During the construction and use of underground pipelines, due to continuous or discontinuous physical, chemical, biochemical and biological erosion, defects of different degrees often occur. The types of pipeline defects include pipeline leakage, pipeline blockage, pipeline displacement, mechanical wear, pipeline corrosion, pipeline cracks, pipeline rupture and pipeline collapse, etc.
There are many reasons for pipeline leakage, generally speaking, there are the following aspects:
① Failing to comply with the standards of relevant specifications, including four aspects: pipeline design, pipeline materials and pipeline components, pipeline construction, and pipeline operation;
②Material aging and other damage.
① Use of inappropriate materials and piping components
a. Failure to consider or wrongly estimate the stresses on the inside and outside of the pipe, and the changes in stress during use.
b. A chemical reaction occurs between the piping material and piping components after they are installed and fixed.
c. The loss of volatile materials in the sealing medium, or the loss of adhesives into the pipe and the soil around the pipeline.
d. The use of unstable sealing materials or artificial rubber gaskets of improper size, resulting in excessive or insufficient reaction force at the seal.
e. Pipe joints with excessive fit tolerances and incompletely hardened concrete pipes or reinforced concrete pipes are used.
② Use of defective or damaged piping components
a. Reinforced concrete or plain concrete pipes have delaminated segregation and insufficient compaction during production, and the shrinkage deformation exceeds the allowable range, resulting in cracks.
b. There are holes in the pipe (cast pipe, steel pipe, plastic pipe) or rubber gasket due to shrinkage.
c. The pipeline is damaged during installation, storage and transportation, and the tolerance of the pipeline size does not meet the requirements.
③Pipeline construction quality is not up to standard
④Pipe joint problem
a. Improper installation of the sealing gasket, the actual working temperature of the sealing material and medium does not meet the requirements, too high or too low will affect its sealing performance.
b. The position of the abutment used for the pipe is not correct or the two pipes are not strictly aligned. The use of mismatched abutments will also cause this problem.
c. Failure of the seal due to the lip of the pipe not fully extending into the socket of another pipe or the socket of the jack.
d. When the pipe is jacked, the pipe jacking speed is too fast, resulting in excessive eccentricity, resulting in damage to the sleeve of the pipe, the gasket and the coaxiality of the jack pipe.
e. In the process of pipe jacking construction, the mud (wall protection, lubrication) selected with bentonite is not suitable, which will lead to excessive pressure.
⑤Connection parts problem
a. The connection between the sewer system and its building structure is too tight and lacks deformability, which often occurs in inspection wells.
b. Improper connection of sewage branch pipe. Especially in pipelines where personnel cannot enter, it is difficult to accurately control the size of branch pipes at the beginning of construction, and many branch pipes used to be connected to previously filled sewers. In this case, it is impossible to achieve very good watertightness, and leakage will occur sooner or later, and its pipe joints are also difficult to install flexibly. In addition, pipeline stress and pipeline deformation will cause cracks in the pipeline, and the loss of the sealing medium used in the pipeline will cause water leakage. The above two effects will cause serious damage to the drainage pipeline.
c. Improper cleaning procedures or cleaning equipment selected in the early stage, or wrong operations by construction personnel, will cause damage to the connecting parts, such as mechanical damage to the pipeline caused by the cleaning equipment during the cleaning process.
The following situations often also cause pipeline leaks:
① pipe position offset; ② mechanical wear; ③ pipe corrosion; ④ pipe deformation, pipe crack, pipe rupture and pipe collapse