河流推移质输沙形态调整受到水动力、阻力以及边界条件的共同影响。本研究以水力半径分割方法为基础，以河岸坡角为θ的等腰梯形为过水断面，以λ表示河岸与河底的相对粗糙度,以d50表示输运泥沙的中值粒径，以nb表示河床泥沙糙率，用Q表示流量，Qs表示输沙率，S表示河道纵比降，通过数理分析解析了各影响因子对河道推移质输沙最优断面形态以及最小输沙比降的影响。结果表明:1）其他因子固定不变时，河流输沙最优断面形态以及最小输沙比降随着λ的增大而减小；随着θ的增大而增大。2）Q流量的增加，如果输沙量Qs不变，河道输沙最小比降减小，河道最优输沙断面向窄深方向发展；Qs输沙率的增加，如果流量不变，河道输沙最小比降增大，河道最优输沙断面向宽浅发展。3）d50中值粒径减小，河道输沙最小比降减小，河道输沙最优断面向宽浅发展；nb河底糙率系数的减小，导致河道输沙最小比降增大，河道向窄宽浅发展。

The adjustment of river cross-section with bed load is affected by hydrodynamic force, resistance and boundary conditions. Based on the hydraulic radius segmentation method, the effects of various influencing factors on the optimal sediment transport section and minimum gradient of the river sediment transport are analyzed through mathematical analysis, such as the bank slope angleθ, the relative roughness of the riverbank to the riverbed λ, the median particle size of sediment transported d50, the roughness of the riverbed nb, the flow discharge Q, and the sediment transport rate QS. The results show that: 1) when other factors are fixed, the optimal cross-section of river sediment transport and the minimum sediment transport gradient decreases with the increase ofλ,and decreases with the increase ofθ. 2) If the sediment discharge QS remains unchanged, with the increase of Q, the minimum gradient of sediment transport decreases, and the optimal sediment transport cross-section of the river becomes narrow and deep; with the increase of QS, if the flow discharge Q remains unchanged, the minimum gradient of sediment transport increases, and the optimal sediment transport cross-section of the river becomes wide and shallow. 3) With the decrease of the median particle size d50, the minimum gradient of river sediment transport decreases, and the optimal cross-section of river sediment transport becomes wide and shallow; the decrease of riverbed roughness coefficient leads to the increase of the minimum gradient of sediment transport, and the optimal cross-section of river sediment transport becomes wide and shallow.

国家自然科学(51979185)；国家自然科学(51879182)