The challenges of rebuilding underground infrastructure in liquefaction-prone Christchurch were put under the microscope in a controlled field assessment of the performance of below ground infrastructure in simulated liquefied soils.
The Liquefaction Trial was carried out after the Canterbury Earthquake Sequence (CES) of 2010-2011 prompted the Christchurch City Council (CCC) to amend infrastructure design standards to incorporate more conservative detailing aimed at providing greater seismic resilience. Changes were made to pipe and chamber material selection, design detailing, and backfill material type.
In the trial, a range of pipes, chambers and backfill materials were assessed. Liquefaction was triggered within the soils through a sequenced detonation of explosives within an array of boreholes.
A report covered the findings and interpretations from the trial, and discussed the current theory around the performance of buried infrastructure during liquefaction events.
The trial provided evidence to support the resilient design solutions incorporated into the SCIRT rebuild, which were found to be pragmatic and practical, exhibiting an appropriate level of resilience and optimised value. The standard details used by SCIRT were appropriate for most conditions in Christchurch and other areas which showed susceptibility to liquefaction.