Evaluating the applicability of conventional CPT-based liquefaction assessment procedures to reclaimed gravelly soils

Abstract

Gravelly soils are not well represented in current semi-empirical liquefaction procedures, which raises the question of whether state-of-the-practice liquefaction evaluation methods based on sands are applicable to gravelly soils. This paper investigates the applicability of Cone Penetration Test liquefaction triggering and settlement evaluation procedures to case histories of well-graded reclaimed gravelly soil at CentrePort, New Zealand. Sensitivity studies of the liquefaction triggering analysis show the uncertainty in the cyclic demand is larger than the uncertainty in the cyclic resistance within a critical layer. However, the modelling uncertainty over the entire depth of the fill is larger for the cyclic resistance, which can vary by over 50% due to a single material-characterization parameter, i.e., the fines content or soil behavior type index. Sand-based procedures for evaluation of liquefaction-induced settlement are found to be generally applicable to well-graded gravels that have a dominant silty sand fraction in the soil matrix, though they can overestimate the relative density and therefore underestimate post-liquefaction settlement of gravelly soils. The paper emphasizes the importance of soil composition, dominant soil fraction of the soil matrix, and its effects on the soil packing, penetration resistance, and liquefaction resistance in the context of current semi-empirical liquefaction evaluation procedures. • CPT-based liquefaction procedures are applicable to some gravel-sand-silt mixtures • Soil composition and dominating soil fractions are key to liquefaction assessment • FS L is more sensitive to uncertainties in PGA than FC or I c • Use of a constant FC throughout seemingly uniform fill could be problematic • Sand-based methods overestimate D R and underestimate settlement of gravelly soils