CN114855709A

CN114855709A - Combined dam and relieving pressure method

Info

Publication number: CN114855709A
Application number: CN202210573623.2A
Authority: CN
Inventors: 张征骥
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-07-08
Filing date: 2022-05-25
Publication date: 2022-08-05
Also published as: EP4116497A1

Abstract

The combined dam comprises a main dam, a relieving dam and a relieving lake and can be used for relieving the loading condition of the main dam. The pressure relieving dam is lower than the main dam and forms a pressure relieving lake together with the main dam. By relieving the hydrostatic pressure in the lake on the main dam, the high head pressure on the lake side in the main dam is partially counteracted, so that the stress load of the main dam is reduced, and the pressure relieving effect is achieved. The method can be used for the existing dam needing to be repaired, and can also be used for building a new high-head dam.

Description

Combined dam and relieving pressure method

Technical Field

The invention relates to the construction of new dams and the repair and reinforcement of existing dams, in particular to a hydropower station combined dam and a method for reducing the load on the hydropower station dam.

Background

A dam or barrage is typically (but not exclusively) part of a hydroelectric power station reservoir.

Dams can be constructed in different ways. Gravity dams, arch dams, buttress dams, and the like are well known.

After the existing dam is used for a long time from decades to hundreds of years, the original dam structure needs to be repaired or even rebuilt. A complete restoration often results in a power station outage of months or even years, resulting in a large operational loss. The emptying of the reservoir and the resulting lack of water supply capacity also causes problems in water management in the area.

In practice, various different repair methods have been available. For example, in the case of leaks in the bottom area, a support structure with a sealed pressure-resistant space can be added outside the dam in connection with the leak (leak stoppage).

In another case, a new dam is built downstream of the existing dam as a complete replacement. After the new dam is built, the original dam is submerged or removed. Other repair or new construction techniques are also known.

Generally, whether the old dam is completely repaired or a comprehensive replacement mode is adopted, the obvious defects are that the engineering is complex, the investment is large and the period is long.

Disclosure of Invention

In order to overcome the above-mentioned disadvantages of the prior art, the present invention provides a combined dam and relieving pressure method, which can be used as an alternative to the repair of existing dams and is also suitable for the construction of new dams. The method has the characteristics of simple technology, economy, reasonableness and effectiveness, and can be implemented particularly under the condition of not emptying the water stored in the reservoir.

In order to achieve the purpose, the invention adopts the technical scheme that:

the combined dam comprises a main dam and a pressure relieving dam, wherein the pressure relieving dam is built at the downstream of the main dam, the height of the pressure relieving dam is lower than that of the main dam, a pressure relieving lake is formed between the main dam and the pressure relieving dam, and the pressure relieving lake reversely acts on the main dam by static water pressure, so that the hydrostatic pressure applied to the main dam is reduced.

That is, a relief dam is constructed downstream of the main dam (existing dam or newly constructed dam) to be lower in height than the main dam. Thereby forming a relieving lake between the main dam and the relieving dam. The purpose of relieving the load of the main dam is achieved by using reverse water pressure.

As an alternative to the repair of existing dams, the present invention provides a method of constructing a relieving dam downstream of the main dam at a height lower than the main dam, thereby forming a relieving lake between the main dam and the relieving dam.

The invention also relates to a novel combined dam which comprises a main dam, a relieving dam lower than the main dam downstream of the main dam and a relieving lake formed between the two dams, so that the aim of effectively reducing the resultant pressure on the main dam is fulfilled.

The water storage level of the lake is released and pressed between the foundation surface of the main dam and the high water level of the upstream reservoir. The pressure applied on the main dam by the high-level water in the upstream reservoir is partially counteracted by the reverse pressure in the lake, and the aim of relieving the stress on the main dam is fulfilled. Thus, repair of existing primary dams can be replaced by relieving pressure through the novel combination. As for the gravity dam, the cross section of the gravity dam is increased downwards, so that the water pressure in the lake is relieved, and meanwhile, a downward pressure is generated on the gravity dam, and the bearing capacity of the gravity dam is additionally enhanced.

