海沟影响下深水海洋管线成环行为研究

在深水海洋管线的安装过程中，制造工艺的偏差和外部环境的影响易导致管线上不均匀的扭矩分布，在张力的共同作用下，管线在其触地区可能出现“成环”现象，受到严重损伤，而海洋管线的触地区也是海沟集中形成的区域。为了研究海沟对海洋管线成环行为的影响，基于OrcaFlex软件和构建海沟模型的经验公式，建立了深水悬链线立管和海沟的三维数值模型。就海沟轮廓、位置和土壤属性对立管成环行为的影响展开参数分析，并研究了不同工况下成环的临界载荷。研究表明：海沟的产生和扩展、立管相对海沟的合理位置以及土壤参数中海床表面不排水抗剪强度和吸力因子的增加，可有效降低立管成环过程中的最大压缩力和最大弯矩，从而减少成环引起的损伤；临界载荷的分析则有助于对成环的临界条件进行预测，避免成环现象的发生。

Investigation into the formation of loops in deep-water pipelines affected by trenches

This study focuses on investigating the behavior of loop formation in deep-water pipelines when influenced by trenches. During the installation of these pipelines, variations in the manufacturing process and external environmental factors can result in uneven torque distribution along the pipelines. When combined with tension, this can lead to the formation of loops in the touchdown zone, causing severe damage. The touchdown zone is precisely where trenches are formed. To examine the impact of trenches on loop formation in deep-water pipelines, three-dimensional numerical models of a catenary riser and a trench are created using the OrcaFlex software, along with an empirical formulation for constructing the trench model. Parametric analysis is conducted to explore the effects of trench profile, location, and soil properties on riser loop formation. Moreover, the study investigates the critical load required for loop formation under various operational conditions. The findings reveal that the generation and expansion of trenches, along with the appropriate riser positioning and enhancement of key soil parameters such as mudline shear strength and suction ratio, can effectively reduce the maximum compression and maximum bending moment experienced by the riser during the loop formation process, thereby mitigating the damage caused by riser loops. Additionally, the analysis of critical load aids in predicting the critical conditions for loop formation, enabling preventive measures to be taken.