RU2498007C1 - Reserve spillway of earth dam - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: reserve spillway of an earth dam represents an artificial outlet of trapezoidal section arranged in a dam crest, with depth to the elevation of the rated level of water overflow, in the bed of which there is a protective coating from a polymer material in the form of a geomembrane fixed in sumps at the side of the upper reach and on the edges of slopes with tightening weights. On the bottom slope of the dam along the width of the artificial outlet there is a conveyance tray that changes into a deflector part of the spillway. The bottom of the conveyance and deflector parts is made of a double cloth of the geomembrane with non-matching holes designed for free discharge of the filtration flow. Walls of the conveyance tray and the deflector part and dampers of energy of the water flow are shaped from flexible shells filled with sand. The double cloth of the geomembrane is fixed to the protective coating of the artificial outlet with arrangement of a welding seam.

EFFECT: invention provides for safe passing of emergency high water preventing damage of a dam and flooding of below territory, to avoid environmental and material damage.

2 cl, 5 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 a soil dam.

There is a known spillway of emergency floods for dams and structures of a similar type (RU Patent No. 2080433, ЕВВ 9/04, published 05.27.1997), including two spillways, one of which is designed to discharge floods with small or medium discharges, and the second is equipped with it ridge barrier element, and the crest of the second spillway is located below the catastrophic retaining level, and the partition element has a height greater than the difference between the level of the crest of the spillway and the catastrophic retaining level.

The disadvantage of this method is that during the operation of such a spillway, damage and deformation are possible when the unit overturns, its destruction. The creation of such a spillway provides for its construction before the start of the dam operation. When floods pass through the spillway, erosion of the lower slope of the dam can be observed, which can cause the destruction of the dam itself.

A known spillway of a retaining structure is known (RU Patent No. 2071527, ЕВВ 9/04, published January 10, 1997), including a washable insert made in the form of a soil dam with a crest mark below the crest mark of a retaining structure and enclosed on the sides and from below in clothes made of indelible material , the ridge of the soil dam is provided with a spillway wall of a zigzag shape and is watertightly connected to the soil dam, the mark of the ridge of the spillway wall is located above the mark of the ridge of the soil dam, but below the mark g guys retaining structure.

The disadvantage of this method is the difficulty in performing and the lack of effectiveness of the operation of the backup spillway due to erosion of the insert in the body of the dam and the need for washing and tipping.

A device for protecting slopes of hydraulic structures from erosion (SU, AS No. 1409720, EV 3/16, BI No. 26 of 07/15/08), consisting of ring-shaped elements and a film antifiltration element in the form of flexible strips of film, laid in the underlying soil layer, is known.

The disadvantage is that this method is time-consuming, fastening from ring-shaped elements can lead to undesirable destruction of slopes during long-term operation, which will reduce the safety of this structure.

Known overflow soil dam (SU, AC No. 968150, ЕВВ 7/06, BI No. 32 of 10.23.82), including the protective fastening of slopes, consisting of wedge-shaped plates laid with increasing thickness down the slope.

The disadvantage of this technical solution is the possible creep of the reinforced concrete structure due to subsidence and heaving of the soil, low deformability, complexity of the structure and the high cost of the spillway as a whole.

The closest technical solution is a hydraulic structure (SU, АС No. 1070262, ЕВВ 7/06, BI No. 4 dated 01/30/84), which serves to increase the reliability of work by reducing the dynamic impact on the slope of the structure from the overflow stream consisting of half-layered film strips coverings forming closed inflatable impermeable shells, divided into compartments.

The disadvantage of this solution is that in case of emergency floods exceeding the calculated one, the strip of film coating can be washed with a stream of water or under the influence of a filtration stream through the body of the dam. During prolonged use, inflatable airtight shells can deflate when damaged or worn due to their own friction against each other, which will reduce the safety of the structure. Another drawback of the design is that the dam crest itself remains unprotected, as a result of which overflow will erode and destroy the entire dam.

The essence of the invention is the creation of a backup spillway to pass an unplanned emergency flood.

