The propagation of wave scour along the spanwise direction of submarine pipelines in case of clear-water regime

The local sediment motion around cylindrical structures laid on erodible seabed occurs with wave and/or current effects and causes significant stability problems. In this study, the development of the scour hole along the spanwise direction of the pipeline and the scour propagation velocity were investigated experimentally. The time dependent measurements beneath the test pipe were performed in a large wave channel. In the experiments, the measurements were recorded by using ultrasonic equipment. Since the coarse bed materials were used, all of the experiments were carried out in the clear-water scour regime condition, differently than live-bed data in literature. The experimental results reveal that the scour propagation along the spanwise direction of the submarine pipe is not relevant with Shields parameter under clear-water condition; however, it is inversely related to the Keulegan-Carpenter number. By analyzing the findings of the study, a new empirical relation was established to estimate the non-dimensional scour propagation velocity based on the Keulegan-Carpenter number along the spanwise direction of submarine pipe, in case of wave effect. The statistical significance of the equation was demonstrated by the correlation coefficient and scatter index.