RU2370590C1 - Culvert under embankment in permafrost soils at periodically operating waterway - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: culvert comprises culvert aqueduct made of metal corrugated sheets and coupled by means of cushion and race to foundation and embankment, and two perforated anti-aufeis pipes, which are installed in cushion one by one aside from culvert aqueduct and at the distance from it. Anti-aufeis pipes within the limits of embankment are perforated and equipped with water intake located upstream embankment in filtering water collector. Cushion and race are made of cohesionless soils, and at the bottom and at sides they are enclosed up to a certain level into common water impermeable membrane, and near bottom slope of embankment they are partitioned by diaphragm, made of filtering geotextile web and coupled with water permeable membrane, which is made of polymer film, enclosed in geotextile. Filtering water collector comprises filtering geotextile cloth, which covers on top water collector of anti-aufeis pipe. Near upper slope of embankment, cushion and race are partitioned with additional diaphragm made of filtering geotextile cloth and coupled with membrane, and cushion on top is coated with filtering geotextile cloth coupled with membrane. Size of openings in geotextile cloth provides in process of filtration through it at first for creation of transition layer in soil directly upstream geotextile cloth from cohesionless soil, and then creation of anti-filtration layer upstream transition layer from cohesionless layer.

EFFECT: preservation of permafrost soils in natural condition, prevention of aufeis in culvert aqueduct and its frozen swelling.

6 cl, 5 dwg

Description

The invention relates to road construction, and more specifically to the design of a culvert under the embankment, made in the conditions of permafrost on a periodically operating watercourse.

Known culvert under the embankment containing a concrete pipe with two channels located one above the other. At the same time, the lower channel (additional) is designed to pass ground water, which can form ice in the upper channel (mainly), and this lower channel can be filled with filtering soil [1] or be free [2].

The disadvantage of such a culvert is the high cost of creating a concrete pipe, especially in harsh climatic conditions and in remote areas. Moreover, the implementation of the lower channel under the bottom of the upper channel with permafrost soils of the base is not technologically advanced, and its proximity to the cavity of the upper channel at negative air temperatures can lead to freezing of the lower channel, which complicates the operation of the culvert [3].

Known culvert construction under the embankment, the culvert of which is made of corrugated metal sheets and paired with made from incoherent soil pillows and clips with the base and the embankment [4].

The disadvantages of such a culvert are as follows.

1. The connection of metal corrugated sheets with each other is usually carried out by means of bolts with the formation of longitudinal and transverse joints. The implementation of such joints waterproof was difficult to implement and unreliable, which is why it is not widely used in practice. Therefore, to prevent the soil from being washed out of the cushion and cage with water that has penetrated into them from the culvert through its permeable walls, as well as with water filtering along the cushion and cage from the side of the upper (pressure) slope of the embankment, it is recommended to cover the pillow with an anti-filter element at the ends of the culvert structure made of reinforced concrete, concrete, cement or clay mixture. At the same time, it is proposed to provide means to prevent the accumulation of water in the pillow [4, p. 4.13] and [5, p. 4.13].

Firstly, it is not possible to reliably couple such an anti-filtration element directly with permafrost soils by economically acceptable means, which causes intense thawing of permafrost soils; secondly, overlapping only the pillows with the anti-filtration element does not exclude the removal of soil from the holder and the thawed part of the embankment located above it. All this significantly reduces the reliability of the culvert.

2. After the onset of negative air temperatures, between the termination of surface runoff and the freezing of the channel of a periodically operating watercourse (hereinafter: the cold season), low-temperature groundwater penetrating the culvert from the upper side through its inlet head and from its sides through its permeable walls, can form ice in the culvert (hereinafter: icy water). The icy water of the underground channel runoff of the watercourse can penetrate the culvert through its head, and the icy water accumulated in the cushion and cage during the warm season, which can significantly reduce the reliability of the culvert and complicate its operation, through its permeable walls.

Additionally, when the pillow freezes due to low temperatures in the cavity of the culvert during the cold season, if there is no means of draining water from the cushion, the water-saturated soil of the cushion will exhibit heaving properties, which can lead to the annual accumulation of bulging of the culvert with all the negative engineering and technical consequences operational consequences.

