Local scour below pipelines commonly occurs due to the erosive action of currents and waves. Such scour may cause pipeline suspension and ultimately leads to pipeline failure. Accurate estimates of the scour depth is important in the design of submarine pipelines. A summary of the research on local scour around pipelines is given. Maximum scour depth formulate below pipelines in the unidirectional flow and waves and important parameters for scour depth in scour process are provided. This will provide safety reference criterions for the design of new pipelines and the maintenance of existing pipelines.
Submarine pipeline system is used to transport mixture of oil, gas and water to the shore. Seabed pipelines under the action of wave flow around the seabed will produce local scour, if pipelines hanging across the long, free vibration under the action of wave and flow lead to pipeline fatigue fracture, resulting in serious economic loss and environmental pollution. Therefore, both for the design of the new pipeline and maintenance of the existing pipelines, accurate estimate of the local scour depth is a important aspect. International scholars are summarized in a series of physical model experiment, it is concluded that the influence factors of the maximum depth of the balance and the maximum equilibrium scour depth results under the action of wave, tidal current.
In the case of scour around a pipe exposed to a steady current, the scour profile is characterized by a steep upstream slope and a more gentle downstream slope. This asymmetry shape is caused by different flow pattern on the pipeline flow upstream and downstream .For shields, theta and the effect of parameters should be divided into clear water wash and wash two cases. Under the condition of water flushing, depth of the pit with theta changes very significant; But for mobile bed scouring, S/D change with theta small .