Mechanics of Pipeline Scour Propagation in the Spanwise Direction

Abstract

This paper presents the results of an experimental study on the mechanics of pipeline scour propagation in the spanwise direction. The experiments were conducted with uniform sediment under a unidirectional steady current in clear-water conditions. The study aims to provide a better understanding of how the differential pressure between the upstream and the downstream sides of the pipeline and local bed shear stress at the span shoulder affect pipeline scour propagation in the spanwise direction. The measured data show that a high differential pressure significantly enhances pipeline scour hole development in the spanwise direction. Its presence increases the propagation velocity of the scour hole and differentiates the rapid from the slack phase of development identified in previous studies. It may be inferred from the relationship of the propagation velocity on pressure gradient that the two factors, namely, the differential pressure and the local bed shear stress, vary proportionally with the strength of the local flow field. They combine to affect the propagation velocity of the scour hole at submarine pipelines in the spanwise direction.