Study On Hydrodynamics Of Ecologically Vegetated Honeycomb-type Revetment Under Regular Waves

In estuary and coastal areas,the ecological slope protection is proposed in order to protect the slope erosion and avoid the drawbacks of traditional revetment as it destroys the ecological environment of the water area.For the ecological revetment,the vegetations are introduced into the construction of revetment projects,which can weaken waves and enhance the stability of bank slopes.The ecological slope protection can control the environmental problems to achieve both ecological and economical benefits.Based on the field investigation of the revetments in Tianjin,a model of ecologically vegetated honeycomb-type revetment with a slope of 1:3.5 is selected and built in the wave flume,then this model is used to study the wave runup,wave overtopping,the near-bed velocity,and the stability of the slope under the action of various regular waves.Based on the experimental data,a non-static pressure model for the wave runup on the ecological slope protection under wave is proposed based on the SWASH.The Manning coefficient is used to define the effect of vegetation and honeycomb on the wave runup and overtopping.The empirical formulas of the coefficient in the presence or absence of vegetation are proposed to provide a reference for future research.The main conclusions are as follows:(1)In this study,a new type of ecologically vegetated honeycomb-type revetment was proposed.The honeycomb was laid on the slope of revetment,and Suaeda was selected as the typical halophyte in Tianjin.At the same time,the gravel was laid in the honeycomb.It can be concluded that vegetations can enhance the stability of revetment under regular wave action,reduce the regular wave runup and overtopping.Furthermore,the wave runup and overtopping decreases with the plant density and height increasing.But vegetations can not decrease the near-bed flow velocity,and the near-bed velocity tends to increase slightly with the increase of vegetations density.(2)A non-hydrostatic numerical model considering the influence of vegetation on wave runup and overtopping is established.The bottom friction effect of vegetation characterized by Manning coefficient shows a trend of increasing with vegetation density and height.The empirical formula of Manning coefficient obtained can reasonably characterize the effect of vegetation on the regular wave runup and the overtopping.