Numerical analysis of the structural response of unburied offshore pipelines crossing active normal and reverse faults

Abstract

This paper presents the results of a series of parametric finite element analyses of a partially embedded (unburied) pipeline resting on a soft fine-grained seabed and subjected to the differential movement of an active tectonic fault. Three-dimensional elastoplastic simulations are carried out for normal and reverse faults with the objective of assessing the vulnerability of pipeline infrastructure to a fault rupture. Geometrical non-linearity is considered in order to be able to capture possible pipeline-wall buckling under compressive loads. The effects of fault slip magnitude, fault dip angle, shear strength at the seabed surface, pipeline thickness and pressurization of the pipeline on the developing stress and deformation state of the pipeline are monitored and compared with appropriate performance criteria of steel pipelines. It is found that the rupture of a normal fault does not impose a severe risk on the pipeline, even for a large earthquake, whereas in reverse fault conditions severe risk is generated due to compressive local buckling.