RU2639047C1 - Reserve spillway for earth dams - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: reserve spillway 2 for earth dams with a washable earth insert is arranged in the dam at the ASL elevation. Reserve spillway 2 consists of a surface that fixes erosion, which can be rectangular or as a trapezoid, and the material can be concrete or asphalt. The water lines are located inside the eroded soil insert, the lower part of which is located at the highest water level elevation, and the outlet is at the elevation, depending on the water channel slope. Water channels serve for initial erosion of the underlying soil. Sand is used as the soil for the eroded soil insert. The technique of calculating the reserve spillway with a washable soil insert at the level of the ASL elevation.

EFFECT: increased reliability of the reserve spillway by secure pass of emergency spillway flood, preventing dam destruction and flooding the underlying territory to avoid environmental and property damage.

3 cl, 2 dwg

Description

The invention relates to the field of hydraulic engineering and can be used to ensure safe passage of emergency flood discharge in the face of the threat of overflow of water through the crest of the earth dam if there is a main spillway in the hydraulic structure.

Known eroded soil reserve spillway dam (RU 2011736, 04/30/1994), including upstream and downstream prisms with slopes, a combined antifiltration device, containing an insert made of material inclined toward the downstream with a coefficient of friction different from the coefficient of friction of the downstream prism soil.

The disadvantage of the above device is that the effectiveness of the backup spillway will depend on the creep of the bottom prism along an inclined sand insert along a synthetic film. However, the shift of the lower prism will occur under the influence of hydrostatic pressure and filtration forces within the lower prism. Since the movement of the filtration flow in the soil mass occurs very slowly, and the friction forces along the shear surface decrease slightly, the creep of the bottom prism will occur for a long period. As a result, the collapse of the dam crest will also be slowed down, which ultimately reduces the erosion efficiency of the soil dam of the spillway. In addition, an anti-filter device in the form of a screen will prevent erosion of the soil dam of the backup spillway, as a result of which the throughput will decrease, which in turn will reduce the efficiency and, consequently, the safety of the structure.

Known reserve spillway of a retaining structure (RU 2071527, 01/10/1997), including a washable insert made in the form of a soil dam with a crest mark below the mark of the crest of a retaining structure and enclosed on the sides and from below in clothes made of indelible material, the crest of the soil dam is provided with a spill wall of a zigzag shape in terms of shape and watertightly coupled to the soil dam, and the mark of the crest of the spillway wall is located above the mark of the crest of the dirt dam, but below the mark of the crest of the retaining structure .

The disadvantage of this device is the difficulty in performing and the lack of effectiveness of the backup spillway due to erosion of the insert in the body of the dam, leaching and tipping.

A spillway structure is known (SU 1209754, 02/07/1986), including a washable soil insert laid on a concrete flute bet between concrete abutments.

The disadvantage of this solution is that when the soil insert is eroded, the reservoir completely empties to the concrete flute, which entails the flooding of the territories located in the downstream of the structure, and the absence of water flow damper in the downstream of the structure will erode the discharge channel.

Known reserve spillway of the soil dam (RU 2498007, 04/13/2012), which serves to pass an unplanned emergency flood that prevents the destruction of the dam and flooding the underlying territory in order to avoid environmental and material damage. The technical result is achieved due to the device of an open backup spillway in the crest of an earthen dam in the form of an artificial opening of a trapezoidal section with a protective coating of its bed with polymer material - a geomembrane, held from the upstream side and on the edge of the slopes with weights, while the culvert and waterway parts of the backup spillway are located from the downstream side along the width of the artificial hole, made of a two-layer polymer material in the form of a geomembrane having mismatched tverstiya (for removal of seepage) stacked on the lower slope is welded to the protective coating and the closure channel at the edges prigruzhennye soft shells, filled with sand, forming the wall of pipe tray, as well as energy dissipating elements (quench stream energy and prevent erosion downstream).

A disadvantage of the known technical solution is that it requires large labor resources due to the complexity of the design (laying of a geomembrane, creation of soft shells filled with sand, their fastening, construction of a bridge crossing, an approximate determination of flow rate (flow rate m = 0.32 ÷ 0, 38)), the high cost of its construction.

The prototype of the proposed technical solution is the backup spillway of an underground retaining structure (options) (RU 2573328, 01.20.2016). The technical result according to the first embodiment is achieved by means of a backup spillway device in the body of an underground retaining structure (for example, a dam or dam) in the form of a trapezoidal prism from an easily destructible soil insert, protected from the upstream side by a geomembrane spillway located between the protective soil layer from the side uphill slope and an insert located in a bed of waterproof polymeric material - a geomembrane, which is mounted on the uphill slope and the edges of the slopes of the gap on using reinforced concrete slabs.

The disadvantage of the technical solution adopted for the prototype, according to the first option, is that it requires large labor resources due to the complexity of the design (laying of geomembranes, plates, their fastening, construction of a bridge crossing), the high cost of its construction. In addition, it is not clear why to find the height of the eroded insert, because it is known and cannot be lower than the mark of NPU. The minimum volume of water for water users is also known. It is limited to the mark of NPU and UMO. As the soil of the eroded insert, soil similar to the body of the dam is taken, but this cannot be done (the soil of the body of the dam may be clay, loam). The disadvantages include the fact that it is located not in the board, but in the body of the dam and therefore requires powerful fastening of the transient and output parts of the structure.

