Inversion Analysis And Research On The Failure Of Stilling Basin Plate In Jin'anqiao Hydropower Station

Scouring damage of energy dissipation protection facilities of spillway structures is a common problem in the operation of hydropower projects.Scholars at home and abroad have done a lot of analysis and Research on it,and the cases of damage are still common.Taking Jin'anqiao Hydropower Station as a case study,this thesis carried out inversion analysis on its spillway operation damage,hydrodynamic characteristics and the causes of stilling basin plate damage by means of investigation,statistics,model test and numerical simulation,and then synthesized the inversion analysis results and the design and operation of typical projects at home and abroad,so as to summarize and discuss the safety control indexes of stilling pond floor.The main research conclusions are summarized as follows:(1)A total of 27 cases on damage of energy dissipation and protection facilities at home and abroad were investigated,and the layout of flood discharge and energy dissipation,operation conditions before damage,damage areas,types and associated reasons were classified and summarized.(2)Based on the prototype observation results,the hydrodynamic characteristics of spillway of Jin'anqiao Hydropower Station were analyzed by means of model test and numerical simulation.The results show that the hydrodynamic characteristics of the starting position of the drop sill before the flow into the pond are complex,the flow velocity near the bottom can reach 37.74m/s under the designed flow condition,the time average pressure appears minimum or even negative pressure-4.66×9.8kPa,and the maximum fluctuating pressure appears 12.04×9.8kPa;the fluctuating pressure is mainly controlled by the single width flow into the pond,gate opening method and downstream water level,so porous,uniform and symmetrical opening mode is recommended and reduces the long-term operation under low tail water level and large discharge per unit width.(3)Inverse analysis of plate failure was carried out by model test of working condition before failure of stilling basin.The results show that the maximum root mean square value of fluctuating pressure is 4.08×9.8kPa,and its occurrence location coincides with the failure location of stilling basin plate,which indicates that fluctuating pressure is one of the main reasons for plate failure.(4)Summarizing and discussing the safety control index of stilling pond floor.Through cases study and inversion analysis results,comparing the typical projects which are well operated,it is suggested that the root mean square of fluctuating pressure should be controlled at 50 kPa(about 5 m head)and the energy dissipation rate per unit water body should be controlled at 25 kW/m~3;For the stability of surface anti-abrasion concrete,it is suggested that the root mean square of fluctuating pressure should be controlled at 40 kPa(about 4 m head)and the energy dissipation rate per unit water body should be controlled at 20 kW/m~3.