Hello everyone, I'm Brother Xue. We often encounter outdoor pipe network projects, for such projects, the focus is on tube wells and pipelines, today we share a very comprehensive technical knowledge of weak current pipe network, you can compare and use in actual projects.
Communication pipeline is a kind of building used to lay underground communication cables, because its location is relatively fixed and can effectively reduce the occupation of above-ground space, and is safe and stable, easy to manage and inspect, favored by major operators. The state also supports the synchronous follow-up of urban communication pipelines in the planning and approval of urban construction projects in densely populated areas.
First, the composition of the pipeline:
1. The pipeline is a system, which is basically composed of three parts: manhole, hand hole and pipeline, and can be divided into user pipeline and inter-local pipeline from the nature of use.
User pipelines include trunk pipes and wiring pipes. The main pipeline generally adopts the construction mode of porous pipe, which is used to penetrate the cable with an increased number of cores. The diameter of the pipe hole varies from 25mm to 110mm, and the spacing between the pipeline man-to-hand wells is generally 100 meters, and its location is generally located on the sidewalk or roadway of the main and secondary roads of the city. New urban pipelines are generally planned and constructed on both sides.
2. Pipeline construction method:
Communication pipelines are divided into three types in terms of construction methods: tunnels, pipelines, and channels
Tunnel pipes are complex, have a long service life, and are located at large site entrances and exits. It is based on reinforced concrete, overlain with arch prefabricated parts, and brick masonry on both sides.
Pipeline is the most common way we currently use, the old pipe is mainly cement pipe or asbestos pipe, and the new pipe is mainly mixed with 7-hole plum pipe or corrugated pipe.
Second, the type of pipeline material
The most common building materials for communication pipelines are generally concrete pipes, plastic pipes, metal pipes, asbestos cement pipes, etc. However, in the current pipeline construction, if there are no special requirements, the basic design is made of plastic pipes. Plastic pipes are divided into single hole, 2-12 holes, etc. We mainly use 7-hole torx tubes and single-hole corrugated pipes for communication.
Plastic pipes and pipes mainly include hard PVC, polyethylene PE, polypropylene PP. The length of a single pipe is generally 6 meters by default. The biggest disadvantage of plastic pipes is that they are greatly affected by the external temperature, and their expansion coefficient is large, which is about 6-8 times that of metal materials. If it is used in an area with large temperature variations, this should be fully considered in the design.
3. Selection of pipeline routes
The construction of communication pipelines is generally in urban planning after water, electricity, gas, heating and pollution, with the improvement of people's awareness of communication resources and the improvement of the close relationship between people and communication systems, communication facilities will also be one of the necessities of people's lives.
(1) On the premise of satisfying the design, choose to build on the route through which the backbone network resources pass.
(2) In order to reduce overhead pole roads, it is necessary to give full consideration to the construction of branch roads and pipelines and improve the flexibility of the pipeline network.
(3) Combined with the urban development plan, according to the planning and allocation of the urban municipal construction department, reasonable construction.
(4) Give priority to the use and combination of original pipeline resources, reduce the scale of construction investment, and improve the utilization rate of resources.
(5) Planning and construction should avoid large-scale facility gathering areas, such as railways.
(6) The section that has a significant impact on the foundation is not suitable for the construction of pipelines. There are mainly rivers, subsidence sections, swamps, sandy soils, and high water levels.
(7) Pipeline construction should also adhere to the principle of shortest route.
(8) The pipeline construction must be inspected on site and must maintain a sufficient clear distance from other buildings or facilities.
(9) Pipeline construction must maintain a certain slope to facilitate the discharge of foreign objects that affect the safety of the pipeline.
(10) The buried depth of the pipeline should be combined with the height of the manholes on both sides, but the height difference should be kept within a reasonable range.
(11) There shall be no S bend and U bend in the pipeline section. The length of a section should be controlled at about 100 meters. The radius of curvature of the curved pipe section is generally not less than 36 meters.
Fourth, pipeline construction
According to the requirements of the design drawings and technical disclosure, the pipeline construction process is marking and positioning, digging the road surface, digging ditches (pits), laying foundations, laying pipelines, pipeline sealing, masonry hand holes, installing auxiliary facilities, backfilling and tamping, waste removal, etc.
1. Marking and positioning, a single pipeline section must be marked and positioned first to determine the environmental and geological conditions along the line. Meet the requirements of design elevation, coordinates, centerline, and hole location.
2. Dig the road surface and dig the trench
Install the determined centerline position, take the total width of the pipeline plus the width of the working face as the width of the upper mouth to excavate the road surface, and excavate to both sides and below. Necessary support measures should be taken when encountering unstable geological conditions.
