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1.
海底管线是海洋石油的重要输运手段。为满足输送工艺的需要,正常工作条件下管线往往被施加较高的温度和压强,高温高压使管线内产生附加应力,当附加应力大于土体对管线的约束力时,管线就会发生整体屈曲。过度的水平向整体屈曲会导致截面产生较大的弯曲应力和压缩应变,对管线系统的安全运行造成威胁,因此需要对发生水平向整体屈曲后的管线进行验算。采用解析解法、规范法和有限元法对管线的整体屈曲进行分析,提出了应用临界屈曲荷载值域空间和值域下限来判断不同缺陷大小下管线是否发生水平向整体屈曲的方法。结合工程实例,分别采用内力控制标准和位移控制标准对管线水平向整体屈曲后是否失效进行了验算。研究指出,相较于位移标准,内力控制标准更为严格。 相似文献
2.
温度应力下海底管线的整体屈曲是海底管线设计中的关键问题之一,不埋或半埋的海底管线较易发生水平向整体屈曲。海底管线会因为制造的缺陷或铺设的原因而具有初始变形,即初始侧向变形。研究了初始侧向变形对海底管线整体屈曲的影响,应用小变形理论建立了单拱侧向变形和反对称双拱侧向变形管线发生低阶模态水平向整体屈曲的理论分析方法,结合工程实例分析了初始侧向变形形态、侧向变形幅值以及地基土体强度特性对管线水平向整体屈曲的影响。结果表明,初始侧向变形的存在使管线更易发生整体屈曲;而反对称双拱侧向变形比单拱侧向变形更易引起管线整体屈曲;随初始侧向变形幅值的增加管线发生整体屈曲所需要的温差降低,且整体屈曲变形形态有所改变管土间摩擦系数的增加会提高管线发生整体屈曲的温差,从而提高管线抵抗整体屈曲变形的能力。 相似文献
3.
温度应力下海底管线的整体屈曲是海底管线设计中的关键问题之一,不埋或半埋的海底管线较易发生水平向整体屈曲。海底管线会因为制造的缺陷或铺设的原因而具有初始变形,即初始侧向变形。研究了初始侧向变形对海底管线整体屈曲的影响,应用小变形理论建立了单拱侧向变形和反对称双拱侧向变形管线发生低阶模态水平向整体屈曲的理论分析方法,结合工程实例分析了初始侧向变形形态、侧向变形幅值以及地基土体强度特性对管线水平向整体屈曲的影响。结果表明,初始侧向变形的存在使管线更易发生整体屈曲;而反对称双拱侧向变形比单拱侧向变形更易引起管线整体屈曲;随初始侧向变形幅值的增加管线发生整体屈曲所需要的温差降低,且整体屈曲变形形态有所改变管土间摩擦系数的增加会提高管线发生整体屈曲的温差,从而提高管线抵抗整体屈曲变形的能力。 相似文献
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海洋油气资源的运输主要通过海底管道进行,管道在工作时受到较大的温度荷载,会产生整体屈曲变形。深海管道设计中常采用人为装置触发一定程度的水平向整体屈曲变形,来释放轴向的温度应力,浮力装置是常用的触发方式之一。本文通过数值模拟研究,分析了不同浮力大小和不同浮力施加范围下,管道水平向整体屈曲的临界屈曲力,得出临界屈曲力随浮力大小和施加范围变化的情况;并研究了不同土体阻力下,浮力装置触发整体屈曲的效果。研究表明,水平向土体阻力较大时,浮力装置触发水平向整体屈曲的效果较好。浮力装置的触发效果对轴向土体阻力不敏感。 相似文献
5.
双拱初始缺陷海底管线水平向整体屈曲数值模拟分析 总被引：1，自引：0，他引：1
为了研究具有双拱反对称初始缺陷海底管线的整体屈曲特性,采用模态分析法将最可能出现的缺陷形态引入数值分析模型中。针对管线在高温高压作用下发生整体屈曲的动态变形特征,运用显式动力数值模拟方法研究了管线整体屈曲过程中水平向变形与轴向变形随温度和内压的变化规律,建立了在整体屈曲过程中屈曲管段与滑动管段轴力的变化过程与初始缺陷形态的关系。将数值模拟结果同经典解析解和室内模型实验结果进行对比,验证了本方法的可靠性。工程算例的分析结果表明,管线整体屈曲的发生是一个由低阶向高阶发展的过程,具有双拱缺陷的管线首先发生二阶模态的整体屈曲,而后过渡到四阶模态;管线整体屈曲的变形包括屈曲段的水平向变形和滑动管段的轴向缩进,其中水平变形释放了管壁内的轴力,轴力的释放量随初始缺陷尖锐程度的降低而增大;轴向缩进变形由于受到地基土的摩阻力使滑动管段内的轴力发生累积,轴力的累积量随初始缺陷的尖锐程度的降低而增加。以上研究成果对指导实际工程具有现实意义。 相似文献
6.
