RU2474647C1 - Method of operating concrete curved gravity dam that creates freezing reservoir and has its top edge directed southward - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: proposed method consists in increasing intensity of heating top curved belt by winter solar rays by covering exposed ice surface in preset zone adjoining top curved belt edge with snow to up reflection of solar rays from reservoir winter surface. Curved belt top edge, above ice level in reservoir, is covered with the layer of dark material to up absorption of solar rays.

EFFECT: higher efficiency.

4 cl

Description

The invention relates to the field of hydraulic engineering and can be used in the operation of a concrete arch-gravity dam in severe climatic conditions if its upper face turns to the south.

The concrete arch-gravity dam has a curvilinear plan, and its stability and strength are ensured mainly by the action of its own weight and partly by the work of the dam as a vault with the transfer of load to the rocky shores - the sides of the gorge. Such a dam is a transitional type between a gravitational and arched dam, usually has a high height and limited distribution. In Russia, such an arch-gravity dam is, for example, part of the Sayano-Shushenskaya hydroelectric power station (hereinafter: SSHHPP).

When operating such an arch-gravity dam in a relatively wide gorge in the lower part of the upper (pressure) face in concrete cooled after the construction period, tensile stresses inevitably arise that exceed the safe (permissible) value. These stresses lead to unsystematic and dangerous opening of horizontal cracks on the upper edge of the dam, decompaction of rocks of the base under the upper technological column of the dam and opening of the rock-concrete contact, which necessitates very complex and insufficiently effective repair work. All this significantly reduces the reliability of the dam during its operation [1, p. 115-143].

There is a method according to which a dam is provided with an enclosing structure during operation, the heat-protective coating of which, together with the bottom face of the dam, forms a cavity heated by heating means, which encloses all turbine conduits and the spillway of the spillway and maintains a positive temperature at the bottom of the dam throughout the year. This creates an artificial climate close to the optimal regime for the entire bottom face of the dam, namely: the temperature in the cavity is always positive, and the cavity itself is protected from atmospheric precipitation. As a result, this thermal effect provides a targeted, additional relative to the existing compression of the concrete of the upper face of the dam and rocks at its base. The method is known from the source [2, the last two paragraphs], and an assessment of its effectiveness is given in the source [3].

However, the implementation of this method in full is associated with complex work and high costs.

The closest technical solution to the proposed one is the method according to which the reduction of tensile stresses in concrete at the upper edge of the dam and at its base is achieved by heat exposure by technical means on the body of the upper arch belt and on the surrounding rocks at the junctions of its heels. At the same time, warm air supplied to longitudinal galleries and drainage grooves and water heated by electric heaters in thermal wells are used as technical means [4].

The disadvantage of this known method is its insufficiently high efficiency due to the complexity of the work and the high cost of their implementation. Therefore, the method is advisable to use in combination with other simpler and less costly methods.

The problem to which the invention is directed is to increase the efficiency of the method of operating an arch-gravity dam, in which the temperature of the body of the upper arch belt of the dam is increased by means of simple and low-cost work.

This problem is solved by the fact that in the method of operating a concrete arch-gravity dam, which creates a freezing reservoir, and its upper face facing south, according to the invention, the intensity of heating the upper arch belt with winter sun rays is increased by covering the open surface of the ice with a layer of snow in a given strip adjacent to the edge of the upper arched belt. This layer of snow is necessary to increase the reflection of sunlight from the winter surface of the reservoir.

Additionally:

- ice is covered with snow by trapping snow on the ice surface;

- the top face of the arched belt above the ice level in the reservoir is covered with a layer of material that is dark in color and increases the absorption of sunlight by the arched belt;

- the edge of the arch belt is covered with a paint layer, which increases the absorption coefficient of sunlight to at least 0.8.

The ability of snow to reflect sunlight (radiant energy, radiation, light) is approximately two times higher than that of ice. The reflection coefficient of sunlight of snow can reach a value of 0.9 or more. The sun's rays falling on the snow in front of the upper edge of the dam are reflected and scattered, with some of them returning to space. However, a significant part of the reflected sunlight falls on the upper edge of the dam and is absorbed by it. As a result, the body of the dam, or rather its upper arched belt, is heated.

At present, at the SShHPP the crest of the dam exceeds the NPU by 8 m, and the ULR by 47 m. Therefore, the calculated level of the winter surface of the reservoir can be taken about 15-20 m below the crest of the dam, and the width of the snow-covered strip, respectively, about 45-60 m The ice is covered with snow by trapping it with temporary barriers, for example, with snow rolls fed from the crest of the dam by a snow blower.

In addition, it is advisable to cover the upper face of the arch belt of the dam above the calculated ice level in the reservoir with a layer of paint and varnish material (paint, enamel, varnish), which has a dark color and increases the absorption coefficient of sunlight to at least 0.8.

Under such conditions, in the case of reproduction of all claims, the currently existing heating of the upper arched zone from the side of its upper face by winter sun rays can increase at least one and a half times. As a result, the applicant expects, during the NPU, an increase in the longitudinal compression stresses in the arch belt by 0.2 MPa, a decrease in the slope towards the downstream of the central section of the dam by 0.4 cm, and a decrease in tensile cantilever stresses of 0.2 MPa in it.

This expected technical result in relation to the dam as a whole is low. However, it is achieved at low cost, which provides the method with high efficiency in relation to the previously mentioned and other known methods, which provide for the impact on the stress-strain state of a concrete arch or arch-gravity dam and, first of all, an increase in the magnitude of compressive stresses in the consoles.

The proposed method can be reproduced both independently and in conjunction with other methods of similar purpose.

Information sources

1. Bryzgalov V.I. From the experience of creating and developing the Krasnoyarsk and Sayano-Shushenskaya hydroelectric power stations. Production Edition. - Krasnoyarsk: Siberian Publishing House Surikov, 1999.

2. Yagin V.P. Turbine waterworks // Hydrotechnical construction. 2005. No. 7.

3. Kaganov G.M., Volkov V.I., Uchevatkin A.A. Ways of strengthening some types of arched dams in wide sections // Hydrotechnical construction. 2011. No8.

4. Patent of the Russian Federation No. 2418911, cl. EB02 7/10, publ. 05/20/2011.

Claims (4)

1. A method of operating a concrete arch-gravity dam that creates a freezing reservoir, and its upper face faces the south side, which consists in increasing the intensity of heating the upper arch belt with winter sunshine by covering the open ice surface in a given strip adjacent to the edge of the upper arch belt , a layer of snow, which is necessary to increase the reflection of sunlight from the winter surface of the reservoir. 2. The method according to claim 1, characterized in that the ice is covered with snow by retaining snow on the ice surface with barriers. 3. The method according to claim 1, characterized in that the top face of the arched belt above the ice level in the reservoir is covered with a layer of material that is dark in color and increases the absorption of sunlight by the arched belt. 4. The method according to claim 3, characterized in that the edge of the arched belt is covered with a paint layer, which increases the absorption coefficient of sunlight to at least 0.8.