3. Pipeline foundation
(1) Basic category
Pipeline foundations are divided into natural foundations, plain concrete foundations, and reinforced concrete foundations. In the case of uniform and hard soil, natural foundations can be used for laying metal pipes and plastic pipes. In the case of soft and uneven soil and disturbance, reinforced concrete foundation is generally used.
Pipeline foundation reinforcement method:
Paving small gravel: Lay 10cm gravel at the bottom of the pipeline trench to make the bottom firm and stable, and the surface is flat.
Paving sand and gravel: remove the soft soil on the surface of the foundation, and tamp the sand and gravel once every 15cm of paving, which can improve the strength of the base surface.
Pipeline basic indicators:
Foundation width and thickness: increase the width of the actual construction pipeline by 8cm on both sides, and the thickness is greater than 8cm.
Foundation position and offset: 3cm away from the center line of the pipeline.
Maintenance time and intensity: 24 hours according to the local climate characteristics, and appropriate heating measures should be taken for winter construction.
The ratio of ash, sand and stone: the ratio of 325# cement is 1:2:4, and the ratio of 425# cement is 1:3:5.
4. Pipeline laying
A: Cement pipeline laying
A: The composite structure of cement pipelines should be built on a solid and reliable foundation. The foundation slope coefficient should generally be 3‰ to 5‰.
B: When the pipe group enters the manhole, the top of the pipe shall not be less than 300mm from the top of the manhole, and the bottom shall not be less than 400mm from the foundation of the manhole.
C: The length of a single section of the pipeline should not exceed 150m. The radius of curvature of the curved pipe should not be less than 36m.
B: Steel pipe pipe laying
Natural foundations can be used for steel pipe pipes.
A: Steel pipes should be made of anti-corrosion materials, and the nozzles should be polished to slopes without edges and thorns. In the actual construction, it must be misconnected.
B: When the two steel pipes are connected in the forward direction, the outer casing pipe hoop is welded firmly. When the pipe group is large, it is bundled and welded with flat iron every 2 meters. The pipe interface should be encapsulated with 80mm thick C15. The nozzle should be recessed 30-50mm, and the window should be wiped into a figure-eight shape.
C: The degree of a single steel pipe should be greater than 2 meters. The gap of the seamed steel pipe should be located on it.
C: Plastic pipe laying
a. Double-wall corrugated pipes
According to the design requirements, the double-wall corrugated pipe of the same material is selected to form the hole group, which should be laid on a flat, solid and reliable concrete foundation.
The bellows are laid every 2 meters and fixed with reinforcement supports, the interval between layers should be 10-15mm, each layer is separated by steel bars with a diameter of 10mm, and the middle gap should be filled with M10 mortar.
The pipe interface should be plugged with a sleeve and a seal should be placed. The interface should be staggered by 300mm. The length of a single pipe is not less than 2 meters. If it is necessary to lay a curved pipeline, the radius of curvature shall generally not be less than 15m. If concrete encapsulation is required, the thickness is 100mm.
The length of the pipe should not exceed 150 meters.
b. Plum Pipe Pipe
When laying plum blossom pipes, plum blossom pipes of the same material should be selected according to the design requirements to form a hole group, and laid on a smooth, solid and reliable concrete foundation. The foundation slope coefficient should generally be 3‰ to 5‰.
When building more than 2 ports, the interfaces should be staggered. The interface is plugged in with a sleeve and smeared with special glue.
When the pipeline needs to be encapsulated with concrete, the encapsulation thickness is 80-100mm.
But the pipe should not exceed 150 meters.
When the plastic pipe is laid, the ambient temperature is not lower than -5 degrees.
The plastic pipe foundation must be made of gravel cushion, for the general soil foundation, the cushion is 0.1 meters, and the thickness of the soft soil foundation is not less than 0.2 meters.
Plastic pipes should be manually transferred and deployed, and tumbling or hanging is prohibited.
The connection of plastic pipes should be connected by bearing bonding, bearing elastic sealing rings or mechanically pressing the pipe body. The degree of joint is generally 200mm.
It is strictly forbidden to heat and bend the plastic pipe for use.
D: Silicon core pipe
The silicon core tube can be laid directly on a natural foundation.
When multiple roots are deployed in the same groove, the pipe spacing is 3mm and tied with nylon cable ties every 2-5mm.
When the pipe group enters the man's hand hole, 2M encapsulation should be done on the outside, and enough residual length should be left in the man's hand hole and blocked.
The length of a single section of the pipeline should not exceed 1000m.
