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1. Overview of the Process

The cushion-lining method is an advanced trenchless rehabilitation technology for water supply and drainage pipelines. It involves installing a flexible liner inside the existing pipe to create a new inner wall, thereby restoring the pipeline’s structural and hydraulic functions.

The process uses prefabricated pad-lining materials customized to match the existing pipeline. These are pulled into position using mechanical equipment and expanded with water or air pressure to form a stable tubular structure.

2. Features and Application Scope

(1) Process Features

1. Trenchless Rehabilitation – No surface excavation required, minimizing environmental disruption and traffic interference. Construction can be completed through existing manholes.

2. Convenient and Safe Construction – Operators do not need to enter the pipeline, ensuring safety and reducing workspace.

3. Flexible and Rigid Combination – The liner integrates the flexibility of thermoplastics with the strength of concrete, significantly improving corrosion resistance and service life.

4. Eco-friendly and Efficient – No pollution during construction; ideal for densely populated urban areas.

(2) Application Scope

• Applicable Materials: Corrugated pipes, reinforced concrete pipes, steel pipes, masonry, and brick pipelines.

• Pipeline Types: Rainwater, sewage, industrial wastewater, box culverts; applicable diameters range from 300 to 2000 mm, including circular, oval, and special shapes.

• Repair Scenarios: Suitable for partial or full rehabilitation, and for pipelines with bends or misalignments.

• Limitations: Not suitable for manhole structural repairs.

3. Working Principle

The lining is pulled into the host pipe through an inspection manhole. The anchoring ribs on the back of the liner form a mechanical interlock with the old pipe wall. Grout is then injected into the annular gap between the liner and the old pipe. After curing, the materials bond tightly, creating a composite pipeline structure with enhanced sealing, corrosion resistance, and load-bearing performance.

• Anchoring Design: The rear ribs on the liner interlock with the old wall, while the grouting material fills gaps to ensure stability.

• Multi-Layer Lining: Additional layers can be applied for thicker reinforcement and improved anti-leak performance.

4. Advantages of the Cushion-Lining Method

1. Excellent Corrosion Resistance – High molecular polymer materials resist acids, alkalis, and chemical erosion, extending pipeline life.

2. High Compressive Strength – Once cured, the liner shares structural loads with the original pipe, improving compressive performance.

3. Strong Deformation Adaptability – The flexible liner adapts to minor ground movement and pipe deformation.

4. Superior Leak-Proof Performance – Outstanding impermeability prevents internal leaks and external groundwater intrusion.

5. Improved Hydraulic Efficiency – The smooth inner surface reduces roughness; despite minor diameter loss, overall flow capacity often increases.

6. Wide Compatibility – Fits various pipe shapes (round, oval, square) and tolerates small bends or offsets.

7. Efficient Construction – Non-excavation technology minimizes traffic disruption, construction time, and environmental impact.

5. Conclusion

The cushion-lining rehabilitation technique combines trenchless efficiency, hybrid strength, and environmental safety, making it an ideal choice for modern water supply and drainage maintenance. Its broad adaptability and high durability help extend pipeline service life, reduce maintenance costs, and enhance urban infrastructure sustainability.