RU2680696C1 - Ground dam - Google Patents

Abstract

FIELD: construction.SUBSTANCE: invention relates to hydraulic structures designed to hold backwater in the water course and to protect areas from overflows during floods. Ground dam is made of sandy soil and includes a threshold, upstream and downstream slopes and drainage system. Sandy soil is laid in layers with geotextile canvases, while the free ends of each geotextile canvases cover the overlying soil layer on the side of both slopes with the inputting beneath the geotextile canvas covering the subsequent layer. Depth of the free ends of the geotextile canvases in the soil is determined by the dependence:, where P is the horizontal pressure of the soil on the inner surface of the geotextile; t is the thickness of the covered soil layer; q is the vertical pressure of the soil; ƒ – coefficient of friction of the soil by geotextile, in turn, the strength of geotextile is calculated by the formula: T≥P⋅r, where T is the tension of geotextile; r is the radius of ground coverage.EFFECT: invention allows to simplify the design of the dam and reduce the time and cost of construction of the structure and at the same time preserve the advantages of the prototype – high stability, filtration strength and reliability.1 cl, 4 dwg

Description

The invention relates to hydraulic structures designed to retain water backwater in the alignment of the watercourse and to protect territories from floods during floods.

Soil dams made of homogeneous sandy material are known, including the dam body with upper and lower slopes and drainage in the zone where the lower slope is interfaced with the base (Hydrotechnical Structures, Designer's Guide, Moscow: Stroyizdat, 1983, pp. 490-491, Fig. 20.3 ; 20.4; 20.5 and 20.6).

These types of structures in terms of stability and filtration strength require the formation of gentle slopes with the laying of slopes of 1: 3 or more. Such structures require a large amount of soil, respectively, significant costs for its preparation in quarries, transportation and laying in the body of the structure.

Known structures where composite materials are used to fasten slopes (Pat. RU No. 2610699, IPC EV 3/02, publ. 02/14/2017; Pat. RU No. 2616301, publ. 04/14/2017, Pat. RU No. 2614072, publ. 22.03 .2017).

The disadvantage of dams is the complexity of the structures, as well as the low efficiency of the drainage device.

Known soil dam (US Pat. RU No. 100527, IPC EV 02/07, publ. 10.11.2010), the technical nature and the achieved result is the closest to the claimed structure and adopted for its prototype. The dam includes an uphill slope, a threshold, a downhill slope, fasteners located along the downhill of a dam, reinforcing nets, anchor devices and flexible shells. The threshold is made multilayer, consisting of a number of layers of flexible shells, and the reinforcing mesh is made of woven synthetic material. Flexible shells made of woven synthetic material are filled with local sandy soil and have an elongated elliptical shape in cross section. Anchor devices in the form of vertical posts are placed in the body of the soil dam. The multilayer fasteners are arranged in steps along the lower slope with the inlet of the upper rows of fasteners on the lower rows. The closed parts of the reinforcing nets are placed around the perimeter of the layers of flexible shells of each fastening element of the bottom slope and the layers of flexible shells of the threshold of the soil dam in such a way that they form a closed loop. The extended parts of the reinforcing nets are attached at one end to the closed parts of the reinforcing nets of the layers of flexible shells of the downhill fastening elements, and at the other end are attached to the anchor devices.

The well-known dam has high stability, filtration strength and reliability in operation, but it has a complex structure and requires significant construction and time costs.

The claimed invention allows to simplify the design of the structure and reduce the time and cost of its construction, but at the same time maintain the advantages of the prototype - high stability, filtration strength and reliability.

, где Р - горизонтальное давление грунта на внутреннюю поверхность геотекстиля; t - толщина охваченного слоя грунта; q - вертикальное давление грунта; ƒ - коэффициент трения грунта по геотекстилю, в свою очередь прочность геотекстиля рассчитывается по формуле: Т≥P⋅r, где Т - натяжение геотекстиля; r - радиус охвата грунта. Для сбора и отвода фильтрующей воды в плотине предусмотрена дренажная система, выполненная в виде перфорированной труб, обернутых фильтрующей тканью и засыпанных щебнем и уложенных в каждом слое в зоне низового откоса, при этом по низовой грани плотины проложены коллекторы, а в сопряжении низового откоса с основанием проложены кюветы для отвода фильтрующей воды в нижний бьеф.To solve this problem, the following set of essential features is used: in a soil dam, made, like the prototype, of sandy soil, and including a threshold, uphill and downhill slopes and drainage system, while sandy soil was layered in layers by geotextiles, in contrast to the prototype the free ends of each geotextile sheet cover an overlying soil layer on the side of both slopes with a plant under the geotextile sheet, covering the subsequent layer, while the depth of free ends Autun geotextiles in the soil is determined by the relationship:

where P is the horizontal pressure of the soil on the inner surface of the geotextile; t is the thickness of the covered soil layer; q is the vertical pressure of the soil; ƒ is the coefficient of friction of the soil by geotextile, in turn, the strength of the geotextile is calculated by the formula: T≥P⋅r, where T is the tension of the geotextile; r is the radius of the soil. To collect and drain filter water in the dam, a drainage system is provided, made in the form of perforated pipes wrapped with filter cloth and covered with gravel and laid in each layer in the downstream slope zone, while collectors are laid along the bottom edge of the dam, and in conjunction with the bottom slope and the base cuvettes were laid to divert filter water into the downstream.