The technical result of the prototype according to the second embodiment is achieved by arranging several eroded soil inserts in the form of sections, which are a dam or dam with a lower elevation than the retaining structure, characterized in that each eroded insert is made in the form of a trapezoidal prism located in the water supply parts of the reserve spillway, where, along the entire perimeter of the bed, as well as on the upper and lower slopes, a protective coating of polymer geomembrane is arranged, which is filled during the construction period with soil similar to the body of the dam, in order to increase the efficiency of erosion of eroded inserts for several sections of the spillway, the top mark of eroded inserts is set: for the first section - at the FPU mark, for the second - at the mark (FPU - 0.5 m), for the third - at the mark (FPU - 1.0 m) and so on, ensuring the sequential inclusion of the last section, then the penultimate and so on.

The disadvantages of this technical solution adopted for the prototype according to the second option is that it has the features of the first option, and most importantly, no one will build several backup spillways for a structure that may not work at all during the operation (1% flood security for class IV dams can be repeated 1 time per 100 years, and their service life is 50 years), in addition, the cost of construction increases due to the construction of the side walls of each spillway.

The objective of the invention is to develop a backup spillway for soil dams when missing an unplanned emergency flood, which does not allow the destruction of the dam and flooding of the underlying territory in order to avoid environmental and material damage.

The technical result of the invention is to increase the reliability of the backup spillway by safely allowing emergency floods to prevent destruction of the dam and flooding of the underlying territory in order to avoid environmental and material damage.

The technical result is achieved due to the backup spillway with eroded soil insert in the dam at the level of the NPU. The backup spillway consists of a surface that fixes the erosion, which may be rectangular or in the form of a trapezoid, and the material may be concrete or asphalt. Water conduits are located inside the eroded soil insert, where the inlet part of the water conduits is located at the FPU mark and the outlet part is at the mark, depending on the slope of the water conduit. Water conduits serve for the initial erosion of the underlying soil. Sand is used as soil for the eroded soil insert.

The hydraulic calculation of the backup spillway with eroded soil insert at the mark of the NPU is carried out in the following sequence.

First, we determine the flow rate passed by the backup spillway:

where Q _rez - reserve spillway discharge, m ³ / s;

Q _1% - calibration consumption of 1% of security, m ³ / s;

Q _water - the flow rate of the spillway, m ³ / s.

Then, the dimensions of the backup spillway are determined depending on the shape according to the form of the spillway with a wide threshold. At the same time, the depth at the threshold of the spillway is known, it should be less than the difference between the elevation of the dam crest and the elevation mark. The width for the backup spillway of a rectangular shape is determined by the formula:

where m is the flow coefficient;

g is the acceleration of gravity, m ² / s;

N - pressure on the threshold of the spillway, m

The width of the spillway of the trapezoidal shape is determined by the formula:

where m ₀ is the slope of the erosion insert.

In order for the sand to erode in the water conduit, it needs to be given an appropriate slope. To do this, you can use the formulas for washing the sump chambers [Hydrotechnical facilities. Designer reference: under the general. ed. V.P. Nedrigi. - M .: Stroyizdat, 1983. - 543 p.]:

where V _CR - sediment washing rate, m / s;

C - Shezy coefficient, m ^0.5 / s;

R is the hydraulic radius, m

The Shezy coefficient is calculated by the formula:

where n is the roughness coefficient, n = 0.0275.

The washing speed is determined by the formula:

where ϖ is the hydraulic size of the particles to be washed with a diameter of d, smaller than which this mixture contains 75%, m / s;

h _CR - washing depth in the water conduit, it will increase with increasing level, m;

d is the average diameter of the washed fractions, m;

p is the percentage (by weight) of sediment in the wash stream, taken from 2% to 8%.

The duration of flushing the backup spillway can be determined by the formula [Hydrotechnical facilities. Designer reference: under the general. ed. V.P. Nedrigi. - M .: Stroyizdat, 1983. - 543 p.]:

where ρ _ex - the soil density of the eroded insert, t / m ³ ;

W is the volume of soil in the eroded insert, m ³ ;

q _CR - specific washing flow, m ² / s per 1 running. m;

In - the width of the backup spillway, m

The specific wash rate is determined by the formula:

where N _pr - the depth at the threshold of the backup spillway, m

The calculation must be carried out in layers, as the water level above the eroded soil will increase.

The invention is illustrated in FIG. 1, 2: FIG. 1 is a diagram of a longitudinal section of a soil dam; FIG. 2 - reserve spillway in the dam body.

The reserve spillway for soil dams may be located on board the dam or bypassing the coastal slope and consists of: dam crest 1; backup spillway 2; main spillway 3; erosion fixing surface; 4; water conduits 5; sand 6; conduit cavities 7.

There is a backup spillway for soil dams as follows. At maximum flood, when the main spillway 3 does not provide the required throughput and the water level exceeds the forced retaining level, water begins to flow into the cavity of the water conduits 7 and begins to erode sand 6 under the water conduits. Water conduits 5 begin to sink, and with them the crest of dam 1 also settles in reserve spillway 2, and there comes a moment when water begins to overflow through the settled crest 1 and erode the insert to the mark of the NPU of the backup spillway 2.

Claims (3)

1. A backup spillway for soil dams, including a soil erosion insert, characterized in that it is located on the dam at the NPU mark, consisting of a surface that fixes the erosion, and water conduits that serve for the initial erosion of the underlying soil, which are located inside the erosion soil insert, where the inlet is located at the FPU mark, and the outlet is at the mark depending on the slope of the water conduit. 2. The backup spillway for soil dams according to claim 1, characterized in that the erosion-fixing surface is made of concrete or asphalt and, accordingly, has a rectangular or trapezoid shape. 3. The backup spillway for soil dams according to claim 1, characterized in that sand is used as the material for the eroded soil insert.

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