Scour of the seabed under a pipeline in oscillating flow

The scour of the seabed under a pipeline is studied experimentally in this paper. Tests are carried out in a U-shaped oscillatory water tunnel with a box imbedded in the bottom of the test section. By use of the standard sand , clay and plastic grain as the seabed material, the influence of the bed m aterial on the scour is studied. The relationship between the critical init ial gap-to-diameter ratio above which no scour occurs and the parameters of the oscillating flow is obtained. The self-burial phenomenon. which occurs for the pipeline not fixed to two sidewalls of the test section, is not ob served for the Bred pipeline. The effect of the pipe on sand wave formation is discussed. The maximum equilibrium scour depths For different initial g ap-to-diameter ratios, different Kc numbers and different bed sands are als o given in this paper.