基于阻力原理的稳定河流几何形态判定方法研究

受上游来水来沙条件影响，自然河道通过自我冲淤调整，常形成稳定的几何形态。稳定河流几何形态设计在工程应用中十分重要，稳定断面有利于水沙输移，且避免河道冲淤平衡破坏发生。本文系统分析了达西水流阻力梯度沿程变化，表明阻力梯度主要作用于三方面：河道深度调整，河道宽度调整，河道坡降调整。若调整宽度与深度的概率为线性关系，可推导出稳定河流几何形态关系式。在泥沙输移作用下，总能坡可分解为两部分，清水对应能坡和泥沙运动产生的附加能坡，其中，清水对应能坡可采用清水河道达西阻力表达式计算，泥沙输移附加能坡，可利用实测资料推求。通过分析含有总坡降的河道几何形态表达式，指出未知函数与坡降的0.3次方呈线性关系，而指数则与参数关系明显，随着参数的增大而呈现减小的趋势。利用收集的野外实测数据确定了这些未知变量，并给出了相应的求解表达式，该表达式不仅适用于沙质河道，还适用于砾卵石河道。以大量野外实测数据与室内试验数据对比分析，本文提出的稳定河道几何关系计算方法具有很高的精度。

Study on the Geometry Determination Method of Stable Channel Based on Resistance Principle

Alluvial channels tend to adjust their themselves and finally develop a stable hydraulic geometry in response to the change of water and sediment from upstream. The design of alluvial channels to conduct a specified flow is one of the major problems in the field of hydraulic engineering, as well as a good channel section can effectively transfer water and sediment and avoid the equilibrium damage of erosion and depositon. In the paper, the Darcy friction factor gradient was analysed, and it was found that the adjustment of friction factor gradient was composed of three parts, namely, the depth adjustment, the width adjustment and the slope adjustment. With the hypothesis that a linear relationship between the probabilities of adjustments of widths and depths exists, an analytical regime method was proposed to determine the stable open channel dimensions. Because of the transportation of sediment, the hydraulic radius in an open channel could be divided into two parts, i.e. the hydraulic radius without sediment transportation and with sediment transportation. The hydraulic radius without sediment transportation could be computed with traditional log or exponential law of Darcy friction factor, also, empirical expression for the hydraulic radius with sediment transportation was proposed based on the measured data. Furthermore, the analytical regime equation showed that a linear relationship exists between the unknown function of the hydraulic radius and the 0.3th power of the slope. The exponential parameter decreases with increasing parameter. Then, the unknown variable and exponential parameter in the new analytical regime equation were also determined using collected field data and the formula was suitable for sandy, gravel and pebble rivers. Finally, the validity of the presented model was tested with field data, and the computed water depth and width were all in good agreement with measured data. The comparison between measured data and computed data with previous modes showed that present equation gets the lowest errors.