RU2376416C1 - Ground heterogeneous rock-fill dam - Google Patents

Abstract

FIELD: construction, hydraulic engineering.

SUBSTANCE: invention relates to hydraulic engineering and construction of ground heterogeneous rock-fill dams. The dam includes transient layer in its cross section. This layer is made from ground consisting of preset grain size. It crosses dam body by height and separates part of dam body consisting of fine grained ground from the part of dam made from macro fragmental ground. The said transient layer is represented with a gabion-tired wall with box-shaped baskets. The said gabions are made from wirework. Each cell of the basket is filled with ground taken from the transient layer. Geo synthetic and/or mineral fiber separating layer is located between gabion wall and fine grained ground of dam. Each ground potion is enclosed into a flexible casing made from geo textile sheet. The box-shaped casing sizes are at least equal to basket cell sizes ensuring tight ground portion fitting to wirework of basket cell. Separating layer is implemented as counter-suffosion element made from water-proof fiber materials, mainly geo textile sheet and/or mineral fiber slabs. Design diametre of water delivery openings in water-proof fiber material

satisfies the following condition:

where d^max - maximum diametre of ground particles. Temporarily, it is acceptable and possible that the above particles could be moved by filtration flow in the direction of counter-suffosion element during dam operation. Separating layer may be made as counter-filtration element containing water-proof membrane.

EFFECT: invention allows for reducing ground amount in transient dam layer and improving dam reliability during operation.

4 cl, 8 dwg

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-grained soil, the dam, in its cross section, contains a transition layer (the same: zone, filter), which is made from soil of a given grain composition. In this case, 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 (Hydrotechnical structures: Textbook for universities: At 2 o’clock Part 1 / L.N. Rasskazov, V.G. Orekhov, Yu.P. Pravdivtsev et al .; Edited by L.N. Rasskazov. - M.: Stroyizdat, 1999.P.270-271, Fig. 11.1, b and f).

From the conditions of production, the thickness of such a transition layer is usually taken at least 4 meters, and such a layer is mated with adjacent soils 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.

These circumstances cause 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 boards), and an anti-filter element in the form of a waterproof geomembrane (hereinafter: membranes) both when pairing herringbones and when flat using them 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 layer made of soil of a given grain composition, crossing the dam body in height and separating part of the dam body from fine-grained soil from part of the dam body from coarse soil, according to the invention, the transition layer is made in the form of a gabion wall of interconnected gabions, the baskets of which are box-shaped and made of wire mesh. Each cell of the basket is filled with a portion of the soil of the transition layer, and between the gabion wall and the fine-grained soil of the dam body, a separation layer is made of geosynthetic and / or mineral fiber material.

Additionally:

- a portion of the soil is enclosed in a flexible shell, which is made of geotextile fabric, has a box shape, and 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 the soil particles, the movement of the filtration stream of which 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.

Namely, the implementation of the transition layer in the form of a gabion wall according to the above rules allows economically and without stratification to lay the soil of the transition layer while simultaneously creating a vertical and relatively even surface, usually from the upstream side, on the upper side. This surface, in turn, creates favorable conditions for making an economical and high-quality separation layer from geosynthetics in the form of an anti-suffusion or anti-filter element between fine-grained soil (core) and coarse-grained soil of a prism. 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 in a flexible shell allows you to not link the cell sizes of the wire mesh of the basket with a given granular composition of the soil of the transition layer.

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

The invention is illustrated by drawings, in which 3 examples of a dam are presented for the case when the gabion wall is located with a lower side, relative to the direction of the filtration flow, from the fine-grained part of the dam body. Example 4 is not illustrated by drawings.

Figure 1-6 shows an earthen dam on a rock base and with a separation layer in the form of an anti-suffusion element, example 1, namely: figure 1 shows a cross section of a 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; 5 is a diagram of the construction of the gabion wall of the dam and its anti-suffusion element; in Fig.6 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 7 shows a stone dam on a rock base with a separation layer in the form of an anti-filter element, example 2, cross section.

