海底管道屈曲传播及止屈试验技术研究综述

海底管道屈曲传播机理极其复杂,涉及到弹塑性稳定后屈曲问题,现有屈曲传播理论尚处于探索阶段,须通过大量的试验进行研究。本文概述了国内外海底管道屈曲传播理论研究发展历程,着重介绍了国外在海底管道屈曲传播与止屈试验技术方面的研究,总结和评述了国外相关试验装置的特点,探讨屈曲传播压力、传播速度、止屈效率等关键因素的试验测定方法,并指明了管道屈曲传播与止屈试验向全比例、多载荷、动态化发展的研究方向,为海底管道屈曲传播及止屈试验设计提供指导。     

深水海底管道止屈器设计研究

随着水深的增加,深水海底管道由于外压导致压溃、屈曲及屈曲传播的可能性大大增加.深水海管设计中,通常采用止屈器来控制海管由于较大的外压可能造成的压溃及屈曲传播.止屈器的主要作用是:在管道受外压的条件下,一旦发生压溃屈曲并发生屈曲传播时,将屈曲传播的破坏限制在一定管道长度范围内.该文进行了深水海底管道止屈器设计研究,并基于有限元模型进行了管道的屈曲和屈曲传播分析.     

国外海底管道局部屈曲研究综述

海底管道是海洋油气集输系统中最重要的组成部分之一,从铺设到服役都将承受多种载荷的作用,并可能发生局部屈曲且沿管道传播开来,由此造成严重的后果。海底管道的局部屈曲在管道安全性方面具有重要意义,已成为海底管道设计与评估中重要的内容。详细阐述了国外关于海底管道受外压、弯矩和轴力作用下的局部屈曲研究成果,论述了在单个载荷和多个载荷联合作用下的局部屈曲破坏机理,并提出了未来研究的建议。     

海底管道整体式止屈器模型试验与数值模拟

整体式止屈器是一种必备的海洋工程装置,它在阻止海底管道屈曲传播和保证海底管道安全运行方面发挥着重要的作用,而穿越压力是其设计和安装的重要的技术参数。为了得到更准确的计算结果,采用模型试验和数值模拟的方法,对整体式止屈器穿越压力公式重新进行设计。将得到的计算公式与其他经典计算方法进行对比,验证了穿越压力计算的准确性,它对整体式止屈器的工程设计和建造具有指导意义。     

Theoretical Studies in Isolated Prop Model of Subsea Pipeline

基于热屈曲理论,考虑独立支撑缺陷对海底管道隆起屈曲的影响,文章推导了独立支撑缺陷海底管道隆起屈曲段长度、隆起屈曲临界荷载和前屈曲荷载,并与已有结果进行了对比,表明:独立支撑缺陷对海底管道隆起屈曲临界荷载有显著的影响,验证了本文研究结果的可行性.     

海底管道侧向屈曲分析

侧向屈曲是非埋设海底高温高压管道运行期间常见的失效形式.由高温和高压造成的管道轴向应力是导致管道侧向屈曲的主要原因.本文对管道侧向屈曲进行了数学解析分析,并给出了管道在实际运行状态下发生侧向屈曲时常出现的四种模态的力学分析结果.对某工程项目的海底管道进行了侧向屈曲的数值计算以验证其工程可靠性.从理论和工程实践两方面分析比较了控制侧向屈曲的各种方法.初步探讨了深水高温高压管道的侧向屈曲控制方法.     

复合材料立管抗屈曲能力的提高方法

由于复合材料具有高比强度、设计性强、扰腐蚀性能好等优点,而广泛应用于海洋立管中,但是复合材料立管设计还不够成熟。本文为探究提高复合材料立管抗面压屈曲能力的方法,研究了复合材料结构参数对复合材料立管抗面压屈曲能力的影响,发现铺层数和铺层角对其抗面压屈曲能力有较大影响。其后对复合材料立管增加止屈器,结果表明止屈器可以较大幅度提高其抗面压屈曲能力。对今后研究复合材料立管抗屈曲能力提供一定的指导意义。     

