护滩带边缘局部冲刷深度计算公式初步研究

长江航道整治工程广泛采用软体排护滩,简称护滩带,当护滩带边缘压载结构不同时,边缘外的局部冲刷会发生变化。采用水槽试验的方法,研究了不同压载体护滩带边缘的局部冲刷规律。研究发现,护滩带边缘冲刷深度随水流流速与泥沙起动流速之比的增加而增大;当排体外不铺设压载体时,排体上压载体透水率越大,局部冲刷深度也越大;当排体外铺设压载体时,局部冲刷深度随压载体铺设宽度的增大呈先减小,后变化不大的特点;当排体上压载体结构和排体外压载宽度相同时,排体外压载体透水率越大,局部冲刷深度也越大。依据试验资料,选取反映水流、河床及压载结构条件的因子,建立了具有一定精度的计算排体护滩带边缘局部冲刷深度的经验公式。

Study on local scour depth along the edge of beach protection belts

Flexible mattress beach protection belts are widely applied in waterway regulation on the Yangtze River,where local scour along the edge of belts varies with the structure of ballast laying.Two flumes were used to study local scour regularity along the edge of beach protection belts with different ballast.Experimental results show that local scour depth along the edge of beach protection belts increases with the ratio of flow velocity to sediment incipient velocity.Without ballast laying outside of the mattress,local scouring depth increases with the permeable rate of ballast on the mattress.While with ballast laying outside of the mattress,local scouring depth will reduce at the beginning,then change little as the width of laying ballast increases.With the same ballast on the mattress and the same width of ballast laying outside of the mattress,local scouring depth increases with the permeable rate of ballast outside of the mattress.On the basis of experimental data,factors which reflect flow character,riverbed and structure of the ballast are selected to establish the empirical formula for local scour depth along the edge of beach protection belts.