During the installation of marine flexible pipelines, components, such as flexible risers, umbilicals, and cables, subject to wave motion and ship yaw can cause torque on such pipelines. In addition, marine flexible pipelines are subjected to low tension at the touch down zone (TDZ), which could result in the torsion instability phenomenon of flexible pipeline in the TDZ, thus forming a loop. Moreover, when the tension on a marine flexible pipeline increases, the radius of the loop decreases and kinks can form, which could result in damage or fracture of the flexible pipeline, affecting its normal operation. In this study, the formation mechanism of a flexible pipeline loop is thoroughly analyzed considering the end torsion, tension, and environmental loads. The bending failure response surface function of the flexible pipeline is constructed considering the randomness of design parameters, e.g., elastic modulus, diameter, and density, and the probability of torsional instability of flexible pipeline is analyzed using both the first-order second moment and Monte Carlo simulation methods, both of which could give almost the same level of accuracy, while the first-order second moment method is computationally less expensive.

在船用挠性管道的安装过程中，易受波动和船舶偏航影响的组件（例如，挠性立管，脐带缆和电缆）会在此类管道上产生扭矩。另外，船用挠性管道在着陆区（TDZ）处承受的拉力较低，可能会导致TDZ中挠性管道的扭转不稳定性现象，从而形成回路。此外，当船用挠性管道上的张力增加时，回路的半径会减小，并且会形成扭结，这可能会导致挠性管道的损坏或断裂，从而影响其正常运行。在这项研究中，对挠性管道回路的形成机理进行了全面分析，其中考虑了端部扭转，张力和环境载荷。