Reinforced concrete pipes sectional structure heading foundations. Information about the structures of culverts and small bridges. II. instructions on the technology of the production process
Prefabricated reinforced concrete pipes, depending on the cross section, are divided into round cylindrical, round bases with a flat heel, rectangular and ovoid (Fig. 7.4).
Round culvert pipes they are used when the height of the embankment is mainly no more than 8 m. Round pipe sections under railway embankments are based on shallow or deep foundations, prefabricated, prefabricated-monolithic or monolithic. The design of the pipe foundation depends on the bearing capacity of the foundation soil. prefabricated reinforced concrete pipes: a - round, rectangular and ovoid, fig. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
When a round cylindrical link is supported on a flat foundation, a patterned block is used (Fig. 7.5).
Reinforcing cage of round links consists of two rows (external and internal) of working spiral reinforcement, transverse reinforcement - clamps, as well as distributive longitudinal reinforcement (Fig. 7.6).
Rice. 7.6. Scheme of the reinforcing cage of a round pipe for a link 1 m long: but- cross section; b– view 1-1 and facade; in- spiral; d k- frame diameter; d H k , d B k- the diameter of the location of the outer and inner spirals
The reinforcing cage consists of the same number of spirals located along the outer and inner contours of the link, which is determined by calculation. Design Institute Lengiprotransmost has developed the following standard designs of reinforced concrete round pipes:
№GS 3.501.1-144– round reinforced concrete culverts for railways and highways;
№GS 3.501.1-144. Issue 0-1. Inv. No. 1313/2- round reinforced concrete culverts with flat support for railways in normal climatic conditions.
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Rice. 7.7. Reinforcement scheme for a round link with a flat base: but- cross section; b– view along the pipe axis; d sq. ,
d book– diameters of the inner and outer frames
Links round pipes with a flat base have more economical reinforcement, the scheme of which, according to the developments of Lengiprotransmost, is shown in fig. 7.7.
The design of the input and output heads reinforced concrete round pipes from the unification condition are taken the same. The heads consist of sloping walls (wings), located at an angle to the axis of the pipe, and portal walls (Fig. 7.8).
Reinforcing frame of sloping wings performed from grids (Fig. 7.9).
Rice. 7.8. Round pipe head structure: but- facade; b - cut along the axis of the pipe; in - plan (mound not shown); 1 - conical link; 2 - portal wall 3 - sloping wall; 4 - pattern block; 5 - foundation
Rice. 7.9. The design of the reinforcing cage of the sloping wings of the head of a round pipe: but - facade; b - plan
The sloping walls of the heads are installed on reinforced concrete slabs laid on crushed stone or gravel-sand preparation. Between the sloping wings, a concrete tray is placed on gravel-sand preparation (see Fig. 7.8).
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Rice. 7.10. Scheme of a section of a reinforced concrete pipe of rectangular section: but- cross section; b– cut along the axis of the pipe
The standard design provides for an increase in elevated links by 0.5 m compared to normal ones. The following standard designs of prefabricated reinforced concrete pipes of rectangular section have been developed:
№GS 3.501-177.93- Reinforced concrete rectangular culverts for railways and roads (JSC Transmost, 1994);
№GS 3.501-177.93. Release 0-2– rectangular pipes for railways in moderate and severe climatic conditions (JSC Transmost, 1994);
№GS 3.501-107. Inv. №1130/1,2– rectangular concrete culverts for railways and highways.
Reinforcing cage of a rectangular pipe link includes grids consisting of working and distribution fittings, located along the outer and inner contours, taking into account the provision of a protective layer of concrete, which are combined using clamps (Fig. 7.11).
Rice. 7.11. Scheme of the reinforcing cage of a rectangular link: but- cross section; b– view along the pipe axis
In the middle part of typical pipe structures, the length of the sections is 2.01 and 3.02 m. The links rest on the foundation along a layer of cement mortar. Section foundations can be monolithic, prefabricated reinforced concrete or concrete blocks, shallow or deep. An expansion joint 3 cm thick is arranged between the sections.