The positive effects and the pressure relieving effects of the pressure relieving dam and the pressure relieving lake can be calculated according to the following method:

to quantitatively evaluate the relieving effect of the main dam, it is assumed that the widths B of the main dam and the relieving dam from the bottom to the top are kept constant. Hydrostatic pressure in upstream and downstream relieving lakes increases linearly with water depth.

When the water level of the upstream reservoir reaches (theoretically) maximum value H, the stress of the main dam is (average pressure)

)

The degree of relieving pressure on the main dam depends only on the water storage level of the relieving lake. When the maximum water level of the relieving lake is equal to the height h of the relieving dam, the relieving effect is calculated as follows:

eventually, the resultant force (water pressure) acting on the main dam is reduced to

The relieving effect can be expressed by relieving degree:

when H/H is 0.5, the relaxation pressure is expected to be 25%. This degree of relief is considerable for a dam that is still in operation and is therefore of great significance. When H/H is 0.7, the main dam relief is more than 50%.

Usually, the lake water is released to have a free surface. This makes the composite dam particularly simple in structure, thereby effectively reducing construction costs. Optionally, the relieving lake may be closed. It should be noted that there is no rigid connection between the primary dam and the relief dam to prevent direct transfer of primary dam pressure to the relief dam.

Preferably, the height of the relieving dam is established to be between 30% and 95% of the height of the main dam. Particularly between 35% and 60%, there is both the best relief effect and the natural coordination of the heights of the two dams. Optionally, the height of the relieving dam may be less than 30% of the height of the main dam. And the water level in the relieving lake is below the highest water level of the reservoir of the main dam, and the height difference is at least 5% of the height of the main dam.

The above preference may also be expressed as the height of the relieving dam being established between 30% and 95% of the height of the main dam. The height of the main dam is calculated from the lowest ground point on one side of the main dam reservoir. Optionally, the height of the relieving dam may be less than 30% of the height of the main dam.

The above-mentioned preference can be expressed as relieving the dam crest of the dam lower than the main dam crest, and the difference in height is at least 5% or more of the height of the main dam.

As a preference, the above-mentioned relieving scheme is applied to relieving of the existing main dam, so as to replace the complex repairing work and achieve the purpose of prolonging the service life thereof. Preferably, the above-described relieving schemes are also used in new dam construction projects, i.e. a combined dam (primary dam plus relieving dam) is used instead of a single dam. This means that the design and construction of the dam can be more economically rational from the beginning because of the relieving effect. In addition, two or more relieving dams can be constructed. In particular, it is theoretically possible to construct the relief dams in a stepped manner, i.e. each subsequent relief dam downstream is lower than the preceding one. It does not matter whether the main dam or the relieving dam is designed as a gravity dam, an arch dam or a buttress dam. The relieving scheme is applicable to any type of primary dam and relieving dam.

Preferably, at least one calibration point is provided on each of the main dam and the relieving dam for monitoring and/or periodically measuring the change in shape of the main dam and/or the relieving dam and/or the relative displacement between the main dam and the relieving dam. As an option, the calibration points may also be omitted.

As a preference, at least one intermediate layer can be added to the relieving lake. For example to form an open swimming pool or similar aquatic casino. The intermediate layer may be fully secured on only one side, such as the primary dam side or the relief dam side, to ensure that the primary dam and the relief dam are not rigidly connected to prevent tension or compression.

The relieving lake between the main dam and the relieving dam can have a variety of different uses. For example, it can be used to build water recreation facilities, sports facilities, open swimming pools, and fish farming and fishing. In addition, the relieving lake can also be used as a stilling pool (also called as a water falling pool) for flood discharge. Other applications are also known to the engineer skilled in the art. As an option, the lake is relaxed or made without any other use.

As a preference, the number of the relieving dams is multiple, and the height of each relieving dam is reduced in a gradient manner along the direction away from the main dam, so that a lake is formed between the adjacent relieving dams.