海底管线是海洋油气输运系统的重要组成成分,其稳定性和安全性尤为重要。通过有限元软件ABAQUS,应用Mohr-Coulomb模型,模拟海底裸置与埋置管线自沉过程。通过平衡初始地应力,设置管土接触,考虑重力和浮力作用,进行土体固结分析,计算裸置与埋置管线的土体与管线竖直位移,并进行管线悬跨研究。计算结果显示,对于裸置管线,参数的改变使土体更容易发生塑性屈服,土体的竖直位移量更大;对于埋置管线,当管线埋深较浅、管线上方土体重量不大时,参数的改变使管线平均密度与周围土体密度相差越大土体越容易发生塑性屈服,土体的竖直位移量越大。当管线悬空时,悬跨长度过大易使管线两端支撑土体被压溃,管线易产生大变形而失稳,因此在管线安装与维护过程中,一定要采取措施降低悬跨长度,保证管线运营安全。 相似文献
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8.
海底管道在深海石油开发工程中有着广泛的应用,管道在工作时受到高温高压会触发水平向整体屈曲变形,蛇形铺管法是控制管道水平向整体屈曲变形的有效手段。采用数值模拟方法,对蛇形铺设管道的关键参数进行研究,分析关键参数对临界屈曲荷载和屈曲后截面应力应变状态的影响。对每一组蛇形铺设管道都设置了直线型铺设管道的对照组,对照组采用引入初始挠曲的方法激发水平向整体屈曲,初始挠曲程度与蛇形铺设管道相同。通过与直线型铺设管道的对比,显示了蛇形铺设管道在激发和控制屈曲方面的优势,并对不同土体阻力情况下蛇形铺设管道的实际效果进行了评估。结果表明,蛇形铺设管道的临界屈曲力和屈曲后的弯矩皆远小于直线型管道。蛇形铺设管道的临界屈曲力随圆心角θ增大而减小,随曲率半径R的增大而增大。增大跨度L、曲率半径R和圆心角θ都能有效减小蛇形铺设管道的截面弯矩。水平向土体阻力对蛇形铺设管道影响较大,水平向土体阻力较小时,蛇形铺设管道控制屈曲的效果更为明显。 相似文献
9.
海底管道是海洋油气工程的重要组成部分，在高温高压运行状态下易发生整体屈曲，开裂破坏后造成油气泄露。海床土体对管道的侧向抗力是影响其屈曲的关键因素，而管道侧向抗力发挥与初始嵌入深度密切相关。构建了海底管道整体屈曲数值模型，对初始嵌入深度等因素进行不确定性分析，揭示了初始嵌入深度变异性对管道屈曲的影响机制。研究发现：当初始嵌入深度越大、初始缺陷越小时，管道临界屈曲轴力越大，屈曲位移越小；管道嵌入深度变异性的存在会导致管道更易屈曲，并诱发不对称的三阶屈曲或更高阶屈曲；管道嵌入深度在空间上的变异性对屈曲发生概率P（p＜pdet）存在影响，而相关性的改变对管道屈曲影响较小；管道存在屈曲模式转变界限升温，当屈曲升温大于界限升温时，管道发生跳跃型屈曲，反之则发生分岔型屈曲。 相似文献
10.
不埋海底管道在高温高压作用下,易发生水平向整体屈曲。实际工程中,常通过在管道路由上设置整体屈曲触发装置,实现对水平向整体屈曲的有效控制,其中以枕木法的成功应用最为多见。本文分析了枕木法的主要影响因素并验证了采用枕木法会出现管道屈曲段应力集中的现象,对比了枕木法、分布浮力法和枕木-浮力耦合法对管道整体屈曲变形规律的影响,采用数值模拟方法系统研究了枕木及浮力参数对管道水平向屈曲和后屈曲的影响规律。研究表明,在枕木两侧设置浮力段的人工触发装置可有效触发管道整体屈曲,同时促使管道虚拟锚固点间轴力的释放,降低了管道中屈曲段的应力,相较枕木法,枕木-浮力耦合法可将管道中的最大应力降低23%。 相似文献
11.
