RU2368727C1 - Soil dam on water-permeable foundation - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention is related to hydrotechnical construction of soil dams on water-permeable foundation. Soil dam on water-permeable foundation comprises draining part installed on water-permeable foundation on lower side from antifiltration device, foot of which is located on water-permeable foundation with creation of coupling in the form of contact of antifiltration device foot with water-permeable foundation. Dam comprises water-permeable web, which is located on water-permeable foundation on lower side from antifiltration device and is coupled with it. Water-permeable web has specified width in cross section and is made of geotextile material. Rated diametre of water-conducting (filtering) holes of water-permeable web

is determined provided that at first transition layer is created directly upstream water-permeable web, within the limits of which pore space in filtering soil is mudded with non-cohesive soil according to reverse filter principle, and then antifiltration layer is created upstream this transition layer, within the limits of which pore space in filtering soil is mudded with non-cohesive soil. Rated diametre of water-conducting holes in water-permeable web

satisfies condition

where

is maximum diametre of soil particles that may be moved by filtration flow to water-permeable web.

EFFECT: invention makes it possible to increase quality of soil dam antifiltration device coupling with water-permeable foundation.

2 dwg

Description

The invention relates to hydraulic engineering, in particular to soil dams (dams) on a permeable base.

A soil dam is known on a permeable, usually non-rocky, base containing a draining part located on a water-permeable base on the lower side of the anti-filtration device, the sole of which is located on the water-permeable base to form a contact in the form of contact between the sole of the anti-filtration device and a water-permeable base (Hydrotechnical Structures. Designer Handbook / Under the editorship of V.P. Nedrigi, Moscow: Stroyizdat, 1983. P. 144). The antifiltration device can be located anywhere in the dam, from the uphill slope to its central part and even to the lower edge of this central part. It can be made both from low-permeable soil materials (loam, sandy loam, clay, and others), and from non-ground materials (concrete, reinforced concrete, asphalt concrete, metal, wood, plastics, and others), and with any combination of materials in different parts of the antifiltration device (screens, cores and ponura). At the same time, the loosening in the dam with the soil antifiltration device, in a pronounced form, may be absent (ibid., Pp. 170-172).

With any known embodiment, regarding the location of the anti-filter element in the dam and the material of its execution, the dam has the following disadvantages.

1. In the area of a water-permeable base, on the surface of which there is a place for the sole of the sole of the anti-filtration device and its bottom face, the flow lines of the filtering water thicken, therefore, the gradients and velocities of the filtration flow in this area of the base increase. The output gradients at the contact of the permeable base with the draining part of the dam also increase, and at this interface, the output gradients reach their maximum value. All this causes a water-permeable base to move fine particles and particles of the skeleton of the soil by a filtration flow and take them out to bypass the anti-filtration device’s washed soles into the draining part of the dam. This can lead to the formation in the soil of the base of the place with increased porosity and to a violation of the strength and stability of the soil in this so-called "Focus erosion."

2. In a dam in which the antifiltration device is made of soil material, mechanical erosion of the antifiltration device at its contact with the base, especially at the place of maximum output gradients, can occur under the influence of high filtration flow rates under conditions of increased porosity at the base. It can also violate the strength and stability of the soil directly at the interface between the antifiltration device and the water-permeable base, and thereby increase the negative impact of the previously indicated “erosion focus”.

These shortcomings reduce the quality of the interface between the anti-filtration device of the soil dam and a water-permeable base, therefore, they reduce the reliability of the soil dam as a whole.

The problem to which the invention is directed, is to increase the reliability of the soil dam on a permeable base.

The technical result from the use of the invention lies in the fact that the quality of the interface between the anti-filtration device of the soil dam and the permeable base is improved due to:

- reduction of gradients, speeds and flow rate of the filtration stream in a permeable base;

- reducing output gradients at the contact of the permeable base with the draining part of the dam;

- prevention of mechanical erosion of the soil antifiltration device at its sole.