These shortcomings were the basis for the appointment of a number of recommendations that narrow the scope of use of such a culvert and introduce restrictions on its design, namely:

- the dimensions of the pipe openings in areas with an estimated minimum air temperature below minus 40 ° C must be at least 1.5 meters [4, clause 1.9], [5, clause 1.8] and [6, clause 4.4.4];

- the use of corrugated pipes with hole sizes less than 5 meters on streams in the presence of ice formation is not allowed [6, p.1.1.3];

- for pipes used in areas with an estimated air temperature below minus 40 ° C and permafrost, the minimum wall thickness should be taken 2.5 mm [4, clause 4.33] and 2.75 mm [5, clause 4.32].

In the sources [4], [5] and [6], the structural elements of the culvert are specified and developed sequentially. Based on this, the applicant made the claims without dividing the first paragraph into a restrictive and distinctive part.

The problem to which the invention is directed, is to increase reliability, expand the field of use and simplify the operation of the culvert.

The technical result from the use of the invention is:

- to prevent thawing of permafrost soils of the base and embankment and removal from them, as well as from the cushion and holder of soil, by the filtration flow in the warm season;

- to prevent the penetration of icy water into the culvert through its head and permeable walls in the cold season;

- to prevent the accumulation of water in the pillow, which, when it freezes, can cause frosty bulging of the culvert in the cold season.

The problem is solved, and the technical result is achieved by the fact that the culvert under the embankment in the conditions of permafrost soils on a periodically operating watercourse contains a culvert (main) made of corrugated metal sheets and, through a pillow and cage, connected to the base and the embankment, and one or more anti-skid pipe (optional), which is located in the cushion at a distance from the culvert, is perforated within the central part of the embankment and provided with a water intake, p memory location before the mound in the filter sump. The pillow and cage are made of incoherent soils and, from below and from the sides, are enclosed to a predetermined level in a common waterproof membrane for them, and near the bottom slope of the embankment they are blocked to the same level by a diaphragm (main) made of a geotextile fabric and paired with a waterproof membrane. The dimensions of the holes in the geotextile fabric first provide a filtering water in the soil immediately before the geotextile fabric of the transition layer, within which the pore space in the soil is clogged with particles of incoherent soil according to the inverse filter principle, and then the creation of an anti-filter layer in front of this transition layer, within which the pore space in the ground, it is collimated by particles of cohesive soil.

In addition, the membrane is made of a polymer film enclosed in geotextile, and the filtering sump contains a filtering geotextile fabric, which covers the top of the intake of the anti-icing pipe. Near the top slope of the embankment, the pillow and cage are blocked up to a predetermined level by an additional diaphragm made also of a filtering geotextile fabric and paired with a membrane, and the pillow is covered with a filtering geotextile fabric from above and is also paired with a membrane.

The pillow and filtering catchment are made in the thawed base of the channel of the watercourse.

The essence of the technical solution consists, first of all, in that, firstly, the pillow and cage are enclosed in a waterproof membrane and near the bottom slope the embankments are blocked by a diaphragm made of a geotextile web and qualitatively interfaced with this membrane, which prevents intensive thawing of permafrost soils and embankments to great depths and removal of soil from the pillows, holders and embankments in the warm season; secondly, the culvert includes an anti-icing pipe, which is located in the cushion at a distance from the culvert and is perforated in length, which prevents the penetration of iced water into the culvert through its head and through its permeable walls in the cold season, and additionally provides drainage from the pillow water squeezed during freezing from a culvert.

The anti-icing pipe works most efficiently in a pressure free mode, both when passing icy ground water in the cold season, and when passing surface runoff through a culvert during the warm season. The non-pressure regime in the anti-icing pipe, with a sufficient size of its opening, is ensured by the fact that the inflow of surface runoff water to it substantially limits the geotextile fabric covering the water intake, and the same geotextile fabric of the additional diaphragm blocking the pillow and the clip near the top slope of the embankment.