In reinforced concrete pipes of rectangular section, socket heads with sloping wings located at an angle of at least 20 ° (Fig. 7.12).
On railways built in areas with harsh climatic conditions, rectangular reinforced concrete and concrete culverts are most widely used. Currently, standard projects of rectangular pipes for harsh climatic conditions have been developed:
№GS 3.501.1-177.93. Issue 0–3. Pipes for railways and roads in particularly harsh climatic conditions. (JSC Transmost, 1994);
№GS 3.501-65. Inv. No. 1016. Culverts for railways and roads at a design temperature of minus 40 ° C and below, deep seasonal freezing and icing. Rectangular concrete pipes. (Lengiprotransmost, 1976).
Rice. 7.12. The design of the outlet head of a rectangular pipe: but - facade; b - cut along the axis of the pipe; in - plan (mound not shown)
Links reinforced concrete pipes of rectangular section they are used with a hole from 1.5 to 6.0 m. They are based on precast-monolithic foundations, consisting of prefabricated reinforced concrete blocks L- or T-shaped (Fig. 7.13, 7.14) and monolithic concrete, as well as deep foundations on piles and pillars (Fig. 7.15, 7.16).
Rice. 7.13. Rectangular reinforced concrete pipe with L-shaped and T-shaped foundations: but - section cross section; b- head façade
Rice. 7.15. Rectangular reinforced concrete pipe with foundations on piles and pillars: but - cap; b, c - section cross section
Rice. 7.16. General view of a rectangular reinforced concrete pipe with foundations on piles
Structures of concrete rectangular pipes used with an opening from 1.5 to 6.0 m, which provide a culvert capacity of up to 150 m 3 / s. The middle sections of pipes are 3–4 m long. The structures of such pipes consist of reinforced concrete floor slabs, concrete blocks of walls, nozzles, a tray and a foundation (Fig. 7.16, 7.17). Pipes with an opening of 1.5–3.0 m have solid foundations, and the rest are separate on a natural foundation, monolithic, prefabricated, as well as deep-laid on piles or pillars. Trays are concreted on sand preparation. Pipes have socket heads with increased input and normal output links.
Typical concrete culverts have similar foundations as reinforced concrete ones (Fig. 7.17, 7.18).
Rice. 7.17. Rectangular concrete pipes: a, b - cross section of the section and head; in - with L-shaped and T-shaped foundations
In a typical design of rectangular culverts, foundations made of reinforced concrete blocks of L-shaped and T-shaped sections are provided for the freezing depth of the base soil, equal to 2.3 and 4 m.
In harsh climatic conditions, in the presence of thawed and weak soils at the base, it is preferable to install the extreme sections and head openings on pile foundations (see Fig. 7.16). The use of pile foundations increases the rigidity of the foundation and protects the pipes from stretch marks. In case of weak foundation soils, it is advisable to use foundations with inclined piles in the extreme sections and openings of the heads.
When constructing culverts on permafrost soils, they ensure the preservation of the natural regime of the foundation without violating natural conditions. In this case, preference is given to pipes with foundations on drill poles with a diameter of 0.6–0.8 m (see Fig. 7.15, in).
Rice. 7.19. The design of the head of a concrete pipe with an ovoid section: a - cross section; b- facade; 1 - cut opener; 2 - general form
Structures of concrete and reinforced concrete pipes ovoid section are used with an opening from 1.0 to 3.0 m (Fig. 7.19, 7.20). Reinforced concrete links of ovoid pipes have reinforcement in the form of closed spirals (Fig. 7.21).This type of reinforcing cage ensures reliable operation of the structure, taking into account the full range of loads. All sections of ovoid tube links work as eccentrically compressed elements.
The use of concrete ovoid pipes makes it possible to reduce the complexity of prefabrication and the consumption of reinforcing steel. They are used at embankment heights up to 20 m.
Reinforced concrete pipes of ovoid section are more efficient structures when compared with round structures in terms of reinforcement consumption on average up to 40-45%.
