Study On The Influence Of External Flood Into Channel On Channel Flow Capacity

Since the operation of the South-to-North Water Diversion Project,problems that affect the operation of the project to different degrees have appeared in some main channel sections.External flood into channel refers to the danger situation in which the river basin where the channel is located suffers excessive flood in flood season,and flood into the main channel causes overflow of dike,which seriously leads to the destruction of the main channel.When the external flood enters the channel,the tributaries of the external flood enter the main stream of the channel,and the confluence of the two causes complex hydraulic phenomena,resulting in the rapid increase of the water volume of the channel,the upstream water level is moderate,the area near the upstream and downstream of the interchange,such as sediment deposition,which seriously hinders the normal operation of the main channel.The safety of the South-to-North Water Diversion Project is of great significance.Therefore,it is urgent to study the impact of channel siltation on the water conveyance capacity after the external floodwater enters the canal,and put forward disposal schemes for improving the stability and safety of the water conveyance buildings,so as to protect the regional flood control safety and the safety of the middle route of the South-to-North Water diversion Project.This topic with Han xing of South-to-North Water diversion Project in Xi Xiao Tun in water main canal as the research object,adopting the method of combining physical model experiment and theory based on the characteristics and river flood control and river flow dry dynamics related theory,excess in the basin flood caused flood into the canal,the water main canal of middle route of south-to-north water transfer project changes the hydraulic elements and sediment deposition in channels are studied,reveals the flood into the drainage channels after the adjustment rule of flow ability.The main work of the paper is as follows:1.The hydrology and sediment distribution data of the basin where the prototype was located were collected and sorted,and then determine the water sediment conditions for the risk of outward flood into the channel;2.Based on the analysis of the hydraulic characteristics of the intersecting flow,two factors affecting the channel flow capacity are concluded—the inflow Angle and the amount of the external flood;3.Through the model of the main channel and the model of the external flood inlet,the experiment of clean water and muddy water was carried out,the new electromagnetic current meter and other instruments were used to simulate and analyze the process of the external flood into the channel.In this way,the variation rule of the channel flow capacity was summarized.4.When the amount of external torrent increases gradually,its influence on the main stream of the main channel increases.A backflow separation zone is formed downstream of the junction,and the size increases with the increase of flow.Squeezing the main stream on both sides makes the water level of upstream and downstream continue to rise,water overflow channel top increases sediment deposition and reduces the channel flow capacity;The increase of inflow Angle will strengthen the mixing of the two and lead to the increase of pulsation intensity of upstream and downstream.With the increase of sediment concentration,channel silting seriously reduces the overcurrent capacity.The results of this study provide a basis for the control of overflow flood into canal engineering caused by excessive flood,and also lay a foundation for the study of emergency rescue and repair technology of flood discharging buildings.