Study On Improvement Measures Of Navigation Flow Condition Of Dafutan Navigation-hydropower Project

Yuanjiang River is the second largest river in Hunan Province and one of the main channels for the layout of high-grade waterways in China.With the fast developing economy of navigation business and releasing of relevant polocies,clearly proposed the goal of accelerating the construction of high-grade waterway in upper Yuanjiang River.At present,the capacity of ships passing through the waterway is not matched with the demand for future growth.Some reaches of this river still have problems with navigation.The middle and upper reaches of the river mainly adopt the channelization method to achieve the stability and improvement of the channel level,the water level may not be connected to the downstream of the cascade hub,resulting in insufficient navigation and the rivered exposure.Then it affects the navigation of ships.Dafutan navigation-hydropower project is the 12th power station planned for the mainstream of the Yuanjiang River at the meandering-anabranching channel.The navigation channel of upper and lower reaches are susceptible to the obique flow caused by the split and the outlet.At the present stage,due to the unreasonable arrangement of the ship locks in the upper reaches of the hub,the navigation conditions of in the entrance area are poor and the angle between the axis of the channel above the head is larger than that of the water flow;the downstream of the hub has a convex bank slope and the intersection of the tail and the road at the exit of the approach channel.Larger,respectively,resulting in a larger intersection angle between the axis of the channel and the flow direction of the port area,a poorer navigation flow condition in the entrance area and the transitional reach of the navigation structures,and a greater intensity of the channel in the channel at the confluence of the continent.In view of the problems of the upstream and downstream navigation flow conditions and the ship model navigation indicators exceeded the standard and other issues.Combining with the test of ship model navigation,we studied the navigation flow condition at the entrance,transitional,and rear of middle island area of the shiplock approach channe.By studying comparatively the upstream's navigation wall,downstream's through-air navigation wall,and diversion pier and tail-type permeable dam and diversion pier.The best recommendation is that the upstream navigation channel is built with a new navigation wall of 200m long,the downstream navigation channel is newly built with a 180m long air-permeable navigation wall and 8 holes,the new tail-opening dam is 300 m long,9 holes are permeable,and the top surface is set to 2‰ slope.Excavation needs to be carried out on the channel between the entrance channel gate area and the deep channel of the downstream channel,with an excavation of 1.9 m deep and 70m wide.The test results under the recommended scheme show that under discharge below 8000m3/s,the navigation flow condition and ship navigation condition of the port area and the connecting section are greatly improved,the maximum lateral flow rate of the upper and lower port areas is reduced to 0.3m/s,0.33m/s,and the ship model navigation parameters meet the requirements of the specification limits.The recommended scheme can better solve the problem of obstacle navigation of the upstream and downstream gate area,the connecting section and the tail channel,and the navigation channel of the upstream and downstream approach channel.The inner water body plays a better weakening role,and the water flow of the right tail of the continent is well adjusted.