5. Pipeline encapsulation
After the laying of the pipeline, if the buried depth is shallow or there are other pipelines around the pipeline, the pipe group should be encapsulated and reinforced, and C15 concrete should be used to encapsulate 80-100mm on both sides and the top of the pipeline. When encapsulation, the template must have sufficient strength and stability, and the template must be removed after the initial setting. The encapsulation deviation should be less than 5mm.
The concrete must be accurately proportioned, evenly mixed, poured densely, and properly maintained. The side and top encapsulation should be poured together continuously. Concrete is poured after the steel bar is tied on the outside and at the top of the pipe group, and the concrete is generally sealed with concrete at the part that crosses the obstacle or is too close to the road surface.
If it cannot be avoided, the joint must be encapsulated, the length is not less than 500mm, and it can be encapsulated, and the thickness of the encapsulation is generally 80-100mm.
6. Pipeline backfill
After the pipeline is laid, it is backfilled from both sides of the pipeline trench at the same time to avoid damage, deformation and displacement due to large pressure on one side. The first layer of soil is filled with fine soil to the top of the pipeline 500mm and evenly tamped.
Then tamp it to a suitable height step by step according to 300mm/layer. After backfilling, it is necessary to do a pipeline test-through test.
The backfill of the communication pipeline should be completed in the pipeline manhole construction sequence, and after 24 hours of maintenance and acceptance of the concealed project
The pipe should be backfilled after the pipe hole has been completely cleared of foreign matter. There must be no stagnant water and silt.
Gravel, small bricks and other hard objects with a diameter greater than 5 cm shall not appear within 30 cm of the top of the pipe. The top is 30cm or more, and each backfill is 30cm and tamped 1 time.
The soil on both sides of the pipeline should be backfilled at the same time, each backfill is 15cm thick, and tamped twice. Both sides take turns.
In any case, it is absolutely forbidden to backfill with sand.
5. Manhole and channel construction technology
The structure of the manhole (hand) hole and passage is divided into three parts: the foundation, the wall and the overlay.
A: The principle of selecting the position of the manhole (hand) hole and channel
1. The position of the manhole (hand) hole should meet the requirements of the use of communication pipelines. In the computer room, building introduction point, etc., a human (hand) hole should generally be set up.
2. When the length of the pipeline exceeds 150m, the manhole (hand) should be appropriately added.
3. When the pipeline crosses the railway and river, the manhole (hand) should be set on both sides.
4. Hand holes should be selected for pipelines, simple plastic pipes, and branch pipes leading to the pipes in the community.
5. Generally, large-capacity cables enter the office, and the channel should be selected at the junction.
6. The manhole (hand) at the intersection of the road should be selected on the sidewalk, biased to the side of the road; The location of the manhole (hand) hole should not be set at the door of the building or unit, or in the low-lying waterlogged area.
B: Human (hand) holes, channel foundations
7. The manhole foundation is generally made of concrete or reinforced concrete structure, and in places with high groundwater level, waterproof concrete with good waterproof performance is used.
8. The specifications, models and concrete strength grades of the foundation should meet the requirements of the design or standard atlas.
9. The thickness of concrete is generally 120-150mm. Special requirements should be stated at the time of design.
10. Stagnant water irrigation should be installed at the position of the orifice ring of the human hand, and 20mm flooding should be done from all around the wall to the stagnant water.
11. After the wall is completed, the foundation should be plastered, and the surface should be smooth and smooth.
C: Wall construction technology
1. Before the construction of the wall, the center position of the foundation, the orientation of the pipeline wellhead and the elevation of the top of the foundation should be checked once.
2. WHEN THE STRENGTH OF THE FOUNDATION CONCRETE REACHES 12KG/CM² (24H AT ROOM TEMPERATURE), THE WALL CONSTRUCTION CAN BE CARRIED OUT.
3. Before building the masonry wall, the foundation should be cleaned and the bricks should be wet with water.
4. It is necessary to first put the ground and swing the joints to determine the masonry method. and maintain the perpendicularity of the wall to the foundation.
5. M10 cement mortar for walls, M10 machine brick masonry; Plastered with 1:2.5 cement mortar, the thickness of the inner wall is 15mm, the thickness of the outer wall is 20mm, and the wall is dense and not hollow.
6. The brick layer of the wall must be pressed with stubble, overlap inside and outside, staggered joints up and down, no through joints, mortar fullness greater than 80%, and brick joints not more than 10mm.
7. The net height of the manhole is generally 1.8M-2.2M. or meet the design requirements.
8. The handhole window is a bell mouth, and the pipe entrance should be terminated in the brick wall, and the window should be tightly plugged, neat and smooth in appearance.