In the construction of culvert systems under automobile and railway lines, sloped wings and portal walls are used, which form pipe heads. In fact, this is a complex reinforced concrete structure, consisting of several main parts. At the end points of pipeline systems, heads are mounted that act as safety and reinforcing elements. The main structural element is the portal wall, framed by sloping wings.
The material for the production of pipe heads is concrete used in monolithic structures. The norms and requirements are regulated by TPR 503-7-015.90 for socket products and series 3.501.1-144 for round pipes. Conical heads are solid structures made of reinforced concrete, including a pipe link and a portal wall (ZKP 11.170 - 1 m diameter, ZKP 12.170 - 1.25 m diameter, ZKP 13.170 - 1.5 m diameter). The production of pipe heads can be carried out by a specialized enterprise with sufficient material and technical capabilities. Due to the fact that there are not many such factories, sometimes there is a shortage of products, this is mainly observed in the spring and summer. Transportation of pipe heads is carried out using trucks. In some cases, special transport is required, for example, when loading slope walls to large-sized pipe links (1,200 mm diameter).
Serial production of caps
At the enterprises, the production of heads is carried out in accordance with the existing standard documentation on pipe elements of culvert systems. Portal walls and slope wings are produced separately. Concrete grades are selected in accordance with the specific purpose of the product.
Culverts are used to divert small runoffs of water and pass them under the road. Their use is more expedient than the construction of a bridge.
General concept
Culverts are used to pass water from the top to the bottom. These include culverts, bridges, drainage systems. The latter are used to pass various channels under the roadway.
Culverts are used in cases where it is necessary to pass small drainage systems under the road (streams, draining water after rain or snow melt, and so on). The passage of water through pipes can be carried out continuously or periodically. Through such structures sometimes organize the passage of livestock or the passage of vehicles.
The installation of culverts does not require narrowing the carriageway and changing the type of road surface. A backfill is arranged over the structure. The thickness of the layer of poured soil reduces the pressure on the structure from cars and softens their impact.
Using pipes for passing water has its advantages:
- passes without damaging the subgrade.
- cheaper than building a bridge.
- With a backfill layer thickness of more than 2 m, the impact on the structure of temporary loads from passing vehicles is minimized.
Pipe dimensions
The diameter of the culvert depends on its length:
- If the length of the pipe does not exceed 2-3 m and the height of the embankment is less than 7.5 m, then the pipe opening is chosen equal to 100-150 cm.
- For an embankment up to 1.5 m, the diameter should be 75 cm.
- The pipes within the ramps are 50 cm in diameter.
Classification
Culverts are classified according to several parameters.
Depending on the material from which they are made:
- Concrete.
- Polymeric (from polymer concrete, polyvinyl chloride and polyethylene).
- Reinforced concrete.
- Stone.
- Metal.
- Fiberglass.
There are several types of pipes depending on the shape of the cross section:
- Round.
- Arched.
- Elliptical.
- Rectangular.
- Trapezoidal.
- Ovoid.
- Triangular.
According to the principle of the section:
- Non-pressure.
- Pressure.
- Semi-pressure.
The cross section of pipes can have one, two or more points.
The main elements of the pipe and their installation
Culverts are made up of several elements:
- Entry cap.
- Pipe links.
- Output cap.
Due to the presence of heads in the pipe, whirlpools and turbulences are not formed, water flows out more slowly. Their presence prevents the flowing water from eroding the embankment and washing away the foundation.
There are several types of heads:
- Portal, which are built in the form of a perpendicular pipe This is the simplest design, but it has its drawbacks. It does not provide smooth water flow. Therefore, its use is recommended in cases with a small amount of water flowing at low speed. Portal heads are used for pipes with a diameter of 50-75 cm.
- Bell-shaped. In addition to the wall, they have two openings forming a bell. The wings are located at an angle of 30 degrees to the pipe. Due to this, the flow of water gradually narrows.
- Collar, in which the extreme element is cut off at the same angle as the embankment. A protective collar is installed along the contour.
