RU2448214C1 - Unit of ground dam coupling with concrete overflow weir - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: coupling unit comprises a coupling abutment made of concrete and a prism made of a cohesive soil. The prism is located within the borders of the ground dam in the upper part of the coupling unit. Within the borders of the coupling unit the surface of the coupling abutment at the side of the ground dam is coated with a geomembrane attached to it and a bentonite mat. The coupling abutment and the prism comprise inside them hollow microballs from compounds containing silicon, which prevent freezing of the coupling abutment in the coupling unit for its entire thickness at the side of the overflow weir and at the side of the ground dam crest.

EFFECT: increased operational reliability.

3 dwg

Description

The invention relates to the field of hydraulic engineering and can be used when pairing a soil dam with a concrete spillway dam mainly in the northern climatic zone.

One of the important problems that arise after the construction of the hydroelectric complex and filling of the reservoir in areas with severe climatic conditions is the possibility of crack formation in the body of the soil dam due to the freezing of the crest of the soil dam or its water-resistant element (core, screen) to the surface of the mating concrete abutment, as a result which part of the soil dam comes off from the settling lower melt of its part. The resulting through crack is the focus of concentrated filtration, usually accompanied by intense suffusion of the dam material or its clay water-resistant element, which leads to low filtration strength of the soil dam.

In the junction of the soil dam with the concrete spillway dam in the cold season, the mating abutment is frozen to its entire thickness from the side of the spillway dam. This is facilitated by the high thermal conductivity coefficient λ of heavy concrete (over 1.5 kcal / m × h × deg), which usually substantially exceeds the thermal conductivity coefficient of dam soils. Such freezing is accompanied by the formation of an ice layer on the mating surface of the abutment, especially at the interface between the abutment and the water-resistant part of the soil dam due to the migration of water from the moist cohesive soil to the freezing front under the influence of temperature gradients. The melting of this layer of ice in the warm season causes the formation of a dangerous focus of concentrated filtration.

Additionally, the friction of the material of the soil dam on a rough concrete surface inevitably leads to a dangerous softening of the soil material at the point of contact, accompanied by the occurrence of cracks in the soil and, as a consequence, dangerous filtration processes.

To reduce the negative effect of freezing the soil dam material and its friction against the concrete surface of the mating abutment on the filtration strength of the soil, it is proposed to cover the surface of the mating abutment with the soil dam within the limits of possible freezing with a geomembrane attached to it (see Russian patent No. 2373330).

The disadvantage of such a mating unit is that the geomembrane only partially reduces both the freezing forces of the soil material to the mating abutment and the friction forces of the soil material against the mating abutment. Moreover, if the soil dam is paired with a concrete spillway dam, the geomembrane practically does not prevent the formation of a continuous layer of ice on its surface during the cold season and, as a result, does not prevent the formation of a dangerous focus of concentrated filtration in the warm season.

Additionally, the smoothness of the surface of the geomembrane causes an increase in the pores of the soil in contact with the geomembrane, which also reduces the suffusion stability of the soil in the interface.

The closest technical solution adopted for the prototype is the interface unit of the soil dam with a concrete structure, including a concrete spillway dam, including a mating abutment made of concrete and equipped with heating elements within the limits of the possible freezing of the interface area between the abutment and the soil dam, t .e. protective means against freezing. Heating elements can be made in the form of electric heaters or in the form of a coil from a high-resistance electric cable. In the first case, they are placed in a longitudinal cavity with respect to the mating surface, in the second case, inside the mating abutment directly during its erection. These heating elements prevent the possibility of freezing the mating abutment to its entire thickness from the side of the spillway dam (ibid .: Russian patent No. 2373330).

The disadvantage of this interface node is the high cost of its creation and operation, due to the complexity of the implementation of the interface node during its creation and the need to maintain the heating elements in working condition throughout the life of the hydraulic unit.

The problem to which the invention is directed, is to reduce costs during the creation of the interface and during its operation. The technical result is to simplify the protective equipment that prevents possible freezing of the mating abutment in its interface from the side of the spillway dam and from the crest of the soil dam at the interface.

The problem is solved, and the technical result is achieved by the fact that the interface unit contains a mating support made of concrete and a prism made of cohesive soil and located within the soil dam in the upper part of the interface. Within the interface, the surface of the interface between the side of the soil dam is covered with a geomembrane and bentonite mat attached to it, and the interface and the prism contain hollow microspheres from compounds containing silicon. These hollow microspheres prevent freezing of the mating abutment at its entire thickness on the side of the spillway dam and on the side of the crest of the soil dam in the interface unit.

It is the content of the abutment in the concrete composition and in the soil of the prism of hollow microspheres (microspheres) from compounds containing silicon that reduces the thermal conductivity of concrete and soil, which prevents freezing of the abutment over its entire thickness.

