RU2377363C1 - Soil non-homogenuous fill dam - Google Patents

Abstract

FIELD: hydraulic engineering construction.

SUBSTANCE: invention refers to hydraulic engineering construction of soil non-homogeneous fill dams. In cross section the dam consists of a transitive zone crossing the body of the dam by height and of the zone separating part of the dam body out of fine grain sand from the part of the dam body out of large-sized soil. The transitive zone is made of two layers out of soil of specified grain composition in form of a two-layer gabion wall out of tied gabions. The basket of each gabion is of a box shape, is made out of wire mesh and is divided into cells with one or more diaphragms. Certain cells are filled with soil of the first transitive layer and form the first layer of the gabion wall, while other sells are filled with soil of the second transitive layer and form the second layer of the gabion wall. Soil of at least the first transitive layer in the cell of the basket is enclosed in a flexible shell; while a dividing layer out of geo-synthetic material is made between a gabion wall and fine grain of the dam body. The flexible shell is made out of geo-textile canvas and has a box shape; the dimensions of the shell are at least equal to dimensions of the basket cell and facilitate tight fit of enclosed in the basket soil to the wire mesh of the cell. The dividing layer is made in form of a counter-suffosion element out of water-proof fibre material, mainly of geo-textile canvas and/or mineral-fibre plates, calculated diametre of water conducting holes of which is limited with mathematic dependence. The dividing layer can be made in form of a counter-filter element containing a water-proof membrane.

EFFECT: invention decreases volume of soil of transitive layer and enhances dam reliability.

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Description

The invention relates to hydraulic engineering, in particular to heterogeneous unpaved bulk dams.

A heterogeneous bulk dam is known whose body consists of soils of two or more types. When pairing a part of the body of the dam from fine-grained soil with a part of the body from coarse soil, the dam in its cross section contains a transition zone (the same: filter), which is made from soil of a given grain composition. If the central part of the dam is made of fine-grained soil (core) or with a diaphragm, including a film, the transition layer crosses the dam body in height and has a view that is close to vertical and can consist of cores located in series with respect to fine-grained soil or to the diaphragm, the first transition layer and the second transition layer. Each of these layers is made of soil of a given grain composition (Hydrotechnical structures: Textbook for high schools: At 2 h. Part 1 / L.N. Rasskazov, V.G. Orekhov, Yu.P. Pravdivtsev et al .; Ed. L.N. Rasskazova. - M .: Stroyizdat, 1999. S.270-271, Fig. 11.1, b and f, p. 350, Fig. 13.22).

From the conditions of production, the thickness of the transition layer is usually taken at least 4 meters, and such a layer is mated with stepped surfaces with stepped surfaces forming a herringbone. Known for USSR author's certificate No. 1802034 and No. 1802035 proposals for the flat pairing of soils (without "herringbone") using removable shields are technologically complex and have not yet been applied.

All this leads to the following disadvantages of the known dam.

1. A large volume of usually scarce soil of the transitional layer when it is thick and when it is combined with adjacent soils “herringbone”, which leads to high costs for the construction of the dam.

2. The lack of reliability of the dam due to:

- stratification (segregation) of the soil of the transition layer during its implementation;

- increase of output filtration gradients in the “herringbone” niche;

- freezing of the soil of the core of the dam on the "Christmas tree", which can create a dangerous "arched" effect;

- difficulties in the quality performance of both an anti-suffusion element made of a water-permeable fibrous material (geotextile fabric and / or mineral fiber plates), and an anti-filter element in the form of a waterproof geomembrane (hereinafter: membranes), both when pairing herringbones and when they are flatly paired with the use of interchangeable shields;

- weak crack resistance of the dam core in the sides, especially during seismic shaking.

These shortcomings increase the cost of dam construction and reduce its reliability.

The problem to which the invention is directed, is to reduce costs and increase the reliability of the dam.

The technical result from the use of the invention is:

- in reducing the soil volume of the transition layer;

- in preventing the formation of "Christmas trees" when pairing the transition layer with adjacent soils;

- in preventing soil stratification of the transition layer;

- in alignment of output filtration gradients;

- in preventing the core from hanging on the transition layer;

- to improve the manufacturability and quality of the implementation of the anti-suffusion or anti-filter element of the dam;

- to increase the crack resistance of the dam core.

