Pipelines crossing mountainous areas are susceptible to ground movement loading from landslides. Structural analysis of pipeline performance from landslide loads is critical for making decisions on the requirement and timing of intervention activities. Current analytical assessment methodologies for pipelines affected by ground movement tend to assume the landslide as an abrupt boundary from the stable region to moving ground, causing an over conservative estimation of the condition of the pipeline. In-line inspection using inertial mapping tools provides invaluable information to assist in the determination of the current pipeline integrity but does not provide a complete picture because axial loads are not defined. Interpretation of in-line inspection data allows the estimation of a transition zone width between stable and unstable ground, where there is a progressive increase in ground movement. Due allowance for the transition zone can remove conservatisms in the assessment methodology and allow a pipeline integrity plan to be created.
This paper investigates the influence of landslide transition zone dimensions on the pipeline response and a methodology is developed for the prediction of the transition zone width. The interaction between the ground and the pipe movement is modelled using finite element analysis techniques.
The definition of the transition zone properties provides a more reliable prediction of the pipeline performance and enables the current and future pipe integrity to be established with greater confidence.