Hollow microspheres in concrete and in the soil perform the same thermal insulation work as they do in the widely used thermal insulation paints - liquid thermal insulation material. The discharged air in the microspheres provides a heat-reflecting effect - heat return in the opposite direction.

Figure 1 shows the interface node, the plan; figure 2 is a section aa in figure 1; figure 3 is a section bB in figure 2.

Example. The interface node of the soil dam 1 with a concrete spillway dam 2 contains a mating abutment made of heavy concrete 3. The soil dam as an antifiltration element contains a core 4 (figure 2) made of cohesive soil, and the mating abutment 3 consists of walls: longitudinal 5, horseback 6 and grassroots 7.

The core 4 is adjacent to the longitudinal wall 5, the concrete of which above the spillway dam 2 contains hollow microspheres (microspheres) 8 of compounds containing silicon, mainly ceramic, silicate, glass, or combinations thereof. These microspheres 8 are mainly sized up to 30 microns, and their number in concrete is set by the project based on research.

The surface of the longitudinal wall 5 from the side of the soil dam 1 is covered with a geomembrane 9, which is made of polyethylene, with polyethylene anchors 10 attached to the wall 5 and is an integral part thereof.

A bentonite mat 11 is adjacent to the geomembrane 9, which consists of a layer of woven geotextile 12 and non-woven geotextile 13, and granules of sodium bentonite 14 are located between these geotextiles.

The bentonite mat 11 is adjacent to the longitudinal wall 5 with a layer of woven geotextile 12, and to the core 4 with a layer of non-woven geotextile 13.

It is advisable to reduce the freezing depth of the core 4 from the side of the ridge 15 of the soil dam 1 directly near the longitudinal wall 5 by known means, for example, by means of a winter mat 16 or by making prisms 17 in the core 4, the cohesive soil of which also contains hollow microspheres 8.

The interface can be equipped with a collecting channel, which can be located at the bottom of the core 4. This channel will receive filtered water through the interface and concentrate through the water meter to direct it outside the soil dam (the channel and water meter are not shown in the drawings).

In the drawing, in addition, the positions indicated:

18 - border freezing;

19 - maximum water level in a soil dam;

20 - base;

21 - seam abutment;

22 - concrete slab;

23 - the longitudinal axis of the dam.

A feature of the work of the proposed interface node is as follows.

1. The beads 8 located in the concrete of the longitudinal wall 5, as well as in the soil prism 17, provide a decrease in the coefficient of thermal conductivity, both in concrete and in the soil. This prevents the freezing of the mating abutment 3 at its entire thickness from the side of the spillway dam 2 at the interface node, and also reduces the depth of freezing of the core 4 from the crest 15 of the soil dam 1.

2. The bentonite mat 11 prevents erosion of the soil of the core 4 by water moving directly over the thawed contact between the soil dam 1 and the matching abutment 3. Non-woven geotextile 13 passes the water necessary for the formation of 14 bentonite gel during hydration and swelling from sodium bentonite, but it is not permeable to bentonite gel, and has a weak, constantly decreasing due to mudding, water permeability in its longitudinal direction. The woven geotextile 12 is able to impregnate with bentonite gel and lubricate the surface of the geomembrane 9 with it, further reducing, thereby, the effect of friction forces.

3. The bentonite gel of the bentonite mat 11 retains ductility at low temperatures, at least up to -5 ° C (N. Tsitovich. Mechanics of frozen soils. Textbook. Manual, Moscow, Vysshaya Shkola, 1973, p. 15). This increases the reliability of the interface in case of unexpected freezing of the longitudinal wall 5.

Designations

1 - soil dam

2 - concrete spillway dam

3 - mating mouth

4 - core

5 - longitudinal wall

6 - upper wall

7 - bottom wall

8 - microspheres

9 - geomembrane

10 - polyethylene anchors

11 - bentonite mat

12 - woven geotextile

13 - non-woven geotextile

14 - sodium bentonite

15 - crest of soil dam

16 - winter carpet

17 - soil prism with beads

18 - border freezing

19 - maximum water level in a soil dam

20 - base

21 - suture abutment

22 - concrete slab

23 - longitudinal axis of the dam

Claims (1)

The unit for coupling an earth dam with a concrete spillway dam, comprising a mating abutment made of concrete, and a prism made of cohesive soil and located within the soil dam in the upper part of the interface, while the surface of the mating abutment on the side of the soil dam is covered within the interface unit a geomembrane and a bentonite mat attached to it, and the matching abutment and prism itself contain hollow microspheres from compounds containing silicon, which prevent the mating assembly eniya freezing mating abutment on its entire thickness by a spillway and dirt from the crest of the dam.

Images