Research On Lining Protection Types Of The Plunge Pool Of High Concrete Arch Dam

A majority of existing and planned high concrete arch dams in our country are built in the valleys of the middle and upper reaches of the rivers in the southwest.Belonging to the landforms of highland and ravine,the rivers are characterized with narrow valley,high head and big flood discharge capacity,together with the complex geological conditions,the anti-washout ability is limited of the slope of the downstream river channel and the flood discharge and energy dissipation is difficult.Whether the scheme of flood discharge and energy dissipation is reasonable or not relates to not only the economy of the project investment,but also the safety of the high concrete arch dam.In this paper,the schemes of flood discharge and energy dissipation at home and abroad are summarized,and the advantages and disadvantages are compared deeply.Combined with geological and topographical conditions and characteristics of flood discharge and energy dissipation of a high concrete arch dam,the detailed study of lining protection pattern of the plunge pool downstream is also carried out in this paper.Through the hydraulic calculation of the scheme of flood discharge and energy dissipation of the dam,One scheme of flood discharge that use the surface and middle outlet,the 3 tunnel spillways,and also use the natural way of the energy dissipation and anti-washout of the plunge pool is carried out.Through the overall physical experiment on the hydraulic model with the scale 1:100,combine with the project design and the results of experiments of the plunge pool to the related high arch dams at home and abroad,the lining protection pattern of the plunge pool is being further confirmed.At the same time,through the overall physical experiment on the hydraulic model with the scale 1:100,we collect the information such as the flood discharge,flow regime of the water in the plunge pool,the time-averaged features of dynamic water pressure of the baseboard and also the features of the fluctuating pressure.The result shows that the scheme is rationality and feasibility.By the related stability calculation,the lining protection pattern of the plunge pool is: the natural way of the energy dissipation of the plunge pool downstream,set the auxiliary weir at the terminal position with the crest elevation 825.50 m.the length of the plunge pool is about 350m(from the toe to the auxiliary weir),the width of the bottom upstream is 50 m,while the downstream is 75m;the elevation of the foundation surface of the auxiliary weir is 730 m,the crest elevation is 825.50m;it is needless to take the protection of the bottom board except the 80 m downstream from the toe;the two sides along the plunge pool are the grounding revetment,with the foundation elevation 732 m,the protection about the splash zone from 140 m behind the dam to the slash line of the slope,the other zone protected to the elevation 860 m,the underslung reverent is arranged along the river from auxiliary weir to the cofferdam downstream,elevation of the bottom board is elevated gradually from the upstream to the downstream along the covering layer,the elevation from the top is 825.50 m.In view of many high concrete arch dams are built currently in western region,this paper can not only provide technological support for determining whether it is need an artificial plunge pool for the high arch dam with the geologic conditions of deep overburden from a specific perspective,but also provide a reference for similar projects in the future.It not only has theory significance,but also has the practical value for projects.