Double wall corrugated pipe construction plan

2017-06-27

First, construction measures

1.1 Construction principles

1) Pipeline construction: first trunk, rear branch, first deep and shallow, branch pipeline construction should be carried out after construction of the structure.
2) The pipe trench is mechanically excavated (manually matched, the base is kept 200mm thick artificial clearing groove), the slope of the pipe ditch slope is 1:1, and the ditch with a width of 1.2m is reserved when the ditch depth exceeds 4m, and the layer is excavated. The small trench is manually excavated. Manual excavation is used when the machine cannot be excavated.
3) Check and test the valve and inspection well before installation.
4) Double-wall corrugated pipe adopts socket-type interface. When single-mouth connection is not available, double-mouth connection can be adopted. The casing is made of PE, fiberglass or stainless steel, and the two-way socket is connected with elastic sealing ring.
5) Before the construction of the double-wall corrugated pipe, the pipe trench needs to be laid with a layer of 200mm thick sand cushion, and the compaction degree needs to reach 85%-90%. When the double-wall corrugated pipe is backfilled, it must be backfilled with medium coarse sand. The backfilling range shall not be less than the design support angle of 2α+30° (180°), and the backfill density shall be above 95%.
6) The connection of the double-wall corrugated pipe to the inspection well may be a rigid connection or a flexible connection.
Rigid connection: When inspecting the masonry of the well, the pipe fittings or short pipes are embedded in the well wall, and the socket is outward, which is convenient for the socket connection. When using this connection, the cement mortar should be full.
Flexible connection: prefabricated concrete ring beam with socket is placed on the inspection well, and the inner diameter of the ring beam and the pipe socket are left with a certain gap, so that the rubber ring of the pipe end and the ring beam are connected to allow a certain rotation angle to adapt to the inspection well. Uneven settlement and deformation requirements between pipes
1.2 Construction process

1.3 Inspection plan

Before the construction, the experimenter shall inspect the quality and strength of the material and check the compaction of the groove; during the construction, check the weld welding, the direction of the pipeline, the elevation and the slope; after the installation of the pipeline, the compactness test shall be carried out, after the backfilling Perform a compaction test. When using the pipe supplied by the supplier, the supplier‘s pipe name, specification, unit price, inspection report and other information shall be reported to the owner for approval.
1.4. Material Management

1) Material inspection
All materials must have relevant certificates such as certificates of conformity and warranty, and the material specifications, models and quality should conform to the provisions of the bidding documents. The quality assurance materials are strictly in accordance with the requirements of the construction specifications.
a. The pipe fittings should be reviewed and verified in kind before the use of the quality certification documents;
b. Appearance inspection is not acceptable;
c. Material substitution must have relevant documentation.
2) Inspection and management of pipelines and pipeline components
a. Before the pipe is accepted and used, the quality certificate shall be reviewed and checked in kind;
b. Before the components of the pipeline are used, the appearance shall be checked. Those who fail shall not be used;
c. Inspection of other special steel components, such as studs, nuts, flanges, gaskets, etc., shall be sampled and accepted according to the standard.
1.5. Measuring the payoff

1) Based on the construction drawings, the pipelines shall be positioned and laid, and the trenches shall be excavated after retesting.
2) After the trench is excavated, the elevation of the trench should be measured. After confirming the correctness, the pipeline foundation can be made.
3) Check the coordinates, elevation and slope of the installation pipe before the lower pipe. It can be installed after confirmation.
1.6. Pipe trench excavation and measures