- Streamlined in section gradually narrow, which creates good conditions for the flow of water.
The pressure on the ground is distributed evenly due to the foundation on which the pipe is laid. It also prevents the shift of individual elements of the structure.
There are the following types of foundation:
- Without foundation (natural foundation).
- Soil pillow, created artificially.
- From monolithic concrete.
- From individual reinforced concrete elements.
The choice of foundation type depends on the diameter of the pipe, the height of the embankment and the geological conditions.
The culvert is located strictly perpendicular to the axis of the road. This gives the minimum pipe length. In some cases, it is recommended to install the structure in the direction in which the flow flows. This reduces the likelihood of whirlpools. In such cases, the construction of culverts in other directions is allowed.
Head blocks are important components of culverts that close its body. These devices, regardless of the geometric shape, perform a number of identical functions. Firstly, they contribute to the uniform inflow and outflow of waters of various origins. Secondly, they have a strengthening function, supporting the slopes of embankments. An important task is to protect the entrance and exit clearance of the structure from clogging with soil.
Heads determine the mode of hydraulic operation of the pipeline: pressure, semi-pressure and non-pressure. There is an inlet section, located on the upper side of the embankment, and an outlet section, located on the downstream side. By design, the head parts are classified into: portal, corridor, socket, collar, streamlined.
Portal heads have the simplest structure. They are presented in the form of a retaining block necessary to maintain the slope of the road embankment. With respect to the longitudinal axis of the pipe, the wall is installed perpendicularly. This design is suitable for low flow rates and low flow rates.
A feature of the corridor head is parallel blocks deployed at their beginning, the height of which is constant.
The socket head includes a portal wall block and sloping wings. Such a structure improves the conditions for the flow of fluid. The device is designed to operate pipes in non-pressure and pressure modes. Socket heads in combination with elevated links are installed in rectangular pipes, and in combination with conical ones - for round ones.
Collar heads are elliptical end links located in the plane of the slope of the embankment.
In the form of a truncated pyramid, a streamlined head is made. Its complex design allows the pipeline to function effectively in floods with a full cross section. These heads are suitable for the installation of round pressure pipes.
Standard designs provide for pipe designs for operation in different modes, as well as for areas of permafrost, ice formation and on slopes. Based on the calculations of the strength of the water flow, its width, frequency, as well as on the characteristics of the soil, a suitable head shape is chosen. The width of the tip, corresponding to the watercourse, captures the flow of water and prevents erosion of a significant part of the road embankment.
The ZHBI MARKET plant successfully carries out sale of reinforced concrete heads. The production of head blocks is based on various standard projects. It is possible to manufacture reinforced concrete products according to the working documentation provided by customers. You can buy products from the manufacturer for equipping road facilities in St. Petersburg and other regions at affordable prices.
TYPICAL TECHNOLOGICAL CHART (TTK)
PERFORMANCE OF WORKS ON THE CONSTRUCTION OF A PREfabricated Culvert With A Hole Of 3.0x2.0 M With Monolithic Heads
I. SCOPE
I. SCOPE
1.1. A typical technological map (hereinafter referred to as TTK) is a comprehensive regulatory document that establishes, according to a specific technology, the organization of work processes for the construction of a structure using the most modern means of mechanization, progressive designs and methods of performing work. TTK is designed for some average conditions for the production of work. The TTK is intended for use in the development of Projects for the production of works (PPR), other organizational and technological documentation, as well as for the purpose of familiarizing (training) workers and engineering and technical workers with the rules for the production of work on the construction of a reinforced concrete, prefabricated culvert with an opening of 3.0x2.0 m with monolithic heads for the embankment of the road.
1.2. This map contains instructions for the construction of a culvert using rational means of mechanization, data on quality control and acceptance of work, industrial safety and labor protection requirements in the course of work.
1.3. The regulatory framework for the development of a technological map is: SNiP, SN, SP, GESN-2001 ENiR, production norms for the consumption of materials, local progressive norms and prices, norms for labor costs, norms for the consumption of material and technical resources.
