Vulnerability of Buried Pipelines to Landslides

Abstract

The movement of a mass of rock, debris or earth down a slope is a landslide, which in the pipeline industry is often referred to as ground movement. Landslides continue to cause pipeline failures throughout the industry, sometimes as the singular cause of failure and in others cases as a contributing factor to failures (such as stress corrosion cracking on slopes). Landslides can originate on slopes above a pipeline and cause impact loads; they can originate below a pipeline and cause unintended spans; and they can encompass the ground crossed by a pipeline, which can lead to high compressive (or tensile) strains and pipeline buckling. This paper focuses on the latter scenario. Similar to the approach recently outlined for watercourses [1], the term ‘vulnerability’ refers to the conditional probability of pipeline failure given that landslide movement spatially impacts a pipeline. This paper presents the development of a statistical and judgment-based vulnerability model for pipeline crossings of slopes that are subject to landslides that can be used to rank the relative importance of slopes at a screening level of assessment. The model is based on case histories where this type of landslide scenario caused pipeline failures (defined as holes, leaks and ruptures), or buckling of pipelines that resulted in the need for immediate repairs. Vulnerability has two main uses: on its own to help prioritize large numbers of slope crossings for further investigation; and, once combined with estimates of the probability of landslide movement, to provide a probability of pipeline failure estimate that can be used to guide integrity management programs.