soils. Using analytical methods, this paper investigates the Buoyancy Load required to trigger lateral buckles along a pipeline, considering a seabed with finite elastic stiffness, and provides suggestions for the Buoyancy design with an elastic-plastic seabed model using an example of finite-element analysis. It was found that the seabed condition significantly influenced the f...
Ruowei Shi - One of the best experts on this subject based on the ideXlab platform.
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Single Buoyancy Load to Trigger Lateral Buckles in Pipelines on a Soft Seabed
Journal of Engineering Mechanics, 2015Co-Authors: Ruowei Shi, Lizhong WangAbstract:AbstractFor exposed subsea pipelines, lateral buckles are usually artificially triggered as an accommodation technique to release thermal expansion by providing temporary flotation with controlled spacing. With the given Buoyancy Load, the pipeline will be uplifted initially and will then buckle laterally under a certain thermally induced axial Load, which is called the bifurcation Load. Previous studies have analyzed this problem and modeled the uplifted pipeline as a fixed-fixed end beam, assuming the lateral seabed stiffness is infinite. However, the lateral seabed stiffness is usually low because the seabed is formed from soft soils. Using analytical methods, this paper investigates the Buoyancy Load required to trigger lateral buckles along a pipeline, considering a seabed with finite elastic stiffness, and provides suggestions for the Buoyancy design with an elastic-plastic seabed model using an example of finite-element analysis. It was found that the seabed condition significantly influenced the f...
Hong Zhang - One of the best experts on this subject based on the ideXlab platform.
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Stress and Deformation Analysis of Buried Gas Pipelines Subjected to Buoyancy in Liquefaction Zones
MDPI AG, 2018Co-Authors: Mengying Xia, Hong ZhangAbstract:Buried pipelines are the main means of long distance transportation of natural gas. These pipelines are in high risk crossing liquefaction areas due to large deformations and stresses that may exist in pipe induced by the Buoyancy Load. In this study, a systematic analytical and numerical analysis were performed to investigate the mechanical behavior of a buried gas pipeline subjected to Buoyancy in liquefaction areas. Soil constraints on pipe were considered accurately in the proposed models through soil spring assumptions. Effects of axial forces on pipe’s bending deformation were also considered via the governing equations for beam under bending and tension. Deformation compatibility condition was utilized to derive the axial forces in pipe. The accuracy of the proposed analytical model was validated by comparing its results with those derived by an established rigorous finite element model. In addition, parametric analysis was finally performed using the analytical model to study the influences of pipe diameter, pipe wall thickness, soil spring stiffness and width of liquefaction zone on pipe’s mechanical responses. This study can be referenced in the strength analysis and performance based safety evaluation of buried gas pipelines crossing liquefaction areas
Yannie Carrasco, Jorge G. - One of the best experts on this subject based on the ideXlab platform.
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On the long-term behaviour of tension Loaded piles in natural soft soils
Chalmers University of Technology Gothenburg, 2016Co-Authors: Yannie Carrasco, Jorge G.Abstract:The complexity and scale of new infrastructure projects have challenged the current geotechnical design practice. Urban areas are growing at a fast pace in the horizontal and vertical direction, with taller buildings and deeper underground constructions in already densely populated areas. The West Link project in Gothenburg city is a good example of the latter. The geotechnical challenges in this project include deep excavations and deep foundations in soft sensitive natural clays. An important aspect in this case is the large Buoyancy Load arising from the ground water pressure, the stability of the soil mass in the excavation vicinity and the unLoading heave from the soil. Typically, these Loads are counterbalanced by the superstructure self-weight and by bedrock anchors. The very deep clay deposits in Gothenburg, however, require traditional floating piles to sustain the permanent tension Loads from these processes. Little is known about the long-term behaviour of pile foundations in deep soft soil deposits under permanent tension Loads. The need for a reliable foundation system for the West Link tunnel and the limited data available on permanently Loaded tension piles in soft clays motivates further theoretical and experimental investigation of this pile type in natural soft structured clays. As a result this Thesis presents new findings on the long-term behaviour of tension Loaded piles in natural soft structured clays. The unique results from the field tests on six pile elements incorporate all significant stages in the pile cycle, i.e. pile installation, set-up and long-term Loading, yet are sufficiently short to link the pile response to the soil behaviour of one particular layer. Furthermore, a novel cost-effective Loading rig using gas springs and remote logging based on open-source software and freely available cloud storage is developed for execution of the field tests. The results indicate that the measured long-term bearing capacity is smaller than the short-term reference capacity. The difference is in the order of 20 – 30 % smaller. This reduction is attributed to the on-going creep deformations in the soil surrounding the pile shaft. These deformations cause relaxation of the effective stresses due to the kinematic constrains at the pile-soil interface. In addition to an analytical system level interpretation of the measured pile head displacement that showed only benign maximum final pile head displacements after 100 years, an advanced numerical analysis that incorporates a state-of-the-art rate dependent soft soil model is performed. The measured data and simulation results are in good agreement and corroborate previous investigations, however, for the first time the physical mechanisms underpinning the measured response are generalised and tertiary creep failure is reproduced. The long-term pile response is directly related to the behaviour of the soil adjacent to the pile shaft. Further work should focus on the evolution of the stress field and soil properties under long-term pile Loading. Deviatoric creep deformations should be studied in more detail by means of element level laboratory test on natural and remoulded soft clays
Mengying Xia - One of the best experts on this subject based on the ideXlab platform.
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Stress and Deformation Analysis of Buried Gas Pipelines Subjected to Buoyancy in Liquefaction Zones
MDPI AG, 2018Co-Authors: Mengying Xia, Hong ZhangAbstract:Buried pipelines are the main means of long distance transportation of natural gas. These pipelines are in high risk crossing liquefaction areas due to large deformations and stresses that may exist in pipe induced by the Buoyancy Load. In this study, a systematic analytical and numerical analysis were performed to investigate the mechanical behavior of a buried gas pipeline subjected to Buoyancy in liquefaction areas. Soil constraints on pipe were considered accurately in the proposed models through soil spring assumptions. Effects of axial forces on pipe’s bending deformation were also considered via the governing equations for beam under bending and tension. Deformation compatibility condition was utilized to derive the axial forces in pipe. The accuracy of the proposed analytical model was validated by comparing its results with those derived by an established rigorous finite element model. In addition, parametric analysis was finally performed using the analytical model to study the influences of pipe diameter, pipe wall thickness, soil spring stiffness and width of liquefaction zone on pipe’s mechanical responses. This study can be referenced in the strength analysis and performance based safety evaluation of buried gas pipelines crossing liquefaction areas
