Scour patterns below pipelines and scour hole expansion rate

Abstract

This paper presents the results of an experimental study on the onset of scour and the propagation of scour hole on the cross-section of a partially buried pipeline under a unidirectional current with uniform sediment. A specially designed device including a transparent pipeline with a mini underwater camera installed inside it is utilized to observe and record the whole scour process. The scour below the pipeline can be divided into an integral scour pattern and a partial scour pattern. In both patterns, the seepage force is the main cause of the onset of scour. However, the scour hole expansion process is driven by the seepage force in the integral scour pattern, while in the partial scour pattern it is driven by the bed shear stress. The effects of pipeline embed-ment, flow depth and the averaged flow velocity on the averaged cross-section expansion rate of the scour hole are also evaluated.