EFFECT: safe passage of an emergency flood preventing the 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 device of an open backup spillway in the crest of an earthen dam, in the form of an artificial cut-out 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 by weights, while the culvert and waterway part of the reserve spillway located on 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 openings (for drainage of the filtration stream) laid on the lower slope welded to the protective coating of the proran and loaded along the edges with soft shells filled with sand forming the walls of the culvert, as well as water elements (to quench the flow energy and prevent erosion in the downstream).

The reserve spillway is designed to pass an emergency flood and prevent dam destruction due to overflow of water over the ridge, it is recommended for use as a reserve or main, if there is none, on class IV earth dams and is designed to operate from the level of water overflow - UPW and to reach the maximum level water - max HC, while part of the flood is passed through the main spillway (coastal or mine).

The reserve spillway of the soil dam for passing the flood through its crest is as follows. Near the coastal abutment of the existing soil dam, an artificial trapezoidal section of the trapezoidal section with a depth of up to the mark of the level of overflow of water is determined by the formula:

UPV = NPU + a ,

where a = 0.3-0.5 m - stock for overflow of water.

The dimensions of the artificial aperture are determined on the basis of ensuring that the maximum estimated discharge rate for floods or floods is greater than the estimated availability for the verification case of 0.5-1% probability, and are calculated using formulas to determine the required dimensions of the penetration depending on the expected flood discharge. The calculation formula for determining the required width of the artificial pro-trapezoidal section is as follows:

;

;

where c is the width of the bottom hole, m;

Q _ΔP% = Q _Pmax -Q _P% - the excess of the maximum flood discharge over the design flow of the estimated supply R% = 0.5-1%;

m = 0.32-0.38 - flow coefficient;

m ₀ - coefficient of laying of the slopes of the proran;

H is the depth of water in the gap equal to the difference between the marks of the dam crest and the water level in the reservoir, corresponding to the NPU, m;

- напор в проране с учетом скорости подхода, м;

- pressure in the gap, taking into account the speed of approach, m;

where V ₀ is the speed of the approach of the flow to the proran, m / s;

α is the Coriolis coefficient.

From the side of the uphill slope, an excavator arranges a recess for laying a load, fixing the protective coating of the artificial proran. Soil, taken out of artificial proran, is moved by mechanisms to a dump in the coastal zone. Then, on a special technological site, polymer material is laid out in rolls in the form of a waterproof geomembrane with a thickness of 1 to 2.5 mm, made in accordance with the requirements of GOST (Polyethylene film. Technical conditions. (GOST 10354-82) [Appendix 2]) and make its cutting and welding with allowance for mounting runs. The made one-piece sheet of the protective coating from the geomembrane is manually laid out freely on the bottom and slopes of the artificial proran. From the upstream side, a load in the form of box gabions (GOST R 52132-2003) or mattresses made of woven geotextiles (TU 2290-001-27-225810-05) filled with stone material is laid on the geomembrane in the recess with a truck crane. Similarly perform the fastening of the protective coating on the slopes of artificial proran.

Next, a two-layer cloth is prepared at the technological site, forming the bottom of the culvert and the water part, which is manually laid on the lower slope of the dam and connected to the protective coating of the artificial pro-hole by welding (for example, the PST-2 extruder). A geomembrane with holes is made in a production environment and delivered to the construction site by road. In this case, the two-layer cloth is made of two geomembrane cloths with the placement of mismatched holes of 2-3 cm in size at a distance L = 0.5-1.0 m, in a checkerboard pattern, designed for free removal of the filtration stream. Then form the side walls of the culvert, with a height of 0.5-0.7 m, and a water hole, with a height of 0.8-1.0 m, from soft shells (TU 2248-008-78145892-08), with a diameter of 0.7-1 , 0 m and a length of 3-5 m, made of a polymeric material similar to the material of a geomembrane filled with sand. Soft shells are made under production conditions and transported by road to the construction site, where they are filled with sand, sealed and laid with a truck crane along the edges of the double cloth, loading and fixing it on the slope.

To extinguish the flow energy in the downstream, a flexible water fastening is arranged with water flow energy absorbers in the form of two or three rows of flexible shells made similar to shells forming the walls of the culvert. Each row of shells is arranged at a distance equal to the length of the jump L _Ave. , determined, for example, according to the formula of N.N. Pavlovsky (Pavlovsky N.N. Collected Works, i.e. I. P1 publishing house of the USSR Academy of Sciences, 1956.). The height of the dampers is determined by calculation from the conditions of flooding of a hydraulic jump.