This problem is solved, and the technical result is achieved by the fact that in a non-uniform ground bulk dam containing in cross section a transition zone intersecting the height of the dam body and separating the part of the dam body from fine-grained soil from the part of the dam body from coarse soil, and the transition zone is made of two-layer and consists of sequentially arranged, in relation to fine-grained soil, the first transition layer and the second transition layer, each of which is made of soil of a given rnovogo composition according to the invention, a transition zone is formed as a double-layer wall of the gabion interconnected gabions. Each gabion basket is box-shaped, made of wire mesh and is divided into cells by one or more diaphragms. Some cells are filled with soil of the first transition layer and form the first layer of the gabion wall, while other cells are filled with soil of the second transition layer and form the second layer of the gabion wall. At least the soil of the first transition layer in the cell of the basket is enclosed in a flexible shell, and a separation layer of geosynthetic and / or mineral fiber material is made between the gabion wall and the fine-grained soil of the dam body.

Additionally:

- the flexible sheath is made of geotextile fabric, has a box-shaped shape, while its dimensions are at least equal to the dimensions of the basket cell and provide a snug fit of the portion soil to the wire mesh of the basket cell;

удовлетворяет условию:- the separation layer is made in the form of an anti-suffusion element of a water-permeable fibrous material, mainly of a geotextile web and / or mineral fiber plates, while the estimated diameter of the water-conducting holes in the water-permeable fibrous material

satisfies the condition:

,

,

where d ^max is the maximum diameter of soil particles, the movement of which by filtration flow in the direction of the anti- ^suffusion element during the operation of the dam is temporarily possible and permissible;

- the separation layer is made in the form of an anti-filter element containing a waterproof membrane.

It is the implementation of the transition layer in the form of a two-layer gabion wall according to the above rules that allows the soil of the transition layers to be laid economically and without delamination while creating a tiered vertical and relatively even surface, usually from the upstream side. This surface creates favorable conditions for making an economical and high-quality separation layer from geosynthetic materials in the form of an anti-suffusion or anti-filter element between fine-grained soil (core) and soil of the first layer of the transition zone (the same: the first layer of the gabion wall). In this case, the anti-suffusion element is understood as a special special case of the anti-filter element, which temporarily has a water-permeable property, and under the geosynthetic material is a synthetic material intended for work in the ground. Additionally, the conclusion of the soil of the transition layer into a flexible shell allows you not to link the cell sizes of the wire mesh of the basket with a given granular composition of the soil of this transition layer.

All this ensures the achievement of the previously specified technical result, and ultimately - cost reduction during the construction of the dam and increase its reliability during operation.

The invention is illustrated by drawings, in which 2 examples of a dam are presented.

Figure 1-8 shows a stone-earthen dam on a rocky base with a sandy loam core and with a separation layer in the form of an anti-suffusion element, example 1, namely: figure 1 - shows a transverse section of the dam; figure 2 is a structural diagram of a box with two cells of a basket of wire mesh; figure 3 is a diagram of hexagonal mesh cells; figure 4 - diagram of a box-shaped flexible shell; figure 5 is a structural diagram of a box with four mesh baskets of wire mesh; figure 6 - scan baskets with four cells (partitions are made separately and installed in place); 7 is a diagram of the construction of the gabion wall of the dam and its anti-suffusion element; in Fig.8 is a section aa in Fig.1, a schematic diagram of the operation of the anti-suffusion element and its conversion in a natural way into an anti-filter element.

Figure 9 shows a stone dam on a rock base with a separation layer in the form of an anti-filter element, example 2, cross section.

Example 1 (FIGS. 1-7). The stone-earthen dam is located on a rock foundation 1. In its cross section, the dam contains a core 2 made of sandy loam (fine-grained soil), thrust prisms of the top 3 and bottom 4 made of stone sketches (coarse soil) with a zonal distribution of the size of the stone ( in Fig. 2, the distribution is shown by a dashed line), and transition zones of the top 5 and bottom 6, made of soils of a given grain composition. Transitional zones 5 and 6 intersect the dam body in height and separate the core 2 from the thrust prisms 3 and 4.