The group of signs assigned to the membrane and the diaphragm, and the group of signs referred to the anti-icing tube, each can be considered as an independent invention. However, in the conditions of permafrost soils (permafrost) on a periodically operating watercourse, ice almost always forms, therefore these two environmental attributes are included in the name of the object. At the same time, the membrane with the diaphragm and the anti-icing tube most effectively solve the previously indicated problem when they work together. The technical result from their joint work additionally consists in the fact that along the anti-icing pipe equipped with perforation, drainage (discharge) from the pillow and the holder of water held by the membrane and diaphragms is carried out. If it is not diverted, this water can seep into the culvert through its permeable wall and form ice in the culvert during the cold season, and also cause frost heap in the pillow and at its base when they freeze. All this allows us to conclude that the condition "Unity of invention" is met.

Comparison of the proposed solution with other known technical solutions shows: firstly, a waterproof membrane and a diaphragm made of geotextile fabric are not found in waterworks under the embankment; secondly, the anti-ice pipe is structurally implemented according to the new rules, which consist in the fact that the anti-ice pipe is located in the cushion, is removed from the cavity of the culvert, and its functions are expanded due to perforation - draining water from the cushion and cage. It is these new material and functional features, and in their totality, that maximally provide a new technical result in the proposed technical solution. All this allows us to conclude that the proposed technical solution, as the criterion of "Novelty" and the criterion of "Inventive step".

The invention is illustrated by the drawings shown in figures 1-5:

figure 1 shows a culvert, a longitudinal section;

figure 2 is a section aa in figure 1;

figure 3 is a section of the culvert, side view;

figure 4 - anti-slip device, design diagram;

figure 5 is a section bB in figure 1 (across the diaphragm).

The culvert was erected on a permafrost base 1 of a periodically operating watercourse 2 (hereinafter: watercourse) in the gap 3 of the embankment 4, made of local soil and freezing during operation to a permafrost state (Fig.2). The culvert includes a culvert 5, which is assembled from corrugated metal sheets 6 (Fig. 3) and, by means of a cushion 7 and a cage 8, is connected to the base 1 and the embankment 4. The culvert also contains an anti-skid device consisting of two anti-skid pipes 9. These pipes are located in the cushion 7 one side of the culvert 5 at a distance of 1.5-2.0 meters from it, perforated within the central part of the embankment (figure 4) and equipped with a common water inlet 10 located in front of the embankment 4 in the filter 11. The cushion 7 and the cage 8 and bottom and sides are enclosed up to a predetermined level 12 in a common waterproof membrane 13, and near the bottom slope 14 of the embankment 4 they are blocked up to a predetermined level 12 by a diaphragm 15 made of a filter geotextile and paired with a membrane 13 .

The membrane 13 is made of a polymer film 16 enclosed in geotextile 17. The membrane 13 can be made on a different basis, for example, instead of a polymer film, it may contain a layer of bentonite clay. The predetermined level 12 is usually equal to the calculated water level 18 before embankment 4 or slightly lower.

The dimensions of the water holes (not shown in FIG. 5) in the filtering geotextile fabric of the diaphragm 15 provide, when filtering water through it, first creating cushions 7 and clips 8 in the soil immediately in front of the geotextile fabric of the diaphragm 15 of the transition layer 19 (Fig. 5), and then - creation before this transitional layer 19 of an antifiltration layer 20. In the transitional layer 19, the pore space is filled (clogged) with particles of incoherent soil according to the inverse filter principle, and in the antifiltration layer the pore space GUSTs filled cohesive soil particles.

The filtering catchment 11 contains a filtering geotextile web 21, which covers the top of the water intake 10 of the anti-icing pipes 9. Near the uphill 22 of the embankment 4 and to the calculated level 18, the pillow 7 and the cage 8 are blocked by an additional diaphragm 23, also made of a filtering geotextile.

In the culvert 5, the connection of the metal corrugated sheets 6 is carried out by means of bolts 24 (Fig. 3) with the formation of lap joints of the longitudinal 25 and transverse 26.

The water inlet 10 is made in the form of a perforated pipe 27 located across the watercourse 2 and hydraulically in communication with the anti-icing pipes 9. If necessary, the water inlet 10 may contain an additional perforated pipe 28 (the pipe is shown in dashed in Fig. 4) located along the watercourse 2. At the free ends of the pipes 27 and 28 of the water inlet 10, plugs 29 are installed, and the perforation of these pipes 27 and 28, their plugs 29 and anti-icing pipes 9 are made in the form of slots 30, usually up to 4 mm wide.

