非线性管土耦合作用下钢悬链式立管触地区敏感性分析

Sensitivity analysis of steel catenary riser TDZ under nonlinear pipe-soil coupling

浮体运动和海床土刚度是引起钢悬链式立管(steel catenary riser,简称SCR)管土相互作用的关键因素,将导致SCR触地区的疲劳损伤。以工作水深为1500 m的浮式平台上生产立管SCR为研究对象,基于法向抗力模型和侧向阻力模型建立管土作用模型,在环境载荷和浮体运动作用下,开展SCR与浮式平台的整体分析,研究海床土参数对SCR触地区动态响应和疲劳寿命的敏感性。通过改变海床土的不排水抗剪强度Su0、强度梯度ρ、吸力因子f_(suc)、吸力衰减参数λ_(suc)以及再贯入系数λ_(rep)等,得到不同参数对触地区动力响应、疲劳寿命的影响规律。研究结果表明:①基于软黏土海床,随着不排水抗剪强度Su0的增加,触地区立管疲劳寿命减幅达到33.23%,敏感性最高;②吸力因子f_(suc)越大,立管疲劳寿命越小且减幅达23.77%,其敏感性较高;③随着再贯入系数λ_(rep)增大,触地区立管疲劳寿命增幅达到15.48%;④海床抗剪强度梯度ρ和吸力衰减参数λ_(suc)对立管疲劳寿命影响较小。研究结论能为SCR设计分析及安全服役提供重要参考。

The motion of floating body and the stiffness of seabed soil are the key factors that cause the cyclic pipe-soil interaction of Steel Catenary Riser(SCR)flowline,resulting in fatigue damage at the TDZ of SCR.Taking a SCR on a semi-submersible platform with a working water depth of 1500 m as the research object,the platform-riser-seabed global analysis model was obtained based on the nonlinear pipe-soil interaction model including normal nonlinear and lateral resistance models.The sensitivity of the dynamic response and fatigue life to the key parameters of the seabed model in the TDZ of SCR was studied based on the global analysis model.The influence of different key parameters on the dynamic response and fatigue life in TDZ of riser was obtained by changing the undrained shear strength Su0,strength gradientρ,suction factor f_(suc),suction attenuation parameterλ_(suc)and re-penetration coefficientλ_(rep)of the nonlinear seabed model.The results are as follows:①The fatigue life of TDP has decreased by 33.23%with the increase of Su0,and its sensitivity is the highest;②The fatigue life of TDP decreases with the increase of f_(suc)and the reduction rate is 23.77%;③The re-penetration coefficientλ_(rep)reflects the degradation of seabed stiffness and can decrease the fatigue damage of riser within a certain range.With the increase ofλ_(rep),the fatigue life of riser increases by 15.48%;④Parameters with low sensitivity include shear strength gradientρand suction attenuation factorλ_(suc).The conclusion can provide important reference for SCR design analysis and security service.