Research On Navigable Flow Conditions And Improvement Measures Of Shipai Acute Bend Reach Between The Two Dams Of The Three Gorges

The navigability between the two dams is mainly limited by Letian Creek,Shuitianjiao,Xitan,Dashaba,Shipai,and Mignao,etc.,which hinder navigation and beach hazards.However,the Shipai’s sharp bend section has a narrow river surface during flood season,and is also affected by curved water flow The impact of the jet turbulence and the poor navigable flow conditions have become the main factor restricting the navigability between the two dams.The Shipai river section with steep bends is steep on both sides,and it is also a high mountain and gorge section with a water depth of 90 m.It is difficult to implement general remediation measures.Therefore,it is necessary to propose new remediation measures to improve the navigable flow conditions of this section.Based on previous researches on the treatment of beach danger between the two dams,this paper uses Mike fluid calculation software to establish a two-dimensional hydraulic calculation mathematical model for the entire river section according to the characteristics of the river section.The main results are as follows:(1)In terms of the impact of the Three Gorges peak shaving on the water level of the Shipai reach,the peak shaving has the most significant impact on the water level change of the Shipai reach.Among the factors affecting the water level variation,the magnitude of the flow rate dominates.When it is greater than 8000m~3/s,the maximum water level of the Shipai River section will vary by more than 1m.The change of the water level in front of the Gezhouba Dam has little effect on the amplitude of the water level.With the increase of the peak shaving duration,the maximum water level change amplitude first increased,then decreased,and then tended to be basically stable.(2)From the perspective of the impact of the Three Gorges peak shaving on the velocity of the Shipai reach,the maximum daily variation and the maximum time variation of the Shipai reach both decrease with the increase of the initial flow or the decrease of the flow variation;The daily variation of the maximum flow rate and the time variation of the maximum flow rate both showed a trend of first increasing and then decreasing with the increase of the peak shaving duration,and then remained basically stable.The rate of velocity change decreases with the increase of the water level in front of the Gezhouba Dam,but the magnitude of the decrease is smaller than that of other influencing factors.(3)When the water level in front of the Gezhou Dam is 63 m,when the discharge flow of the Three Gorges is less than 35000m~3/s,the flow velocity along the Shipai reach is less than 3m/s;when the discharge flow of the Three Gorges is greater than35000m~3/s,the local maximum flow velocity of the Shipai reach Both reach 3m/s.When the water level of Gezhouba rises to 66 m,the river flow velocity decreases,and when the discharge flow of the Three Gorges is less than 45000m~3/s,the local maximum flow velocity of the Shipai reach is less than 3m/s.(4)In the natural state,the Shipai river section with sharp bends has obvious characteristics of obstructing navigation under large flow.This paper proposes a tunnel diversion and navigation tunnel plan.Due to the small flow gradient of the Shipai section,the diversion capacity of the diversion tunnel is poor,which is not sufficient to fundamentally improve the navigable flow conditions of the Shipai section.Therefore,this paper mainly analyzes and researches the navigation tunnel scheme,and proposes two schemes with a tunnel width of 34m and 44m.