Parametric Solutions for Slide Impact on Pipelines

Pipelines are frequently subjected to active loading from slide events both on land and in the offshore environment. Whether the pipeline is initially buried or lying close to the surface, and whether it crosses the unstable region or lies in the path of debris originating from further away, the main principles are unchanged. The pipeline will be subjected to active loading over some defined length, related to the width of the slide, and as it deforms will be restrained by transverse and longitudinal resistance in adjacent passive zones. Ultimately the pipeline may come to a stable deformed shape where the continued active loading from the slide is equilibrated by the membrane tension in the pipeline in addition to the passive resistance. This problem has been explored by various writers and these principles are well established. However, to date no attempt has been made to develop a standard set of parametric solutions, which is the purpose of the current paper. Both analytical and numerical solutions of the problem have been developed, initially for slides acting normal to the pipeline but later extended to general conditions with the slide impacting the pipeline at some angle. It is shown that analytical solutions based on certain idealizations maintain their accuracy over a wide parameter range, and the net effect of the slide in terms of stresses induced in the pipe wall and maximum displacement of the pipeline may be captured in appropriate dimensionless groups. Design charts are presented for slide widths of up to 10,000 times the pipeline diameter for a practical range of other parameters such as the ratios of passive normal and frictional resistance to the active loading. Although the solutions are limited by some of the idealizations, they should provide a useful starting point in design, providing a framework for a more detailed numerical analysis for the particular governing conditions.