深海管道水平向管-土相互作用大变形连续极限分析

Modelling lateral pipe-soil interaction on soft clay using large displacement sequential limit analysis

管道被广泛应用于油气产业,其中管-土相互作用机制是管道可控屈曲设计的关键。采用新开发的连续极限分析(SLA)方法对深海管道与软土水平大变形相互作用进行了研究。该方法基于极限分析对变形体进行一系列求解与更新模型,能够考虑模型的极端几何变形和材料的应变软化与率效应。该研究对固定管道竖向位移条件下水平加载这一工况进行了探讨,分析了不同初始埋深的管道在位移过程中所受竖向及水平向反力(V、H)的发展。通过与多组离心机试验数据对比,验证了SLA对管-土水平大变形相互作用研究的有效性和高计算效率。主要成果有:提取了管道在不同位置的V-H屈服包络面以考虑加载路径变化对管道受力行为的影响,发现了管道的等效摩擦系数H/V随水平位移的线性增加规律。该研究以期为深海管道的可控屈曲设计提供参考,并推广SLA法在大变形土结相互作用问题中的应用。

Pipelines are widely used in the petroleum industry for oil and gas transportation, and the interaction between pipelines and seabed is crucial for assessing pipeline behavior during lateral thermal buckling. This paper presents a numerical investigation on the pipe-soil interaction behaviour using a recently developed sequential limit analysis approach for deep-water pipelines on soft clay. This approach, primarily based on upper-bound limit analysis, is capable of handling the extremely large deformation problems and implementing the strain softening and strain rate effects. During the analysis, the pipe was laterally driven forward with the elevation of its invert fixed, differing from existing work in which the pipe can dive or rebound during the lateral displacement. The evolution of vertical(V) and horizontal(H) soil resistance was examined, and the validity of the present model is demonstrated using comparisons with centrifuge data. V-H yield envelopes were derived during the analysis to investigate the influence of load path on pipe response. The equivalent friction ratio, H/V, was found to increase linearly with lateral displacement. This study aims to provide guidance for the controlled buckling design for deep-water pipelines, and show the potential of SLA in solving large displacement soil-structure problems in undrained clay.