Experimental Study On Combination Of Ring-wing Plate And Slot To The Local Scour Around Piers

Owing to the limitations of traditional protection technology for piers local scour,based on the previous research results,the new protection measure was introduced,which combined ring-wing plate with slot.It protected riverbed by reducing falling water and flowing around the piers side.To study the influence of preventing scour,under the condition of three kinds of discharge-water level,by combining the half round shape,different installation position of plate with the different height,different location of slot,the physical model test was carried out.First of all,the influence of slot prevention and the combination prevention were analyzed quantitatively by using the characteristics of the scour hole,the average velocity around the piers.Proceeding to the next step,in order to get the optimal combination scheme,the combination prevention were analyzed quantitatively by using the average velocity,turbulence intensity and turbulence kinetic energy around the piers.The conclusions included:(1)Under the condition of the same height and position,the decrease rate of the pit depth was significantly greater than that of the slotted protection,the effect of reducing the pit depth under the slot position close to the riverbed was better than that of the slot position near the water surface,the best way to reduce the depth of the pit was that the slot position close the riverbed under the combined protection.Under the two kinds of protection,with the increase of the slot’s height,the depth of the scour pit decreased obviously.(2)Relative to the piers without protection,two kinds of protection can reduce the vertical average velocity before piers,thus,weakening the impact of the downward flow to river bed,and the combination protection weakened the effect of falling water was significantly better than the slotted protection.(3)Under the combination protection,when the slot was close to the river bed,the combination of the plate and slot made the reducing function of vertical average velocity under plate position obviously enhance,the effect was better than that of the combination of slotted near the water surface with plate.In the six combinations,the effect of the combination of slot which closed to the river bed and the plate which located on the third of water depth on the decrease of the vertical average velocity in front of the piers was the best.(4)Under the combination protection,when the slot was close to the river bed,the combination of the plate and slot could obviously reduce vertical turbulence intensity and turbulence kinetic energy on the near river bed,so that the interaction between the water flow and the river bed was weakened,and the scouring action of the water flow to the bottom of the pier was reduced.Based on the analysis of the vertical turbulence intensity and turbulent kinetic energy,the combination of slot which closed to the river bed and the plate which located on the third of water depth was the best in the six combinations.The study indicates that the effect of the combination prevention is prominent for local scour of cylinder piers.It provides a basis for combination prevention to piers scour.