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Municipal pipeline engineering construction?
Municipal pipeline construction is very important, and every detail of pipeline construction is directly related to the construction efficiency and quality, especially the later use effect. Zhong Da Consulting will introduce you to the municipal pipeline construction.

As an important part of urban infrastructure, urban drainage pipeline construction plays an important role in urban sewage discharge and environmental protection. Although the construction technology is relatively uncomplicated, the existing underground pipelines and cables are unknown because most of the projects are built in urban areas and the environment is complex. On the premise of ensuring the safety of the project under construction, we should also consider the influence of the above-ground traffic and other factors, which leads to the increase of construction difficulty, and the construction quality and time limit are often not guaranteed.

According to the actual situation of municipal pipeline construction, the whole construction process can be divided into three stages: project preparation, pipeline laying and construction site restoration.

1, preparation work

Demolition of roads. In the process of urban pipeline construction, a certain number of existing pavements will be destroyed. In order to ensure construction safety and subgrade quality, safety and warning signs should be set up and fenced during construction. When the pipeline is excavated on the road, the opening width should be calculated according to the design requirements of the construction drawings, the road surface should be cut by a cutting machine, excavated by an excavator, and transported to the garbage dump. Protection of above-ground and underground public facilities. During trench excavation, support should be taken in time according to the geological and soil conditions to avoid collapse and collapse. The excavation slope and supporting form shall be examined and approved by the project supervisor and the owner's technical personnel before construction. When excavating near buildings and structures, telephone poles and lamp post foundations, measures to prevent them from sinking or deformation, calculations and drawings of reinforcement works shall be reported, and submitted to the project supervisor and the owner's technical personnel for approval. Some sections need drainage, so that the digger can always work in a dry environment. The drainage process shall not cause excessive ground subsidence, which will affect the normal use and safety of buildings, structures and other public facilities around the site. Excavation near buildings and structures, telephone poles and lamp post foundations shall be reinforced with steel sheet piles. When digging under high-voltage lines, excavators are required not to work directly under the wires, and manual excavation is required when necessary. Dig trenches on the roadside, set up safety warning signs such as guardrails, roadblocks and danger flags on the side near the road, and hang red lights at night. In the process of excavation, in case of cables, pipelines or other structures, contact the relevant units in time to deal with underground pipelines and various structures and try to move them temporarily; Those that cannot be moved must be dug out and exposed, and reinforcement measures such as suspension and support should be taken.

2, pipeline laying

Excavation and support of pipeline trench. Before excavation, check its plane position and elevation. If it is inconsistent with the position or elevation provided by the construction drawing and related materials, notify the designer to change and adjust it in time. According to the trench depth, soil quality, groundwater conditions, pipeline structure, trench formation mode and construction season, the trench section and trench slope are selected. Before excavation, find out the positions of existing underground pipelines, cables and other structures one by one, and send the investigation results and treatment plans to relevant management units for confirmation, so as to take corresponding measures such as protection and relocation to ensure the continuity of excavation. During excavation, it is forbidden to disturb the soil at the bottom of the ditch, soak in water or freeze. Support wood and support plate must be firmly fixed to each other, and should be checked frequently. If it is found loose, it should be reinforced in time. Pipeline laying. Selection and inspection of pipes: pipes and main accessories are provided by selected qualified manufacturers. After the pipes enter the site, the quality of the products shall be verified by the engineering supervisor and the construction party's material engineer. When the appearance inspection can't guarantee the quality of the pipeline, internal and external pressure tests should be carried out. The pipes entering the site must be products that have been inspected in batches by professional laboratories and obtained inspection reports. Pipe lowering: according to the measuring and releasing center line, control one side edge of the pipe with a string. The crane is used to lower the pipeline, and the crane travels along the groove to a distance of 1m from the edge of the groove to avoid the collapse of the groove wall and affect the stability of the groove slope. Use special hook or flexible sling when running the pipe, and it is forbidden to use wire rope to penetrate into the pipe for lifting. At the same time, there is a special person to command, and the center of gravity should be found when tying the pipe, and the pipe should be handled with care when hanging it, so as to avoid disrupting the basement pipeline and colliding with each other. In the narrow construction site where it is inconvenient to mechanically run pipes, artificial ropes are used to run pipes. Keep a safe distance when there are overhead lines. When the pipe joint goes into the groove, avoid colliding with the groove wall bracket and the pipeline under the groove, and strictly control the level and direction. The installation of the pipeline must meet the quality requirements: the pipeline must be padded, the slope at the bottom of the pipeline must not flow backwards, the joint width should be uniform, and there should be no debris such as mud, masonry, mortar and wood blocks in the pipeline; The concrete of the pipe socket should be dense and closely combined with the pipe wall; Coarse sand backfilled by pipe joints shall be dense. Pipeline closed water test. Before the pipeline is backfilled, the closed water method should be used for leak test. Inspection work before water shut-off test: check that the appearance quality of pipelines and inspection wells is qualified; The pipeline is not returned to the soil, and there is no water in the tank; All reserved holes shall be sealed and watertight; The bearing capacity of the blocking plates at both ends of the pipeline is calculated to be greater than the hydraulic resultant force; Except for the reserved inlet and outlet pipes, the rest of the plugs are firm and watertight. Closed water test method: the closed water test of drainage pipeline should be carried out in sections from upstream to downstream. After the upstream section test is completed, water can be injected into the downstream section to save water. The test section should be separated according to the well spacing, and the test should be carried out by the well, and one section should be designated by the supervision engineer every three sections. When the upstream design water head of the test section does not exceed the inner wall of the pipe top, the test water head should be 2m from the inner wall of the pipe top upstream of the test section. When the upstream design head of the test section exceeds the inner wall of the pipe top, the test head shall be calculated as the upstream design head of the test section plus 2m. When the calculated test head exceeds the wellhead of the upstream inspection well, the wellhead height of the upstream inspection well shall prevail.

