Experimental study on seabed scour around submerged single pile and group pile foundations under wave-current action
Pile foundations beneath the seabed are extensively utilized in marine engineering;however,research on localized scour around submerged pile foundations remains limited.Based on a series of laboratory flume experiments,this paper investigates the localized scour around submerged single and group pile foundations under the combined action of waves and currents.It analyzes the characteristics of scour depth over time,influencing factors,and the morphological features of scour pits.The results indicate that for single pile foundations,an increase in bed roughness Kd attenuates the difference in wave-current conditions.When the structural ratio Kh ranges from 1.00 to 2.33,the relative time scale Tc gradually increases,whereas Tc begins to decrease when Kh>2.33.For group pile foundations,the evolution of scour depth over time is similar to that of single piles.However,the arrangement of pile groups suppresses the turbulence of the flow at the foundation's base.Additionally,when the pile spacing coefficient Ksp is small,a collective scour pit forms,showing a trend of gradual separation into individual scour pits as Ksp increases.With the increase in Kh and Ksp,Tc increases,but the growth rate of Tc decreases with the increase in Ksp.A modified equation for predicting the equilibrium scour depth using Kh,Kd,and Ksp is proposed,which can accurately predict the equilibrium scour depth of single and group pile foundations under wave-current action as demonstrated by the experiments conducted in this study.
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