Since the rise of pipeline trenchless rehabilitation technology in developed countries in the 1980s, it has become a widely used method for underground pipeline rehabilitation. By avoiding large-scale excavation, this technology reduces the impact on urban traffic, the environment, and residents' lives, hence gaining extensive attention and preference. This article will provide a detailed introduction to the main methods and application fields of trenchless rehabilitation technology and analyze its important role in urban network renovation.
Lining Method
Trenchless rehabilitation technology using the lining method involves installing a new lining pipe inside the old pipeline to give it new service life. This process involves pulling new cast iron pipes, polyethylene pipes, or steel pipes into the old pipeline, or using specialized equipment to reduce the diameter or deform a high-density polyethylene (HDPE) pipe that is larger than or equal to the original pipeline diameter into a "U" shape before pulling it into the old pipeline as part of the pipe cleaning system. Utilizing the memory properties of HDPE, the pipe diameter can restore itself and closely adhere to the old pipeline.
Cement Mortar Spraying Method Inside the Pipe
The cement mortar spraying method is mainly applied in water supply pipelines. By uniformly spraying cement mortar inside the original pipeline using a mortar spraying machine, it forms a lining layer. This method effectively prevents pipe scaling, reduces water transport resistance, improves water supply capacity, and enhances the anti-corrosion performance of the pipe, reducing leakage problems. The trenchless rehabilitation technology's cement mortar spraying method simplifies the construction process and enhances the overall performance of the pipeline.
Pipe Bursting Method
The pipe bursting method uses a pipe-bursting machine to crush or burst the old pipeline and squeeze it into the surrounding soil, while dragging in a new pipe made of HDPE, steel, etc. This method is suitable for replacing old pipelines, but in complex pipeline environments, it may damage surrounding pipelines, thus requiring careful selection.
Short Pipe Lining Method
The short pipe lining method involves welding short pipes section by section and dragging them into the old pipeline, finally filling the gap between the new and old pipes with mortar. This method is low-cost but results in significant loss of cross-section and reduced flow rate in the rehabilitationed pipeline, thus it is less commonly used nowadays.
Lining HDPE Pipe Method
The lining HDPE pipe method is one of the important methods in trenchless rehabilitation technology. The principle is to deform an HDPE lining pipe, with an outer diameter slightly larger than the main pipeline's inner diameter, through multi-stage diameter reduction or "U" deformation, making its cross-section smaller than the main pipeline's, and quickly insert it into the main pipeline under traction. The lining HDPE pipe restores its original shape using its memory properties or with the aid of pressure and temperature, closely adhering to the main pipeline's inner wall, thereby restoring the main pipeline's function and extending its service life.
"U" Shape Deformation Technology
"U" shape deformation technology uses the shape memory property of materials to deform the lining HDPE pipe into a U-shape, then restore its original shape under pressure. This method is suitable for both structural and non-structural rehabilitations and is widely used for pipeline lining rehabilitations.
Multi-Stage Diameter Reduction Technology
Multi-stage diameter reduction technology uses a specialized diameter reduction machine to pull the lining HDPE pipe at normal temperature or after heating, reducing its pipe diameter, and then quickly dragging it into the old pipeline under the traction of the winch. Relying on the long-molecule memory property, the lining HDPE pipe gradually restores its diameter, forming a tight lining layer. This method reduces the cross-sectional area reduction of the pipeline, and due to the smooth inner wall of the lining HDPE pipe, increases water flow speed and transportation capacity.
Inversion Lining Method (CIPP)
The inversion lining method uses water pressure or air pressure to invert a resin-coated soft pipe into the old pipeline, and then cures the lining material through heating or other measures to form a rigid pipeline lining layer.
Spiral Wound Lining Method
The spiral wound lining method uses a specialized winding machine to spiral a strip-shaped PVC profile inside the pipeline to form a new pipe, filling the gap between the new and old pipes with cement mortar.
In summary, trenchless rehabilitation technology is widely applied and effective in pipeline rehabilitation. Its various restoration methods ensure that different types of pipeline issues can find suitable solutions, providing strong technical support for urban network renovation and maintenance.
Trenchless rehabilitation technology not only improves construction efficiency and reduces costs but also effectively minimizes negative impacts on the environment and society, making it an indispensable important technology in modern urban construction.
