双拱初始缺陷海底管线水平向整体屈曲数值模拟分析

Numerical solution of pipeline global buckling with double arch imperfections

为了研究具有双拱反对称初始缺陷海底管线的整体屈曲特性,采用模态分析法将最可能出现的缺陷形态引入数值分析模型中。针对管线在高温高压作用下发生整体屈曲的动态变形特征,运用显式动力数值模拟方法研究了管线整体屈曲过程中水平向变形与轴向变形随温度和内压的变化规律,建立了在整体屈曲过程中屈曲管段与滑动管段轴力的变化过程与初始缺陷形态的关系。将数值模拟结果同经典解析解和室内模型实验结果进行对比,验证了本方法的可靠性。工程算例的分析结果表明,管线整体屈曲的发生是一个由低阶向高阶发展的过程,具有双拱缺陷的管线首先发生二阶模态的整体屈曲,而后过渡到四阶模态;管线整体屈曲的变形包括屈曲段的水平向变形和滑动管段的轴向缩进,其中水平变形释放了管壁内的轴力,轴力的释放量随初始缺陷尖锐程度的降低而增大;轴向缩进变形由于受到地基土的摩阻力使滑动管段内的轴力发生累积,轴力的累积量随初始缺陷的尖锐程度的降低而增加。以上研究成果对指导实际工程具有现实意义。

The stability of submarine pipeline under high temperature and high pressure is one of the important contents of pipeline stability design. Usually, there are initial imperfections on the submarine pipeline which are presented due to the pipeline manufacturing or lying. In this paper, double arch initial imperfections were assumed on the pipeline; buckle analysis method was adopted to introduce the mode which is most likely to happen; ABAQUS/Explicit method was used to analyze the change rule of the lateral and axial deformation on the process of global buckling based on the dynamic deformation. The relationships between axial force on buckled section and on slip section and the mode of imperfection were established. The comparison of the numerical results and classical analytical results and tests results were obtained to verify the reliability of this method. Engineering case results show that the global buckling is a process of deformation which develops from low to high order. Pipeline with double arch imperfection firstly happens to the second order mode global buckling and then transits into the fourth order mode. The global buckling deformation includes a lateral deformation on buckled section and a feed-in deformation on slip section. The lateral deformation releases the axial force of buckling section and the quantity which lateral deformation releases is increasing with the sharp level of imperfection. Due to the frictional resistance of soil foundation, the feed-in deformation accumulates the axial force of slip section and the quantity which feed-in deformation accumulates is increasing with the sharp level of imperfection.