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Seismic Performace of Plastic Pipe Systems in 2010/11 Canterbury Earthquakes

The re-build of the damaged water and wastewater networks in Christchurch following the 2010/11 Canterbury earthquake series has almost exclusively been undertaken with modern Poly-vinyl Chloride (PVC) and Polyethylene pipe materials. 

Assessments of the seismic performance of water and wastewater pipe networks to date have been dominated by initial repair records, but also include CCTV assessments, leakage and infiltration studies.

Polyethylene pipes performed exceptionally well, with only a handful of documented mains failures in the water and sewer networks. Polyethylene service connection pipes did not perform as well as larger diameter mains, with a number of pipe repairs required to restore service. Service connection failure issues associated with polyethylene pipe include historical material issues and fitting failures. Significant damage of PVC gravity pipe networks was limited to areas of high liquefaction and to older pipes. The majority of the damage and loss of service to PVC pipe networks occurred within pressurized pipe networks, with pipe joint damage/failure the predominant failure mechanism. 

Assessment of damage which was not critical to the operation of the networks is on-going, as the effects become apparent in the operation of the networks. This in particularly evident in parts of the wastewater gravity network which have experienced increased infiltration rates, but is less evident in the pressurized water supply and wastewater networks.


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