Study On The Waterway Regulation Method And Regulation Level Of Gravel Shoal At The Straight Transition Region

The hydrodynamic conditions and gravel movement mechanism are both relatively complex, and some complex gravel shoals characteristics and riverbed evolution aren't understanded sufficiently in the course of waterway regulation, so the adoptive regulation method maybe failed to solve navigation obstruction fundamentally, they often need regulated repeatedly. Therefore, based on the in-depth study of the characteristics of gravel shoals, this paper researched the regulation method of straight transition section gravel shoals and regulation water level by means of generalized model tests and two-dimensional mathematical model.Single dredging regulation method can't fundamentally change the flow structure in dredging zone. The flow structure is influenced by the surrounding riverbed morphology. Dredging zone is still in the belt of bed-load transport. During flood period, the upstream bed-load begin to transport to downstream, and there will still be sediment falling in dredging zone. There will be deposition in the dredging zone possibly.Damming regulation method can obviously change the flow structure near the spur dyke, and the flow structure strongly shows the 3D characteristics. The local scour near the head of spur dyke is mainly caused by the generated eddy system. The scour pit is gradually forming under the action of bottom spiral flow. Bed-load transport over the head along the edge of scour pit, bed-load transport path begin to change obviously. The belt of bed-load transport changes in the direction of the opposite side of spur dyke, this action is in favor of the continuous regulation effect of the spur dyke.The variation of flow field before and after dredging or damming regulation can be modeled by two-dimensional mathematical model in Yanziqi gravel shoal, and the regulation effects also can be evaluated by measured data. The result of dredging modeling verified the conclusions of above generalized model tests. Although the local velocity in dredging zone is bigger than the starting velocity of bed-load, the flow structure don't change fundamentally, the dredging zone is in the belt of bed-load transport, and there will be deposition in the dredging zone possibly; The variation of flow field and riverbed morphology in the damming regulation method is in agreement with the result of model tests, this phenomenon proves that the damming regulation method is in favor of the continuous regulation effect of gravel shoal.This paper puts forward the regulation water level determination method that in case of the determination of the position of spur dyke or other regulation structures, the regulation discharge is the discharge with the biggest scour effect, namely the second bed-building discharge, and the corresponding water level is the regulation water level. This paper shows the application example of this regulation water level determination method by Yanziqi gravel shoal regulation project.