温压荷载往复作用下深海管道—土体耦合轴向移动研究

This program focuses on mechanism and countermeasures of the pipeline walking phenomena which is caused by applying high cycle temperature and pressure on submarine pipeline system. Submarine pipelines system is a huge system in deep-water oil and gas development, and the cost of pipeline system accounts for 50% of the total investment. The pipelines often be shut down many times during their service life, and it causes pipeline directly moving several meters. This considerable axial displacement will reach the limit of tolerant range of connections, threatening the safety of pipeline system. To solve this problem, this program study three key issues: the soil restraining force model based on pipeline penetration, duration and direction of moving; the coupling of pipeline lateral buckling and axial pipeline walking under high cycle temperature and pressure; the model test methodology of pipeline walking under complex load and boundary condition. Based on these three key issues, the following researches will be carried out: the research on soil restraining force to unburied or shallow buried pipeline; the research of pipeline walking mechanism and simulated method under high cycle temperature and pressure; the research of the iteration of lateral global buckling and axial walking; the research on the factors influenced the axial walking displacement and corresponding control measures. As a consequence of these researches, a method which can simulate and predict the axial walking displacement of submarine pipeline under complex load and boundary conditions will be established. The mechanism of pipeline walking couple with lateral global buckling will be revealed. Efficient control measures will also be proposed to provide a theoretical and technological sustain for our deep-water pipeline system independent design and construction.

本项目针对深海海底管道在高温高压往复作用下出现的轴向移动现象开展研究。深海油气工程中管道工程的投资占总投资的50%。深海油气输送过程中较为频繁的启闭操作，导致了管道轴向移动量达到数米，超过了连接结构的耐受范围，是深海油气工程的重大安全隐患。为解决这一工程难题，本项目围绕三个关键科学问题：基于管道入土深度-运动历程-运动方向的土体约束力模型；海底管道轴向移动与水平向整体屈曲耦合作用机理的精细化模拟方法；海底管道轴向移动机理研究的实验验证方法。开展土体对不埋或浅埋管道水平向与轴向约束力研究；温压荷载往复作用下管道轴向移动机理与精细模拟分析；管道轴向移动与水平向整体屈曲耦合作用规律研究；影响管道轴向移动量的因素及控制方法研究。最终建立复杂荷载条件与边界条件下管道轴向移动量计算方法，揭示轴向移动与水平向整体屈曲耦合作用机理，提出管道轴向移动控制方法。为我国深海管道自主设计与施工提供理论与技术支持。

温压荷载往复作用下深海管道—土体耦合轴向移动分析是海底管道工程中遇到的新兴问题。本项目围绕海底管道轴向移动现象，开展了以下四方面的研究工作:（1）开展室内不埋及浅埋管道-土体相互作用试验，并将数值模拟方法与模型试验相结合，研究管道在软弱土体中的自沉特性，建立考虑土体扰动与强度恢复特性的管道自沉量计算方法；研究不同自沉深度地基土体对管道的约束力，建立管道水平向、轴向移动位移与土体约束力的关系，最终建立能综合考虑管道入土深度-运动历程-运动方向的土体约束力模型；（2）建立了复杂边界条件下管道轴向移动精细化模型，并结合管道约束状态及诱发因素阐明了轴向移动机理，运用MATLAB对大量数值结果进行多元非线性回归分析，提出了多因素耦合作用下管道轴向移动量评估方法；（3）建立了能有效模拟管道整体屈曲与轴向移动耦合变形的非线性有限元模型，基于该模型研究了管道轴向移动与水平向整体屈曲的耦合作用规律，确定了轴向移动与水平向整体屈曲协同激发的条件。（4）通过对不同轴向移动防护方案的对比，确定了最佳锚固点及锚固方式，分析了滑动基础对消减轴向移动的作用；对含屈曲段的轴向移动防护方案进行研究，探讨锚固点位置及数量对屈曲与轴向移动相互转化规律的影响，最终建立了科学的管道轴向移动量评估方法并提出了有效的控制措施。以上研究为我国深海油气管道在温压荷载循环作用下发生轴向移动的精细模拟分析和控制措施设计提供技术基础。