1) Earth excavation must first understand the underground condition of the excavation area. When there are unknown objects such as cables and pipes in the area, mechanical excavation is strictly forbidden.
2) Excavation width at the bottom of the pipe groove
When the excavation depth H<4m, it should be calculated according to the calculation formula (1).
B=D0+2(b1+b2+b3)..............................(1)
Excavation depth H>4m and calculation of steel sheet pile support should be calculated according to formula (2)
B=D+2S ....................................(2)
3) Pipe trench excavation According to the soil condition of the site, the slope of 1:1 is left on both sides. The earthwork excavation must be consistent with the design conditions, and follow the “grooving support, first support and then excavation, layered excavation, strictly prohibited. The principle of over-excavation.
4) When a large area is used to excavate the pipe trench, the excavated earthwork is transported to the off-site waste slag yard by dump truck in time. A small part can be used for earthwork backfilling, and can be temporarily stacked more than 1m away from the pipe ditch. Place, the rest of the earth is shipped out, and returned when backfilling.
5) When the mechanical excavation earthwork is close to the design base height of 200mm, manual excavation should be used to design the elevation, and over-excavation is strictly prohibited. If over-excavation or disturbance occurs locally, 10~15mm natural grade sand stone material or 5~40mm gravel should be replaced and leveled.
6) The pipeline foundation shall be constructed in strict accordance with the design requirements. All pipelines shall be reserved for operation pits before installation.
7) If the trench depth is greater than 4m, both sides of the trench shall be supported by steel plates, and the groundwater level and surrounding environment shall be tested and protected as necessary.
8) Manually excavate the drainage ditch of 300mm×300mm in the pit. The accumulated water should be discharged in time. When the submersible pump is pumping, no one should work in the water. The mobile submersible pump must use hemp rope. Do not use strong conductive rope such as iron wire.
9) After the excavation of the foundation pit, the protective rod should be set immediately. The height of the guardrail is not less than 1.2m, the crossbar is two, and the warning sign is set. The guardrail is more than 1m away from the side of the pit.
10) The overlap with the civil works should be reserved in the civil engineering backfill to the pipeline bottom elevation.
1.7. Substrate treatment and foundation laying

1) After excavation of the pipe trench, it is found that the soil of the foundation is soft and the bottom is uneven. The handling unit and the design unit will determine the treatment measures and will sign the design change and negotiate the record. The base is strictly prohibited from over-excavation, and if necessary, it can be backfilled with sand. When the foundation needs to be changed, it should be thoroughly cleaned up. The backfilling materials, operation methods and quality standards are determined according to the specific conditions. After the base is qualified according to the design requirements, the pipeline foundation construction shall be carried out according to the design requirements.
2) After the substrate is compacted, spread a 200mm thick sand cushion directly at the bottom of the trench, and stabilize the tube after compacting. For general soil quality, when the local base bearing capacity characteristic value fak≥80kPa, the base can be laid medium coarse sand; if the local base soil quality is poor, the bearing capacity characteristic value of the foundation is 55≤fak<80kPa or the bottom of the tank is below the groundwater level, The gravel foundation layer with a thickness of not less than 200mm may be laid in two layers. The lower layer is made of gravel with a particle size of 5 to 40 mm, and the upper layer is laid with medium coarse sand with a thickness of not less than 50 mm; for the soft soil foundation, the base bearing capacity characteristic value Fak<55kPa, or due to construction reasons, when the undisturbed soil of the foundation is disturbed and affects the bearing capacity of the foundation, the foundation must be first reinforced. After the required foundation bearing capacity is reached, the medium coarse sand foundation layer is laid.
1.8. Lower tube

The lower pipe is based on the principle of safe construction and convenient operation. According to the proficiency of the workers, the weight of the pipe, the length, the construction environment, the depth of the trench, and the supply conditions of the hoisting equipment, the lower pipe method is reasonably determined. The key to the downpipe is the safety issue, which must be commanded by experienced workers. When the lower pipe is used, it is necessary to use a reliable spreader to smoothly lower the ditch. It must not collide with the ditch wall or the bottom of the trough. There should be two lifting points when lifting, and it is strictly forbidden to hoist. It is strictly forbidden to stand under the lifting pipe; when the pipe is manually lowered, the staff in the tank must avoid the position of the lower pipe. When the pipe is laid down, the groove must be thoroughly inspected, including the base soil, the base debris, and the groove stability.
1.9. Pipe installation