On Fig 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 3, cross section.

Example 1 (FIGS. 1-6). The earthen dam is located on a relatively permeable non-rocky base 1 and in cross section contains an upper thrust prism 2 made of gravelly sand (fine-grained soil), a lower thrust prism 3 made of pebble soil (coarse-grained soil), and located between these prisms 2 and 3 the transition layer (zone) 4, made of soil of a given grain composition. The transition layer 4 intersects the dam body in height, which actually consists of these soil parts 2, 3 and 4.

The transition layer 4 is made in the form of a gabion wall 5, consisting of interconnected gabions 6, baskets 7 of which are box-shaped and made of wire mesh 8 (FIGS. 2 and 3). Each cell 9 of the basket 7 is filled with a portion of the soil of the transition layer 4. Between the gabion wall 5 and the gravelly sand of the upper abutment prism 2, there is a separation layer 10, which is made of composite materials and fits snugly against the flat upper side surface 11 of the gabion wall 5.

Each portion of the soil of the transition layer 4 is enclosed in a flexible sheath 12 (Fig. 4), which is made of a geotextile web, has a box shape, and its dimensions are at least equal to the dimensions of the cell 9 of the basket 7 and provide a snug fit of the soil of the portion to the wire mesh 8 baskets 7.

удовлетворяет условию:

, где d^макс - максимальный диаметр частиц грунта верховой упорной призмы 3, перемещение фильтрационным потоком 15 которых в направлении разделительного слоя 10 (то же: противосуффозионного элемента) при эксплуатации плотины временно возможно и допустимо.The separation layer 10 is made in the form of an anti-suffusion element made of permeable fibrous materials and consists of a web 13 and a leveling pad 14. The web 13 is made of geotextiles, for example, two layers of Dornit-500, and the leveling pad 14 is made of mineral fiber boards and gives softness to the top the lateral surface 11 of the gabion wall 5. In this case, the estimated diameter of the water-conducting holes in the permeable composite fibrous material (web 13 and gasket 14)

satisfies the condition:

, where d ^max is the maximum diameter of the soil particles of the upper thrust prism 3, the movement of which by the filtration stream 15 in the direction of the separation layer 10 (the same: anti-suffusion element) during the operation of the dam is temporarily possible and permissible.

и d^макс устанавливаются проектом по известным математическим формулам и исследованиям в соответствии с нормативными требованиями.Grain composition of the transition layer 4, 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.

The number of cells 9 formed in the basket 7 by diaphragms 16, the need to make covers 17 (FIG. 2) in them, the diameter of the wire of the edge 18 and the main wire 19, the mesh sizes in the wire mesh 8 (FIG. 3), the need to make closing aprons 20 in flexible shell 12 (figure 4) are also installed by the project.

The dam, as well as its separating layer 10 with the base 1, is coupled by means of a horizontally located web 21 made of geotextile and similar to web 13, and element 22 made of cohesive soil.

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

23 - a layer of filled soil;

24 - reinforcing panel;

25 - water level in front of the dam;

26 - transition layer (microlayer in front of the canvas 13 or 21, Fig.6);

27 - antifiltration layer (a thin layer in front of the transition layer 26);

28 - a protective layer;

29 - mount riding slope.

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

First, the dam is mated with the base 1. For this, element 22 is made from a cohesive soil and a web 21 is laid on the prepared base 1. Then, the first (lower) tier of the gabion wall 5 is raised with a height of H _i1 = 2H _to , where H _to is the height of the basket 7. Moreover, each gabion 6 is formed by filling cells 9 of the basket 7 enclosed in a flexible sheath 12 with a portion of the soil of the transition layer 4. It is advisable to form gabions 6 on special sites, and transport them and carry out gabion masonry using means adapted for this purpose. forklift trucks with pickup or grapple. Gabions 6 in the tier are connected to each other, after which, from the lower side of the gabion wall 5, to the height of the tier Н _{н1, the} soil is laid in layers 23 in the lower thrust prism 3, and on the vertical side surface 11 of the gabion wall 5 from the strip 14 and the web 13, a separation layer 10 is made Then lay the soil in layers in a stubborn stubborn prism.