The bottom transition zone 6 is made in the form of a gabion wall 7 and in two transition layers: the first, with respect to the core 2, layer 8 and the second layer 9. The gabion wall 7 is made of interconnected gabions 10, each basket 11 of which has a box shape ( figure 2), made of wire mesh 12 (figure 2 and 3) and the diaphragm 13 is divided into two cells 14, forming one pair of cells. Some cells 14 pairs are located, relative to the axis 15 of the gabion wall 7, from the side of the upstream side, filled with soil of the first transition layer 8 and form the first layer 16 of the gabion wall 7. Other cells 14 pairs are located on the side of the downstream side, filled with soil of the second transition layer 9 and form the second layer 17 of the gabion wall 7. The soils of the transition layers 8 and 9 have predetermined grain compositions. At least the soil of the first transition layer 8 in each cell 14 of the first layer 16 of the gabion wall 7 is enclosed in a flexible shell 18 (Fig. 4). Between the gabion wall 7 and the core 2 is a separation layer 19, which is made of composite materials and fits snugly to the flat upper side surface 20 of the gabion wall 7.

The flexible sheath 18 is made of geotextile fabric, has a box shape, and its dimensions are at least equal to the dimensions of the cell 14 of the basket 11 and provide a snug fit of the portion soil to the wire mesh 12 of the basket 7.

удовлетворяет условию:

, где d^мaкc - максимальный диаметр частиц супеси ядра 2, перемещение фильтрационным потоком 23 которых в направлении разделительного слоя 19 (то же: противосуффозионного элемента) при эксплуатации плотины временно возможно и допустимо.The separation layer 19 is made in the form of an anti-suffusion element made of permeable fibrous materials and consists of a web 21 and a leveling pad 22. The web 21 is made of geotextiles, for example two layers of Dornit-500, and the leveling pad 22 is made of mineral fiber boards and gives softness to the upper side the surface 20 of the gabion wall 7. In this case, the estimated diameter of the water-conducting holes in the permeable composite fibrous material (web 20 and gasket 22)

satisfies the condition:

, where d ^max is the maximum particle diameter of the sandy loam of core 2, the movement of which by filtration flow 23 in the direction of the separation layer 19 (the same: anti-suffusion element) during the operation of the dam is temporarily possible and permissible.

и d^мaкc устанавливаются проектом по известным математическим формулам и исследованиям в соответствии с нормативными требованиями.Grain composition of transition layers 8 and 9, as well as diameters

and d ^max are set by the project according to well-known mathematical formulas and studies in accordance with regulatory requirements.

Basket 11 can be divided by diaphragms 13 by the number of cells more than two, but always by an even number depending on the given number of pairs of cells 14 in one basket 11. As an example, FIGS. 5 and 6 show a basket 11 with four cells 14, i.e. e. with two pairs of cells.

The number of pairs of cells 14 in the basket 11, the need to make covers 24 (FIG. 2) in them, the diameter of the wire of the edge 25 and the main wire 26, the mesh sizes in the wire mesh 12 (FIG. 3), the need to make closing aprons 27 in a flexible shell 18 (figure 4) are set by the project.

In the upper part of the dam within the upper transition zone 5, a single-layer gabion wall 28 is adjacent to the core 2 (with or without a separation layer 19), the basket cells of which are filled with soil of the first transition layer of this transition zone 5 (Fig. 1).

The tip 29 of the dam is equipped with an anti-filter element in the form of a waterproof membrane (geomembrane) 30.

The dam is connected with the rock base 1 by means of a concrete slab 31 and cementation 32.

In low dams, the separation layer 19 may consist only of the web 21 or of the gasket 22.

In the drawings, other elements of the dam are indicated, namely:

33 - technological layer (bottom thrust prism)

34 - technological layer (core)

35 - transition layer (microlayer in front of the canvas 21)

36 - antifiltration layer (a thin layer in front of the transition layer 35).

The dam is erected in a belt in the following sequence.

