Pipeline Engineering Construction Process

Municipal Pipeline Engineering Construction Process

1. Ductile Iron Pipe (Rubber Ring Interface)

Measurement and Layout → Grooving, Grooving Inspection → Pipeline Foundation → Pipeline Installation, Stabilization → Rubber Ring Installation → Interface → Pipeline Installation → Water Pressure Test → Backfilling;

2. Steel-Plastic Water Supply Pipe (Threaded Connection)

Measurement and Layout → Grooving, Grooving Inspection → Pipeline Foundation → Pipe Cutting → Threading → Pipeline Installation, Stabilization → Straightening → Pipeline Installation → Water Pressure Test → Backfilling;

3. Galvanized Steel Pipe (Threaded Connection)

4. Seamless Steel Pipe (Welding)

Measurement and Layout → Grooving, Grooving Inspection → Pipeline Foundation → Pipe Cutting → Beveling → Straightening → Bend → Eye Digging and Pipe Connection → Different Diameter Pipe Production → Matching → Welding → Pipeline and Pipe Fitting Installation → Water Pressure Test → Backfilling.

5. Welded steel pipe (welding)

Measurement and layout → slotting, slot inspection → pipe foundation → pipe cutting → groove → straightening → bending → eye cutting and pipe connection → reducer production → butt joint → welding → pipe and pipe fitting installation → water pressure test → earth backfilling; (Note: The groove is made to allow the welding rod to backfill the earth; leave some space to increase the firmness of the weld) (electric hoist) → water pressure test;

6. Socket cast iron drainage pipe (asbestos cement interface)

Measurement and layout → slotting, slot inspection → pipe foundation → pipe cutting → pipe and pipe fitting installation → preparation of interface materials → interface maintenance → water pressure test → earth backfilling;

7. Socket cast iron drainage pipe (cement interface)

8. Rigid polyvinyl chloride (UPVC) Water supply pipe (bonding connection)

Measurement and layout → slotting, slot inspection → pipe foundation → pipe cutting → adjustment, joint bonding → pipe and pipe fitting installation → water pressure test → earth backfilling;

9. Plastic water supply and drainage pipe (hot melt connection)

Measurement and layout → slotting, slot inspection → pipe foundation → pipe cutting → joint bonding → pipe and pipe fitting installation → water pressure test → earth backfilling;

10. Plastic water supply and drainage pipe (electric fusion connection)

Measurement and layout → slotting, slot inspection → pipe foundation → pipe cutting → joint bonding → pipe laying → slope finding → alignment → pipe and pipe fitting installation → water pressure test, etc.

11. Reinforced concrete pipe

Measurement and layout → slotting, slot inspection → pipe foundation → pipe laying, pipe stabilization → digging joint working pit → joint bonding → water or air tightness test → earth backfilling.

Preparation for pipeline construction

Before construction, you should be familiar with the drawings, and compare the professional pipelines in the design drawings to check the following issues:

1. Based on the positioning completed on site, whether there is a deviation between the pipelines in the design drawings and the on-site location;

2. According to the drainage slope specified in the design drawings, check whether the drainage direction of the pipelines and the elevation of each pipe well are correct; the location of the wells in this project should try to avoid the pipe wells being located on the main road;

3. Check whether there is any collision between the professional pipelines (mainly the problem of cross elevation);

4. Finally, all drawings checked and adjusted by the network manager are submitted to the design unit in the form of documents and electronic files, and signed or stamped to take effect.

Common problems in municipal pipeline construction

1. Inadequate preparation

The construction unit is not detailed and in-depth in the on-site survey work, resulting in unreasonable preparation of the quality control plan, as well as problems such as construction period, inspection procedures and methods, quality control points and control levels.

2. Problems in the design of silt wells

During the construction design of some municipal engineering water supply and drainage pipelines, silt wells were not independently designed, which often leads to blockage of the drainage pipes of municipal engineering.