3, the construction site recovery

Trench backfilling. After the pipeline is installed and passed the water pressure test, the trench shall be backfilled in time after being approved by the supervision engineer and technical director. The quality of trench backfill will directly affect the quality and use function of the road. Before the inspection well is backfilled, the cover plate should be covered with cement slurry, and after the elevation is measured to ensure accuracy, the shaft wall and the periphery of the shaft should be backfilled at the same time. Before backfilling the pipe trench, remove the wooden boards, straw curtains, bricks, steel bars and other sundries left in the pipe trench, and there shall be no water in the pipe trench. Both sides of the pipeline shall be backfilled simultaneously.

Plain soil shall be backfilled within 500mm of concrete pipe top, and compacted by layers with electric light rammer. When backfilling with frog rammer, the virtual soil layer of each layer shall be controlled within 250mm. After each layer is rammed and filled, full-time testers shall measure its compactness with a nuclear densitometer to ensure that the compactness reaches more than 95%. Road surface recovery. Subgrade should be solid and stable, and the compactness and smoothness should meet the design requirements; Lime base should use clods broken, qualified lime, accurate ingredients, uniform mixing, optimal water content control and compaction. Cement with high strength, small shrinkage, strong wear resistance and good frost resistance should be used, with a label of not less than 32.5, a product certificate and a test sheet, and the acceptance variety, label, packaging, quantity and factory date should be checked. It is forbidden to mix different types of cement; Sand should be clean, hard and coarse medium sand with a gradation fineness modulus of more than 2.5; Gravel should be hard and graded according to regulations, the maximum particle size should not exceed 40 mm, the template must be firmly supported, and the board face should be neat and angular; According to the cement used and the construction climate, the maximum allowable time for paving and vibrating the mixture until it is formed is determined. During transportation and construction, the mixture will not leak slurry, dry or segregate, and the unloading height will not exceed1.5m. If there is obvious segregation on site, it should be re-mixed before paving.

The virtual paving thickness of concrete paving is generally 2-2.5cm higher than that of formwork, and it shall be vibrated uniformly with a flat vibrator. After vibrating, the mortar and other things remaining on the top surface of the formwork shall be removed immediately; Pull the lever, push, pull, flatten, push and rub until the surface is smooth and meets the requirements, and then smooth it with a trowel; In general, construction joints are set at expansion joints; After concrete pouring, when the curing reaches more than 20%-30% of the design strength, it should be cut with a slit knife according to the contraction joint position, and the cutting time should not be too early or too late. According to the site temperature, properly grasp the cutting opportunity. In order to make the road surface have a certain friction, the road surface should be roughened to facilitate safe driving. The pavement maintenance time is controlled at about 28 days, and the maintenance methods include covering maintenance, water storage maintenance and film maintenance. , make it back to the state before construction, and reach the degree of approval by the supervisor. Trowel leveling; In general, construction joints are set at expansion joints; After concrete pouring, when the curing reaches more than 20%-30% of the design strength, it should be cut with a slit knife according to the contraction joint position, and the cutting time should not be too early or too late. According to the site temperature, properly grasp the cutting opportunity. In order to make the road surface have a certain friction, the road surface should be roughened to facilitate safe driving.

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