Liquefaction resistance and possible aging effects in selected Pleistocene soils of the Upper North Island

The assessment of a soil’s liquefaction potential can often have major financial implication for infrastructure projects. An overly conservative assessment can lead to unnecessary expenditure on foundations or ground improvement.

The assessment of liquefaction potential in recent deposits of alluvial soils with grains of lithic origin is becoming increasingly well defined, however where older soils or soils of volcanic origin are analysed, the level of uncertainty is higher. It has been suggested that comparison of liquefaction analysis based on the most commonly applied investigation methods e.g. Standard Penetrometer and Cone Penetrometer Tests against smaller strain methods e.g. Shear Wave Velocity might provide useful evidence of aging, cementation or particle crushing effects in some soils.

We have sought evidence of such effects by comparing liquefaction potential of soils of Recent and Pleistocene age and/or volcanic origin at sites in the Waikato Region using large and small strain methods. Our analyses, utilising a small strain method, indicated a higher liquefaction resistance than large strain tests in a selection of the Early Holocene and Late Pleistocene soils.