9. When the pipeline enters the hole, the elevation of the opposite pipe should be symmetrical. Generally, 1/2 of the pipe group should not be wrong; Branch clusters can be higher than trunk clusters.
Sixth, the construction technology of the overlay
1. The handhole is covered to the mouth ring, and the oral cavity of not less than 200mm and not more than 800mm should be built with M10 cement mortar bricks, and the oral cavity and the overlying mouth should be concentric circles. The inside of the mouth should be plastered and the joints should be firm.
2. The size of each part covered on the hole of the human hand is consistent with the size of the upper mouth of the hole wall.
3. According to the requirements of the design drawings, the bottom of the upper cover should be smooth, and the thickness should be uniform, not bulging, and not dented.
4. The entrance and exit and the façade of the outer edge should be perpendicular to the bottom, and the lines of each part should be neat and smooth.
5. When covering according to and prefabrication, find a flat layer at the junction of the wall and the overlay, and use 1:2 between the joints of the plates. 5. The mortar is tightly plugged. The hoisting ring should be plastered with mortar into a mushroom shape.
6. The upper covering plate presses the wall about 200mm, and the joints of the wall are wiped with the splayed corners and there are no burrs, fractures and stubbles.
7. On-site pouring covering, steel bars and concrete strength grades should meet the requirements. In order to prevent the deformation of the concrete, the reinforcement skeleton formwork must be fixed and strong. The formwork can be removed after the curing reaches strength. The surface must be smoothed with the indenter.
7. Accessory facilities
1. The nails should be installed according to the different types of human (hand) holes and the positions specified in the drawing. The nails should be embedded in the wall 50 to 70mm, the upper and lower nails should be on the same vertical line, the allowable deviation should not be greater than 5mm, the spacing deviation should not be more than 10mm, and the interval deviation between the two adjacent groups of nails should not be greater than 20mm.
2. The bracket should be close to the wall, fixed on the nail with a nut, and the nut should be firm, and the nut should not be loose.
3. The tensile ring should be embedded in the wall. The tensile ring should be 80 to 100mm out of the wall, and the position on the wall should be aligned with the center line of the opposite pipe, and the bottom of the other pipe should prevail 200mm downward.
8. Pipeline slope, buried depth and section length
When designing the pipeline, the slope should be fully considered in order to avoid foreign objects entering the pipeline and damaging the communication facilities, and it is also conducive to the maintenance personnel to clean the pipeline.
The specified pipeline slope is generally 0.25%-0.4%. The slope is divided into herringbone slope, slotted slope and slope slope.
The underground burial depth of the pipeline should meet the requirements of the minimum buried depth of the pipeline. The depth of the manhole should be determined according to the height of the pipes on both sides into the manhole. After entering the manhole, the relative height of the oral cavity on both sides should be the same or close, and the height difference should not be more than 0.5 meters.
The distance between the centerlines of each 2 adjacent manholes is called the pipe segment length. The longer the section, the more economical the construction cost. In order not to damage the cable during construction, it is best to have a terminal tension of no more than 1500kg in all types of pipes. The length of the straight pipe section is generally within 150 meters. The actual construction is subject to the design. The curved pipe is shorter than the straight pipe, the radius of curvature is not less than 36 meters, and the S bend is not allowed in the curved pipe, and the U bend is not allowed under any circumstances.
9. Pipeline cleaning
The pipe must be cleaned before use, so that the cable can be smoothly threaded and placed, there are two main methods:
1. Thread through with a pipe threader or bamboo piece.
When the pipe threader or bamboo piece is threaded out of the pipe, one 4.0 iron wire must be tied to the end and brought into the pipe hole as a lead. During construction, the previous builder must reserve a lead for the next contractor. A set of tools is attached to the end of the lead, including an iron swivel, a hammer, a wire brush, a rag, a wooden stick, etc. It can effectively remove the silt and debris in the pipe hole, and at the same time remove the stagnant water.
▲A complete set of tools for pipeline cleaning
2. Pressurized air cleaning method
If it is a pipe hole with good sealing performance, this method is the best. When the pressure in the pipe hole reaches a certain value, the plug is suddenly pulled out, and the strong convective air will quickly discharge the silt, stagnant water and other debris will be quickly discharged. This method is not practical in the current situation of pipeline construction quality.
10. Principles for the use of pipe holes
In order to facilitate the later maintenance and subsequent cable deployment. The selection of pipe holes must comply with a principle: first down and then up, first on both sides and then in the middle. Important, core cables should be routed in the bottom or side holes. Try to use the same pipe hole in the same position in each complete pipe section. In principle, a cable can only occupy one pipe hole. Armoured fiber optic cables are not recommended to be deployed in pipes.
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