Similarly, the second and subsequent tiers of the gabion wall are erected and the soil is laid in thrust prisms 3 and 2. At the same time, the height of the tier can be increased, for example, Н _я2 = 3Н _к . In this case, each basket 7 of the lower row of gabions 6 is performed with a reinforcing (anchoring) panel 24.

If the cells 9 of the basket 7 are filled with soil directly in the gabion wall 5, one of the baskets 7 in the mating pair can be made with an open end, i.e. without wire mesh 8 at the mating end.

After raising the water level 25 in front of the dam, the structure works as follows.

The filtration water stream 15 through the dam initially has a high flow rate, and the water velocity along its streamlines has a maximum value. Suspended small particles of soil in the upper thrust prism move along the pores to the separation layer 10. Particles whose diameter is less than the diameter of the water supply holes D _o in the geotextile of the web 13 and gasket 14, in most cases pass through the separation layer 10 and merge with the water into the lower beef. Larger particles are retained by the web 13 and they create the first microlayer of the transition layer 26 (Fig.6). Subsequently, sequentially decreasing particles are retained up to colloidal particles. This ends the natural creation of a transition layer 26, the thickness of which usually does not exceed 1 millimeter, and in which small particles are washed that do not create a supporting skeleton of the soil. This layer 26 covers on the upper side of the web 13, in which the pores of the soil, which was originally adjacent to the web 13, are coiled with incoherent soil, and the particle sizes are sharply reduced as the distance from the web 13 decreases according to the inverse filter principle. Therefore, the transition layer 26 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 15 on the soil skeleton, a high-quality anti-filtration layer 27 is created over time. In this thin, but extremely dense layer 27, the pores are colmatized with cohesive soil, therefore, the filtration rates of the flow 15 decrease over time, and the build-up of the thickness of the antifiltration layer 27 slows down . As a result of all this, the conversion of the anti-suffusion element into an anti-filtration one occurs naturally in the dam.

Similarly, transition layers 26 and antifiltration layers 27 are formed in front of the web 21 at the sole of the upper thrust prism 2 and in the base 1 under the lower thrust prism 3.

The high deforming properties of the gabion wall 5, the web 13, the web 21 and the gasket 14, as well as the high quality of the antifiltration layer 27 provide high reliability of the dam, which is preserved during seismic shaking.

The grain composition of the transition layer 4, enclosed in a flexible shell 12, is selected from the condition of preventing the dangerous peeling of clay particles of the antifiltration layer 27 and from the condition of its filtration strength at the contact with the ground of the lower thrust prism 3. Therefore, the dam remains reliable even in case of complete loss of strength over time properties in the elements of the separation layer 10, the flexible sheath 12 and the wire mesh 8 baskets 7. Moreover, by this time in the dam will consolidate its entire body.

Example 2 (Fig.7). The stone dam is also erected on a relatively permeable rock base 1, contains a similar gabion wall 5 and has the following design features.

1. The separation layer 10 is made in the form of an anti-filtration element, which consists of a waterproof membrane (waterproofing polymer roll geomembrane) 30 adjacent to the leveling pad 14. This membrane 30 is a polymer film enclosed in geotextile, and the leveling pad 14 is made of mineral fiber plates.

2. The coupling of the dam with the base 1 is carried out by means of a horizontally located same membrane 30 and element 22.

3. Thrust prisms of the top 2 and bottom 3 are made of coarse rock mass and are separated from the membrane 30 and the gabion wall 5 by transition zones (layers) of the top 31 and bottom 32.

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

Example 3 (Fig. 8). A stone-earthen dam was erected on a rocky base 33, contains a gabion wall 5 and has the following design features.

