Investigation of scour onset under seabed pipelines with geometric irregularities

Abstract

Based on previous studies, it is well understood that the hydrodynamic pressure difference across the pipeline is responsible for initiation of piping and the onset of scour. However, the influence of geometric irregularities such as field joints on the onset of scour has not previously been investigated. This new study has been stimulated by field observations of subsea pipelines that have indicated that scour holes tend to occur at field joint locations. This paper summarizes a series of experimental results using The University of Western Australia’s (UWA)’s unique O-tube test facilities investigating onset of scour underneath scaled model pipelines with a field joint in steady currents. The results of this work are benchmarked against experimental tests and published results for prismatic / uniform pipes. It is demonstrated that periodic geometric irregularities such as field joints have a significant influence on the onset of scour underneath a pipeline. KEY WORDS: Scour, piping, subsea pipeline, field joint, anode, STABLEpipe JIP.