1.4. The purpose of creating the TC is to describe solutions for the organization and technology of construction work in order to ensure their high quality, as well as:
- cost reduction of works;
- reduction of construction time;
- ensuring the safety of work performed;
- organization of rhythmic work;
- unification of technological solutions.
1.5. On the basis of the TTK, as part of the WEP (as mandatory components of the Work Execution Project), Working Flow Charts (RTC) are developed for the performance of certain types of work on the construction of a culvert. Working technological maps are developed for the specific conditions of a given construction organization, taking into account its design materials, natural conditions, the available fleet of machines and building materials, tied to local conditions. Working technological maps regulate the means of technological support and the rules for the implementation of technological processes in the production of work. Structural features for the construction of a culvert are decided in each case by the Working Design. The composition and level of detail of materials developed in the RTC are established by the relevant contracting construction organization, based on the specifics and scope of work performed.
Working flow charts are reviewed and approved as part of the PPR by the head of the General Construction Contractor, in agreement with the Customer's organization, the Customer's Technical Supervision.
1.6. The technological map is intended for the foremen of work, foremen and foremen performing construction work, as well as employees of the technical supervision of the Customer and is designed for specific conditions for the performance of work in the III temperature zone.
II. GENERAL PROVISIONS
2.1. The technological map has been developed for a complex of works on the construction of a culvert.
2.2. Culvert construction work is carried out in one shift, the working hours during the shift are:
Where 0.828 is the coefficient of use of mechanisms in time during the shift (the time associated with preparing for work and conducting ETO - 15 minutes, breaks associated with the organization and technology of the production process and the driver's rest - 10 minutes every hour of work).
2.3. The scope of work sequentially performed during the construction of a culvert includes:
- preparatory work;
- marking works;
- excavation;
- installation works (installation of the outlet head, installation of the foundation for the pipe body, installation of pipe sections, installation of the inlet head);
- waterproofing works;
- fortification works.
2.4. The technological map provides for the performance of work by an integrated mechanized link with truck jib crane KS-4561A(see fig. 1 and fig. 2) with a lifting capacity of 25.0 t as a driving mechanism.
Fig.1. General view of the truck crane KS-4561A
Fig.2. Altitude and load characteristics of the crane KS-4561A
2.5. Work should be carried out in accordance with the requirements of the following regulatory documents:
- SP 48.13330.2011. Organization of construction;
- SNiP 3.01.03-84. Geodetic works in construction;
- SNiP 3.02.01-87. Earthworks, foundations and foundations;
- SNiP 3.06.04-91. Bridges and pipes;
- SNiP 3.03.01-87. Bearing and enclosing structures;
- SNiP 3.04.01-87. Insulating and finishing coatings;
- SNiP 3.04.03-85. Protection of building structures against corrosion;
- Manual to SNiP 3.02.01-83*. Manual for the production of work in the construction of foundations and foundations;
- VSN 32-81. Waterproofing of bridges and pipes;
- SNiP 12-03-2001. Labor safety in construction. Part 1. General requirements;
- SNiP 12-04-2002. Labor safety in construction. Part 2. Construction production;
- RD 11-02-2006. Requirements for the composition and procedure for maintaining as-built documentation during construction, reconstruction, overhaul of capital construction facilities and the requirements for certificates of examination of work, structures, sections of engineering and technical support networks;
- RD 11-05-2007. The procedure for maintaining a general and (or) special journal for recording the performance of work during construction, reconstruction, overhaul of capital construction projects.
III. ORGANIZATION AND TECHNOLOGY OF WORK PERFORMANCE
3.1. In accordance with SP 48.13330.2011 "Organization of construction", prior to the commencement of construction and installation works at the facility, the Contractor is obliged to obtain from the Customer project documentation and permission to perform construction and installation works in the prescribed manner. Work without permission is prohibited.
