Field and laboratory-based characterisation of pumiceous soils in the Bay of Plenty

The behaviour of pumiceous soil deposits to cyclic loading remains a topic of active research, and methods to evaluate liquefaction hazard in response to earthquake shaking are currently evolving. Recent industry guidelines have highlighted the uncertainty in pumiceous soil response and call for practitioners to adopt a more nuanced approach to assessing liquefaction hazard. This paper presents a recent project where field profiling, advanced sampling, and cyclic laboratory testing methods were employed to characterise the behaviour of pumiceous deposits considered to pose a potentially critical hazard for a site in Bay of Plenty, New Zealand. This paper discusses how the field and laboratory testing provided justification for the use of a less conservative triggering curve for liquefaction assessment, significantly reducing the extent of liquefaction under a design earthquake compared to previous estimates, allowing for significant cost savings for the client and reduced disruption to business. This paper reflects on the benefits which can be provided in the specification of high-quality undisturbed and specialised dynamic laboratory testing of pumiceous soil deposits, and provides recommendations for future application.