The objective of the study is to substantiate the conditions of using reserve spillways for earth dams at the river hydro systems. Reserve spillways requires for simplicity of design and low cost. The spillway defects are permitted during it operating but this shall not decrease the reliability of main constructions. The greater part of a flood is passed through the main spillway (e.g. shore spillway), situated at the mark of normal water level and the remaining part is passed through one or several sections of reserve spillway at reaching maximum water level in the upstream. The research results in establishing that benefits of the proposed construction comparing with others spillway design are low cost of building, simplicity of design, and significantly less potential total damage in dam emergency because the part of excess flood will beforehand pass through the reserve spillway and distribute for a longer time. Standard methods for spillway hydraulic calculating were used during the development of calculating technique for the main parameters of proposed reserve spillway. The article presents flow chart for calculation by the proposed technique including algorithm. The main parameters of scoured insert are found by hydraulic calculation on the base of the equation of hydraulic performance of water discharge part of the reserve spillway with the trapezoid cross-section after the scouring of ground insert which works according to scheme of spillway with broad-crested drop. The developed technique is realized by the computer software Mathcad. For practical testing of the technique a sample clarifying the calculation specifics for main parameters of the reserve spillway is considered in the article. For the first case, height of an insert, number of sections and height of a drop of the reserve spillway were Hâñò = 8.18 m, N = 1, Hïðã = 4.82 m, and for the second one – Hâñò = 6.08 m, N = 2, Hïðã = 6.92 m.
Keywords: earth dam, flood, reserve spillway, scouring earth insect, design, parameters, hydraulic calculation.
