Can plastic sewer pipes be laid with a similar cover to clay and concrete pipes?
Yes - Plastic pipes can be buried with similar minimum cover to traditional pipe materials.
- The above statement is based on the findings of the TEPPFA Project on the Design of Buried Thermoplastic Pipes.
- This extensive field based project involved the controlled installation of plastic sewer pipes of various materials and stiffness classes.
- Pipes were installed in different soils with varying levels of compaction.
- In all 16 pipelines each between 10 and 25 metres long were installed with different combinations of pipe material, pipe stiffness class, bed & surround material, native soil and level of compaction of backfill.
- Pipes with a cover of 1.15 metres were subjected to traffic loads which exerted a surface pressure of 240 KN/m2. No significant change in final deflection of the pipe was recorded.
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Other conclusions from the Buried Pipe Project include :
- No failures were encountered even though some pipelines were installed in an extremely poor way.
- The quality of pipeline installation and good workmanship is by far the most influential factor with regard to the level of deflection of the pipe.
- Depth of cover is not an important influence on pipe deflection.
- Traffic load has no significant effect on pipe deflection.
- The creep ratio is not important for the determination of the deflection.
- A good pipe deflection prediction can be obtained by use of a simple design graph.
- Deflection calculation methods are load driven and generally tend to over estimate the level of deflection.
Want to know more?
Go to the Civils section of the TEPPFA website where you can access the full report on the Buried Pipe Project.
Refer to PrCEN/TR15233.
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