3. Imperfect construction plan of drainage wells If the construction plan is not scientifically and reasonably designed, it is easy to hinder citizens' travel. In addition, during the construction of drainage wells, there will often be a certain amount of gravel residue.

4. Material and process problems

The quality of construction equipment and engineering materials is defective: aging and rusting of pipes and components, sand holes, etc.

The construction process is defective: the construction process and technical level are defective, resulting in insufficient processing accuracy of pipe fittings, poor sealing or slope problems.

The backfill soil is seriously subsided: the backfill soil is not compacted in place, the soil layer is not stable and the strength does not meet the standard, and the water content exceeds the standard, resulting in serious backfill soil settlement.

Prevention and control of common quality problems of municipal pipelines

1. Pipeline position deviation or water accumulation

(1) Causes

Measurement errors, construction deviation and accidental avoidance of the original structure will cause position deviation on the plane, water accumulation on the facade and even reverse slope.

(2) Prevention and control measures

① Before construction, carefully re-measure and protect the handover piles in accordance with the construction measurement specifications and regulations.

② Construction layout is combined with hydrogeological conditions, and layout is carried out according to the burial depth and design requirements and relevant regulations. It must be re-measured and tested to ensure that the error meets the requirements before it is delivered for construction.

③ During construction, the sample piles must be strictly followed, and the axis and longitudinal slope measurement and acceptance of the trench and flat foundation must be completed. If structures are encountered unexpectedly during construction, they must be avoided. Connection wells should be added at appropriate locations, connected in a straight line, and the angle of the connection wells should be greater than 135°.

2. Pipeline leakage, water sealing test failure

(1) Causes

Uneven foundation sinking, poor construction quality of pipes and their interfaces, loose sealing of the water sealing section ends, poor well construction quality, etc.

(2) Preventive measures

① Poor foundation conditions of pipelines

Construct carefully according to the design requirements. If the local geological and hydrological conditions are poor, carry out soil replacement and improvement treatment;

If the soil at the bottom of the trench is disturbed or soaked in water, first remove the soft soil layer and then fill the over-excavated part with stable materials such as sandstone or gravel to make it dense;

When excavating below the groundwater level, do a good job of draining and lowering water at the bottom of the pit. If necessary, reserve a 20cm thick soil layer at the bottom of the pit and remove it as you dig.

② Poor quality of pipes

The pipes used must have a quality certificate;

The appearance quality of the pipes meets the requirements;

Check each section before installation.

③ Poor quality of pipe interface fillers and construction quality

Select good quality interface fillers and follow the test mix ratio and reasonable construction process;

When applying the tape, the interface seam should be clean and roughened if necessary.

④ Poor construction quality of inspection well

The mortar for inspection well masonry is full and the joints are fully grouting; clean and moisten the surface before plastering, and press and collect the mortar in time and maintain it during plastering; when encountering groundwater, plastering and grouting should be completed in time with masonry, and internal plastering or internal grouting should not be carried out after backfilling;

The outer surface of the pipe connected to the inspection well should be moistened and evenly brushed with a layer of cement mortar, and the inner and outer surfaces should be plastered after the mortar is in place to prevent leakage.

⑤ The planned reserved branch pipe is not densely sealed

Before masonry, the inner wall of the pipe within 0.5m of the pipe mouth should be cleaned and painted with cement mortar, and the bricks used should be moistened for standby;

The mortar grade for masonry should not be lower than M7.5 and have good consistency;

The cement mortar grade for grouting and plastering should not be lower than M15. When the pipe diameter is large, the inner and outer sides should be grouted or plastered. When the pipe diameter is small, only the outer side should be grouted or plastered. The plastering should be constructed according to the waterproof 5-layer construction method.

In general, the sealing should be carried out before the inspection well is built.

3. Inspection well deformation, sinking, poor quality of components

(1) Causes

Inspection well deformation and sinking, poor quality of manhole cover and installation quality, and too much randomness in the installation of ladders in the well.

