陡坡河段变动回水区推移质运动特性的试验研究

The characteristic motion of the traction load in typical fluctuating backwater area, including the plane conformation, the promotion track of the sedimentation during the drawdown process of the reservoir, and the increasing process of the upstream flow, were studied based on the physical model tests. The results indicated that due to the large specific drop in the reach, the upstream and downstream flow patterns of the reservoir pinch-out point were different, and the sediment transport capacity would drop sharply in the course of the water flow changing from a jet to a slow flow. During the drawdown process of the reservoir, keeping the upstream water at a constant level until sediment transport distance was similar to the advancing distance of reservoir pinch-out point and the downstream level fell to 875 m, the siltation near the top of river bay would be cut into the upper and lower parts separately. The difference of sediment gradation between two grades of silt was more obvious, reflecting the separation effect of water flow. Comparatively, increasing the upstream flow while keeping sediment supply and the downstream level unchanged, the bed-load sediment of the downstream propulsion was relatively small,which showed that the bedload transport in the area of fluctuant backwater was greatly influenced by the backwater action in the lower reaches of the river. Under the premise that the total amount of the upstream sediment was given, the promoting of the frontier sedimentation was mainly affected by the decreasing water level of the reservoir, and the effect by the upstream flow was relatively small.