水沙变化条件下不同边界弯曲河道演变特征研究

Evolution characteristics of curved river channels with different boundaries underwater-sediment variation conditions

弯曲河道具有迂回曲折的外形和蜿蜒蠕动的动态特征,其形成、发展和演变是受多种因素综合影响的复杂过程。为研究水沙变化条件下弯曲河流的河道演变特征,采用自然模型法在室内水槽中塑造出相对自然的弯曲河道,设置有、无护岸措施两种工况进行模型试验。结果表明:在有护岸措施条件下,河道纵剖面上游段冲刷下切、下游段变化不大,河道整体比降呈减小趋势,河道深泓弯曲度减小,其演变响应特性对含沙量的变化更敏感;在无护岸措施条件下,河道滩槽演变调整作用较强,纵剖面呈整体式下切,且下游段纵剖面下切幅度较上游段大,河道深泓弯曲度逐渐增大,其演变响应特性对流量的变化更敏感。弯曲河道发生演变的实质是变化的水沙条件与河道形态调整之间相互适应的过程,演变的最终趋势是河道的形态结构与水沙条件达到相互协调的平衡状态。

The curved river channel has a tortuous shape and dynamic characteristics of meandering and creeping.Its formation,development and evolution are complex processes affected by many factors.In order to study the evolution characteristics of curved river channels under water-sediment variation,the natural model method was used to create a relatively natural curved river channel in an indoor flume,and the model test was carried out under two working conditions of whether implementing riverbank protection measures or not.The results showed that under riverbank protection measures,the upstream of the longitudinal section was scoured and cut down,the downstream section didn t change much,the thalweg curvature of the river decreased,and its evolution response characteristics were more sensitive to the variation of sediment concentration.For no riverbank protection measures,the evolution and adjustment of the river channel was strong,and the longitudinal section was integrally incised with larger magnitude at downstream section than that at the upstream section,the thalweg curvature of the river channel gradually increased,and its evolution response characteristics was more sensitive to flow variation.The essence of the curved river channel evolution was the process of mutual adaptation between the water-sediment variation and the river channel morphology adjustment.The final trend of the evolution was that the morphological structure of the river channel and the water-sediment conditions reach a balanced state of mutual coordination.