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1.
Study on Interaction Relationship for Submarine Pipeline with Axial Corrosion Defects 总被引：2，自引：0，他引：2
Corrosion is one of the main reasons to cause the operation accident of submarine oil and gas transmission pipelines. As the major corrosion pattern in submarine pipelines, the effects of corrosion clusters consisting of the adjacent corrosion defects on failure pressure are investigated through non-linear large-deformation finite element method. Typically, the failure behavior and limit strength of submarine pipeline with axial groove-groove corrosion defect pair exposed to internal pressure are analyzed. The effects of corrosion depth and axial spacing between a pair of corrosion defects on failure pressure are concluded. An interaction relationship for corrosion defects in pipelines, as well as prediction formulations for assessing the remaining strength of corroded pipelines are proposed. The expressions based on the proposed interaction relationship give more accurate results than the methods used in the existing design guidelines. 相似文献
2.
The axial friction response of subsea pipelines in soft clays is a very important aspect for designers of subsea pipelines but the response is not well understood so far. There is a pressing need for the comprehension of the response. In this paper, model tests are performed using full-scale pipes coated with polyethylene (PE) to study the effects of the set-up period, the pipe diameter, the buried depth of the pipe, the shear strength of soft clays and the loading rate on the axial friction response of pipelines in soft clays. The variations of the axial friction coefficient are analyzed using the effective stress method based on model test results. The results show that the axial friction resistance increases with the increasing pipe diameter but the effect of the pipe diameter on the axial friction coefficient can be neglected. The ultimate axial resistance also increases with the increase of the buried depth of pipelines, the undrained shear strength of soft clays and the loading rate. The axial friction coefficient increases with the increasing loading rate. However, the axial friction coefficient decreases with the increasing buried depth. The method to determine the axial friction coefficient is developed by analyzing model test results, which considers the effects of the diameter, the buried depth, the undrained shear strength of soft clays and the loading rate. The study results not only extend the industry data base but also supply a basis to determine the axial friction coefficient of PE-coated pipes in soft clays for ocean engineering geological investigations. 相似文献
3.
It is well known that the design of submarine pipelines relies on accurate test results for the local buckling collapse of pipes subjected to bending loading. The present paper analyses apparently anomalous values of axial tensile and compressive strains from recent test results in comparison to the values that would be expected on the basis of simple bending theory. This could have important consequences for the efficacy of the design factors derived using these results. The cause of the differences between the strain values obtained in the tests and those expected on the basis of simple bending theory are explained using finite element modelling. The differences result from the type of collars and supports commonly used in bending tests, the effects of which persist for a greater length along the test pipe than has hitherto been assumed. In general, it is pointed out that the application of the simplified engineering theory of bending can be erroneous when ovalisation is imposed or, on the contrary, the boundary conditions of the section are restrained from ovalising deformations. The influence of the D/t ratio is also analysed.The results contribute to the understanding of a crucial limit state for the design of onshore and offshore pipelines. 相似文献
4.
初始几何缺陷被认为是影响管道极限承载力和稳定性的重要因素,但是大部分的管道力学特性研究都没有考虑初始缺陷的影响。基于管道几何尺寸测量机,获得管道的壁厚和直径沿轴向以及环向的分布规律。据此建立了四个三维实体有限元模型,分别为完好管道模型、只考虑直径缺陷的管道模型、只考虑壁厚缺陷的管道模型以及考虑所有缺陷的管道模型。分析了初始缺陷对管道的极限内压承载力、极限轴力承载力和极限弯矩承载力的影响。结果表明,直径缺陷对管道的极限内压承载力影响较大;壁厚缺陷对管道在复杂荷载作用下的极限弯矩承载力影响较大。 相似文献
5.
The maximum bending moment or curvature in the neighborhood of the touch down point (TDP) and the maximum tension at the top are two key parameters to be controlled during deepwater J-lay installation in order to ensure the safety of the pipe-laying operation and the normal operation of the pipelines. In this paper, the non-linear governing differential equation for getting the two parameters during J-lay installation is proposed and solved by use of singular perturbation technique, from which the asymptotic expression of stiffened catenary is obtained and the theoretical expression of its static geometric configuration as well as axial tension and bending moment is derived. Finite element results are applied to verify this method. Parametric investigation is conducted to analyze the influences of the seabed slope, unit weight, flexural stiffness, water depth, and the pipe-laying tower angle on the maximum tension and moment of pipeline by this method, and the results show how to control the installation process by changing individual parameters. 相似文献
6.