Lateral Global Buckling of Submarine Pipelines Based on the Model of Nonlinear Pipe–Soil Interaction
With the increasing development and utilization of offshore oil and gas resources, global buckling failures of pipelines subjected to high temperature and high pressure are becoming increasingly important. For unburied or semi-buried submarine pipelines, lateral global buckling represents the main form of global buckling. The pipe–soil interaction determines the deformation and stress distribution of buckling pipelines. In this paper, the nonlinear pipe–soil interaction model is introduced into the analysis of pipeline lateral global buckling, a coupling method of PSI elements and the modified RIKS algorithm is proposed to study the lateral global buckling of a pipeline, and the buckling characteristics of submarine pipeline with a single arch symmetric initial imperfection under different pipe–soil interaction models are studied. Research shows that, compared with the ideal elastic–plastic pipe–soil interaction model, when the DNV-RP-F109 model is adopted to simulate the lateral pipe–soil interactions in the lateral global buckling of a pipeline, the buckling amplitude increases, however, the critical buckling force and the initial buckling temperature difference decreases. In the DNV-RP-F109 pipe–soil interaction model, the maximum soil resistance, the residual soil resistance, and the displacement to reach the maximum soil resistance have significant effects on the analysis results of pipeline global buckling. 相似文献
12.
Yang Cao 《Marine Georesources & Geotechnology》2013,31(4):477-487
AbstractThe deep-water pipeline is the main means of transportation in offshore oil and gas development engineering. The deep-water pipeline may incur lateral global buckling due to the high temperature and pressure that are applied on the pipeline to ensure the contents’ liquidity. With the increasing operating water depth, a higher temperature and pressure are applied to the pipeline, causing large lateral deformation and a large bending moment. Due to the inhomogeneous distribution of the bending moment on the cross-section, different points on the cross-section will deform differently. This kind of deformation causes the cross-section to turn into an oval ring. The cross-section ovalization caused by global buckling was rarely analyzed in former engineering practice since the load is relatively low. With the increase in operation water depth and operation load, the ovality caused by global buckling is noticeable. This article analyzed cross-section ovalization caused by pipeline lateral global buckling with a numerical simulation method. The pipelines with different initial cross-section shapes were simulated, and the influence of several impact factors, including load, pipeline and soil factors on the ovality of the cross-section, were analyzed. The results show that the initial cross-section shape type has little effect on the pipeline ovalization pattern. The initial ovality of the pipeline with an oval ring cross-section shape has little influence on the residual ovality. Among all the factors analyzed in this paper, the pressure difference is the primary factor that should be considered in a pipeline ovalization check. 相似文献
13.
Submarine pipelines are the primary component of an offshore oil transportation system. Under operating conditions, a pipeline is subjected to high temperatures and pressures to improve oil mobility. As a result, additional stress accumulates in pipeline sections, which causes global buckling. For an exposed deep-water pipeline, lateral buckling is the major form of this global buckling. Large lateral displacement causes a very high bending moment which may lead to a local buckling failure in the pipe cross-section. This paper proposes a lateral global buckling failure envelope for deep-water HT/HP pipelines using a numerical simulation analysis. It analyzes the factors influencing the envelope, including the thickness t, diameter D, soil resistance coefficient μ, calculating length Lf, imperfection length L and imperfection amplitude V. Equations to calculate the failure envelope are established to make future post-buckling pipeline failure assessment more convenient. The results show that (1) the limit pressure difference pmax (the failure pressure difference for a post-buckling pipeline when it suffers no difference in temperature) is usually below the burst pressure difference pb (which is the largest pressure difference a pipeline can bear and is determined from the strength and sectional dimensions of the pipeline) and is approximately 0.62–0.75 times the value of pb and (2) thickness t has little influence on the normalized envelopes, but affects pmax. The diameter D, soil resistance coefficient μ, and calculating length Lf influence the maximum failure temperature difference Tmax (the failure temperature difference for a pipeline suffering no pressure difference). The diameter D also significantly affects the form of the normalized envelope. 相似文献
14.
Offshore oil and gas exploration are gradually heading toward the deep sea and even the ultra-deep sea. According, the working temperature and pressure intensity of subsea oil and gas pipelines have increased by a considerable degree. This situation is accompanied by the global buckling problem in deep sea pipelines, which has become increasingly common. Meanwhile, ordinary single-layer pipelines cannot last for a long time under harsh deep-sea working conditions. Thus, multilayer pipelines, such as the pipe-in-pipe (PIP) structure and bundled pipelines, have gradually become top choices. However, the global buckling mechanisms of these multilayer pipelines are more complicated than those of single-layer pipelines. The sleeper–snake lay pipeline, which is an active control method for global buckling, was used in this study. The change and development laws of global buckling in a PIP structure at different wavelengths and amplitudes were determined through an experimental study. A dynamic solution method that considers artificial damping was adopted to establish finite element global buckling models of a PIP structure with initial imperfections. The effects of various factors, such as pipeline laying shape, sleeper–pipe function, and seabed–pipe function, on global buckling were analyzed. By the result of finite element method analysis, the initial imperfection, and sleeper–pipeline friction were determined to be the key factors that influenced critical pipeline buckling force. Accordingly, a reference for the design of PIP structures is presented. 相似文献