采用无黏性中粗沙进行河流演变的自然模型试验，通过调整流量、初始河道形态等在室内模型河流中进行河湾塑造的尝试，分析冲积河流河道展宽规律，另外对典型河湾的演变规律进行试验研究。研究表明，河道的横向稳定性是河湾发育的重要条件，试验中泥沙抗冲能力的低弱使得河岸的稳定性难以保持，致使河流向分汉、游荡和辫状河型的方向发展；河岸后退的方式不但与河岸土体抗冲能力有关，而且与当地河道水动力特性和河岸坡降等因素有关；河道展宽速率反映了河流断面与水流条件不相协调的程度，随时间呈指数下降趋势，河流横断面演变所需的时间尺度远小于横向摆动所需的时间尺度；典型的河湾形态以局部扰动引起河岸失稳的方式横向发展。%Laboratory experiments on riverbed evolution were carried out with non-cohesive sand. River meanders were created in model test by adjusting the rate of flow and the initial river pattern. The law of widening of alluvial rivers was analyzed and studied with experiments. Additionally the evolution of typical river meanders was also investigated. It was revealed that the lateral stability of channels is vital to river meander growth, and the river in this experiment evolved into branching or braided patterns due to the lack of anti-erodibility of sediment, which leading to bank failure. The pattern of bank retreat is related not only to the anti-erodibility of bank, but also to local hydrodynamics feature and bank slope etc. The channel widening rate declines exponentially with time, reflecting the degree of incompatibility between cross section and flow conditions in river. The time-scale of river cross section evolution is far smaller than that of lateral migration of river channel. Typical river meanders develop laterally in the way of local disturbance causing bank failure.
展开▼
