【作者】 杨树青； 白玉川； 徐海珏；

【Author】 YANG Shuqing;BAI Yuchuan;XU Haijue;Institute of Sediment on River and Coast Engineering,Tianjin University;State Key Laboratory of Hydraulic Engineering Simulation and Safety,Tianjin University;

【机构】 天津大学河流海岸工程泥沙研究所； 天津大学水利工程仿真与安全国家重点实验室；

【摘要】 本文介绍了在实验室条件下,采用无黏性沙进行的冲积平原河流平面形态塑造的研究。在一个尺寸为4m×2m的小水槽中进行,分别选用两种不同粒径的床沙进行实验,细沙d₅₀=0.22mm,粗沙d₅₀=0.62mm。通过给定不同的初始流量、坡降及河岸植被覆盖率,从而塑造出不同河型。不同的水流条件和坡降形成了不同的水动力条件,不同的床沙组成及岸坡植被构成了不同的河岸稳定条件。当河岸抗冲能力较低难以保持稳定时,河道向弯曲、分汊及游荡的河型方向发展。岸坡植被对河岸及床面稳定性影响强烈,一方面植被根部对河岸起到了加筋固定作用,增加了河岸抗剪强度;另一方面当水流淘刷含植被河岸增加了局部扰动,降低了河岸及河床的稳定性,导致了在河道演变的初始阶段,沿植被带冲刷严重且水深较大。对比分析了不同条件下河道的河岸侵蚀特性,主流线变化规律,近岸高程变化规律,输沙及渗流特性等。研究表明,粗沙的渗流量较细沙大,岸坡植被增加了河道的渗流能力;不同的河岸植被覆盖具有不同的河流演变特性,增大河岸植被覆盖可以有效降低蜿蜒河流的曲率及稳定河宽,但对河岸展宽影响不是简单的线性关系;同时一定的河岸植被覆盖率条件下可以有效地减少河道输沙。更多还原

【Abstract】 This paper presents recent works on the simulation of river planforms in the laboratory conditions using cohesionless sand.Experiments were carried out in a size of 4 m×2 m tank,respectively using two different sizes of bed sand,d₅₀=0.22 mm and d₅₀=0.62 mm.The controlled condition of initial discharge,slope,riparian vegetation coverage rate creates different end results of planforms.Different flow condition and slope formed different hydrodynamic conditions,and different sediment composition and vegetation coverage rate determined different riverbank stability.When the resistance of riverbank is low and it is difficult to maintain stability,and the river develops to straight,meandering,anabranching and braided.The riparian vegetation has a strong influence on the stability of the riverbank and riverbed.On the one hand,the roots of vegetation play a reinforced and fixed role on the riverbank with increasing the shear strength;On the other hand,when the water flows undercut the vegetation bank,the local disturbance will increase and the stability of the riverbank and riverbed will reduce.At the initial stage of the river evolution,serious scour produces along the vegetation belt and the water depth is larger.The characteristics of riverbank erosion,the variation of mainstream linethe law of elevation change,the characteristics of sediment transport and seepage which under different conditions were compared and analyzed.The results show that the seepage of coarse sand is larger than that of fine sand,and the riparian vegetation increases the seepage capacity of the river.Different riparian vegetation has different river evolution characteristics,increasing riparian vegetation coverage rate can effectively reduce the curvature and width of the meandering rivers,but the impact on the riverbank widening is not linear.At the same time,a certain riparian vegetation coverage rate can effectively reduce the river sediment transport capacity.更多还原