определен из условия сначала создания непосредственно перед водопроницаемым полотном переходного слоя, в пределах которого поровое пространство в фильтрующем грунте кольматировано несвязным грунтом по принципу обратного фильтра, а затем создания перед этим переходным слоем противофильтрационного слоя, в пределах которого поровое пространство в фильтрующем грунте кольматировано связным грунтом, то есть расчетный диаметр водопроводящих отверстий в водопроницаемом полотне

удовлетворяет условию:This problem is solved, and the technical result is achieved by the fact that in a soil dam on a water-permeable base containing a draining part located on a water-permeable base on the bottom side of the anti-filtration device, the sole of which is located on the water-permeable base with the formation of a pair in the form of contact between the sole of the anti-filtration device and the permeable the base, according to the invention, the soil dam further comprises a permeable sheet. This web is located on a water-permeable base on the bottom side of the anti-filtration device, paired with an anti-filtration device, has a predetermined width in the cross section of the dam, is made of geotextile material, and improves the quality of coupling of the anti-filtration device with a water-permeable base. The estimated diameter of the water-supplying (filtering) holes of the permeable sheet

determined from the condition of first creating immediately in front of the permeable sheet of the transition layer, within which the pore space in the filtering soil is clogged with incoherent soil by the principle of the inverse filter, and then creating before this transitional layer an anti-filtration layer, within which the pore space in the filtering soil is clogged with cohesive soil, that is, the estimated diameter of the water holes in the permeable sheet

satisfies the condition:

,

,

- максимальный диаметр частиц грунта, которые могут быть перемещены фильтрационным потоком к водопроницаемому полотну.Where

- the maximum diameter of soil particles that can be moved by filtration flow to a permeable sheet.

It is the supply of the soil dam with a water-permeable sheet made according to the indicated rules that provides the solution to the problem and the achievement of the technical result: improving the reliability of the soil dam by improving the quality of the interface between the antifiltration device and the water-permeable base.

The proposed soil dam on a permeable base is illustrated by the drawings shown in figures 1 and 2.

Figure 1 shows a cross section of a soil dam, figure 2 - section aa in figure 1.

Soil dam (hereinafter: dam) was erected on a water-permeable foundation (hereinafter: foundation) 1. From the upper pool to the lower pool, the dam consistently includes a load 2, an upper transition zone 3, an anti-filtration device made of cohesive soil in the form of a screen 4 and ponura 5, the lower transition zone filter 6, the lower transition zone 7 and the lower prism 8, made of stone outline. On the surface of the base 1, within the transition zone 7 and the lower prism 8, a leveling filter 9 is made of gravel-pebble soil. The lower transitional zone-filter 6 and the leveling layer-filter 9 form the inner surface of the drainage part of the dam, located on the lower side from screen 4.

The dam contains a water-permeable web (hereinafter: web) 10, which is located on the base 1 from the bottom side of the screen 4 and interfaced with it by positioning part of the web 10 under the sole of the screen 4. The web 10 is made of geotextile material and has a predetermined width in the cross section of the dam at. The position of the bottom edge, relative to the screen 4, of the edge 11 of the web 10 is established by the project after determining the parameters of the filtration flow in the base 1 and when leaving it, as well as the stability of the bottom prism 8.

The estimated diameter of the water supply (filtering) holes of the canvas 10

удовлетворяет условию:determined from the condition from the beginning of the creation immediately before the web 10 of the transition layer 12 (Fig.2), within which the pore space in the filtering soil is clogged with incoherent soil by the principle of the inverse filter, and then create before this transitional layer 12 of the antifiltration layer 13, within which the pore space in the filter soil is clogged with cohesive soil, that is, the estimated diameter of the water holes in the canvas

satisfies the condition:

,

,

- максимальный диаметр частиц грунта, которые могут быть перемещены фильтрационным потоком к полотну.Where

- the maximum diameter of soil particles that can be moved by filtration flow to the canvas.

назначают исходя из результатов исследования полотна, т.е. геотекстиля, выполненного по специальной программе, а предварительно - исходя из представленных изготовителем данных об эффективном размере пор в геотекстиле.The estimated diameter of the water holes in the canvas

prescribed based on the results of the study of the canvas, i.e. geotextiles made in accordance with a special program, and previously, based on the data provided by the manufacturer on the effective pore size in geotextiles.

устанавливается проектом исходя из результатов исследования и/или по известным математическим формулам исходя из конкретных грунтов основания и параметров фильтрационного потока.Maximum diameter of soil particles

established by the project on the basis of the results of the study and / or according to well-known mathematical formulas based on specific base soils and filtration flow parameters.

The following water parameters are indicated in the drawings:

14 - water level (in front of the dam);

15 - plot of the output gradients (after the first rise in the water level in front of the dam);

16 - plot of output gradients (during the operation of the dam);

17 - streamlines (filtering water).

The dam works as follows.

