平滩流量下的水力特性对分汊河道的滩槽冲淤、分流分沙比及污染物的输移等均有较大的影响。以长江中游戴家洲河段为原型,通过开展概化定床模型试验,分析了弯曲分汊河道不同特征流量下水动力特性的沿程差异性和平滩流量下分汊河道不同区域水力要素的突变特性。试验结果表明:纵比降沿程变化规律为分流区小流量下沿程增加、大流量下沿程减小,凸岸汊道与之相反,而凹岸汊道沿程增加;在平滩流量附近,分流区水面纵比降出现极大值、沿程比降变幅出现极小值,主流线、最大床面切应力所处位置由凹岸汊道转移至凸岸汊道。试验结果为水沙变异条件下分汊河道冲淤机制的研究提供了基础。

The hydraulic characteristics of bifurcated channel under bankfull discharge have great impact on the sediment deposition and erosion, the diversion ratio and sediment distribution ratio, as well as the transport of pollutants. In this research, generalized fixed-bed experiment was performed on Daijiazhou segment of the middle stream of Yangtze River as a case study. The variations in hydrodynamic characteristics along curved bifurcated channel under different characteristic flows were analyzed, and the abrupt changes of hydraulic characteristics in different regions of the bifurcated channel under bankfull discharge were examined as well. Results implied that in flow diversion region, the longitudinal slope gradient increased under small discharge, while declined under big discharge; and vice versa in the convex bank; but in concave bank, the longitudinal slope gradient increased along the flow direction. In the adjacent of bankfull discharge, the longitudinal slope gradient in flow diversion region experienced a maximum value, whereas the amplitude of slope gradient undergone a minimum value. In addition, the locations of mainstream line and maximum bed shear stress transferred from the concave bank to the convex bank.