海底管道整体屈曲摄动解与Galerkin解的对比分析

海底管道在高温高压下的整体屈曲是管道设计中需要考虑的重要问题。由于地基土体对管道作用的非线性特点,使得求解高温高压下海底管道整体屈曲变形的理论解非常困难。摄动法和Galerkin法是求解海底管道整体屈曲的重要方法。文章在考虑土体对管道抗力的分析模型基础上对海底管道水平向整体屈曲变形的摄动法解与Galerkin法解进行了对比,发现两者得到的结果差异较小,但Galerkin法求解过程复杂,计算量大,且土抗力的函数表达式较为单一。     

带止屈器的复合材料圆柱壳结构屈曲分析及优化

针对海洋工程上的复合材料圆柱壳结构,基于有限元软件ABAQUS,利用Python语言编程实现参数化建模、屈曲分析以及在后处理中提取屈曲因子。研究复合材料圆柱壳结构在单独受到轴向压力、侧向压力以及两种压力组合作用下止屈器的位置对屈曲极限强度的影响,并利用遗传算法多参数优化的方法对止屈器的位置进行优化,最终找到最优解。研究结果可以为复合材料圆柱壳结构抵抗屈曲失效的优化设计提供参考。     

壁厚所致几何不连续性对卷管法安装管道的影响

对于深水管道,止屈器起到了很好的防止屈曲传播的作用,但是在卷管法安装中,管道在上卷和退卷的过程中将产生塑性变形,而由于止屈器导致的管道壁厚几何不连续性将使局部管段的变形增大,可能加剧塑性变形的影响。针对这个问题,建立ABAQUS非线性有限元模型模拟管道安装过程,研究上述问题对卷管、铺管中管道性能的影响并作参数敏感性分析。结果表明:壁厚所致几何不连续性的存在导致卷管安装时管道局部曲率和应变明显增大;增加回拉力可降低上述不连续性的影响,但管道残余椭圆度也将增加;增大卷筒半径或减小管道直径将使不连续性的影响降低;增大管道壁厚可降低不连续性的影响,但会增加建造成本。文章研究结论可为卷管法安装中管道设计提供理论指导。     

Modelling upheaval buckling in marine buried pipelines by coupling the shear stresses and soft soil stiffness

Buried marine pipelines employed in the Oil & Gas industry are subjected to pressure and temperature gradients, which cand produce local high compression loads leading to the onset of upheaval buckling failure. Upheaval buckling occurs when the localized stresses across the pipeline are high enough to induce constant deformation due to the low soil restriction in the upward direction. Therefore, models to predict upheaval buckling in buried marine pipes caused by high pressure and high temperature (HP/HT) and soil stiffness have been developed based on Euler-Bernoulli beam theory (EBT). However, this theory does not consider stresses and strains due to shear stresses which can play an important role in upheaval buckling failure. Therefore, in this work an analytical model that takes into account Engesser-Timoshenko beam theory (TBT) and considers the shear effects on pipelines was developed to predict upheaval buckling in buried marine pipelines. Furthermore, equations that govern vertical buckling of buried pipelines considering a plastic soil with initial imperfection were considered. Analytical results were compared with finite element models of buried pipeline and other models reported in the literature, and it was observed that analytical results fall in the range of those reposted in the literature. It was also observed that the incorporation of shear stresses in buried marine pipelines has low effect on upheaval buckling onset and propagation, but the soil stiffness has a strong influence on upheaval failure in buried marine pipelines.     

Propagating buckles in corroded pipelines

Rigid–plastic solutions for the steady-state, quasi-static buckle propagation pressure in corroded pipelines are derived and compared to finite element predictions (ABAQUS). The corroded pipeline is modeled as an infinitely long, cylindrical shell with a section of reduced thickness that is used to describe the corrosion. A five plastic hinge mechanism is used to describe plastic collapse of the corroded pipeline. Closed-form expressions are given for the buckle propagation pressure as a function of the amount of corrosion in an X77 steel pipeline. Buckles that propagate down the pipeline are caused by either global or snap-through buckling, depending on the amount of corrosion. Global buckling occurs when the angular extent of the corrosion is greater than 90°. When the angular extent is less than 90° and the corrosion is severe, snap-through buckling takes place. The buckle propagation pressure and the corresponding collapse modes also compare well to finite element predictions.     