Corresponding main dam relieving method, namely, constructing a relieving dam at the downstream of the main dam, wherein the height of the relieving dam is lower than that of the main dam, water is injected between the main dam and the relieving dam to form a relieving lake, and the relieving lake reversely acts on the main dam by static water pressure, thereby relieving the main dam.

The main dam is an existing main dam needing to be repaired or a newly built main dam.

Compared with the prior art, the high-head pressure on the lake side in the main dam is partially counteracted by relieving the hydrostatic pressure in the lake on the main dam, so that the stress load of the main dam is reduced, the load condition of the main dam is relieved, and the pressure relieving effect is achieved. The method can be used for the existing dam needing to be repaired, can also be used for building a high-head dam, and can be constructed without emptying the stored water of the reservoir.

Drawings

FIG. 1 is a schematic cross-sectional view of a gravity dam and a stress situation.

FIG. 2 is a schematic cross-sectional view of a gravity dam and its alternative arched dam (example).

Fig. 3 is a schematic cross-sectional view of a gravity dam, a relieving dam and a relieving lake.

FIG. 4 is a schematic cross-sectional view of a gravity dam and resultant pressure distribution.

Figure 5 is a schematic cross-sectional view of a gravity dam with static pressure distribution and additional gravity induced by relieving lake water pressure.

Figure 6 is an elevation view of the relief dam.

Fig. 7 is a schematic cross-sectional view (reverse example) of a gravity dam in which the building material is used to reinforce the main dam instead of constructing the relieving dam.

Fig. 8 is a schematic view of the interlayer laid in fig. 3, including relieving the lake interlayer and the calibration points.

Detailed Description

The embodiments of the present invention will be described in detail below with reference to the drawings and examples. From the following detailed description, it will be seen that the present invention is one advantageous embodiment, having the beneficial combination of features.

The primary dam 1 shown in fig. 1 is a gravity dam. Since it has been in use for decades to hundreds of years, refurbishment is required. The hydrostatic pressure 3 is shown in the corresponding region upstream of the main dam 1. The restoration requires emptying the reservoir 2 and shutting down the plant for months to years, thus causing significant operational losses. In some cases one chooses to build an alternative dam 4 according to the solution of figure 2. In this case, the old main dam 1 is completely replaced with the replacement dam 4 of the same height. The old main dam 1 is usually left in place and then submerged. In the case of the old main dam 1 enjoying the cultural heritage protection, its alternatives entail a resistance in the pertinent sector. In the case of fig. 2, which completely replaces the existing main dam, the relieving pressure of the main dam is 100% (this is not necessary).

Also, in case the existing main dam 1 needs to be repaired, the construction of the substitute dam 4 is generally expensive and will take many years.

In order to save construction costs and time, in particular without causing interruption of the power production, the combined dam structure scheme is adopted, and the existing dam to be repaired, referred to as the main dam 1, achieves the effects of reinforcement and relieving pressure at the same time with low construction cost. As shown in fig. 3, instead of constructing an alternate dam 4 having the same height as the main dam 1, a relief dam 5 having a lower height than the main dam 1 is constructed downstream of the main dam 1. The minimum distance between the relieving dam 5 and the main dam 1 may be as small as desired (e.g., as low as 0.1 m). The upper limit distance is not limited and mainly depends on the geographical position of the valley and the construction cost.

The space between the main dam 1 and the relieving dam 5 stores water to form a relieving lake 6 under atmospheric pressure. The water level of the lake 6 can be changed. Generally, the set water level remains unchanged. For some applications, a certain amount of temporary or continuous inflow and outflow of the lake 6 is allowed.

The relieving lake 6 has a free surface and acts on the main dam 1 in a reverse direction of static water pressure, so that the hydrostatic pressure resultant force applied to the main dam 1 is reduced,

the main dam 1, the relieving dam 5 and the relieving lake 6 form a combined dam 13 with the relieving effect. The main dam 1 may be a gravity dam, an arch dam or other form of dam. In particular, the main dam 1 may also be a new or proposed dam.

