河岸淘刷及其对河岸崩塌的影响

Study on bank erosion and its influence on bank collapse

通过研究河岸岸脚淘刷机理与岸滩稳定性,把岸脚淘刷与岸滩崩塌有机地连接在一起。在分析岸滩泥沙起动特点和顺直河段剪切力分布的基础上,指出在同样的水流条件下,河岸泥沙比河底泥沙更容易起动和冲刷,顺直河道的河岸冲刷主要发生在岸边的中下部或岸脚的地方。借用水流泥沙运动理论、水流动力理论和水流涡流理论就弯曲河道的淘刷机理进行了分析探讨,指出在主流和副流的共同作用下,弯道进口处的凸岸、弯道及其出口处的凹岸都属于高剪切力区,河岸淘刷严重,其中凹岸岸脚处的剪切力最大、淘刷最严重。河岸的侧向冲刷,特别是岸(堤)脚的冲刷,导致岸滩泥沙块体的滑力(矩)增加,阻滑力(矩)减小,相应的稳定系数减小,当冲刷到一定程度,岸滩崩塌。

The relation between lateral erosion and collapse of banks was studied in this paper by means of analyzing bank erosion and bank stability. Sediment particles at banks would mobilize more easily than those in riverbed under a same flow regime. Analysis on distribution of shearing stress in a straight reach shows that serious erosion of a bank would occur at lower places as well as the bank foot. Erosion mechanism in curved reach banks was studied according to the theories of flow-and-sediment movement, distribution of sheafing stress and flow vortex. For curved reach, banks would seriously collapse in the convex bank apex at the entrance, and the concave bank apex at the exit, among which maximum erosion would occur at the foot of concave apex. Lateral erosion of banks, especially erosion at the foot of banks. would result in enhancement of motive force moment and decreases of resistance moment, this could lead to the reduction of stability coefficient and cause bank collapse.