二段线弹性海床上悬链线立管触地段贯入响应解析解

Analytical solution for penetration response of steel catenary riser at touchdown zone on bilinear seabed

钢悬链线立管触地段管土作用对管线埋深及管线寿命的影响显著。对触地段管土相互作用p–y曲线用二段线弹性近似,考虑了土体刚度的非线性,更好地反映土体刚度随管线贯入深度增大而降低的特性。根据贯入深度建立了多段管线控制微分方程,结合边界条件求得静力状态下管线贯入响应的解析表达式。在验证解析解正确的基础上,对土体刚度变化、泥线处土体不排水抗剪强度、土体强度梯度、外部弯矩荷载及管线自重下的管线贯入响应进行了分析。结果表明二段线弹性模型中得到的土体阻力与p–y曲线更接近。管线贯入深度随泥线处土体不排水抗剪强度、土体强度梯度的增大而减小。外部弯矩荷载的增大会使管线贯入深度及触地段管线的最大剪力变大。管线自重增加会使管线贯入深度增加,弯矩增大。

The pipe-soil interaction at touchdown zone（TDZ） of steel catenary riser（SCR） has important influences on the penetration depth and fatigue life of pipelines. A model considering non-linearity of soil stiffness is established by using bilinear linear soil stiffness approximation of p-y curve. The model reflects the characteristics of the soil stiffness deceasing with the increase of the penetration depth of the pipelines. The differential equation for pipelines is established and the analytic expression for the penetration response of pipelines in static state is obtained based on boundary conditions. After justifying the correctness of the model, four factors that influence the penetration response of pipelines are analyzed： the shear strength of mudline, the gradient of soil shear strength, the external bending moment load and the weight of pipelines. The results show that the penetration depth of pipelines increases with the decrease of the shear strength of mudline and the gradient of the soil shear strength. And if the external bending moment load increases, the penetration depth of pipelines will increase and the maximum shear force will also increase. Due to the increase of weight of pipelines, the penetration depth of pipelines and bending moment will increase.