Experiments have been carried out to determine the scour depth below submarine pipelines that are placed rigid position on bed under only wave conditions. The relative scour depth depends on Keulegan-Carpenter number (KC) and frequency parameter (13) and their ranges are 1.31 and 35, 3.5×102 and 1.3×104 respectively. Experimental results agree with the previous works with variation KC number of the relative scour depth. It was found that the relative scour depth is also proportional to the frequency parameter and the grain size gradation doesn't affect the scour depth below the submarine pipelines.
Scour below submarine pipelines plays very" important role in the construction process and the management of submarine pipelines. However, rapid development of offshore oil fields has increased the construction of submarine pipelines for transport of crude oil to onshore refineries, and also disposal of waste water into the seas has been increasingly used. Interaction between the pipelines and an erodible bed under current and/or wave conditions tend to cause to scour around the pipelines. Scour under the submarine pipeline may expose part of the pipe and causes it to suspend in water. If the free span of the pipe is long enough, the pipe may experience resonant flow-induced oscillation leading to structural failure. Design of a submarine pipeline is a rather complicated problem due to complex flow field and sea bed feature. Numerous researches have been carried out on the scouring process by many investigators. However, little has been published regarding studies of the structural Stability of the submarine pipeline as affected by only wave condition. Scour depth has been extensively studied in the steady current case (Kjeldsen et al, 1973, Bijker and Leeuweistein, 1984, Mao, 1986, Hansen et al, 1986).
