Study On Failure Mechanism Of The Stepped Spillway

In recent years,the staircase spillway has been widely used in energy dissipation.In the middle and high water head power station,the staircase energy dissipation combined with the pick flow and the bottom flow energy dissipation structure can effectively reduce the flow energy of the outflow or bottom flow into the pool.The energy dissipation effect is better than the single flow and bottom current dissipation.In practical engineering,the local area of stepped spillway is easy to be destroyed under the action of water erosion and cavitation erosion.Therefore,it is of great engineering significance to study its failure mechanism.At present,the research on the failure mechanism of stepped spillway mainly starts with the optimization of spillway structure,the anti-wear ability of concrete,the force of water flow on the ladder and so on.In this paper,according to the effect of flow structure on spillway,the distribution of parameters such as velocity,flow impact pressure and cavitation negative pressure are analyzed,and the failure mechanism of the staircase spillway is studied.In this paper,the physical model,mathematical simulation and field observation are used to analyze the external flow structure of the staircase spillway.The distribution of the flow velocity,the maximum flow impact pressure and the minimum cavitation negative pressure in the spillway is analyzed,and the potential damage region is predicted.The main factors that cause the failure of the staircase spillway and its influence weight are determined by comparing the site damage area of the threshold beach to the prediction results,and the classification method is put forward to determine the damage mechanism of the flow action of the staircase spillway.The analysis results are applied to the staircase spillway of the Bayi Bridge Hydropower Station.According to the results of the physical model test and the three-dimensional mathematical model,the distribution of the maximum flow velocity,the maximum flow impact pressure,the minimum cavitation negative pressure and other parameters of the Bayi Bridge spillway are analyzed,and the failure mechanism summarized by the gate sill beach power station is combined.Measure whether the spillway of Bayi Bridge will be damaged,and the high risk area easily damaged after long term operation.The research results can be applied to the energy dissipation structure of the similar hydropower station with the staircase spillway,and provide technical support for the risk analysis of energy dissipation structure,the design optimization of staircase energy dissipation structure and the management and maintenance.