黄河“揭河底”判别指标理论研究及验证

Research and verification on discriminating index for bottom tearing scour

在广泛的原型调研及模型试验研究基础上,作者认为,河床淤积物层理结构中胶泥层(块)的存在为"揭河底"发生提供了必要的前期条件,而高含沙洪水期水流作用于胶泥块引起上下表面脉动压力波传播速度不同形成瞬时上举力,是发生"揭河底"现象的直接原因。本文基于"揭河底"发生时的力学关系分析,创新性地利用瞬变流模型,建立了"揭河底"现象发生的临界判别指标;通过开展的"揭河底"室内模拟试验,确定了临界指标中的系数K值,并利用跟随性较强的模型试验资料及黄河小北干流放淤输沙渠资料及黄河龙门站资料对公式进行了验证,结果吻合较好。该成果为天然河道中"揭河底"现象的预测预报提供了理论支撑。

The field survey and physical model experiments indicate that the layered sedimentation formed on the river bed is the necessary pre-conditions of the occuring of bottom tearing scour phenomena and the instantaneous uplift force due to different propagation speeds of pulse pressure waves acting on the upper and lower surfaces of the mud layer during sediment hyper-concentrated flood is the direct cause excitating the tearing scour.In this paper,based on the analysis on dynamic relationship and the transient flow model,a critical index of bottom tearing scour is established,in which the coeffient K is determined by experiments.It is found that the experimenal results agree well with sediment transport data observed in the North Main Reach of the Yellow River and the observation data obtained from the Longmen Hydrological Station.