关键词: 滇中引水工程, 引水防沙, 物理模型试验, 水流特性, 泥沙淤积

Abstract:

[Objective] For water intake projects, the arrangement of the intake location is of paramount importance, as it must ensure the required water diversion volume while simultaneously preventing excessive sediment from entering the diversion channels and power station turbines. This balance is critical for the smooth operation of water diversion and power generation at the station. This study specifically focuses on the water diversion and sediment control challenges at the intake hub of the Central Yunnan Water Diversion Project. [Methods] Physical model testing was utilized, whereby a normal model of a 5.5 km river reach from Bachawan to Ma’anshan was established. The model primarily simulated the transport of suspended sediment, with the time scale serving as the primary control parameter for the experiments. The main objectives were to analyze the impact of project construction on flow and sediment transport within the study reach and the sediment deposition within the diversion channel. [Results] (1) Channel flow velocity and patterns were influenced by inflow conditions and morphological resistance. Higher separation walls effectively isolated flow in the left and right channels, regulated flow toward the respective pump stations, promoted smoother flow within the channel, and enhanced sediment settling.(2) In the Jinsha River, flood peak flows were characterized by short duration, while medium and low flow conditions persisted for longer periods. Since identical intake locations and shapes were adopted in both long and short separation wall schemes, their effects on flow and sediment movement had negligible differences.(3) Under medium and low flow conditions, flow control at the pump stations was easier with the long separation wall scheme. It also produced a smaller recirculation zone and a more uniform velocity distribution across the cross-section. When the flow exceeded 2 180 m³/s, the short separation wall scheme exhibited slightly lower velocities in both the left and right channels of the diversion channel than those for the long wall scheme. The main flow zone in the right channel narrowed, and the recirculation zone expanded. However, overall, the flow patterns in the diversion channel showed minimal differences between the two separation wall schemes.(4) Under high flow with high sediment load conditions, sediment began to deposit immediately downstream of the intake and progressively increased along the channel, while the sediment concentration in the flow gradually decreased. No significant difference in sediment concentrations entering the pump stations was detected between the long and short separation wall schemes. Sediment particle size was coarser at the channel intake entrance but finer at the pump station inlets due to in-channel deposition. [Conclusion] Although the long separation wall scheme exhibits slightly higher total volume of sediment deposition compared to the short separation wall scheme, it demonstrates superior accessibility for channel inspection and sediment dredging. Therefore, the long wall scheme is recommended as the preferred scheme. The proposed scheme, integrating a diversion wall with a long separation wall, has been adopted for construction and operation. For the low-head reach water diversion project in the Jinsha River in Yunnan, a hub layout that combines the convex bank diversion with internal flow separation within the diversion channel is an effective solution for sediment control. This approach offers a valuable reference for similar projects.

Key words: Central Yunnan Water Diversion Project, water diversion and sediment control, physical model experiment, flow characteristics, sediment deposition