Comparing laboratory-based liquefaction resistance of a sand with non-plastic fines with shear wave velocity-based field case histories

The semi-empirical simplified procedure for liquefaction triggering of level-ground is largely based on correlating post-earthquake field observations such as presence/absence of sand boils to field measurements such as penetration resistance or shear wave velocity (Vs). These correlations could be interpreted in such a way that for a given penetration resistance or Vs, the cyclic resistance ratio (CRR) increases as fines content increases. However, some studies have indicated that this interpretation may not be correct, particularly for soils containing non-plastic fines. An experimental research program involving cyclic triaxial tests was undertaken to investigate cyclic resistance of F-75 sand with varying amounts of non-plastic fines (Sil-Co-Sil 125). Bender elements were incorporated in the triaxial cell to facilitate Vs measurements. Other similar data sets found in the literature were used to supplement the laboratory data and evaluate the overall trends implied by the Vs-based field CRR curves. The comparison suggests that the laboratory data are generally consistent with the trends embedded in the field curves, with boundary curves shifting slightly to the left with increasing fines content.