Sayano-Shushenskaya HPP shore spillway
The safety of hydropower facilities is always a relevant question, especially when it is about such a large object as the Sayano-Shushenskaya Hydro-Electric Power Station. For preventing the flooding of the surrounding area under flooded condition the special spillway facility started operating in 2011 with the spillway capacity of 13,090 cubic metres per second of water.
The spillway of the Sayano-Shushenskaya HPP during the flooding period allows exercising additional volume of water up to 4000 cubic metres per second and this reduce the pressure at the service spillway and provide partial execution mode for the hydraulic stilling basin while flushing. The construction of the additional shore spillway of the Sayano-Shushenskaya HPP was absolutely necessary for the increasing of the safety of the structure.
History of construction
The construction of the shore spillway of the Sayano-Shushenskaya HPP Station started in 2005. The strength design was confirmed by research results for full-scale model executed by JSC “NIIES”. The Structure safety is secured by the strict implementation of all the design solutions.
The first phase of the shore spillway construction started operating on 1st of June, 2010. The start-up facilities allowed performing of the additional river discharge pass up to 2,000 cubic metres per second. The final phase started operation on 12th of October, 2011.
The additional spillway facilities allowed exercising additional volume of water up to 4000 cubic metres per second. It is possible to start the river discharge at the structure after the mark of 527 metres is reached in the system of elevations of the Baltic Sea. Only when this mark is reached, the transportation of the water from the sluiceway entrance through two free-flow tunnels towards the shore spillway begins.
Composition of structures
There are the following structures:
- sluiceway entrance,
- two free-flow tunnels with the cross section 10х12 m,
- downstream portal,
- five-stage drop,
- tailrace canal.
Sluiceway entrance serves to organize the smooth flow for two 1,130 metres long free-flow tunnels. The capacity of each tunnel is 2,000 cubic metres per second. The spillway tunnels are strengthened with the reinforced concrete lining of the hat section. The design speed of water discharge is 22 metres per second, the tunnels have free-flow mode of operation.
Five-stage drop consists of 5 disperse wells, 100 metres wide and with the length from 55 to 167 metres, divided by the dams. The drop secures the dispersion of the floe energy and its smooth fusion with the river corridor. The maximum speed of the current at the entrance reaches30 metres per second in the first well, at the exit to the river it becomes slower – 4-5 metres per second.
Tailrace canal is 100 metres wide and 700 metres long (axis length) serves for the fusion of the flow and the river.
The sluiceway tunnels with the section of 10×12 metres are strengthened by the cast-in-place concrete shell 0.6-1.2 metres wide. Additional strengthening concreting work is performed for the exit and entrance and where tectonic issues are possible.
The wells drainage protects from the ground waters where it is necessary. The downstream portals of the tunnels are covered with the protective shields during the wintertime. The junction well of the shore spillway is protected with the supporting walls. The drainage gallery is in the basement of the dams, the dams’ bodies have gallery with the section 3х4 metres for air supply for the placement of the aerating pipes and equipment.
The dam #3 has the larger transport gallery (6х6, 25 metres) for the organization of the acting passage to the grand complex of the station.
The soils under the five-stage drop are quite strong for the concrete structures above. The additional reliability is secured with the strengthening concrete work at the base of the dams, drainage work near the rocks at the base of the slabs of the hydraulic stilling basins and supporting walls. The basement and side walls of the structure are attached to the basement by metal anchors.
All the elements of the spillway are made of the hydraulic concrete of the following classes: В20, В25 and В30. The design requires resistance to frost and waterproofing of the concrete. The structures have the remote and geodetic monitoring and measuring equipment. All the deformations and shifts can be measured with this equipment. All together there are 308 control points planned in the design.
One of the most important part of any hydraulic structure, defining the safeness for people living down the river, is the waterfront with its structures. Usually it is a dam. The mountain with the height of 1,174 metres and more than 1,000 metres width is the dam for the shoe spillway of the Sayano-Shushenskaya HPP, the water sluiceway entrance is located there. It is not possible to destroy the million years old mountain quickly. So the possibility of the catastrophic destruction of the water front is non-existent and the safety of the shore spillway is secured.
Relatively small backwater effect (14 metres) at the sluiceway entrance is created by the designed level of the spillway, which also raises the safety of the shore spillway of the Sayano-Shushenskaya HPP. At the waterways of the sluiceway entrance the emergency gate opening is installed along with the regular gate.
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