黄河上游沙漠宽谷段高含沙支流对干流的淤堵影响

Hyperconcentrated Tributary Flows in the Main Stream of Desert and Wide-valley Reaches of the Upper Yellow River

黄河上游沙漠宽谷段支流——十大孔兑的高含沙洪水多次淤堵黄河干流,造成灾害。基于实测水文泥沙资料和模型试验手段对孔兑高含沙洪水特点、淤堵干流过程和交汇区沙坝形态进行了研究。结果表明:孔兑洪水具有陡涨陡落、持续时间短、洪峰流量大、含沙量高、输沙量大等特点;孔兑洪水形成沙坝、淤堵黄河的过程可分为形成、相对稳定和冲刷3个阶段,支流洪水量级较大,形成的沙坝规模较大,沙坝冲刷历时也较长;孔兑高含沙水流入黄交汇区水流结构分区包括壅水区、回流区、高流速带、剪切层等组成要素,沙坝淤积形态模式包括壅水区、回流区、回流区下游淤积体和交汇区输水输沙窄槽;基于沙坝淤堵判别方法以及实测和试验数据提出了孔兑入黄交汇区沙坝判别条件。

The hyperconcentrated flood of the tributaries of the desert and wide-valley reaches of the Upper Yellow River formed sandbars in the confluences blocking the main stream several times.Based on field and experimental data,the properties of hyperconcentrated flood,the process of blocking and the sandbar morphology in the confluence were analyzed.The results indicate that the hyperconcentrated floods from the tributaries feature steep rising and dropping,short duration,high peak,large flood volume,high sediment concentration.The evolution process of the sandbar included three stages,the forming,the stability and the scouring.The larger the magnitude of the flood,the greater the scale of the sandbar,and the longer the time of sandbar scouring.The hyperconcentrated flow confluence can be divided into five hydraulic regions,the backwater zone,the separation zone,the maximum velocity area,and the shear layer.The bed morphology consists of four basic elements,the sandbar in the backwater zone,the bar in the separation zone,the bars in the reach downstream of the separation zone,and the channel for flow conveyance and sediment transport.Based on field and experimental data,the inequations were established for discriminating the magnitude of sandbar blocking caused by hyperconcentrated floods of the tributaries.