The pillow 7 and the filtering sump 11 are made in the frozen layer 31 of the base of the channel of the watercourse 2.

The cushion 7 is made of gravel with a grain size of 5-50 mm, the cage 8 is made of sand-gravel, gravel-pebble or wood-gravel, not containing fragments larger than 50 mm of soil. If necessary (set in the project by calculation according to well-known mathematical formulas), the pillow 7 is covered with a filtering geotextile cloth 32 (dotted in figure 2), conjugated with a membrane 13 and preventing the movement of small particles of soil from the holder into the pillow 7.

Membrane 13 (geotextile 17), diaphragms 15 and 23, filter catchment 11 (geotextile fabric 21) and cushion cover 7 (geotextile fabric 32) use an artificial filter geotextile fabric of the Dornit type, fiberglass, fiberglass, etc.

The construction of the culvert is carried out mainly in the warm season and within the frozen layer 31 of the base of the channel of watercourse 2, using well-known construction technologies. The holder 8, if necessary, is reinforced with composite materials with geotextiles, and in the holder 8, spacers made in the form of volume geogrids can be installed [4-7].

In the drawings, there are other symbols:

33 and 34 - the highest position of the surface of the water saturation of the cage in the case of operation of anti-icing pipes, respectively, in pressure or in non-pressure mode;

35 - fastening with gabions;

36 - mount with a stone;

37 - maximum water level in the culvert;

38 - construction berm.

The construction works as follows.

In the warm season, the estimated surface runoff at a water level of 18 in front of embankment 4 is freely passed through a culvert 5 and partly through anti-icing pipes 9. At the same time, casing 8 is saturated with water through the permeable walls of the culvert 5 and filter cushion 7. At the same time, the membrane 13 prevents the penetration of pressure water into the frozen soils of base 1 and embankment 4, which substantially slows down the process of thawing of these soils in the warm season. The membrane 13 does not prevent the restoration of permafrost in the cold season, and the diaphragm 15 prevents the removal of soil from the cushion 7 and the cage 8.

With the onset of the cold season, perforated anti-icing pipes 9 allow concentrated icy ground water to pass through and drain water from the cushion 7 and cage 8 leaked into them from the culvert 5 during the warm season, which prevents the formation of ice in the culvert. Additionally, perforated anti-slip pipes 9 can be considered as “geocryological” drainage, which prevents the formation of cryogenic (including lifting action) loads on the culvert 5.

When working in the warm season, anti-icing pipes 9 in pressure mode in the cage 8, the maximum position of the water saturation surface 33 is set — in Fig. 2 this surface is shown with a dashed line. It is preferable to constantly non-pressure mode in anti-icing pipes 9, in which they operate in a drainage (water intake) mode and in which the holder 8 has a lower position of the water saturation surface 34. This mode is ensured by the fact that the flow from above of the surface drain 18 to the water intake 10 is substantially limited due to the mud of the pound in front of the geotextile web 21, and to the pillow 7 - due to the mud of the soil in front of the geotextile web of the additional diaphragm 23.

The possibility of creating an antifiltration layer by mudding the soil in front of the geotextile web from the top (pressure) side is indicated in [8], however, the mechanism and conditions for creating the antifiltration layer 20 in the source have not been disclosed. Therefore, for clarity, this mechanism is presented in the following example.

Let the study establish the value of the estimated diameter of the water supply hole in the geotextile web D _o ^{calculation g} = 0.1 mm After the water level rises in front of the geotextile web, the transition layer 19 is created by the principle of the inverse filter with very thin layers (hereinafter: microlayers), in which the particles of incoherent soil gradually decrease as the microlayer moves away from the geotextile cloth. In the first (counting from the geotextile web) microlayer contains particles with a minimum diameter

d ^{min i} = D _o ^{calculation g} = 0.1 mm

In each subsequent i-th microlayer, using the well-known formulas of VNIIG [9, p. 76], from the condition of shedding, we determine the minimum diameters

d ^{min i} = 0.77 D _about ^{max il}

where D _о ^{max il} is the maximum diameter of the filtration pores in the previous il microlayer.

