深海腐蚀缺陷管道屈曲失稳机理与极限承载力研究

The deep-sea oil and gas pipelines with complicated force conditions are inevitably corroded by surrounding ocean environments and inside conveying mediums during the long-term service, as a result, the wall of the tube thins and the load-carrying capacity decreases, and it is prone to induce the buckling and collapse failure of the pipeline at the corrosion defects under deep-sea high hydrostatic pressure, which will cause economic losses and environmental disasters. Thus, it is extremely important to scientifically and reasonably evaluate the ultimate load-carrying capacity of deep-sea corroded pipelines. In this project, according to the force characteristics of deep-sea in-service pipelines, the combined research methods of theoretical model analyses of nonlinear buckling and collapse, small scale model experiments of deep-sea pressure chamber, and numerical simulations are applied to investigate the buckling and collapse mechanism of deep-sea corroded pipelines under different combinations of external pressure, axial compression force, and bending moment. The present study aims to clearly explain the influencing mechanisms of the defect shape, geometric dimensions of the defect, the defect location, the spacings between adjacent defects, geometric parameters and material mechanical properties of the pipe, and the loading path etc. on the buckling and collapse of the corroded pipelines, and systematically reveal the intrinsic relationships between the collpase pressure and the ultimate bending moment of the deep-sea corroded pipelines, and the defect location, geometric dimensions of the defect, axial force, geometric parameters and material mechanical properties of the pipe, and finally establish an effective method to evaluate the ultimate load-carrying capacity of deep-sea corroded pipelines using the external pressure and the bending moment as the control loads. The research findings will lay a solid theoretical foundation for the integrity evaluation of deep-sea corroded pipelines.

深海油气管道受力复杂，在长期服役过程中不可避免地受到周围海洋环境和内部输送介质的腐蚀作用，导致管壁变薄和承载力降低，在深海高压环境下易诱发腐蚀缺陷部位管道屈曲失稳破坏，造成经济损失和环境灾害。因此，科学合理地评估深海腐蚀缺陷管道的极限承载力就显得尤为重要。本项目拟采用非线性屈曲失稳理论模型分析、深海压力舱比例模型试验和数值模拟相结合的研究方法，基于深海服役管道的受力特性，开展外压-轴压-弯矩不同组合作用下深海腐蚀缺陷管道屈曲失稳机理研究，阐明缺陷形状、缺陷几何尺寸、缺陷位置、相邻缺陷间距、管道几何参数和管材力学特性、加载路径等对管道屈曲失稳的影响机制，揭示深海腐蚀缺陷管道屈曲失稳压力和极限弯矩与缺陷位置、缺陷几何尺寸、轴力、管道几何参数和管材力学特性之间的内在联系，建立以外压和弯矩为控制荷载的深海腐蚀缺陷管道极限承载力的有效评估方法，为深海腐蚀缺陷管道的完整性评价奠定坚实的理论基础。

腐蚀是海底管道失效破坏的主要原因。深海油气管道易受外部环境和内部输送介质的腐蚀作用，导致管道壁厚变薄和承载力降低，在外部压力作用下易诱发腐蚀缺陷管道的屈曲失稳破坏，造成重大的经济损失。本项目采用理论分析、压力舱小尺度模型试验和数值模拟相结合的研究方法，基于深海服役管道的受力特性，分别开展了外压作用下深海单腐蚀缺陷管道屈曲失稳机理及影响因素、深海双腐蚀缺陷管道屈曲失稳机理及影响因素、多种缺陷耦合作用下深海腐蚀缺陷管道屈曲失稳机理、外压及轴拉共同作用下深海单腐蚀缺陷管道屈曲失稳机理等方面研究，充分明确了深海单腐蚀缺陷管道屈曲失稳的影响机理，系统深入揭示了单腐蚀缺陷管道、双腐蚀缺陷管道以及非对称腐蚀缺陷管道屈曲失稳压力和失稳模式与管道几何尺寸和管材力学特性、初始椭圆率、腐蚀缺陷尺寸和缺陷位置之间的内在关系，阐明了双腐蚀缺陷相互作用的影响机理和不同类型缺陷间的耦合作用机制，分别提出了考虑缺陷耦合效应的外压作用和外压轴拉共同作用深海单腐蚀缺陷管道屈曲失稳压力的经验计算公式，形成了复杂荷载作用下深海腐蚀缺陷管道剩余承载力评估模型，为深海腐蚀缺陷管道的完整性评价奠定了理论基础。研究成果已在国际权威期刊发表高水平论文8篇，国内期刊论文2篇，已培养毕业博士研究生1人和硕士研究生1人。