A research on super-long piles has been primarily based on cast-in-place bored piles. In this article, field tests associated with selected measuring technologies were conducted on two super-long steel pipe piles in offshore areas to investigate the behaviors and performance of super-long steel pipe piles. The strain along the pile shaft was monitored by adopting the Brillouin optical time domain reflection and fiber Bragg grating techniques. Static load tests were also conducted on two test piles to determine the bearing capacities. In addition, the axial forces, relative displacements between piles and soils and pile shaft resistances were calculated based on the measured strain. According to the results of the static load tests, the ultimate bearing capacities of the two test piles are greater than 15,000 and 15,500 kN. Both of these values meet the design requirements. In addition, the two test piles can be treated as pure friction piles, and the load transfer mechanism and relationships between the pile shafts and relative displacements are also discussed. Finally, recommendations for practical engineering and significant conclusions are presented. 相似文献
7.
采用卷管法进行海底管道铺设过程中,管道首先通过牵引作用上卷于卷筒进行储存。管道与卷筒发生非线性接触,可能会产生复杂的塑性变形和局部屈曲。通过全尺寸柔性管力学性能试验获得柔性管轴力—应变以及弯曲—曲率等非线性力学性能关系,将试验所得的非线性材料性能参数导入建立的两种柔性管上卷ABAQUS有限元模型（梁—实体单元模型与壳和桁架—实体单元模型）,实现柔性管较大轴向抗拉刚度和较小抗弯刚度的同步模拟以及管道与卷筒的非线性接触响应特征。通过对比分析两种有限元模型数值模拟得到的管道弯矩、弯曲曲率、管道轴力、管道与卷筒的接触压强等数据,发现在管道上卷过程中管道沿副法线方向的SM3弯矩占据其弯曲变形主导地位;管道与卷筒之间的摩擦效应对于管道轴力的影响较为显著;管道与卷筒的最大接触压强主要发生在卷管过渡段区域。 相似文献
8.
砂土对管道约束力的模型试验研究 总被引：1，自引：1，他引：1
为研究砂土与海底管道的作用机制，验证计算模式，我们用细砂和原型管道进行了模型试验。对埋入土中的管道，主要进行了轴向摩阻力试验，并将试验结果与多种计算方法进行了比较。对半埋管道，首先进行了管道静置沉降试验，试验结果与国外有关资料进行了对照，并验证了以极限分析理论为基础建立的计算方法；其次进行了管道侧向阻力试验以及往复荷载作用下管道侧向阻力及沉降试验 相似文献
9.
海上风机中,上部支撑结构和基础之间的连接是通过灌浆连接段实现的。近年来,风力发电发展迅速,风力发电机的功率越来越大,对单桩基础灌浆连接段的受力性能提出了更高的要求。在复杂荷载作用下,灌浆连接段受到轴力和弯矩的共同作用,有必要对压-弯共同作用下的灌浆连接段进行受力性能的研究。采用数值分析方法,分析了压-弯作用下不同轴压比时灌浆连接段的极限承载力、钢管与灌浆料之间的接触压力情况和灌浆连接段的应力情况。同时,根据学者Lotsberg提出的弯曲承载力组成理论,通过提取钢管与灌浆料之间的接触力,并对它们进行数值积分,分析了不同轴压比下灌浆连接段抗弯承载力组分的变化规律。通过分析,明晰了带剪力键的灌浆连接段的受力性能,为设计工作提供依据。 相似文献
10.
How to reconstruct a dynamic displacement of slender flexible structures is the key technology to develop smart structures and structural health monitoring(SHM), which are beneficial for controlling the structural vibration and protecting the structural safety. In this paper, the displacement reconstruction method based on cubic spline fitting is put forward to reconstruct the dynamic displacement of slender flexible structures without the knowledge of modeshapes and applied loading. The obtained strains and displacements are compared with the results calculated by ABAQUS to check the method's validity. It can be found that the proposed method can accurately identify the strains and displacement of slender flexible structures undergoing linear vibrations, nonlinear vibrations, and parametric vibrations. Under the concentrated force, the strains of slender flexible structures will change suddenly along the axial direction. With locally densified measurement points, the present reconstruction method still works well for the strain concentration problem. 相似文献
11.