3.2. Prior to the start of work on the construction of a culvert, it is necessary to carry out a set of preparatory work and organizational and technical measures, including:
- appoint persons responsible for the quality and safe performance of work;
- briefing the members of the safety team;
- place the necessary machines, mechanisms and inventory in the work area;
- arrange temporary passages and entrances to the place of work;
- provide communication for operational and dispatching control of the production of works;
- establish temporary inventory household premises for storing building materials, tools, inventory, heating workers, eating, drying and storing work clothes, bathrooms, etc.;
- provide workers with tools and personal protective equipment;
- prepare places for storing materials, inventory and other necessary equipment;
- fence the construction site and put up warning signs illuminated at night;
- provide the construction site with fire-fighting equipment and signaling equipment;
- draw up an act on the readiness of the object for the production of work;
- obtain permits for the performance of work from the technical supervision of the Customer.
3.3. Prior to the construction of the pipe, the following activities and works must be performed:
- the construction site prepared for the production of works was accepted from the customer;
- construction materials, necessary equipment, tools, reinforced concrete pipe sections were delivered and stored;
- Arranged entrances and exits from the site;
- ensured water drainage from the place of work;
- a geodetic breakdown of the contour of the pit was made.
3.4. Reinforced concrete structures brought to the construction site (see Fig. 3) are unloaded from vehicles by a truck crane KS-55713-4.
Fig.3. Site plan
1 - fittings; 2, 3 - lumber warehouse; 4 - the path of the crane; 5 - warehouse block of pipe links; 6 - container with cement; 7 - concrete mixer; 8 - water tank; 9 - power plant; 10 - crushed stone warehouse; 11 - sand warehouse
The pipe sections delivered to the construction site are laid in one tier on a sand cushion. Dropping pipe sections from vehicles or into the pit is prohibited. The pipes are laid along the pipe pit, in accordance with the technological sequence of installation, leaving a berm with a width of at least 4.0 m for the crane access.
Mounting loops on the links of the pipe body are cut flush with the surface of the concrete by electric welding before the pipe is installed. cutting loops with a chisel or bending them is not allowed.
To ensure the drainage of water from the work site, the existing watercourse is directed around the installation site - a pit under the pipe body.
3.5. Geodetic marking works
3.5.1. The geodetic breakdown of the pit is to designate it on the ground. The breakdown is carried out in two planes: horizontal and vertical. With a horizontal breakdown, the position of the axes is determined and fixed on the ground, and with a vertical breakdown, the estimated depth of the pipe laying.
3.5.2. The breakdown of the pit for the pipe begins with finding and fixing the longitudinal axis of the pipe, performing the following steps:
- restore the axis of the road;
- measure with a steel tape (twice) the distance from the PC to the longitudinal axis of the pipe along the axis of the road;
- a steel nail 100-120 mm long is hammered at the obtained point;
- the theodolite is centered over the nail and the angle between the axis of the pipe and the axis of the road is transferred to nature;
- fix the resulting longitudinal axis of the pipe with four control posts, two on each side, installed no closer than 3 m from the boundaries of the pit;
- transfer to the control posts the mark of the nearest benchmark, as well as the marks of the inlet and outlet trays of the pipe;
- check the compliance of the future channel of the drainage ditch with the project;
- break the outlines of the pit according to the layout drawing with fixing its contours. To do this, cast-offs are installed parallel to the axes of the pit at a distance of 2-3 m from its border (see Fig. 4), the position of which is fixed in the layout drawing. On cast-offs, the main axes of the pipe are marked with a tape measure, fixing them with risks and appropriate inscriptions.
Fig.4. Inventory cast-off
2 - steel wire string; 3 - plumb
3.5.3. The surveyor, using a theodolite, transfers the alignments of the axes to the upper edge of the cast-off and fixes them with risks. The breakdown of the places of drawing risks is carried out by the method of alignment serifs from the axes X and Y center grid available in the working drawings. For a relative mark 0,000
the mark of the top of the pipe was adopted corresponding to the absolute mark available on the general plan. The position of the center axes of the pipe is fixed with steel wire strings stretched on a cast-off. Then they are transferred to the surface of the site with the help of plumb lines lowered from the stretched strings and this point is fixed with metal pins. The accuracy of the planned laying out of the pit should be within 5 cm. The fixing marks (pegs with marks) are kept until the pipe is put into operation by the customer. Stakeout points damaged in the course of work must be immediately restored.