The water level of the relieving lake 6 determines the relieving effect of the main dam 1 (see above). Hydrostatic pressure 7 in the relieving lake 6 partially counterbalances hydrostatic pressure 3 in the corresponding region upstream of the main dam 1, thereby reducing the total pressure 8 carried by the main dam 1, see fig. 4. This is the most relieving effect, since the maximum load of the main dam 1 is always located in the dam base area.

Relieving the water pressure in the lake 6 while generating downward pressure. This allows the main dam 1 under consideration to be additionally reinforced by acquiring additional gravitational forces 9 (fig. 5). The relieving effect and the additional reinforcement of the main dam 1 depend on the water storage level of the relieving lake 6. For example, the main dam 1 of fig. 5 is reinforced by the additional gravity 9 of the water. The degree of reinforcement is also related to the inclination of the outer wall of the main dam 1.

The relief of 20-30% is significant for a main dam 1 that is still in operation. Even if the old main dam 1 is conventionally completely restored, it will not be as strong or will only be able to achieve the same effect as the described relieving means in special cases.

The reinforcing and pressure relieving effects of the pressure relieving dam 5 and the pressure relieving lake 6 on the main dam 1 are only dependent on the water storage level of the pressure relieving lake 6. They are independent of the impoundment of the relieving lake 6 and therefore of the distance between the relieving dam 5 and the main dam 1. In theory, the relieving dam 5 can be constructed as close as possible to the main dam 1 as long as the two dams are separated by the relieving dam 6.

The thickness of the relieving dam can be small due to the relatively low relieving dam 5 and the relatively small hydrostatic pressure exerted on it by the relieving lake 6 (fig. 3 and 5). At the same time, because of the smaller width of the lower part of the valley (fig. 6), a large amount of building material (stone, concrete) can be saved overall. Depending on the height of the relieving dam 5, the amount of construction of the relieving dam 5 can be reduced from 1/2 to 1/8 in place of the amount of construction of the dam 4.

It should be noted that the stiffening and relieving of the main dam 1 by the relieving dam 5 and the relieving lake 6 is much more effective than the simple addition of equal building material 5a to the existing gravity dam (fig. 7). The situation in fig. 7 corresponds to a mechanical support or reinforcement rather than a hydraulic relief to the main dam 1.

If the main dam 1 is a cultural relic dam which is classified as 'worth protecting' by government authorities, the main dam disappears because of not being submerged, and therefore is automatically protected.

With respect to the newly constructed main dam 1, and regardless of the dam type (gravity dam, arch dam, etc.), if the relief dam 5 is also constructed to constitute a composite dam 13, the thickness of the main dam 1 can be reduced accordingly, thereby reducing the total amount of construction materials. In addition, the construction of the dam 5 is relieved, and based on the latest dam construction technology, the safety of people can be greatly improved (the people do not directly face to a vertical dam with the height of one hundred meters or even hundreds of meters).

At the same time, the lake 6 can be constructed as an amusement facility like an open-air swimming pool. To ensure safety, an intermediate layer 10, such as a floor, may be laid, as shown in fig. 8.

The plant is operated, still taking water from the upstream reservoir 2. If faced with a primary dam 1 that needs to be repaired, the existing piping system is retained and continues to be used. The water in the lake 6 is released downstream and is not typically used for power generation.

The importance of the combination of the relieving dam 5 and the relieving lake 6 is that it can achieve 25% to 90% relieving of the main dam (see above).

The combined dam 13 is composed of a main dam 1, relieving dams 5 and relieving lakes 6, wherein the main dam 1 is often an old dam and needs to be repaired. Thus, as a particular option, a composite dam solution may be used instead of a repair solution.

As a preference, the relieving dam 5 downstream of the main dam 1 may have any dam shape and thickness (wall thickness). Wherein the main dams include various types of dams, barrages, and reservoir dams.

The height of the relieving dam 5 is preferably 30% to at most 95% of the height of the main dam 1. Wherein the height of both dams is measured from the lowest ground point 12 of the main dam 1 (fig. 3).