The maximum diameter of the filtration pores in each i-th microlayer D _about ^{max i} according to the formula of VNIIG [9]:

where, for each microlayer of the transition layer 18, taking into account the peculiarities of its creation, we take the soil different grain coefficient η = d ₆₀ / d ₁₀ = 2, porosity n = 0.4, and the particle diameter of the layer of 17% coverage d ₁₇ = 1.2 d ^{min i} .

The calculation results for microlayers are summarized in the table.

No. of the i-th microlayer (from geotextiles) d ^{min i} , mm D _about ^{max i} , mm one 0.1000 0.0450 2 0,0347 0.0156 3 0.0120 0.0054 four 0.0042 0.0019 5 0.0014 0,0006 Amount 0.1523

From the table it follows that when passing from one microlayer from incoherent soil to another, their parameters d ^{min i} and D _о ^{max i} decrease by 1 / 0.77 × 0.45 = 2.9 times. Already in the 6th microlayer clay particles with a diameter of less than 0.001 mm are present. Such particles are colloidal and in the presence of about 2.5-3% or more of them in the soil, they give colmatant, and consequently, the soil as a whole has structural strength. The sum of the diameters d ^{min i of the} five microlayers is about 0.15 mm. Despite the forced assumptions and conventions, the above calculations show that the total thickness of the incoherent microlayers, and therefore, the entire transition layer 19 covering the geotextile fabric, is always less than 1 mm. Moreover, the creation of incoherent microlayers of the transition layer 19 is carried out mainly by removal of fine soil particles from it and their movement through the geotextile web from the filtration stream. Subsequently, immediately before the transitional layer 19, an anti-filtration layer 20 is created by filling (collating) the pore space in the soil adjacent to the geotextile web with colloidal particles of cohesive soil moved by the filtration stream.

The mechanism described above allows us to formulate conditions that, when determining (designating) the estimated diameter of the culverts in the geotextile D _{o, the} ^{calculation of} each structural element necessary to create in the natural way, first the transition layer 19, and then the antifiltration layer 20 in the following form:

- firstly, in the soil adjacent to the geotextile web from the top (pressure) side, or at least in a suspended solid runoff of the watercourse, there should be a sufficient number of small particles, the sizes of which provide the creation of layers of transitional 19 and anti-filtration 20;

- secondly, the pore sizes in the soil adjacent to the geotextile fabric on the upper side should provide the ability to move these small particles to the geotextile fabric;

- thirdly, at each stage of creating the transition layer 18 and the antifiltration layer 19 and throughout the shielded working area of the geotextile web, the parameters of the filtration flow should provide the ability to move to the geotextile web the required number of small particles of the required size.

The feasibility of these conditions is verified by research using well-known mathematical formulas, and the need for fulfillment and their sufficiency is established by the project.

For the geotextile web of the diaphragm 15 (near the bottom slope) and the geotextile web 32 (covers the pillow), only the first condition may be sufficient. For the geotextile web of the additional diaphragm 23 (near the uphill slope) and the geotextile web 21 (in the filter catchment), all three conditions are preferable.

Under natural conditions, in the warm season, in the channel of watercourse 2, the soil thaws usually to a depth of 2-3 meters and forms a thawed layer 31. Therefore, this layer 31 does not contain ice inclusions, is a good base and it is easy to make a pillow 7 and a filter catchment 11 in it.

In the cold season, the groundwater flow gradually stops, and pipes 27 and 28 in the water intake 10 freeze. In this case, excess water, if it is in these pipes, is squeezed out of them through slots 30. At the same time, soils of cushion 7 and cage 8 freeze around the culvert 5, however, this is not dangerous, since water is squeezed out of them into perforated anti-ice pipes 9, which are located at a distance from the culvert 5 and which, if they freeze, then only at the end of the cold season, when they are guaranteed to be in an empty state.

The proposed design of the culvert under the embankment ensures the conservation of permafrost soils in their natural state, prevents the formation of ice in the culvert and its frosty bulging, which increases the reliability of the culvert, expands the area of use and simplifies its operation.

Information sources

1. Culverts for railways and roads at an estimated temperature of -40 ° C and below, deep seasonal freezing and ice. Typical designs 3.501-65: Rectangular concrete pipes. Issue III. Ministry of Transport, Glavproekt, p. 58-59.