HDPE double-wall corrugated pipe construction: After the sand cushion is compacted, installation can begin. The double-wall corrugated pipe requires the same color appearance, the inner wall is smooth and flat, the pipe body shall not have cracks, the continuous defect of the corrugation shall not exceed 2, and the pipe mouth shall not have defects such as damage, crack, deformation; the end surface of the pipe shall be flat, and the central axis of the pipe Vertical, axial direction shall not have obvious bending; in addition, the internal pressure strength and rigidity of the pipe shall meet the design requirements. For the installation of double-wall corrugated pipe, the socket should be installed in the direction of water flow, and the socket should be installed in the direction of reverse flow from the low point to the high point. The pipeline installation can be manually installed. When installing, the workers at the two ends of the pipeline are transferred to the construction personnel at the bottom of the tank. If the tank body is larger than 3m or the pipe diameter is more than 400mm, the non-metal cable can be used to make the pipe smoothly placed in the groove. On the tube position. It is strictly forbidden to use metal ropes to hook the ends of the nozzles or to roll the pipes from the groove side into the slots. The length of the pipe can be adjusted by hand saw, but the section should be vertical. When working on the interface, first clean the socket, put on the rubber ring, check whether the rubber ring is well matched, and apply lubricant. Align the center of the socket end with the center axis of the socket and slowly connect it. It is strictly forbidden to use the construction machinery to forcibly push the top tube into the socket. If the pipeline is seriously damaged during pipeline construction, it needs to be inspected by professionals. It can be used after passing the inspection. If the damage is not serious, it can be repaired before use.
1.10. Pipeline affiliated well masonry

1) Inspection well: The rectangular concrete rainwater well is equipped with a heavy-duty φ700mm ductile iron manhole cover and well ring with a spacing of about 40m. The cover should have the word “rain” or “stain”. During construction, firstly, 100mm cushion concrete is poured with C10 concrete. After reaching a certain strength, the ribs and vertical molds are started, and the bottom plate and the borehole wall are poured with C25 concrete. The flow cell is made of M7.5 cement mortar and MU10 brick, and the surface is covered with 1:2 waterproof cement mortar. The thickness of the surface is 20mm. Both the pulp and the ash ash are made of 1:2 waterproof cement mortar. The wellbore is a precast concrete wellbore. The installation of the manhole cover and the well seat should be kept at the level. The well cover at the intersection is flush with the pavement. The green cover of the green belt should be 15mm-20mm higher than the ground. See "06MS201-3" for the specific installation method.
2) Drop water well: When the water head is more than 2.0m, a water well should be set.
3) Shooting the door well and the water outlet: The rainwater pipeline system has 5 outlets, 2 into the Caijiagang open channel, and 3 are discharged into the water. To prevent the drowning, the end of the outlet pipe is set. The door is usually built together with the water outlet, or it can be placed in the gate well upstream of the water outlet for easy maintenance. When constructing the door well, firstly, the cushion concrete should be poured, and the cushion layer should be poured with C15砼. After reaching a certain strength, the vertical mold is poured into the gate well, and the well chamber well and the cover are precast concrete. Among them, the door and the flange should be treated with anti-corrosion treatment, and the STIC preservative is used.
1.11. Closed water experiment

