黄河高含沙水流的高效输沙特性形成机理(黄河下游河道存在巨大的输沙潜力)

利用黄河主要干支流渭河、北洛河、黄河下游及三门峡水库大量实测资料,结合高含沙水流流变特性分析得出:河道中的高含沙水流的阻力与低含沙水流相同,均可用曼宁公式进行阻力计算;由于黄河泥沙组成较细,d50=0.03~0.10mm,随着含沙量的增加颗粒的沉速大幅度降低,泥沙在垂线上分布变得更加均匀,当含沙量大于200kg/m3以后发生改变;从泥沙存在对水流结构,流速在垂线上的分布特性上分析,含沙量200kg/m3左右时输送最困难,并得到河道实测资料的证实。由于粘性的增大,粗颗粒泥沙在河道中也能顺利输送,洪水期实测含沙量可达800~900kg/m3,表现出高含沙水流的高效输沙特性;黄河下游艾山以下河段实测洪水的最大含沙量为200kg/m3,在流量2 000~3 000m3/s时,高含沙洪水均可顺利输送。利用河道输送高含沙水流入海的主要障碍是改造宽浅游荡河段为窄深稳定的河槽。

Efficient sediment transport theory of the hyperconcentrated flow in the lower Yellow River

Analyses on field data from the main stem and tributaries of the Yellow River gives the following conclusions.The hyperconcentrated flow roughness can be calculated by Manning function.The settling velocity decreases more obviously and the vertical distribution of concentration becomes more uniform with the increase of sediment concentration,especially for concentration over 200kg/m~3.The impact of sediment concentration on flow structure and vertical velocity distribution indicates that it is most difficult to transport sediment if the concentration is about 200kg/m~3.Due to the increase of viscosity of hyperconcentrated flows,even coarse sediments could be transported to the downstream which presents the high efficient transport characteristics of hyperconcentrated flows.In the reach from Aishan to Lijin,the hyperconcentrated flows with concentration of 200kg/m~3 can be smoothly transported to river mouth if the flow discharge between 2000 and 3000m~3/s.The key problem of using hyperconcenterated flows to transport sediment is how to form a narrow and deep channel in the lower Yellor River.