2. Guidance on the design, construction and operation of artificial structures of roads on watercourses with ice. / Voronezh engineer. builds, in. - M .: Transport, 1989.

3. Copyright certificate of the USSR No. 1548311, cl. E01F 5/00, publ. 03/07/90.

4. Instructions for the design and construction of corrugated metal culverts: VSN 176-78. Ministry of Transport of the USSR. - M., 1979.

5. Guidelines for the use of corrugated metal culverts. / TsNIIS OJSC. - M., 2001.

6. Guidelines for the use of large-diameter metal pipes in the conditions of icing and permafrost (for experimental construction) / FSUE SoyuzdorNII. - M., 2003. Adopted and enforced by order of the Ministry of Transport of the Russian Federation of 08.25.2003.

7. Patent of the Russian Federation No. 2280124, cl. E01F 5/00, publ. 07/20/2006.

8. Patent of the Russian Federation No. 2272095, cl. E01F 5/00, publ. 03/20/2006.

9. Goldin A.L., Rasskazov L.N. Design of soil dams: Textbook. manual for universities. - M .: Energoatomizdat, 1987.

Designations

1 - permafrost base (hereinafter: base),

2 - periodically operating watercourse (hereinafter: watercourse),

3 - failed

4 - embankment

5 - culvert,

6 - metal corrugated sheets,

7 - pillow,

8 - clip

9 - anti-icing pipe,

10 - water intake,

11 - filtering catchment,

12 - set level (membranes, diaphragms),

13 - waterproof membrane (same: membrane),

14 - lower slope (embankment),

15 - diaphragm (near the bottom slope),

16 is a polymer film,

17 - geotextiles (membranes),

18 - water level (before the embankment),

19 - transition layer

20 - antifiltration layer,

21 - geotextile cloth (filter catchment),

22 - riding slope,

23 - additional diaphragm (near the uphill slope),

24 - bolts

25 - longitudinal joint

26 - transverse joint

27 - perforated pipe (water intake),

28 - additional perforated pipe (water intake),

29 is a stub

30 - slots

31 - thawed layer (layer of seasonal thawing-freezing),

32 - geotextile fabric,

33 and 34 - the highest position of the surface of the water saturation of the cage in the case of the anti-icing pipe, respectively, in pressure or in non-pressure mode,

35 - mount gabions,

36 - stone mount

37 - maximum water level in the culvert,

38 - construction berm (in the gap).

Claims (6)

1. A culvert under the embankment in the conditions of permafrost soils on a periodically operating watercourse, characterized in that it contains a culvert made of corrugated metal sheets and, by means of a pillow and cage, connected to the base and the embankment, and one or more anti-icing pipes, which are located in cushion at a distance from the culvert, perforated within the central part of the embankment and equipped with a water intake located in front of the embankment in the filtering catchment, and this cushion and cage are made of incoherent soil and from below and from the sides are enclosed to a predetermined level in a common waterproof membrane, and near the bottom slope of the embankment they are blocked to the same predetermined level by a diaphragm made of geotextile fabric and paired with a waterproof membrane, and the size of the holes in a geotextile web, in the process of filtering water through it, first, in the soil, a transition layer is created in the ground immediately before the geotextile web, within which the pore the soil soil is clogged by particles of incoherent soil according to the inverse filter principle, and then the creation of an antifiltration layer in front of this transition layer, within which the pore space in the soil is clogged by particles of cohesive soil. 2. The culvert according to claim 1, characterized in that the membrane is made of a polymer film enclosed in geotextile. 3. The culvert according to claim 1, characterized in that the filtering sump contains a geotextile web that covers the top of the intake of the anti-icing pipe. 4. The culvert according to claim 1, characterized in that near the uphill slope of the embankment, the pillow and cage are blocked to a predetermined level by an additional diaphragm made of a geotextile web and paired with a membrane. 5. The culvert according to claim 1, characterized in that the pillow is covered with a geotextile fabric paired with a membrane. 6. The culvert according to claim 1, characterized in that the cushion and filtering catchment are made in the frozen base of the channel of the watercourse.

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