基于共旋坐标法的钢悬链线立管管土作用数值分析

Numerical analysis of pipe-soil interaction of steel catenary riser based on co-rotational coordinate method

为分析钢悬链立管(SCR)在顶部浮体小范围垂降、侧向漂移运动下的立管触地段垂向、侧向管土作用,将立管初始贯入海床及侧向移动过程作为准静态问题,在共旋坐标框架内建立三维有限梁单元模型,并耦合p-y加载曲线模拟立管初始贯入海床过程,并对比了线性、双线性及非线性管土模型在计算管土响应上的差异,分析了立管顶部水平牵引载荷、海流作用及土体抗剪强度对立管触地段垂向管土作用的影响,进一步研究了浮体小范围漂移工况下的侧向牵引力、土体特性参数对立管触地段侧向、垂向组合的管土作用影响。结果表明:在共旋坐标框架下,非线性管土模型对立管贯入海床的响应模拟更准确;顶部水平牵引力及海流流速增大,均会导致立管贯入海床深度及垂向土阻力减小;土体抗剪强度增大导致立管贯入深度减小但垂向及侧向土阻力增大;顶部浮体侧向牵引力增大致使立管触地段的侧向位移及土阻力增大,但垂向土阻力减小;侧向摩擦系数的增大可显著提高立管触地段的侧向稳定性。本文所述共旋坐标法利用刚体与变形解耦的特性高效求解了立管全局运动及触地段的管土作用,为立管与海床作用研究提供了参考。

In order to analyze the vertical and lateral pipe-soil interaction of the steel catenary riser(SCR)in the touchdown zone under the small-scale vertical drop and lateral drift motion of the top floating object,taking the initial penetration into the seabed and the lateral displacement process of the riser as quasi-static problems,a three-dimensional finite beam element model was established in the co-rotational coordinate framework,and the p-y loading curve was coupled to simulate the initial penetration of the riser into the seabed.The differences between linear,bilinear and nonlinear pipe-soil models in pipe-soil response were compared,the effects of horizontal traction force at the top of the riser,current and soil shear strength on the vertical pipe-soil interaction of the riser touchdown section were analyzed,and the effects of lateral traction force and soil parameters on the lateral and vertical pipe-soil interaction of the riser touchdown section under the different conditions of small-scale drift were further studied.The results show that the nonlinear pipe-soil model simulates the response of riser penetration into the seabed more accurately in the co-rotational coordinate framework;the increase of the top horizontal traction force and the current flow velocity will lead to the decrease of penetration depth and vertical soil resistance;the increase of the shear strength of the soil will lead to the decrease of the riser penetration depth but the increase of the vertical and lateral soil resistance;as the lateral traction force of the top floating body increases,the lateral displacement and soil resistance of the riser touchdown section increases,but the vertical soil resistance decreases;and the increase of the lateral friction coefficient can significantly improve the riser's lateral stability of the touchdown section.In this paper,the global motion of the riser and the pipe-soil interaction are efficiently solved by using the co-rotational coordinate method with the property of decoupling the rigid body and the deformation,which provides a reference for the study of riser-seabed interaction.