LABORATORY INVESTIGATIONS ON OSCILLATORY SEABED RESPONSES AND SCOUR AROUND A PIPELINE UNDER WAVE-CURRENT LOADING

In this paper, a series of preliminary experimental data for wave (current)-induced hydrodynamics, pore-water pressure and scour around an exposed pipeline is presented. Unlike previous studies, the combined action of waves and currents is considered in this study. Wave flume experiments were conducted to investigate the temporal and spatial variations of pore-water pressures and seepage, as well as the development of scour around a pipeline. The experimental results indicate that the seabed response caused by the combined action of waves and currents are significantly different from those caused by wave load alone. It was found that the amplitudes of pore-water pressures increase, while the attenuation of pore-water pressures slows down under the large wave height with a large current. Additionally, the amplitude of seepage force under the combined action of wave and current is significantly greater than that under wave-only action, which subsequently affects the scour process around the pipeline. As the current velocity increases, the equilibrium scour depth increases, and the time to reach the equilibrium depth is also longer. Moreover, under the action of wave and current, the maximum scouring depth is more significantly affected by the high current velocity.