| Coastal areas are characteristic of dense population, rapid economic development andthriving tourism. And the beach is a popular tourist place with colorful recreation andaquatic activities. However, the interaction effects of the climate changes and humanactivities have caused serious loss of beach sediment budgets and led to damage on thedynamic balance of ocean dynamics, sediment transport and beach evolution. Therefore,the eroded beach area has enlarged; beach width becomes narrower; slopes become steeperand the marsh surface material gets coarser, which all becomes serious problems. It hasaroused widespread concerns in the water and marine industry and becomes one of the hottopics of coastal engineering as well.Essentially, coastal erosion results from scour stronger than deposition. Consequently,it is the key to prevent erosion that we promote deposition by changing the shorelinedynamics condition or increasing the sediment sources. As for engineering, this can beachieved by physical buildings such as dam, pervious structures (pile, rocks with wholes,flexible floating curtains) as well as the cultivation of organisms, which result in changeson the hydrodynamic characteristics of the wave, water flow and sediment movement.Since the water flow slows down, the amount of sediment carried away decreases.HARD engineering, used to protect against coastal erosion, however has manydisadvantages. Compared with the HARD engineering, beach nourishment is a relativelynew method for beach protection and nourishment. The filling sediment is poured belowthe low tide level as artificial sand bar, and transport to the beach under the wave action,thus “feeding” and “sheltering” beach with minimum impact on the marine environmentand beach tourism resources. But in view of the complexity and variation of ocean dynamicenvironment, many nonlinear problems remain unresolved such as the complex movementof sediment of bars, non-uniformity of the bar recession process and nonlinearity of stabileprofile. Therefore, researches on artificial filling sand bar not only enrich the theoriesrelated to coastal dynamics, mechanics of sediment transport and coastal engineering, butalso contribute to the protection of coastal environment, development and maintenancetourism resources and many other applications.The paper analyses the interaction process between waves and the artificial sand bars,then establishes the formula of wave deformation and wave energy near artificial sand bars.Starting from the artificial sand dam wave dissipation mechanism theory, the authoranalyzes the wave effect on dam deformation and describes the process from the erosion ofbar section to the dynamic balance.The2D and3D model tests were carried out.The cross section (2D) experimentsmeasured and analyzed that design parameters(including offshore distance, bar height, crestwidth), wave dissipation, nourishment effect and morphological response of the bars themselves. The main conclusions have been derived as below:（1）Wave transmission coefficient gradually decreases as the increase of relativeheight of dam, crest width, artificial sand bar distance from the shore, wave steepness andthe time of wave action. When the relative height of bar is in a certain range, the wavetransmission coefficient increases with the increase of relative crest depth and maintains thebasic stability when it reaches the maximum.（2）Along with the increase of dam height, beach berm width of the siltationgradually increases; when the erosion area of the waves to beaches approaches shore,erosion area is enlarged.Through the whole (3D) physical model tests of different schemes, different levels anddifferent wave conditions, coastal waters wave distribution, shoreline stabilization shape,stable coast profile shape, offshore sediment and tidal wave effect of underwater barriereffect are measured and analyzed, the main conclusions are obtained as follows:（1）In the same wave height and different wave–direction conditions, when it ispositively incident, the waters off the coast of Cape Bay, high wave heights are distributedmost widely. Scheme C (shoulder patch of sand beach plus underwater barriers) because ofextinction wave effect of the artificial sand dams, wave height is smaller in the foreshorearea.（2）The regular wave will lead to coastal erosion, while under the influence ofirregular waves, the coastline has certain self repair capacity. In terms of the effectivenessof restoration, the more the shoreline erosion is weakened, the better the effect of shorelinerestoration will be.Under the regular wave erosion, comparing the amplitude of shoreline retreat: schemeA (status)> B (berm fill sand)> C; strong restoring ability in irregular wave recoveryscheme of C.（3）Under the action of regular waves, there is erosion on beach profile and higherthe wave is, the more serious the erosion of beach is; Under the influence of irregular wave,beach berm profile is formed and if the erosion wave is small, the recovery is better.Comparing of three schemes for coastal profile, C can broaden the beach berm,prompt the silting beach and cure governance effectively. When the tide level is higher,berm filling sand in scheme B mainly moves to the sea. Scheme B has the effect ofemergency governance on the beach, but in strong wave loads, dynamic adjustment and thecapability of control and governance is limited.（4）Under the action of regular waves, sediment offshore transport intensity is greaterthan shoreward transport intensity, while under the action of irregular waves, sedimentshoreward transport intensity is greater than the offshore transport intensity.Based on the test section on the physical model, in this essay, FLOW-3D software isused to establish a wave tank, and the wave damping effect of artificial sand dam in thenearshore wave conditions, sand bar, sand dam near the velocity response, beachdeformation are studied by numerical simulation and analysis. By comparing with theresults of the physical model test, the better effect of the simulation is obtained. |
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