1. The central part of the dam is made of sandy loam in the form of a core 34, the bottom face of which is adjacent to the separation layer 10, made, as in example 1, in the form of an anti-suffusion element of a permeable fibrous material: web 13 and gasket 14.

2. Gabion wall 5 is given a slight bias towards the upper pool.

3. The tip 35 of the dam is equipped with an anti-filter element in the form of a waterproof membrane 36.

4. Side thrust prisms 2 and 3, as in example 2, are made of coarse rock mass.

5. The coupling of the dam with the rock base 33 is carried out by means of a concrete slab 37 and cementation 38.

The main features of the operation of such a dam are as follows.

1. At the bottom edge of the core 34 immediately in front of the canvas 13, a high-quality anti-filter layer 27 is formed, which significantly increases the efficiency of the sandy core 34.

2. The soil material of the transition layer 4 in the baskets 7 is initially in a slightly compacted state, which prevents the core 34 from hanging on the transition layer 4. This is due to the fact that the under compaction of the soil of the transition layer 4 temporarily increases its (ie, gabion wall 5) deformability , which increases the reliability of the core 34, therefore, and the dam as a whole in the most critical initial period of operation of the dam.

The present dam design is proposed, as an option, for the Tuva (Uyuk) hydroelectric power station 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 4, the drawings are not illustrated. The dam is low temporary. A specific feature of the dam is that the mesh sizes of the wire mesh of the basket are accepted as minimally acceptable from the conditions of the economy, and the cells are filled with the soil of the transition layer directly without enclosing this soil in a flexible shell, i.e., without using claim 2 of the claims.

The above examples do not exhaust the cases of possible use of the invention, for example, cases of the location of the gabion wall in front of the core of the dam.

Designations

1 - base (non-rock)

2 - riding persistent prism

3 - bottom persistent prism

4 - transition layer (zone)

5 - gabion wall

6 - gabions

7 - basket (gabion)

8 - wire mesh (baskets)

9 - cell (baskets)

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

11 - upper side surface (gabion wall)

12 - flexible shell (from geotextile fabric)

13 - canvas (geotextile)

14 - gasket (mineral fiber boards)

15 - filtration flow

16 - aperture (in the basket)

17 - cover (baskets)

18 - edge wire

19 - the main wire

20 - locking apron

21 - canvas (geotextile)

22 - element (from cohesive soil)

23 - a layer of filled soil

24 - reinforcing panel

25 - water level in front of the dam

26 - transition layer (microlayer in front of the canvas 13 or 21, Fig.6)

27 - antifiltration layer (thin layer in front of the transition layer 26)

28 - protective layer

29 - fastening of an uphill slope

30 - waterproof membrane (geomembrane waterproofing polymer roll)

31 - horse transition zone (layer)

32 - lower transition zone (layer)

33 - base (rocky)

34 - core (sandy loam)

35 - tip of the dam

36 - waterproof membrane (in the tip of the dam)

37 - concrete slab

38 - cementation

Claims (4)

1. Soil heterogeneous bulk dam containing in the cross section a transition layer made of soil of a given grain composition, crossing the dam body in height and separating the part of the dam body from fine-grained soil from the part of the dam body from coarse soil, characterized in that the transition layer is made in in the form of a gabion wall of interconnected gabions whose baskets are box-shaped and made of wire mesh, with each cell of the basket filled with a portion of the soil of the transition layer and between the gabion wall and the fine-grained soil of the dam body, a separation layer is made of geosynthetic and / or mineral fiber material. 2. The dam according to claim 1, characterized in that the portion of the soil is enclosed in a flexible shell, which is made of geotextile fabric, has a box shape, and its dimensions are at least equal to the dimensions of the cell basket and provide a snug fit of the soil portion to the wire mesh cell baskets. 3. The dam according to claim 1, characterized in that the separation layer is made in the form of an anti-suffusion element made 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 D _about ^calculation satisfies the condition:

,
Where

- the maximum diameter of the soil particles, the movement of the filtration stream of which 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 from a waterproof membrane.

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