What should we pay attention to when connecting cement drainage pipes?

Technical key points and precautions for cement drainage pipe connection methods

As an important part of the urban drainage system, the connection quality of cement drainage pipes is directly related to the operation effect and service life of the entire drainage system. This article will discuss in detail the key technologies and precautions in the process of connecting cement drainage pipes to provide reference for engineering practice.

1. The main methods of connecting cement drainage pipes

1.Socket connection

Socket-type connection is a common traditional connection method. The connection is achieved through the cooperation of the socket at one end of the pipe and the socket at the other end. Things to note about this connection method:

The dimensions of the socket and socket must match accurately. Generally, the outer diameter of the socket is required to be 23mm smaller than the inner diameter of the socket.

Before connection, the debris and burrs at the socket and socket must be cleaned

The rubber sealing ring should be intact and must not be twisted during installation

2. Flat port docking connection

Flat-mouth butt joint is suitable for large-diameter cement pipe connections. The technical requirements include:

The butt end faces must be flat and the unevenness shall not exceed 2mm/m.

Use special butt glue or cement mortar to fill the joints

After docking, it needs to be temporarily fixed with steel strips or clamps. It can be removed after the filling material solidifies.

3.Flange connection

Flange connections are mainly used for frequent disassembly or special parts. Things to note are:

The flange must be perpendicular to the axis of the pipe, and the deviation must not exceed 1°

Bolts should be tightened evenly at the corners to avoid unilateral stress.

Flange gaskets should be made of corrosion-resistant and elastic materials

2. Preparation work before connection construction

1.Pipeline quality inspection

Check the appearance of the pipe for defects such as cracks, honeycombs, exposed ribs, etc.

Measure whether the geometric dimensions of the pipeline meet the design requirements

Carry out necessary pressure tests to ensure that the pipeline strength reaches the standard

2.Basic processing requirements

The bottom of the trench should be flat and compacted, and the bearing capacity should meet the design requirements.

The foundation cushion should be made of well-graded sand and gravel materials

Concrete foundations should be added or other reinforcement measures should be taken on weak foundations

3. Construction environment control

Precipitation measures should be taken on rainy days or when the groundwater level is high

Insulation measures should be taken when the ambient temperature is below 5℃

Ensure there is sufficient operating space at the construction site

3. Key technical points in the connection process

1. Rubber sealing ring installation

The sealing ring should be intact and undamaged, and special lubricant can be applied before installation.

Do not use sharp tools during installation to avoid scratching the sealing surface

The sealing ring should be pressed evenly into the groove without any distortion or flipping.

2.Pipeline docking operation

Use special lifting equipment to lower the pipe smoothly to avoid collisions

When docking, the axes of the two pipes should be kept consistent, and the deviation should not exceed 3°.

Large-diameter pipelines should adopt multi-point synchronous jacking technology

3.Seam treatment process

The gap between the socket and socket should be filled tightly with cement mortar or special caulking material.

The caulking material should be compacted in layers, with the thickness of each layer not exceeding 20mm.

After the joint filling is completed, it should be maintained in time to prevent cracking.

4. Quality inspection after completion of connection

1. Appearance inspection

Check whether the interface is smooth and dense, and there are no cracks or leaks.

Measuring the axis deviation of the pipeline, the straight line segment should not exceed 15mm every 10m

Check whether the rubber sealing ring is evenly compressed and whether the compression amount meets the requirements.

2. Closed water test

The length of the test section should not exceed 500m, and the water injection height should not be less than 2m.

The constant pressure time should be no less than 30 minutes, and the allowable water seepage should comply with the specifications.

Leakage points should be marked and repaired promptly when found

3. Backfill quality control

Backfilling should be carried out after the interface strength reaches the design requirements

Both sides of the pipeline should be backfilled symmetrically, and the height difference should not exceed 300mm.

Manual tamping should be used within 500mm of the top of the pipe

5. Precautions for connection under special conditions

1. Soft soil foundation treatment

Foundation reinforcement or concrete foundation should be provided

Pipes should be backfilled promptly after connection to prevent pipes from floating.

Consider setting up flexible joints to accommodate foundation deformations

2. Construction requirements in earthquake zones

Anti-seismic measures should be added at the interface, such as anti-seismic clamps

Flexible connections should be provided when pipelines pass through building foundations

Appropriately increase the number of inspection wells to improve the seismic performance of the system

3.Corrosive environment protection

Use sulfate-resistant cement or apply anti-corrosion coatings

Anti-corrosion treatment should be added to the interface

Regularly check pipeline corrosion conditions

6. Common problems and solutions

1. Interface leakage

Cause analysis: The sealing ring is damaged, improper installation or improper caulking

Solution: Reinstall the sealing ring or use special plugging material to repair it

2. Pipe misalignment

Cause analysis: foundation settlement or improper backfilling

Solution: Excavate locally and reconnect, and reinforce the foundation if necessary

3. Interface cracking

Cause analysis: temperature difference stress or uneven settlement of foundation

Solution: Repair cracks and install expansion joints

7. Maintenance and Maintenance Points

1. Regularly check the condition of pipe joints, especially before and after the rainy season

2. Clean the sediments in the pipes promptly to keep drainage smooth.

3. Deal with small problems promptly to avoid developing into big problems

The connection quality of cement drainage pipes is the key to ensuring the long-term stable operation of the drainage system. Construction personnel should strictly follow the specifications and control every detail to ensure that the connections are firm and the seals are good. At the same time, appropriate connection methods and supporting measures should be selected based on the actual conditions of the project to ensure that the drainage system can work reliably under various conditions. Through scientific construction management and quality control, the service life and operating efficiency of the cement drainage pipe system can be significantly improved.