(2) Prevention and control measures

① Carefully prepare the base and cushion layer of the inspection well, and use the method of breaking the pipe to make a flow channel to prevent the well body from sinking.

② The quality of inspection well masonry should control the center position and height of the well chamber and wellhead to prevent the well body from deforming.

③ The manhole cover and seat should be matched; the seat mortar should be full during installation; the light and heavy models and the surface bottom should be used well. The iron climber should control the position of the first step up and down, and the plane position should be accurate.

4. Backfill soil subsidence

(1) Causes

The backfill around the inspection well is not dense, the layers are not compacted as required, the filler quality is poor, the water content is not well controlled, etc., which affect the compaction effect and cause excessive settlement.

(2) Prevention and control measures

① Prevention

When backfilling the pipe trench, it is necessary to select appropriate fillers and compaction (tamping) machinery according to the backfill location and construction conditions.

When the trench is narrow, manual or frog-type tamping machine can be used for tamping. Different fillers and different filling thicknesses should use different tamping tools to achieve the most economical compaction effect.

The silt, tree roots, turf and their decaying plants in the filler not only affect the compaction effect, but also shrink and rot in the soil to form holes. These materials should not be used as fillers to avoid subsidence.

Control the moisture content of the filler to be about 2% higher than the optimal moisture content; when encountering groundwater or after rain, the water must be drained first and then the layers are filled and compacted.

② Treatment

Minor settlement that does not affect other structures may not be treated or only surface treatment may be performed. For example, local filling can be adopted on asphalt pavement to avoid water accumulation;

If it causes the foundation of other structures to be hollowed out and damaged, pumped cement slurry can be used for filling;

If it causes structural damage, the bad filling materials should be removed and replaced with materials with good stability, and the damaged structures should be restored after compaction.

Maintenance of municipal pipelines

1. Inspection of urban pipelines

(1) Inspection of pipelines includes pipeline leakage point monitoring, underground pipeline positioning monitoring, pipeline deformation inspection, pipeline corrosion and scaling inspection, pipeline ancillary facilities inspection, and quality inspection of pipeline network media.

(2) The main methods of pipeline inspection include manual inspection, automatic monitoring, zoning detection, regional leakage survey system, etc. Detection means include detection radar, sonar, infrared inspection, closed-circuit surveillance system (CCTV) and other methods and instruments.

2. Emergency repair of urban pipelines

(1) Emergency repair methods for pipelines of different types, materials and structures are different. For example, if the welds of steel pipes are mostly cracked or corroded, they can generally be repaired by welding or cover welding; prestressed reinforced concrete pipes are filled with hemp and ash and then fixed with a chuck; if cracks appear on the pipe body, two sleeves can be used or cast iron pipes or steel pipes can be replaced depending on the size of the cracks, and the two ends can be connected to the original pipes with conversion interfaces.

(2) Various pipeline ancillary facilities such as water pumps and gate valves should also be inspected regularly according to their usage, and repaired and replaced in time if problems are found. All equipment and monitoring instruments in the dispatching system of the pipeline network system should also be properly operated and maintained in accordance with the prescribed working conditions and operating rules.

(3) The large amount of data generated during pipeline inspection, clearing, updating, repair and other maintenance should be processed in a meticulous and systematic manner, and archived and managed well, so as to provide basic information and guarantee for the normal operation of the pipeline network system. When conditions permit, geographic information systems can be used in the pipeline network.

3. Pipeline maintenance safety protection

(1) Maintenance personnel must receive safety and technical training and can only take up their posts after passing the assessment.

(2) When necessary, workers can wear gas masks, waterproof clothing, protective boots, protective gloves, safety helmets, etc., wear protective belts with ropes, and be equipped with wireless communication tools and safety lights, etc.

(3) Based on the assessment of possible gas hazards and germ infections caused by pipeline maintenance, effective safety protection measures and preventive measures should be taken, and dedicated personnel should be on duty in the operation area and on the ground to ensure personal safety.