Trenchless repair is to lay, repair or replace underground utilities, pipelines and underground cables using slight trenching or trenchless technology. Compared with traditional repair by trenching for replacing pipeline, trenchless repair makes full use of the original pipeline, and has the advantages of minor destroy to environment, small interference to the public and traffic, good economic effect of construction, wide applicable conditions, short construction period, saving heavy earthwork, etc. Trenchless repair and updating technology for pipeline include overall repair, local repair and online replacement and expansion for pipeline. Since a plenty of new type materials harmless to environment are adopted, the material has small coefficient of friction resistance, and good corrosion resistance, can effectively increase the discharge capacity of pipeline and improve the service life of original pipeline, and has favorable social, economic and environmental benefits. At present, the most frequently used repair methods by the Company are cured-in-place pipe (CIPP) and local pipeline repair technology. 

 

1、 Cured-in-place pipe (CIPP) is widely applied for repairing pressure pipelines including sewage pipeline, water supply pipeline, chemical and industrial pipeline, etc. It has the advantages that the liner pipe is tightly fit to the original pipeline, it is unnecessary to grout with fast construction speed and short construction period, it can be used for repairing noncircular pipelines, and the continuous liner pipe with smooth surface is favorable for reducing the loss of flow. tages that the liner pipe is tightly fit to the original pipeline, it is unnecessary to grout with fast construction speed and short construction period, it can be used for repairing noncircular pipelines, and the continuous liner pipe with smooth surface is favorable for reducing the loss of flow. 

 
 

       Before repair                                                                                                         After repair


2、Local pipeline repair technology
    Spot CIPP repair technology is mainly used for repairing pipeline with local damage, and it is one of the most common local repair methods. 

                                   
  Before repair                                                                                                  After repair

      Stainless foaming cylinder method is to enter into the underground pipeline through the inspection well, form a stainless liner in the position to be repaired so as to maintain the structural strength of the damaged pipeline, and then seal the local leakage of the pipeline. The segment repair technology is only applicable for repair large-diameter pipelines above 900mm.