The slender circle submarine pipeline possesses both shell and beam characteristics, which are widely used in practical engineering. Unfortunately, for some reason, there will be some geometric defects in the cross-section of the pipeline (such as machining errors and seawater corrosion, etc.), resulting in the stiffness of the circular submarine pipeline being different. The cracked variable stiffness pipeline is actually a typical three-dimensional complex crack problem. In this paper, taking the outer circle and inner ellipse submarine pipeline as an example, a method based on elementary mechanics and the concept of the conservation law is proposed to determine the stress intensity factors (SIFs) of variable stiffness pipeline, and a series of closed-form expressions of SIF are derived for the cracked pipeline. The results from the present method are shown to agree well with available solutions and FEM. In particular, the present method can also be easily applied to other similar variable stiffness submarine pipelines.

细长圆形海底管道兼具壳梁特性，在实际工程中得到广泛应用。不幸的是，由于某种原因，管道的横截面会存在一些几何缺陷（如加工误差和海水腐蚀等），导致圆形海底管道的刚度不同。开裂的变刚度管道实际上是一个典型的三维复杂裂缝问题。本文以外圆和内椭圆海底管道为例，提出了一种基于基本力学和守恒定律概念的变刚度管道应力强度因子（SIFs）的确定方法，并提出了一系列SIF 的封闭形式表达式是针对破裂的管道导出的。本方法的结果显示与可用的解决方案和 FEM 非常吻合。特别地，本方法也可以很容易地应用于其他类似的变刚度海底管道。