RU78815U1 - UNDERGROUND WEIR UNDER HARVEST CLIMATE CONDITIONS - Google Patents

Abstract

A soil dam in severe climatic conditions, including a top and bottom prisms, a crest, a core, transition layers of a reverse filter, characterized in that it contains a horizontal thermal curtain, which is placed in the cross section of the dam at the mark of the top of the core and is made in the form of a series in series located along the length of the dam pipes for circulation of the coolant, the number of pipes in a row and the distance between them, as well as the parameters of the coolant are selected so that the core in the crest of the flesh It is in a melt condition created by a horizontal thermal curtain.

Description

The utility model relates to the field of hydraulic engineering in the northern climatic zone, in areas of permafrost, which serve as the basis of hydraulic structures, and can be used in the design, construction and operation of dams located in this zone.

The northern construction and climatic zone is characterized by severe climatic, complex engineering-geological and geocryological conditions:

- winters with air temperatures up to minus 60-70 ° С, short summers with maximum temperatures 30-40 ° С and average annual air temperatures up to minus 8-14 ° С;

- the presence of continuous or island permafrost, through or closed taliks;

- frozen soils and rocky fractured rocks, as a rule, have a sharp decrease in bearing capacity and high permeability after thawing.

Structural, technological and layout solutions developed for a temperate climate are not fully suitable here and should be supplemented with new solutions that meet the conditions of the Far North.

To assess the novelty of the claimed technical solution, we consider a number of well-known technical means of a similar purpose.

It is known that soil dams constructed in the northern climatic zone are constructed and operated according to two principles: with the preservation of permafrost in the body and the base of the dam - the first principle (frozen) and with a possible warm core or sinking and thawing of the soil of the dam base during operation - 2nd principle (thawed).

There are well-known soil dams built and operated according to the first (frozen) principle, including a core or screen coupled to the base, upstream and downstream prisms (see, for example, AS USSR No. 331150, 1486558, EV 7/06). For reliable operation of such dams, it is necessary to ensure the safety of anti-filtration devices and the base in frozen

condition, for which artificial permafrost curtains are arranged in the body of the dam and the base.

Known soil dams on permafrost, erected and operated according to the second (melt) construction principle, including a crest, upper and lower prisms, an anti-filter element (core) and transition layers adjacent to it (see, for example, AS USSR No. 1583521 , EB02B 7/06)

The crests of such dams are under the volumetric temperature effect of the outside air and the reservoir. In winter, when the reservoir is discharged, the dam crest freezes to a depth of 8-12 m. In spring and summer, when the reservoir is filled, the dam crest with the upper part of the core adjacent to it (tip) is thawed. As a result of alternate freezing-thawing in the crest, complex cryogenic processes occur that cause soil heaving, a decrease in the filtration and suffusion strength of the dam core, which can lead to a decrease in the reliability and safety of operation of the structure.

In order to avoid heaving of soils, in the aforementioned analogue, the core tip is proposed to be erected from non-porous frozen soil, maintained during the operation of the dam in the permafrost state.

Known soil dam on permafrost, including the upper and lower prisms, the core, the transition layers and located in the lower prism of the drainage containing the thermal curtain, which is placed in the cross section of the dam in the zone of the transition layers, and made in the form of a series of consecutive wells, each of which is equipped with at least one heating device, and the number and pitch of wells, as well as the number and parameters of heating devices are selected so that the transition layers and drainage are xia in the zone of influence of positive temperatures created by the thermal curtain, see RF patent No. 2250296, EV 7/06. An ohmic electric heater can be selected as a heating device in the thermal curtain.

Known soil dam on a permafrost base in the presence of a through filter talik in it, including upper and lower prisms, the core and the transition layers of the filter (see attached drawing No. 1158-10-436,

Institute Lenhydroproject, Kolyma hydroelectric station on the river. Kolyma. Earthen dam. L., 1970).

According to the greatest number of similar features and the result achieved using them, this technical solution is selected as a prototype of the claimed utility model,

This dam was designed and built according to the second principle with the assumption of thawing of permafrost soils of the base on the coastal sections of the alignment and with talik in the river channel. During the operation of the hydroelectric complex, the upper prism and the core of the dam are heated as a result of the warming effect of the reservoir and are in a melted state in the annual cycle, with the exception of its crest part. In most cases, transitional layers of the inverse filter at the end of construction are in a frozen state and only when a filtration stream has filtered through the core (screen) into the downstream, the first, and then partially and the second layers of the filter begin to thaw more intensively.

