Numerical Study On Tideway And Sediment Transport Near Sea Bridge

The area of earth surface is 500 million square kilometers and 71% of the area is covered by seawater.With the development of human beings,the land resource is getting lack.Therefore,people started to focus on exploring the marine resources to meet the requirement of development.Land reclamation is a way to explore the area covered by water,which is most used.As an important method of land reclamation,artificial island works well in extending available area for coastal cities and it can also help exploring the marine resources.However,artificial islands are individual island supported by upholder or other bracing structures,which will affect the characteristics of tidal and sediment erosion and deposition near to the bridge,working area and estuary.For these reasons,a numerical model was employed to analyze and estimate the difference of characteristics of tidal,sediment erosion and deposition,which is affected by the constructions and has important value on artificial island building.This paper will focus on planning to build an artificial island in Lingshui Bay.2D numerical model is used to simulate and analyze the changes of tideway and sediment transport caused by artificial island.The effects on the tidal and scourare also summarized.Theachievements of the research are listed as follows.(1)According to the hydrographic and bathymetric data,the numerical model of sediment under the influence of wave and tide is establishedbased on the theory of 2D sediment transport and some basic equations.This model is used to do the numerical simulation for the sediment transport in Lingshui Bay area.Numerical discrete methodhas been used and the model is verified by three cases including water droplets,contraction channel of dam break andBohai Sea tideway.Good agreements between numerical results and analytical solutions or measured data are obtained.(2)Tide is a major factor considered in coastal and estuarine dynamic analyze.Model test and numerical simulation are usually used to find out the character of the flow field in these areas.However,both methods have to face open-boundary problem.This paper presents two methods to obtain the open-boundary condition by predicting the tidal change.One is TPXO model and the other is Harmonic analysis model.By comparing the predicted accuracy at offshore area,it shows that both of these two model works well in fitting the measured data but harmonic analysis model has higher accuracy.Harmonic analysis model is more suitable to obtain the open-boundary condition of estuary tidal current field.(3)By using the numerical sediment model considering the influence of wave and tide,the flow field and sediment transportwere analyzed.The current and erosion characteristics changes are analyzed by the numerical simulation.The result shows tidal current is obviously in reversing current form andthe velocity of flood current is much higher than ebb current.Piers has small water-blocking effect and the scour is not serious.As a conclusion,the project has small impact on narrow channel scouring.The bridges havealmost no effect on velocity field and tidal level.