First, the dam is mated with the base 1. For this, a concrete slab 31 and cementation 32 of the base 1 are made. Then, the first (lower) tier of the gabion wall 7 is built with a height of H _i = 3H _k , where N _k is the height of the gabion 10. Each gabion 10 is formed by filling the cells 14 of the baskets 11 with the soil of the lower transition zone 6. The cells 14, located with respect to the axis 15 of the gabion wall 7 from the side of the upper pool, fill the ground with the first transition layer 8, and the cells 14 located on the side of the lower pool with the soil of the second transition layer 9 . Moreover, each n soil rtsiyu first transition layer 8, intended to fill the cell 14 is enclosed in a flexible casing 18.

If the cells 14 of the basket 11 are filled with soil directly in the gabion wall 7, one of the baskets 11 of the mating pair can be made with an open end, i.e. without sidewall - wire mesh 12 at the mating end.

In the case of using baskets 11 with one pair of cells 14 (Fig. 2), it is advisable to form gabions 10 on special platforms, and transport them and carry out gabion masonry by means of forklifts adapted for this purpose with forks or jaws. Gabions 10 in tier associated with each other, after which the downstream side of the gabion wall 7 to the height of storey H _I layers 33 deposited soil in grassroots abutment prism 4, and the vertical side surface 20 of the gabion wall 7 of the gasket 22 and the blade 21 operate spacer layer 19 Then, layers 34 lay the soil in the core 2.

Similarly, the second and subsequent tiers of the gabion wall are erected and the soil is laid in the lower thrust prism 4 and core 2, and all other elements of the dam are also performed.

After raising the water level in front of the dam, the structure works as follows.

The filtration flow of water 23 through the dam initially has the highest flow rate, and its speed, especially at the exit from the core 2, has a maximum value. Small particles of soil at the exit from the core 2 are moved to the separation layer 19. Particles whose diameter is less than the diameter of the water holes D ₀ in the geotextile of the web 21 and the gasket 22, in most cases pass through the separation layer 19 and merge with the downstream together with water. Larger particles are retained by the web 21 and they create the first microlayer of the transition layer 35 (Fig. 8). Subsequently, sequentially decreasing particles, including colloidal particles, are retained. This ends the natural creation of a transition layer 35, the thickness of which usually does not exceed 1 millimeter, and in which small particles are washed that do not create a bearing skeleton of the soil. This layer 35 covers on the upper side of the web 21, in which the pores of the soil, originally adjacent to the web 21, are coiled with incoherent soil, and the particle size decreases sharply as the distance from the web 21 by the principle of the inverse filter. Therefore, the transition layer 35 retains all small, including colloidal particles, and does not pass them through itself even with a strong seismic shock.

As a result of the high force impact of the filtration stream 23 on the soil skeleton, a high-quality anti-filtration layer 36 is created over time. In this thin but exceptionally dense layer 36, the pores are colmatized with cohesive soil, therefore, the filtration rates of the flow 23 decrease over time, and the build-up of the thickness of the antifiltration layer 36 slows . As a result of all this, the anti-suffusion element is transformed naturally into the dam into an additional anti-filter element to the core 2 in the form of an anti-filter layer 36.

The high deforming properties of the gabion wall 7, the web 21 and the gasket 22, as well as the high quality of the impervious layer 36 provide high operational reliability of the dam, which is preserved during seismic shaking.

The grain composition of the soil of the first transition layer 8, enclosed in a flexible shell 18, is selected from the condition of preventing dangerous peeling of clay particles of the antifiltration layer 36 and from the condition of its filtration strength in contact with the soil of the second transition layer 9. Therefore, the dam remains reliable even in the event of complete loss of the time of the strength properties in the elements of the separation layer 19, the flexible sheath 18 and the wire mesh 12 baskets 11. In addition, by this time the consolidation of the entire body will take place in the dam.

The present dam design is proposed as an option for the Tuva (Uyuk) hydroelectric power plant planned for construction, located on the B. Yenisei River 70 kilometers above the city of Kyzyl. One of the features of the construction of a thermal power plant is that in the dam site, the reserves of sand and gravel soil are limited, and the nearest cohesive soil deposit is located at a distance of 25 kilometers and is represented by sandy loam.