The bottom prism and the crest of the dam as a result of heat exchange of the surface of the soil with the atmosphere at average annual negative air temperatures of minus 12 ° C are cooled and in the intra-annual cycle are frozen. Thus, the dam under consideration belongs to the frozen structure.

The core of the dam freezes to a depth of 15–20 m, and in winter, when the reservoir is discharged, the crest of the dam, including the soil of the dam, freezes, and partially thaws during the filling of the reservoir in spring and summer. Freezing and thawing of cohesive soils lead to structural cryogenic formations with violation of filtration and suffusion of their strength. The greatest danger is the boundary between the thawed and frozen zones, which follows the depression curve, descending to the lower prism of the dam. Frozen core below the level of NPU leads to the creation of pressure filtration on the dam. In addition, the frozen crest of the dam forms a frozen massif, under which through cracks in the soil of the body and the base of the dam, through cracks can form, leading to the occurrence of dangerous water filtration.

The utility model solves the problem of ensuring the safe and reliable operation of a soil dam on a permafrost foundation, for which it is necessary to maintain cohesive soils in the crest of the dam in a thawed state.

The essence of the claimed utility model is expressed in the following set of essential features, sufficient to achieve the goal.

An earth dam in severe climatic conditions, including the upper and lower prisms, the crest part, the core, the transition layers of the inverse filter, is characterized by the fact that it contains a horizontal thermal curtain, which is placed in the cross section of the dam at the mark of the location of the top of the core and is made in the form of a series in series located along the length of the dam pipes for circulation of the coolant, the number of pipes in a row and the distance between them, as well as the parameters of the coolant are selected so that the core in the crest of the otina is in a melt condition created by a horizontal thermal curtain.

The claimed technical solution is characterized by the presence of a new set of features, absent in the technical solutions known from the prior art. This allows us to conclude that the proposed technical solution meets the criterion of "novelty."

The essence of the utility model is illustrated by drawings, where Fig. 1 shows a cross section through a soil dam, Fig. 2 shows heat pipes forming a horizontal heat curtain, and Fig. 3 shows a temperature field typical of soil dams without a horizontal heat curtain.

The soil dam was erected in severe climatic conditions on a permafrost base in the presence of a through filter talik in it (not indicated by a separate position). It includes the upper prism 1, the lower prism 2, the core 3 and the transition layers of the filter 4. In the crest of the dam a horizontal thermal curtain is made, located at the top of the core, which is a series of pipes 5 located in series along the length of the dam at a distance S from each other, through which the coolant circulates in the winter. In this case, the number of pipes in a row and the distance between them, as well as the parameters of the coolant are selected so that the core in the crest of the dam is constantly in the zone of action of positive temperatures (melt zone) created by a horizontal thermal curtain. Border

between thawed and frozen soils in the crest of the dam in the presence of a thermal curtain is indicated by 6. Position 7 shows the boundary between thawed and frozen soils, characteristic of soil dams without a thermal curtain, erected at different time periods in the northern climatic zone.

Soil dam works as follows.

Due to the circulation through the pipes 5 of the heat carrier curtain (warm air or liquid heat carrier) in the winter, the boundary 6 between thawed and frozen soils in the crest of the dam is clearly formed and maintained constant, as a result of which the cohesive soils in the core of the dam remain throughout in a thawed state, the processes of freezing and thawing of soils are excluded, leading to structural cryogenic formations with a violation of their filtration and suffusion strength. This increases the reliability and safety of operation of dams erected in the northern climatic zone. Preliminary results of thermotechnical calculations for the installation of an areal horizontal heat curtain in relation to the conditions of the Kolyma hydroelectric station show that it is possible to maintain cohesive soils in a melted state during the operation of the structure. Unloading of the filtration stream, filtered into the downstream, is carried out at the lower elevations of the inverse filter 4 with its gradual thawing to full height and flowing into the channel talik.

The claimed solution during the construction period is implemented at no additional cost, and during the reconstruction of the dam - with the help of well-known structural elements and technologies, which determines, according to the applicant, compliance with his criterion of "industrial applicability".

Claims (1)

A soil dam in severe climatic conditions, including a top and bottom prisms, a crest, a core, transition layers of a reverse filter, characterized in that it contains a horizontal thermal curtain, which is placed in the cross section of the dam at the mark of the top of the core and is made in the form of a series in series located along the length of the dam pipes for circulation of the coolant, while the number of pipes in a row and the distance between them, as well as the parameters of the coolant are selected so that the core in the crest of the flesh It is in a melt condition created by a horizontal thermal curtain.