Experimental Study of Soil Responses Around a Pipeline in a Sandy Seabed under Wave-Current Load

Wave and current coexist widely in the oceans. Ever-changing wave characteristics, such as height and length, have a significant influence on the dynamic response within the seabed soil due to the presence of currents. Some aspects of wave, seabed and pipeline interactions have been widely investigated over past years, incorporating both experimental and numerical approaches. However, previous studies on seabed dynamic response around pipelines have mainly focused on cases with wave loading. In this experimental laboratory study, the current loading and diverse backfill conditions which commonly occur far offshore are discussed in depth. It is found that when subjected to the combined wave and current loads, the response of the seabed around a pipeline is more complex than that subjected to pure wave loading as current velocity and propagation direction would significantly change the wave characteristics as well as seabed response. Most notably when comparing with the pure wave loading, the pore pressure amplitude and its attenuation rate within the seabed increases when current and wave travel in the same direction. This could increase the possibility of liquefaction around the pipeline. When current travels in opposing direction to the wave, the effect of current on the decrease of pore pressure and its attenuation rate is more significant than that of the co-current actions. This means that the counter-current will reduce the probability of soil liquefaction.