If the crest of the earthen dam has a carriageway, then after completion of the backup spillway device, a removable bridge is mounted, which, in case of a flood threat, is moved to a safe area.

The invention is illustrated by figures 1-5: Figure 1 - Scheme of the backup spillway of the soil dam. View from above; Figure 2 - Scheme of the backup spillway of the soil dam. Section AA; Figure 3 - Scheme of the backup spillway of the soil dam. Section BB; Figure 4 - Diagram of the spillway tray of the soil dam. Section B-B; Figure 5 - Two-layer double coating of the tray - a geomembrane with mismatched holes. Node A.

The backup spillway is performed as follows: in the crest of the dam, an artificial pro-hole 1 (Fig. 1, 2) of trapezoidal section is formed, in the bed of which a protective coating from the geomembrane 2 (Figs. 1, 2, 4) is laid, loaded in the pits 3 from the upstream side and on the edge, with ghosts 4, for example box gabions or mattresses made of woven geotextile filled with stone material. Next, the water-supplying and water-bearing parts of the reserve spillway of the soil dam are formed made of a double cloth of the geomembrane 5 (Figs. 1-3, 5) forming the bottom, as well as flexible shells 6 of the material of the geomembrane filled with sand forming the walls of the culvert and the water-borne parts and the energy absorbers of the water flow 7 The double panel of the geomembrane 5 is attached to the protective coating of the proran 2, with the implementation of the weld 8.

The reserve spillway of the soil dam works as follows: when the water level rises in the upper pool of the reservoir and the level of water overflow reaches UPV (Fig. 1), the flow rushes into the bed of the artificial hole, and then into the culvert limited by walls 6 (Figs. 1-3) from flexible shells, after which in the waterway with absorbers 7 (Fig.1,2) it calms down. The filtration stream passing through the body of the soil dam is diverted to the culvert through the mismatched holes in the double cloth of the geomembrane 5 (Fig.3-5).

The use of a backup spillway will increase the safety of the soil dam under the threat of overflow over the ridge and carry out an additional discharge of a part of the emergency flood into the downstream. The protective coating of the bed of artificial pro-hole and the culvert from the geomembrane will increase the throughput of the pro-hole due to the small roughness of the material and protect the crest and downhill slope of the soil dam from erosion.

Claims (2)

1. The reserve spillway of the soil dam designed to allow emergency floods, made in the crest of the dam, having a protective film waterproof cover of the lower slope, characterized in that the artificial crest of the trapezoidal section is arranged in the crest of the dam, with a depth of up to the mark of the calculated level of overflow of water, in the bed of which a protective coating of polymeric material was laid in the form of a geomembrane fixed from the upstream side and on the edges of the slopes of artificial proran with weights, and on the bottom The spit of the dam, along the width of the artificial gap, is equipped with a water supply tray that passes into the waterway of the spillway, the bottom of which is made of a double geomembrane panel with mismatched holes designed to freely drain the filtration stream welded to the protective coating of the artificial gap, and the walls and absorbers of the energy of the water stream formed from flexible shells filled with sand. 2. The spillway according to claim 1, characterized in that the dimensions of the artificial aperture in the dam body are determined by hydraulic calculation based on the possibility of passing a flood discharge through it, exceeding the estimated spillway coverage; The calculation formula for determining the necessary width of the artificial pro-trapezoidal section is:

where b is the width of the bottom hole, m;
Q _ΔP% = Q _Pmax -Q _P% - the excess of the maximum flood discharge over the design flow of the estimated supply R% = 0.5-1%;
m = 0.32-0.38 - flow coefficient;
m ₀ - coefficient of laying of the slopes of the proran;
H is the depth of water in the gap, equal to the difference between the marks of the dam crest and the water level in the reservoir, corresponding to the NPU, m;

- pressure in the gap, taking into account the speed of approach, m;
V ₀ is the speed of the approach of the flow to the proran, m / s;
α is the Coriolis coefficient.

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