本文基于历年检测资料统计分析了杭州湾海底输油管道裸露埋深状态变化规律,结合水文地形测量资料、辅以数学模型手段,从Spoiler自埋设计、杭州湾水流特性、管道路由海床演变特性以及人类活动等多因素探索了杭州湾海底管道裸露埋深状态变化的原因。研究结果表明:杭州湾管道80%以上处于埋深状态,局部管段长期裸露,裸露管段主要位于北岸深槽和庵东边滩滩坡区域;管道冲刷与管道路由海床演变特性、水流与管道夹角以及Spoiler自埋设计的发挥密不可分;杭州湾南岸围垦工程的实施与该区域管道裸露、掩埋状态密切相关。 相似文献
12.
Free spanning pipelines are suspended between two points on an uneven seaffoor. The variations of structural conditions, such as the changes in soil property, flow velocity, axial force and span length etc., directly affect working performance of the whole submarine pipeline system. But until now few researches have focused on condition identification for free span （CIFS）. A method to identify the operational conditions of free spanning submarine pipelines based on vibration measurements is proposed in this paper. Firstly, the ill-posedness of CIFS is analyzed in detail. Secondly, the framework for CIFS based on the nonlinear kernel discriminant analysis （KDA） is established. Thirdly, the internal structural characteristics of natural frequencies, normalized frequencies and frequency change ratios are studied. And then the condition feature vector for CIFS is extracted by use of the vibration measurements. Finally, the validity of the proposed approach is evaluated by a case study. The results demonstrate that the proposed approach can effectively identify each condition of free span when condition variation occurs even if under measurement noise. It is concluded that the proposed method is a promising tool for CIFS in real applications. 相似文献
13.
14.
考虑波-管-土耦合作用的海底管道在位稳定性分析方法 总被引：8，自引：1，他引：7
以水动力加载试验得到的描述管道在位稳定性的波浪环境参数、管道参数和海床土性参数之间的无量纲耦合关系为基础,提出了一种考虑波-管-土动力耦合作用的海底管道在位稳定性分析方法,并通过算例与挪威船级社推荐的DnV设计规范进行了比较分析。分析表明,考虑波-管-土耦合作用的管道稳定性分析方法与DnV管道设计规范有很好的可比性．而且物理机理更清晰,可为管道稳定性设计提供有益的参考。 相似文献
15.
Zhu Dashan Huang Yuying Cheng Jiangtian
Asso. Prof. Dept. of Mechanics Huazhong University of Science Technology 《中国海洋工程》1991,(1)
A plastic ring-beam model simulating the longitudinal transition zone of submarine pipelines in the buckle propagation is presented. The nonlinear relationships between the buckle propagation pressure and the length of the transition zone and the position parameter of the longitudinal plastic hinge are derived using the energy principle. The related values are obtained by means of solving a set of nonlinear equations. The model conforms better to reality than the ring models for considering the effect of the longitudinal plastic bending of the transition zone. The computations for some stainless steel and aluminium tubes with different geometrical parameters are performed. The results obtained agree better with the experimental results than existing theoretical predictions. 相似文献
16.
Because of the complex geological conditions of the seabed, submarine pipelines buried beneath the ocean floor become suspended over the seabed under the long-term scour of waves eroding the surrounding sediment. Further, most oil fields were built in offshore areas while the country was developing. This gives the waves seen in shallow water obvious nonlinear features, and the abnormal characteristics of these waves must be considered when calculating their hydrodynamic forces. Particularly under such conditions, these suspended spans of submarine pipelines are prone to damage caused by the action of the external environment load. Such damages and eventual failures may result not only in great property losses but also pollution of the marine environment. The span length of these areas is a key predictive factor in pipeline damages. Therefore, determining the allowable span length for these submarine pipelines will allow future projects to avoid or prevent damage from excessive suspended span lengths. Expressions of the hydrodynamic loads placed on suspended spans of pipeline were developed in this work based on the first-order approximate cnoidal wave theory and Morison equation. The formula for the allowable free span length was derived for the common forms of free spanning submarine pipeline based on the point where maximum bending stresses remain less than the material’s allowable stress. Finally, the allowable free span length of real-world pipelines was calculated for a subsea pipeline project in Bohai Bay. This research shows that, with consideration for the complicated marine environment, existing suspended spans are within allowable length limitations. However, continuing to limit the length of these submarine pipeline spans in the Nanpu oil field will require ongoing attention. 相似文献
17.
