On-bottom stability design of subsea pipelines transporting hydrocarbons is important to ensure safety and reliability but is challenging to achieve in the onerous metocean (meteorological and oceanographic) conditions typical of large storms (such as tropical cyclones, hurricanes or typhoons). This challenge is increased by the fact that industry design guidelines presently give no guidance on how to incorporate the potential benefits of seabed mobility, which can lead to lowering and self-burial of the pipeline on a sandy seabed. In this paper, we demonstrate recent advances in experimental modelling of pipeline scour and present results investigating how pipeline stability can change in a large storm. An emphasis is placed on the initial development of the storm, where scour is inevitable on an erodible bed as the storm velocities build up to peak conditions. During this initial development, we compare the rate at which peak near-bed velocities increase in a large storm (typically less than 10−3 m s−2) to the rate at which a pipeline scours and subsequently lowers (which is dependent not only on the storm velocities, but also on the mechanism of lowering and the pipeline properties). We show that the relative magnitude of these rates influences pipeline embedment during a storm and the stability of the pipeline.
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机译：运输碳氢化合物的海底管道的底部稳定性设计对于确保安全性和可靠性很重要，但要在大风暴（例如热带气旋，飓风或台风）所特有的繁重的海洋（气象和海洋）条件下实现该挑战就很难。目前，行业设计指南未提供有关如何整合海床移动性潜在好处的指导，这一事实加剧了这一挑战，因为这可能会导致沙质海床上的管道下降和自行掩埋。在本文中，我们展示了管道冲刷实验模型的最新进展，并提供了调查在大风暴中管道稳定性如何变化的结果。重点放在暴风雨的初期发展上，因为暴风雨的速度不断加快，到了高峰期，在可侵蚀的床上不可避免地要进行冲刷。在此初始开发过程中，我们将大风暴（通常小于10 −3 m s −2 ）附近近地层速度峰值增加的速率与该速率进行比较。然后管道冲刷并随后降低（这不仅取决于风暴的速度，还取决于降低的机制和管道的特性）。我们表明，这些速率的相对大小会影响暴风雨期间的管道嵌入和管道的稳定性。
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