A pipeline on the seabed may expand and buckle due to thermal effects, requiring buckle initiators such as sleepers to manage its deformation. Sleepers create low friction supports but induce pipeline spans that can grow if scour propagates along the pipe, away from the sleeper. Excessive spans may lead to vortex-induced vibrations, increasing fatigue damage. This study conducted a series of model-scale experiments in different flow conditions (unidirectional and tidal) to investigate scour propagation along a pipeline. A unique aspect of the experiments is that they simulated the buckling process of the pipe, modelled by translating the pipe laterally with different amplitude. The results reveal that (i) under tidal conditions, the pipe may experience a higher scour rate compared to unidirectional flow and it is suspected to be due to the difference of sand ripples under different flow conditions; (ii) lateral movement of the pipeline reshapes the surrounding bed profile and slows scour propagation; and (iii) greater embedment depth can halt span growth. These findings enhance the understanding of span growth along subsea pipelines and provide insights for mitigating scour development in engineering applications.

local scour,pipeline,tidal flow,Laboratory Experiment,3d scour