Experiments on Interaction Between Current-Induced Vibration and Scour of Submarine Pipelines on Sandy Bottom 总被引：2，自引：0，他引：2
SHEN Zhonghan 《中国海洋工程》2000,14(4):423-434
In order to understand the dynamic behavior of submarine pipelines exposed to current andthe mechanism of the interaction between current-induced vibration and scour of pipelines on a sandy bot-tom,an experimental investigation is conducted with a small scale model.A test model which can be testedin the flume is set up by taking into account the typical working conditions of the pipelines and by ap-plying the similarity theory.The interactions between the shape of the scour hole and the behavior of thepipeline as well as the flow patterns of the current are detailed,and the interaction mechanism outlined.The effect of vibration of the pipeline on the development of dynamic scour at different stages is foundout.The proposed experimental method and test results provide an effective means for design of marinepipelines against scouring. 相似文献
18.
Cheng-Lin Zhang 《Marine Georesources & Geotechnology》2017,35(7):1018-1027
When a subway train moves through a tunnel, vibrations are generated and transmitted to soils around the tunnel and adjacent structures. Subway train operation has an impact on the shield tunnel lining and the soils around tunnel, especially soft soils that are mostly marine sediments having poor engineering properties. An elastoplastic dynamic finite difference model was built by considering the hysteretic behavior of these marine soft soils and the interaction between the soils and the tunnel to study their dynamic response. Elastic and plastic constitutive models were adopted for tunnel lining and soft soils, respectively. Hysteretic damping was obtained with the Hardin–Drnevich model to reflect the hysteretic behavior of soil under the dynamic load. There are two peaks of the cumulative vertical displacement within 2?s of train moving and it reaches a dynamic balance after 2?s. The soil layers below the shield tunnel are under the compression and the soil layers above the tunnel are in the extrusion state, and turn to uplift. Maximum bending moment and shear forces of lining vary and appear at different places. A parametric study indicates that the speed of train and the interface have an impact on the dynamic behavior of soft soils. 相似文献
19.
Offshore floating facilities are fixed by anchoring systems embedded in seabed soils through chains or ropes. The chain inverse catenary profile embedded in soils influences both the anchor failure mechanism and the anchor holding capacity. The chain mobilizes varying soil normal and tangential resistances during motion, hence it is with difficulty to depict the chain profile. The present work proposed a modified method to estimate the chain inverse catenary profile with high accuracy based on the chain equations and the chain yield envelope. A testing arrangement with three load cells and two MEMS (Micro-electromechanical systems) accelerometers included was designed in model tests. By model tests, the loading combinations of the soil tangential and normal resistances on the chain were obtained and the yield envelopes for both chain and rope were determined. In addition, supplemental model tests were performed to validate the modified method proposed in this study, and the testing results indicated that the estimated chain inverse catenary profile was in good agreement with the actual one. Moreover, the testing arrangement is beneficial in investigating the chain-soil-anchor interaction. 相似文献
20.
波浪作用下孔隙海床-管线动力相互作用分析 总被引：1，自引：0，他引：1
波浪作用下海床中的孔隙水压力与有效应力是影响海底管线稳定性的主要因素。然而,在目前的海床响应分析中一般将管线假定为刚性,并不能合理地考虑海床与管线之间的相互作用效应,同时也没有考虑土体和管线加速度对海床动力响应的惯性影响,从而无法确定由此所引起的管线内应力。为此考虑管线的柔性,分别采用饱和孔隙介质的Biot动力固结理论和弹性动力学理论列出了海床与管线的控制方程,进而采用摩擦接触理论考虑海床与管线之间的相互作用效应,基于有限元方法建立了海床-管线相互作用的计算模型及其数值算法。通过变动参数对比计算讨论了管线几何尺寸、海床土性参数对波浪所引起的管线周围海床孔隙水压力和管线内应力的影响。 相似文献