Abstract: The Scour of the bed below a pipeline in oscillating flow is studied experimentally ina U-Shaped water tunnel with a sand box at the bottom of the test section. The artificial plasticsand is used as bed material. The relationship between the maximum equilibrium scour depth andKc number, and the relationship between the critical gap above which no scour occurs and Kcnumber are obtained. It is shown in this test that the critical amplitude in the presence of thepipeline at which the sand wave is formed is sma...