The essence of the invention lies in the fact that the geotextile cloths, laid in layers in the body of the dam, with free ends cover with an interference fit each above the laid layer on the sides, thereby ensuring the stability of the slopes. The length of the free ends of the canvas (the depth of the soil) is selected taking into account the creation of the necessary tension and reliable retention of the canvas in the dam body without additional anchor devices, which is ensured by the upper layers of soil pressing on the geotextile. The inventive structure has high stability, filtration strength and reliability. Moreover, in comparison with the prototype, it is structurally simpler and requires significantly less time and material costs during construction.

A comparison of the proposed structure and the prototype showed that the task - reducing the time and cost of building the dam - is solved as a result of a new set of features, which proves the compliance of the invention with the patentability criterion of "novelty".

In turn, the information search in the field of hydraulic structures did not reveal solutions containing individual distinctive features of the claimed invention, which allows us to conclude that the proposed design meets the criterion of "inventive step".

The invention is illustrated in the drawing, where

in FIG. 1 is a schematic representation of a dam,

in FIG. 2, 3 - shows the drainage system,

in FIG. 4 - presents a diagram for determining the depth of the geotextile.

The dam of FIG. 1 represents a soil embankment 1, on the slopes of which geotextile sheets 2 are laid, while the free ends of each sheet are brought into the body of dam 1. A tubular drainage is laid in the lower part of the geotextile sinus 3. The drainage of each layer on the lower slope (Fig. 2) is perforated a pipe 4 wrapped with geotextile (not shown in the drawing) and a gravel or crushed stone prism 5. On the lower slope from the threshold to the base, drainage collectors 6 are installed, paired with a tubular drainage 3 laid along the lower slope of the dam, while the lower end of the collectors 6 is displayed in the drainage tray 7.

The following is a sequence of actions when choosing the brand and size of geotextiles suitable for reinforcing slopes of an earth dam with specified parameters. As canvases can be used materials from Tensar, Geostroy, Geolon, Techpolymer, the friction coefficient of which at the peak is 0.8-1.0 (structured membranes). The depth of the free ends of the geotextiles in the soil is determined by the dependence:

where P is the horizontal soil pressure on the inner surface of the geotextile kN / m ² (kPa); t is the thickness of the covered soil layer, m;

where ρ is the density of the soil, ρ = 1.8 t / m ³ (sand);

g = 9.81 m / s ² - acceleration of gravity;

h is the thickness of the sand massif above the geotextile web (tape), m

ƒ is the coefficient of friction of the soil in geotextiles.

The strength of geotextiles, in turn, is calculated by the formula:

, λ _а =tg²(45-ϕ/2)≈0,33 (при ϕ=30°).Where

, λ _a = tg ² (45-ϕ / 2) ≈0.33 (at ϕ = 30 °).

For verification calculation, the following initial data are set:

- the height (thickness) of the soil layer above the settlement tape h = 5 m;

- soil density ρ = 1.8 t / m ³ ;

- coefficient of friction of a structured geotextile (geomembrane) over sand ƒ = 0.35;

- thickness of the wrapped soil layer t = 1 m;

The vertical soil pressure according to the formula (2) will be:

q = 5⋅1.8⋅9.81⋅2 = 177 (kPa).

Horizontal (lateral) soil pressure:

P = 0.5⋅5 ² ⋅1.8⋅9.81⋅0.33 = 73 (kPa)

Sheath Force:

T = P⋅r = 73⋅0.5 = 36.5 (kN / m)

Depth of free ends in the ground:

At q = 177 kPa, P = 73 kPa, ρ = 1.8 t / m ³ , t = 1 m, ƒ = 0.35, r = 0.5 m, taking into account the technological need for filling the soil, the strength of geotextiles is taken not less than 36.5 (kN / m), and the depth of free ends in the ground is not less than 1.2 m. Geomembrane type 1 TU 2246-001-56910145-2014 NORA with a thickness of 1.5 mm and tensile strength are not suitable for rated strength less than 40 kN / m. Given the guaranteed retention of the canvas in the soil, the depth of free ends is selected with a margin of ≈ 2 m.

According to the authors, the construction of such a dam will require 1.5 times less time and money than with the construction of an earth dam according to US Pat. RU No. 100527.

The proposed design was developed by specialists from the Department of Hydrotechnical Structures, Structures and Hydraulics of the State University of the Sea and River Fleet named after Admiral SB. Makarova. " The invention was used in the flood protection project of the Bovanenkovo oil and gas condensate field in the floodplain of the Se-Yakha River (Yamal Peninsula) when the university carried out the theme “Development of fundamental technical solutions for regulating the flow of high floods in the flow formation zone - on tributaries of the river. Se-Yah. "

The above allows us to conclude that the invention meets the criterion of "industrial applicability".

Claims (2)

1. A soil dam made of sandy soil and including a threshold, upper and lower slopes and a drainage system, while the sandy soil is layered in layers with geotextile sheets, characterized in that the free ends of each geotextile sheet cover the overlying soil layer from both slopes with a plant under a geotextile fabric covering the subsequent layer, while the depth of the free ends of the geotextile webs in the soil is determined by the dependence:

where P is the horizontal pressure of the soil on the inner surface of the geotextile; t is the thickness of the covered soil layer; q is the vertical pressure of the soil; ƒ is the coefficient of friction of the soil by geotextile, in turn, the strength of the geotextile is calculated by the formula: T≥P⋅r, where T is the tension of the geotextile; r is the radius of the soil. 2. Soil dam according to claim 1, characterized in that the drainage system is made in the form of perforated pipes wrapped with filter cloth and covered with gravel and laid in each layer of the dam in the downstream slope zone, in turn, collectors are laid along the bottom edge of the dam, and in mating the lower slope with the base, cuvettes were laid to divert filter water to the downstream.

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