Liquefaction Resistance of Hamilton Pumiceous Sands

Conventional empirical methods used to assess the liquefaction resistance of soils from in situ tests, such as CPT and SPT, have been developed for hard-grained sands, and may not accurately characterise the liquefaction resistance of sedimentary pumiceous sands. The NZ Transport Agency commissioned a programme of cyclic triaxial laboratory testing, to better understand the liquefaction resistance of pumiceous sands local to the Hamilton Basin. The results of this testing confirm that the pumiceous sands in the Hamilton area are susceptible to liquefaction, and that the risk of liquefaction cannot be ruled out by the observation that the sand is pumiceous. When compared to similar testing on relatively hard-grained sands found in geotechnical literature, the results show that Hamilton pumiceous sands are generally more resistant to liquefaction than hard-grained sands of the same relative density. Current empirical methods for estimating liquefaction resistance from common field tests (SPT, CPT, Shear wave velocity) are mainly based on data from hard-grained sands, so these may underestimate the resistance of pumiceous sands to liquefaction.