After the first rise, a filtration water flow with a relatively high speed and high gradients 15 (I) is established in front of the water level dam 14 at the base 1 when this stream exits from the base 1 to the transition zone-filter 6 and the leveling layer-filter 9. In this case, the web 10 practically does not affect these initial parameters of the filtration flow.

Such a filtration flow in the base 1 weighs small particles of soil and moves them primarily to the canvas 10, where the flow velocities and its gradients I at the exit from the base 1 are greatest.

Particles, the diameter of which is less than the diameter of the water supply holes of the blade 10, in most cases pass through the blade 10 and, together with water, go to the downstream. Larger particles are retained by the web 10 and they create the first microlayer of the transition layer 12. Subsequently, sequentially decreasing particles are retained up to colloidal particles. This completes the natural creation of a transition layer 12, the thickness of which usually does not exceed 1 mm. This layer 12 covers on the top side, i.e. below, the web 10, in which the pores are sealed with incoherent soil, the particles of which are located in the pores of the soil of the base 1 according to the principle of the inverse filter. Therefore, the transition layer 12 retains all small, including colloidal particles, and does not pass them through itself even with a strong seismic shock. As a result of the forceful effect of the filtration flow on the soil skeleton, a thin, measured in centimeters, but exceptionally high-quality anti-filtration layer 13 is created over time. 13 In this layer 13, the pores are sealed with cohesive soil, therefore, the filtration flow velocities in the base 1 significantly decrease over time and the thickness of the anti-filtration increases layer 13 slows down and eventually stops. At the same time, the thickness of the antifiltration layer 13 decreases as it approaches the bottom edge 11 of the web 10, and its water permeability increases.

At the same time, the maximum value of the output gradients 15 I ^max moves from the screen 4 to the lower edge 11 of the web 10. The value of I ^max decreases significantly, the output gradients I form a plot 16, the flow lines 17 of the filtering water deviate towards the downstream and are rarefied, and the speed and flow rate of filtering water are reduced.

Thus, in the base 1 of the dam in the right place and of the specified size, after raising the water level 14 in front of the dam, a high-quality reverse ponder is created in the form of a thin antifiltration layer 13, which is protected by a web 10 made of non-suffusion geotextile material.

As a result of all this, the work of the proposed dam, in contrast to the work of the nearest known dam, is characterized by the following positive features:

- reduced gradients, speeds and flow rate of the filtration flow in the base;

- the gradients I of the filtration flow output from the base are reduced;

- prevented mechanical erosion of the screen from the side of its sole.

These features in the operation of the soil dam appear regardless of the location of the anti-filter element in the dam and the material of its implementation. These features, due to the high quality of the antifiltration layer 13, are preserved after a long (centuries-old) operation of the soil dam, when the canvas is destroyed and, as it were, disappears.

The consequence of these features is to increase the quality of the interface between the anti-filtration device of the soil dam and a water-permeable base, and therefore, increase the reliability of the soil dam as a whole.

Designations

1 - permeable base (hereinafter: base)

2 - loading (screen)

3 - horse transition zone

4 - screen

5 - ponur

6 - lower transitional zone-filter

7 - lower transition zone

8 - grassroots prism

9 - leveling layer filter

10 - permeable canvas (hereinafter: canvas)

11 - bottom edge (canvas)

12 - transition layer

13 - antifiltration layer

14 - water level (in front of the dam)

15 - plot of the output gradients (after the first rise in the water level in front of the dam)

16 - plot of the output gradients (during the operation of the dam)

17 - streamlines (filtering water)

Claims (1)

A soil dam on a water-permeable base, containing a drainage part located on a water-permeable base on the bottom side of the anti-filtration device, the sole of which is located on a water-permeable base with the formation of a pair in the form of contact of the sole of the anti-filtration device with a water-permeable base, characterized in that it additionally contains a permeable sheet, which is located on a permeable base from the bottom side of the anti-filtration device, sop It is connected with an antifiltration device, has a predetermined width in the cross section of the dam, is made of geotextile material and provides an increase in the quality of interfacing of the antifiltration device with a water-permeable base, while the estimated diameter of the water-conducting (filtering) holes of the permeable web

determined from the condition of first creating immediately in front of the permeable sheet of the transition layer, within which the pore space in the filtering soil is clogged with incoherent soil by the principle of the inverse filter, and then creating before this transitional layer an anti-filtration layer, within which the pore space in the filtering soil is clogged with cohesive soil, those. design diameter of water holes in a permeable sheet

satisfies the condition

Where

- the maximum diameter of soil particles that can be moved by filtration flow to a permeable sheet.

Images