The top of the relieving dam 5 is lower than that of the main dam 1. The difference in height is preferably greater than 5% of the height of the main dam 1.

The relieving lake 6 between the main dam 1 and the relieving dam 5 can be fully or partially stored with a water level below the highest water level of the reservoir of the main dam with a height difference of at least 5% of the height of the main dam 1, and the top of the relieving dam 5 is located below the top of the main dam 1 with a height difference of at least 5% of the height of the main dam 1.

As a preference, all or part of the lake 6 is relieved of other special uses such as recreational facilities, swimming pools, water sports, fish farming and fishing. Water sources may also be provided for other uses.

Preference is also given to constructing one or more intermediate layers 10 in the relieving lake 6, the intermediate layers 10 being fixed to the main dam 1 or to the relieving dam 5 in the relieving lake 6 to ensure that no rigid connection between the main dam 1 and the relieving dam 5 occurs, avoiding tensile or compressive stresses.

Preferably, the combination dam 13 is provided with a plurality of calibration points 11 on each of the main dam 1 and the relieving dam 5 for monitoring and/or periodically checking the change in shape of the dams and/or the relative displacement between the dams.

The preference also includes that the number of the relieving dams 5 is multiple, the height of each relieving dam 5 is reduced in a gradient manner along the direction away from the main dam 1, and the relieving lakes 6 are formed between the adjacent relieving dams 5.

For the construction of the new main dam 1, it is also preferable to consider the combination dam 13 including the relieving dam 5 and the relieving lake 6.

In conclusion, the invention creates a method which is equivalent to the method for repairing the existing dam, and has more effectiveness and economic value. The method not only avoids the power station shutdown condition caused by reservoir emptying, but also saves a large amount of building materials and reduces the construction amount.

Claims

1. The combined dam is characterized by comprising a main dam (1) and a relieving dam (5), wherein the relieving dam (5) is built at the downstream of the main dam (1), the height of the relieving dam (5) is lower than that of the main dam (1), a relieving lake (6) is formed between the main dam (1) and the relieving dam (5), and the relieving lake (6) acts on the main dam (1) in a reverse direction of static water pressure, so that the resultant hydrostatic pressure on the main dam (1) is reduced.

2. The combined dam of claim 1, wherein said relief lake (6) has a free surface.

3. A combined dam according to claim 1 characterised in that said relief dam (5) is between 30% and 95% of the height of said main dam (1).

4. The combined dam according to claim 1, wherein the water level in the relieving lake (6) is below the highest water level of the reservoir of the main dam with a height difference of at least 5% of the height of the main dam (1), and the top of the relieving dam (5) is below the top of the main dam (1) with a height difference of at least 5% of the height of the main dam (1).

5. A combined dam according to claim 1, characterised in that the main dam (1) and the relieving dam (5) each comprise at least one calibration point (11) for monitoring and/or periodically measuring changes in shape of the main dam (1) and the relieving dam (5) and/or relative displacement between the two dams.

6. The assembled dam according to claim 1, characterized in that said relieving lake (6) comprises at least one intermediate layer (10), said intermediate layer (10) being fixed to the main dam (1) or to the relieving dam (5) in the relieving lake (6) to ensure that no rigid connection between the main dam (1) and the relieving dam (5) occurs, avoiding tensile or compressive forces.

7. The combined dam according to claim 1, characterized in that the number of said relieving dams (5) is plural, and the height of each relieving dam (5) is reduced in a gradient manner along the direction away from the main dam (1), and the relieving lakes (6) are formed between the adjacent relieving dams (5).

8. The main dam relieving method is characterized in that a relieving dam (5) is built downstream of the main dam (1), the height of the relieving dam (5) is lower than that of the main dam (1), water is injected between the main dam (1) and the relieving dam (5) to form a relieving lake (6), and the relieving lake (6) acts on the main dam (1) in a reverse direction by static water pressure, so that the main dam (1) is relieved.

9. Relieving pressure method according to a main dam according to claim 1, characterized in that said main dam (1) is an existing main dam to be repaired or a newly built main dam.