Example 2 (Fig.9). A stone dam was erected on a non-rock base 37, contains a similar gabion wall 7 and, unlike example 1, has the following design features.

1. The separation layer 19 is made in the form of an anti-filtration element, which consists of a waterproof membrane (waterproofing polymer roll geomembrane) 38 adjacent to the leveling pad 39. This membrane 38 is a polymer film enclosed in geotextile, and the leveling pad 39 is made of mineral fiber plates and similar to gasket 22.

2. In the upper part of the dam, the upper transitional zone 5 is made in two transitional layers of the upper 40 and the lower 41 without a gabion wall.

3. The coupling of the dam with the base 37 is carried out by means of a horizontally located same membrane 38 and an element 42 made of cohesive soil.

The main difference between the operation of such a dam is that there is practically no filtration flow in its body.

Designations

1 - base (rocky)

2 - core

3 - riding thrust prism

4 - bottom persistent prism

5 - horse transition zone

6 - lower transition zone

7 - gabion wall (lower transition zone)

8 - the first layer (lower transition zone)

9 - second layer (lower transition zone)

10 - gabion

11 - basket (gabion)

12 - wire mesh

13 - aperture (in the basket)

14 - cell (baskets)

15 - axis (gabion wall)

16 - the first layer (gabion wall 7)

17 - second layer (gabion wall)

18 - flexible shell

19 - separation layer (geosynthetic and / or mineral fiber material)

20 - upper side surface (gabion wall 7)

21 - canvas (geotextile)

22 - gasket (mineral fiber boards)

23 - filtration flow

24 - cover (baskets)

25 - edge wire

26 - the main wire

27 - locking apron

28 - gabion wall (in front of the core)

29 - tip of the dam

30 - waterproof membrane (geomembrane)

31 - concrete slab

32 - cementation

33 - technological layer (bottom thrust prism)

34 - technological layer (core)

35 - transition layer (microlayer in front of the canvas 19)

36 - antifiltration layer (thin layer in front of the transition layer)

37 - base (non-rock)

38 - waterproof membrane (geomembrane waterproofing polymer roll)

39 - gasket (mineral fiber boards)

40 - the first transitional layer (top of the dam, upper transition zone)

41 - second transition layer (top of the dam, upper transition zone)

42 - element (from cohesive soil).

Claims (4)

1. Soil heterogeneous bulk dam containing in the cross section a transition zone intersecting the height of the dam body and separating the part of the dam body from fine-grained soil from the part of the dam body from coarse soil, while the transition zone is made of two-layer and consists of sequentially arranged, relative to fine-grained soil, the first transition layer and the second transition layer, each of which is made of soil of a given grain composition, characterized in that the transition zone is made in the form e of a two-layer gabion wall of interconnected gabions, each basket of which is box-shaped, made of wire mesh and is divided into cells by one or more diaphragms, while some cells are filled with soil of the first transition layer and form the first layer of the gabion wall, and other cells are filled the soil of the second transition layer and form the second layer of the gabion wall, and at least the soil of the first transition layer in the cell of the basket is enclosed in a flexible shell, and between the gabion wall and fine-grained the soil body of the dam made a separation layer of geosynthetic material and / or mineral fiber material. 2. The dam according to claim 1, characterized in that the flexible sheath is made of geotextile fabric, has a box shape, while its dimensions are at least equal to the dimensions of the basket cell and provide a snug fit of the soil enclosed in it to the wire mesh of the cell. 3. The dam according to claim 1, characterized in that the separation layer is made in the form of an anti-suffusion element of a permeable fibrous material, mainly of geotextile fabric and / or mineral fiber plates, while the calculated diameter of the water-conducting holes in the permeable fibrous material

satisfies the condition:

,
where d ^max is the maximum diameter of soil particles, the movement of which by the filtration flow in the direction of the anti-suffusion element during the operation of the dam is temporarily possible and permissible. 4. The dam according to claim 1, characterized in that the separation layer is made in the form of an anti-filter element containing a waterproof membrane.

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