A case study on the seismic performance of wastewater pipelines following the Valentine's Day earthquake

Miao (Melanie) Liu - Beca Ltd, Marcus Gibson - Beca Ltd, Kelly Tang - Beca Ltd, Greg Preston - UC Quake Centre

A study is undertaken to compare the performance of wastewater pipelines in Christchurch in the aftermath of the 14 February 2016 earthquake (Valentine’s Day Earthquake). The strong ground motion of this earthquake is similar to the Ministry of Business, Innovation and Employment earthquake serviceability limit state loading ground acceleration for the Canterbury region. As a result, this earthquake presented an opportunity to assess the seismic performance of wastewater networks during a SLS equivalent event. 

In this study, a small sample of 26 gravity pipelines were selected from the wastewater network in North New Brighton and Parklands suburbs in eastern Christchurch. The study compared CCTV records collected pre- and post-Valentine’s Day Earthquake for the selected assets. Among the selected wastewater pipelines, 36% were in areas where liquefication was observed. Earthquake induced structural defects have been the focus of the study. All structural defects were categorised into three groups: lateral pipe related, pipe related and pipe joint related structural defects. The pre- and post-earthquake CCTV footage of the 26 pipelines were compared to identify the changes to the defects.

This study is funded by the EQC/Quake Centre Industry Fellowship Scheme. The size of the sample was limited by the availability of baseline pre-Valentine’s Day earthquake CCTV records that was not influenced by any of the significant previous earthquakes. This paper summarises the method adopted, key findings and presents some recommendations for further analysis.