I. Project Overview and Construction Objectives
The pipe-jacking method is suitable for the installation of water supply pipelines across rivers, lakes, and other water bodies, with its core process involving the sinking of prefabricated pipe sections to form an underwater passage. Construction objectives include:
Ensure pipeline密封性 to prevent tap water leakage.
2. Ensure pipeline stability, resisting external forces such as water erosion and geological subsidence.
3. Meets long-term operation requirements, balancing construction efficiency and economy.
II. Construction Process and Key Technologies
Preparation and Site Survey
Hydrogeological Survey: Determines water depth, flow velocity, riverbed geology (bearing capacity, silt thickness), tidal patterns, etc.
● Design Proposal: Determine pipeline length, material (steel pipe/Reinforced Concrete), corrosion prevention measures, and laying path.
Excavation of the foundation trench: Use dredging vessels or shield machines to excavate the foundation trench at the predetermined location on the riverbed. The width should be 1-2 meters wider than the pipe section, with the depth accounting for erosion allowance.
2. Pipe Segment Pre-fabrication and Transportation
● Pre-manufacturing Requirements:
Steel pipes require welding or flange connections, with internal wall anti-corrosion coating (such as epoxy coating).
Reinforced concrete pipe sections require casting of high-strength concrete, with temporary closure walls (steel closure plates + waterstop rubber) at both ends.
● Transportation and Floatage:
The pipe sections are transported to the construction area by barge, floated on the water surface using buoys or air bags, and precisely positioned.
3. Pipe Segment Sinking and Installation
● Positioning and Market Penetration:
○ Utilize GPS or underwater sonar positioning systems to slowly lower the pipeline sections above the trench.
Load ballast water (or concrete blocks) into the section, gradually submerge to the designed elevation, controlling the sinking speed ≤0.5m/min.
Pipe Segment Connection
Hydraulic jointing method: Compresses the rubber waterstop at the ends of adjacent pipe sections using water pressure to create a seal.
Mechanical Connections: Underwater welding or flange bolt connections are used for steel pipelines, requiring assistance from divers or ROV operations.
● Basic Treatment:
After the pipe section is laid, the base trench gap is filled with crushed stone or grout (cement mortar or underwater non-settling concrete) to enhance stability.
4. Sealing and Protection
● Demolition of Enclosures: After the immersion is completed, divers underwater cut the temporary enclosures to connect the cavities of each pipeline section.
● External Protection:
Top cover with stone slabs or concrete protective layer, thickness ≥ 500mm, to prevent anchor damage.
Install sacrificial anodes or coatings for corrosion prevention in critical areas to extend service life.
5. Quality Inspection and Acceptance
Sealability Test: Pressure testing through water injection to inspect the sealing integrity of pipe joints and wall seals.
● Structural Inspection: Utilize CCTV robots or divers to check external pipeline damage and foundation compaction.
● Functional Testing: Conduct water trial operation, monitor flow, pressure, and sedimentation data.
Section 3: Key Technical Points and Challenges
Precision positioning and penetration control
Due to the influence of water flow and tides, real-time adjustments to the ballast loading must be made to prevent segment displacement or tilt.
The deep-sea deployment can be assisted in positioning with a multi-point anchoring system.
2. Underwater Connection Sealing
The reinforced concrete pipe section utilizes a "GINA waterproofing tape + OMEGA waterproofing tape" dual-sealing structure to ensure foolproof performance.
The steel pipeline welding must comply with AWS D3.6M underwater welding standard, performed by divers or dry chamber welding.
3. Basic Treatment & Erosion Resistance
When the silt layer is thick,地基reinforcement is required (such as vibration compaction, stone pile).
In the riverbed scour area, the top covering layer should be enhanced with erosion-resistant materials (such as chained blocks or eco-bags).
4. Emergency Response Plan
Equipped with a backup ballasting system and quick-sealing devices to handle pipeline leaks or sudden settlement.
Deep-water operations require the support of diving bells or saturation diving systems.
IV. Safety and Environmental Protection Measures
Construction Safety
Divers must hold CMAS/PADI professional certification and receive decompression sickness prevention training prior to operations.
○ Temporary closure of the construction area, with warning signs and security boats in place.
High-pressure and welding equipment are operated by designated personnel to prevent electric shock or fire.
2. Environmental Measures
Wastewater from construction (such as ballast water discharge) must be treated to meet standards before discharge.
Avoid operations during fish spawning periods to minimize ecological impact.
V. Summary
Sewer pipe installation requires precise construction, sealing techniques, foundation reinforcement, and stringent safety and environmental protection measures. It is recommended to optimize the construction plan based on specific hydrogeological conditions and to use corrosion-resistant materials (such as PE pipes or coated steel pipes) to ensure long-term stable operation of the pipeline.
