低含沙量条件下张瑞瑾挟沙力公式中参数确定及其在荆江的应用

水流挟沙力公式及其参数选取的合理性,直接影响到悬沙输移及河床冲淤变形的计算精度。在少沙河流,张瑞瑾水流挟沙力公式被广泛应用,但其系数和指数在不同研究中取值差异较大。本研究首先选取长江中游相对冲淤平衡状态下的水流含沙量资料共计573组,将其近似等于水流挟沙力;然后点绘水流挟沙力和水沙综合参数的关系,从而确定参数k和m的计算关系;最后将完善后的水流挟沙力公式嵌入到一维水沙动力学模型中,模拟了长江中游荆江段2016年的水沙输移过程。计算结果表明:当挟沙力公式中参数采用计算式确定时,各水文站计算和实测含沙量平均相对误差在26%～36%之间;而这些参数取为常数时,含沙量平均相对误差范围为39～49%。因此当采用计算式确定张瑞瑾挟沙力公式中的参数时,相较于取值为常数,水沙输移过程的计算精度更高。故该方法解决了以往在低含沙量条件下不易确定挟沙力公式中关键参数的难题,提高了水沙数学模型的计算精度。

Determination of parameters in the Zhang Ruijin's formula for sediment-transport capacity in low sediment-laden flows and its application in the Jingjiang Reach

The selection of the formula for sediment-transport capacity and the determination of its parameters directly affect the simulation accuracy of morphodynamic models. In the rivers with low sediment concentration, Zhang Ruijin''s formula is more applicable to calculate the sediment-transport capacity. However, the parameters k and m in the Zhang''s formula have different values in various studies with many uncertainties. Therefore,573 sets of data were selected in the Middle Yangtze River (MYR) at a quasi-equi-librium stage, which were used to calculate the sediment-transport capacity. Then the relationship between the sediment-transport capacity and the comprehensive flow-sediment parameter was plotted,with the calculation formulas for parameters k and m being proposed. Finally, the improved calculation formula of sediment-transport capacity was embedded in a one-dimensional morphodynamic model to simulate the processes of flow and sediment transport in the Jingjiang Reach of the MYR in 2016. The results show that when the parameters of Zhang''s formula were determined by calculation formulas,the average relative errors (MREs) of the calculated and measured sediment concentrations at the hydrometric stations were between 26% and 36%; when these parameters were taken as constants, the values of MREs were in the range of 39%-49%. Therefore, the simulation accuracy of sediment transport was improved when the calculation formula was adopted to determine the parameters of Zhang''s formula. In summary, the calculation formulas of parameters can enable the model to adjust the parameters of Zhang''s formula based on the actual flow and sediment conditions,which helps to improve the adaptability of morphodynamic models applied to natural rivers.