1. Closed water test: After the pipeline construction is completed, the water shut-off test shall be carried out in time, and the pipeline shall be filled with water for 2-3 days and nights. When the upstream design head of the test section does not exceed the inner wall of the pipe top, the test head shall be in the test section. The inner wall of the upstream pipe top is added with 2m; when the upstream design head of the test section exceeds the inner wall of the pipe top, the test head should be calculated by adding 2m to the upstream design head of the test section; if the calculated test head is less than 10m, but the test head has exceeded the upstream inspection well, the test The water head should be based on the height of the upstream inspection well. When the test head reaches the specified head, the time is counted, and the water seepage of the pipeline is observed. Until the end of the observation, the test pipe section should be continuously replenished with water to keep the test head constant. The observation time of water seepage shall not be less than 30 minutes.
The measured water seepage should be calculated as follows:
q= W/(T*L)................................................(3)
Where q is the measured water seepage (L/min·km);
W——the amount of water (L);
T——measured water seepage observation time (min);
L - length of the test pipe section (m).
The double-wall corrugated pipe allows the seepage flow to be less than or equal to the allowable seepage flow calculated by the following formula:
q=0.0046Di..........................................(4)
Where q is the allowable seepage flow m3/24h·km
Di——pipe inner diameter (mm)
2. Pipe deformation and decompression
1) After the trench is backfilled to the design elevation, the initial deformation of the vertical diameter of the pipeline shall be measured within 12 to 24 hours, and the initial deformation rate of the vertical diameter of the pipeline shall be calculated. The value shall not exceed 2/3 of the allowable deformation rate of the pipeline diameter.
2) The deformation of the pipeline can be tested by circular mandrel or closed-circuit television. The measurement deviation should not exceed 1mm.
3) When the initial deformation rate of the pipe vertical diameter is greater than 2/3 of the allowable deformation rate of the pipe diameter, and the pipe itself is not damaged, it can be corrected according to the following procedure until it meets the requirements:
1) Excavate the trench backfill to 85% of the pipeline height, and manually excavate within 0.5m above the pipe roof;
2) Inspect the pipeline, and the damaged pipe should be repaired or replaced;
3) Re-compact the backfill material at the bottom of the pipe;
4) Use appropriate backfill materials to refill the compaction according to the required compactness;
5) The initial deformation rate in accordance with the vertical pipe diameter.
1.12. Layered backfill

Immediately after the closed water test is passed, the bottom is filled back to prevent the exposure time from being too long or soaked in water. HDPE double-wall corrugated pipe backfilling construction must use medium coarse sand backfilling, the backfilling range should not be less than the design support angle 2α+30° (180°), and the backfill compactness should reach over 95%. The backfill thickness of each layer should not be greater than 0.2m. The groove backfill in the range of 50cm above the pipe side and above the pipe top can be crushed stone, gravel with particle size less than 40mm, high (medium) calcium fly ash (free calcium CaO content above 12%), medium coarse sand or ditch The good soil excavated from the trough. From the bottom of the pipe to the top of the pipe, within 0.5m, both sides of the pipeline and the inspection well must be manually symmetrical and layered backfilled and compacted. It is strictly forbidden to backfill with mechanical bulldozing. Temporary limit measures are taken on both sides of the pipe to prevent the pipe from floating. At the time of backfilling, the compaction layer is sampled for each compacted layer, and the upper layer is backfilled after passing the test. There should be no water in the groove when backfilling. Do not backfill silt, organic matter and frozen soil. The backfill shall not contain stones, bricks and other hard objects with angular edges. When the groove is supported by steel sheet piles, the pile can be pulled out after the backfill reaches the specified height. Pulling piles should be carried out at intervals, and with the sanding, if necessary, the measures of grouting while pulling the piles can also be used.
Second, quality assurance measures

In order to ensure quality and strive for quality projects, our project department takes the following measures:
1. All raw materials entering the construction site must be carefully inspected, sampled by quality inspectors and test personnel, and the quality of raw materials should be evaluated. The unqualified materials should be rejected and accepted, and reported to the project manager of the project site for record. The various mix ratios and various data in the construction must be in compliance with the specifications and approved by the supervision engineer.
2. Take the visa order or error value of the metrological department or manufacturer for the measuring instruments, tools and equipment used on the construction site.
3. The on-site technician shall strictly control and inspect the construction project in accordance with the drawings, specifications and supervision procedures.
4. Each process adopts the “three-level supervision” system, that is, the self-inspection of the team and the second inspection of the full-time staff. After the qualification is considered, the supervision engineer should check and approve. If there is any problem in any of the inspections, it is necessary to find the cause and take measures to remedy the problem. Rework can be done in a place that cannot be remedied.
5. Technical supervision should be done before the construction of each process, and the technical personnel should always be on site during the construction process. The problems found should be dealt with or reported in time, and the construction should be organized in strict accordance with the requirements of technicians and supervisors.
6. Excavation of the trench shall comply with the requirements of Table 6.1:
Table 6.1 Allowable deviation of trench excavation
7. Allowable deviation of pipeline laying

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