The accuracy of the layout work must comply with the requirements of SNiP 3.01.03-84 and SNiP 3.02.01-87. The scheme for the production of geodetic breakdown of the pit is shown in Fig.5.
Fig.5. Scheme of production of geodetic breakdown of the pipe
3.6. Pit development
3.6.1. The development of a pit for the pipe body and heads is carried out single-bucket excavator ET-16(see Fig. 6), a special swamp modification, the pressure of which on the ground does not exceed 20-25 kPa, which has a broadened and elongated caterpillar track. Detected underground outlets of water into the pit (keys, springs, etc.) are drowned out with a clay plug.
Fig.6. Excavator ET-16
The cleaning and leveling of the bottom of the pit to the design marks (by 5-10 cm) is carried out manually, under the rail, taking into account the design slope and the specified building lift equal to 1/50 of the height of the embankment, directly in front of the foundation.
The soil developed by the excavator is placed in a dump, with subsequent removal outside the construction site. The bottom of the pit is sealed vibrating plate LF-70, up to 0.95.
A break between the end of the development of the pit and the construction of the foundation for the pipe body, as a rule, is not allowed.
If the foundation is delayed, it is necessary to develop the foundation pit with a shortfall to the design mark, and cover the pit with heat-insulating material. When using peat (0.16-0.18 g / cm 3), the layout, layout and compaction are done manually. Insulating blocks made of aerated concrete, polystyrene, etc. installed with a truck crane. The completed work is presented to the Customer for signing on the construction of the pit, in accordance with Appendix 3, RD-11-02-2006.
3.7. Installation of a monolithic concrete foundation slab for the pipe body
3.7.1. Under the prefabricated reinforced concrete sections of the pipe, it is necessary to build a foundation in the form of a monolithic slab of concrete class. B20, W6, F150 0.20 m thick by layer crushed stone M 800 fraction 20-40 mm 0.10 m thick.
Rubble is brought up wheel loader VOLVO L-45B(bucket capacity 1.2-2.5 m), leveled by hand, compacted vibrating plate LF-70D up to at least 0.95.
The completed work is presented to the Customer for signing of certificates of examination of hidden work on the installation of a "cushion", in accordance with Appendix 3, RD-11-02-2006.
3.7.2. For the installation of a monolithic concrete slab, a collapsible formwork 20 cm high is installed on the finished "cushion". Anchor points are fixed on a cast-off located outside the work area. For a relative mark 0,000
the mark of the top of the pipe was adopted, corresponding to the absolute mark indicated on the general plan. The formwork is assembled from edged softwood lumber VI c. 40-50 mm thick and bars 40x40 (50x50) mm. On the inside, the boards are fixed to the desired size with spacers, and on the outside with stakes driven into the ground close to the boards, which, like boards, perceive the lateral pressure of the concrete mixture.
3.7.3. Wooden "beacons" 30 mm high are installed on the compacted crushed stone "pillow" and on them, to give strength to the monolithic foundation, grids of reinforcing steel A-III, grade 35GS with a diameter of 12 mm, with a cell pitch of 100x100 mm, are laid. Grids are laid with an overlap of at least 25-30 reinforcement. The grids are connected by tying the joint in three places (in the middle and at the ends) with a knitting, steel wire with a diameter of 0.8 ... 1.0 mm using special hooks.
The supply of reinforcing meshes to the work area is carried out by a truck crane. Manual installation is allowed only with a mass of reinforcing elements up to 20 kg.
