This paper presents the results of failure analysis of a 16-in. natural gas pipeline that ruptured due to ground movement caused by a 40 m wide landslide. The rupture occurred at a girth weld in the middle of a double bend located 120 m from the center of the landslide. The Finite Element Analysis (FEA) method was used to evaluate the response of the pipeline to the ground displacement. The pipeline and the surrounding soil were simulated by the Winkler-type beam-on-spring model and nonlinear static analyses were carried out to establish the root cause of the failure. The results of the analyses indicated that the ground movement was primarily resisted by the membrane action of the pipeline. The pipe axial force due to the membrane action extended well beyond the landslide zone and encompassed the bend region. The axial force at the bend location caused high local shear and bending moment in the bend region. Assessment of the state of stresses on three girth welds in the bend region indicated that the rupture was mainly due to the high shear demand on the girth weld in the middle of the bend.

This study indicates that fabricated bends are vulnerable if they are placed within a critical length of the pipeline where the landslide-induced axial force is substantial. To reduce the risk of pipe rupture in pipelines crossing a potential landslide, fabricated bends should be avoided along this critical length. The critical length of a pipeline crossing a potential landslide includes the landslide zone and the anchor length on either side of the landslide. This study also indicates that the anchor length calculated by the relevant equation in the PRCI guidelines may underestimate the actual anchor length.

本文介绍了16英寸故障分析的结果。天然气管道因40 m宽的滑坡引起的地面运动而破裂。破裂发生在距滑坡中心120 m的双弯道中间的环缝焊缝处。有限元分析（FEA）方法用于评估管道对地面位移的响应。用Winkler型弹簧弹簧模型对管道和周围土壤进行了模拟，并进行了非线性静力分析，以确定故障的根本原因。分析结果表明，地面运动主要受到管道膜作用的阻碍。由于膜作用而产生的管道轴向力远远超出了滑坡区，并涵盖了弯曲区域。弯曲位置的轴向力在弯曲区域引起较高的局部剪切和弯曲力矩。对弯曲区域中的三个环缝焊缝的应力状态进行评估表明，断裂主要是由于在弯曲中部对环缝焊缝的剪切要求很高。

这项研究表明，如果将预制弯头放置在管道的临界长度内（其中滑坡引起的轴向力很大），则这些弯头很脆弱。为了降低穿越潜在滑坡的管道中管道破裂的风险，应避免在此临界长度上出现弯曲。穿越潜在滑坡的管道的临界长度包括滑坡带和滑坡两侧的锚固长度。这项研究还表明，由PRCI指南中的相关公式计算出的锚固长度可能会低估实际锚固长度。