深海管道在位稳定性的流固土耦合机理及分析方法研究

In order to meet the urgent national demand for the long-distance installation of deepsea pipelines, especially for the engineering application of submarine pipelines at the continental slopes in the South China Sea, the instability modes and the corresponding wave/current-pipeline-soil coupling mechanisms are to be investigated intensively. Employing large-scale pipe-soil interaction tests, the flow-structure-soil coupling flume tests and numerical analyses, the proposed multi-physics coupling analysis is an innovative study to reveal the complicated mechanism for the pipeline stability on a sloping seabed in the severe waves and current. Focusing on the typical engineering cases (i.e. transverse laying, climbing laying), the key aspects for the on-bottom instability will be investigated, including the pipeline hydrodynamics in the wave/current layer boundary and its coupling with the soil scouring, the ultimate axial anti-sliding soil friction against the pipeline on the sloping seabed, the critical conditions for the lateral instabilities and the corresponding flow-pipe-soil coupling mechanisms, etc. Based on the flow-pipe-soil coupling mechanisms, an updated analysis method for on-bottom stability of deepwater pipelines is to be proposed, taking into account the multi-physics coupling effects. The research results may provide a scientific reference for the engineering design and the security evaluation of the submarine pipelines in the complicated deepsea environments.

面向我国深海长输油气管道建设的工程需求，特别以南海大陆坡海底管道工程为应用背景，深入研究波流环境载荷和斜坡海床条件下，海底管道的在位失稳模式及"波流－管道－海床"之间的流固土耦合力学机理。通过设计管土相互作用试验和流固土耦合水槽试验并辅以数值模拟，侧重于多物理场耦合分析，是揭示复杂海洋环境条件下管道在位稳定性机理的新探索。针对管道顺坡和横坡铺设等典型工况条件，研究获得波流底床边界层附近管道水动力响应及冲刷耦合规律，进而分析管道侧向失稳的临界条件、管道轴向极限抗滑特性等。在揭示管道在位失稳机理的基础上，提出考虑流固土耦合效应的深海管道稳定性分析方法，为我国深海油气开发中的长输管道设计及安全评估提供科学依据。

我国南海深水海域油气资源开发亟待解决长输海底管道稳定性设计分析难题。本项目深入研究了波流环境载荷和大陆坡斜坡海床条件下，海底管道在位失稳模式及流固土耦合力学作用机理。通过设计管土相互作用机械加载和流固土耦合水槽模型试验，并辅以数值模拟和理论分析，为揭示复杂海洋环境条件下管道在位稳定性机理开展了系统研究。取得的主要研究成果包括，分别获得了砂土和粘土典型海床条件下海底管道地基极限承载力的塑性滑移线场理论解；基于极限平衡分析方法，建立了斜坡海床管道侧向失稳理论预测模型；揭示了斜坡海床管土轴向相互作用物理机制并给出了分析方法；理论推导得出了海床瞬态液化深度预测公式，并获得了管道周围土体超静孔压响应规律；揭示了海底管道侵蚀悬空和侧向失稳典型失稳模式之间的竞争机制。在项目执行期间，发表学术论文16篇，包括期刊论文10篇、会议论文6篇。SCI收录7篇、EI收录5篇。作特邀学术报告5次，包括国际学术会议2次、国内学术会议3次。共授权发明专利5项。研究成果应用于我国南海北部湾东方气田管道稳定性设计；管道地基极限承载力滑移线场理论解被2017年颁布的挪威船级社海底管道设计规范采纳。