3.7.4. The process of laying the concrete mixture consists of work operations associated with its supply to the formwork and compaction. Prior to placing the concrete mixture in the formwork, it is necessary to check:
- formwork fastening elements;
- the quality of formwork cleaning from debris and dirt;
- quality of rebar cleaning from rust deposits;
- drawing out the axes of the structure (with paint) on the reinforcing cage;
- with slats or tow, close up large cracks in the formwork;
- cover the internal surfaces of the formwork with a plastic film to reduce the adhesive force of concrete with boards;
- present the finished formwork and the installed reinforcing mesh with outlets to the Customer for examination and signing of the Act for covert work on the formwork and installation of the reinforcing cage, in accordance with Appendix 3, RD-11-02-2006.
3.7.5. The concrete mixture is delivered to the site truck mixers SB-049A(4.0 m) and unloaded into swivel buckets with a capacity of 0.8 m located within the radius of the crane, after which the bucket is set in a vertical position by a truck crane, transported to the place of laying and unloaded into the formwork.
3.7.6. When laying the concrete mix, the following basic rules must be observed:
- adding water when laying the concrete mixture is not allowed;
- cold water separated from the mixture must be removed;
- the height of the free dropping of the concrete mixture should not exceed 1.0 m.
During the laying of the concrete mixture, it is necessary to provide for the protection of the manufactured structure from atmospheric precipitation with a polyethylene film.
The stripping of the concreted structure and its loading with pipe sections is allowed when the concrete reaches a strength equal to at least 75% of the design strength.
3.8. Monolithic head device
3.8.1. Operations for the device of heads from monolithic concrete are performed in the following order:
- a pit is being developed for the portal wall and sloping wings;
- install the formwork of the portal wall with the adjustment of the shields and their fastening;
- install the formwork of the left sloping wing with alignment and fixing;
- install the formwork of the right sloping wing;
- take the concrete mixture from the tub, filed by a truck crane;
- lay the concrete mixture in the formwork and compact it with a vibrator;
- smooth the open surface of the freshly laid mixture;
- Maintain concrete.
3.8.2. The development of a pit for heads is carried out single-bucket excavator ET-16. The cleaning and planning of the bottom of the pit to the design marks (by 5-10 cm) is carried out manually. The soil developed by the excavator is placed in a dump, with subsequent removal outside the construction site. The bottom of the pit is sealed vibrating plate LF-70, up to 0.95. Crushed stone is poured into the pit under the head with a design layer, taking into account the safety factor for compaction equal to 1.25, leveled and compacted with a vibrating plate.
3.9. Installation of collapsible formwork for heads
3.9.1. The formwork serves to give the required shape, geometric dimensions and position in space of the erected heads (portal wall and sloping wings) by laying the concrete mixture in the volume limited by the formwork.
3.9.3. Formwork panels are made of edged lumber 50 mm thick 100 mm wide and wooden bars 50x50 mm. The front parts of the shields in contact with concrete are sheathed with waterproof, bakelite, plywood 16 mm thick (FBS-16), fixed to the shields with self-tapping screws.
3.9.4. For concreting the heads, a collapsible formwork is used. Collapsible formwork is assembled from ready-made elements - shields. Formwork panels are assembled at the assembly site in a certain sequence:
- the boards are laid with the working surface down, wooden slats are placed at the installation sites of the mounting and working fasteners;
- verify the overall dimensions of the shields, along their contour, wooden blocks-limiters are nailed;
- shields are interconnected with wooden plates;
- holes with a diameter of 18-20 mm are drilled in wooden slats in places where screeds are passed;
- wooden fights are laid out on top of the shields;
- fights with shields are connected with nails or staples;
- rigidity ties are laid on top of the contractions perpendicular to them, for which the same contractions are used;
- struts are attached to the lower tiers of the bouts or stiffeners, ensuring the stability of the panels in a vertical position.
3.9.5. The formwork shields are installed in the design position according to the risks applied to the crushed stone preparation according to the marking axes fixed on the cast-off, with the simultaneous alignment of the verticality of the shields along the marking axes with theodolites.
The place of installation of the formwork is cleaned of wood chips, debris, snow, ice. When installing shields, you need to monitor the density of their adjoining to each other. When installing the formwork, it is necessary to ensure its stability with the help of racks, resting them on a solid foundation and unfastening them with girders.