小径厚比深水管道的压溃屈曲研究

深水管道所处的特殊海洋环境极易导致其发生压溃屈曲破坏.通过深入分析不同径厚比深水管道的压溃屈曲特点,并对具有不同径厚比及初始椭圆度的深水管道模型进行了压溃屈曲及后屈曲行为的计算分析.研究发现,压溃屈曲的经典理论公式并不适用于小径厚比深水管道.文章基于经典理论和数值模拟结果,得到了适用于小径厚比深水管道压溃屈曲分析的临界压力修正公式,进而对小径厚比深水管道的压溃屈曲评估提供理论支撑和工程推荐.     

Three-dimensional pipeline element formulation for global buckling analysis of submarine pipelines with sleeper

Submarine pipelines can utilize sleepers to control global buckling location, which mitigates potential risks under high temperature and pressure. However, pipelines with sleepers require execution in three-dimensional space and experience lateral buckling modes. As such, this paper proposes a 3D pipeline element for lateral buckling analysis, building on previous 2D element formulations. This new element considers non-linear pipe-soil interactions, thermal expansion, axial load, initial imperfections, large deflection, and other major factors that affect lateral buckling. The derivations of the 3D pipeline element are provided in detail, and the numerical analysis procedure is elaborated. To validate the accuracy and efficiency of the proposed 3D pipeline element, several examples are presented.     

Experimental and theoretical studies on lateral buckling of submarine pipelines

Global buckling of a submarine pipeline during high pressure/high temperature (HP/HT) operation results in a loss of pipeline stability that is similar to a bar in compression; this phenomenon constitutes one of the key factors affecting pipeline integrity and design. To intuitively study the buckling response, a test system was designed that can account for thermal loading and pipe-soil interactions, and this system was used to perform a series of small-scale model tests on the lateral buckling of submarine pipelines with different initial imperfections. Based on the hat-shaped buckling profiles of the test pipelines, a new buckling mode called "hat-shaped buckling" was proposed. In an attempt to study the conditions under which the pipeline exhibits this hat-shaped buckling mode, the changing law of the buckling mode was investigated through finite element analyses of pipelines with different parameters, including the length of the pipeline and the amplitude and wavelength of the initial imperfection. Subsequently, an analytical solution for calculating the buckling amplitude of a pipeline with a hat-shaped buckling profile was proposed. The theoretical solution was compared to the experimental data, which verified the feasibility of the model in calculating pipeline buckling deformation. The experimental data, the buckling mode based on these data and the corresponding analytical model discussed herein may provide a reference for future experimental studies of pipeline buckling.     

海水中环天线的辐射特性研究

使用电磁波进行水下通信具有传播速率高等优势,文章针对电磁波水下通信中环天线的设计,在对电磁波传播特性进行研究的基础上,分析了传播速度和波长对环天线的影响,推导出了水下环天线的辐射功率和辐射阻抗的解析表达式,仿真分析了水下环天线的辐射特性,得出了天线尺寸和工作频率对辐射特性的影响,为环天线的设计和应用提供了参考。     

水下爆炸冲击作用下舰船管路动响应研究

舰船管路是船舶抗冲击的薄弱环节之一,开展船舶管路抗冲击研究对提高舰船生命力很有意义。文中对大型船舶的压缩排气管路进行有限元建模,并基于有限元计算,分析了管路模型在水下爆炸冲击载荷作用下的响应。通过对管路应力、应变、加速度和位移等响应的归纳,得到空气管路在水下爆炸载荷作用下的响应规律并给出结论,可以为船舶管路系统的抗冲击研究提供参考。     

基于γ界面捕捉模型的近场水下爆炸数值模拟

随着对水下爆炸现象研究的逐步深入,近场水下爆炸的数值模拟研究越来越受到重视。近场水下爆炸数值模拟当中的主要难点在于多相流运动以及界面捕捉方法的研究。文章提出一种较为稳定的近场水下爆炸数值模拟方法,其包含了五阶WENO重构以及HLLC近似黎曼求解器的格式,对于多相流界面的捕捉方法基于γ模型。文中的求解格式通过了一维激波管问题以及二维轴对称问题的验证,计算结果与理论解和实验结果吻合较好。在此基础上将该方法推广到近场水下爆炸过程中冲击波传播以及近水面爆炸现象的模拟,模拟结果较为满意。该文的研究方法能够为后续的近场水下爆炸过程中的空泡以及水射流的研究提供指导。