Deterministic and Probabilistic Assessment of Liquefaction Hazards Using the Liquefaction Potential Index and Liquefaction Reduction Number

Abstract

The liquefaction potential index (LPI) has increasingly been used for assessing liquefaction hazards induced by earthquake shaking. The LPI allows an integral number of soil horizons to be evaluated for liquefaction potential. Considerable uncertainty exists in cases where the LPI thresholds for classifying liquefaction hazards statistically rely on the data sets and/or the framework. This study explored what the appropriate LPI classification thresholds should be and developed a liquefaction reduction number (RL) to better account for the impact of nonliquefiable layers. The LPI and RL values were then analyzed at the standard penetration test (SPT) data sites reported in case studies. The results suggested that most SPT-based LPI thresholds should be modified upward in comparison with Iwasaki’s original scale. These corrections are of particular importance when clay minerals are part of the soil mixture, rather than simply using the minus 200-sieve fraction as the liquefaction susceptibility criterion. Nonliquefied sites appear to exhibit higher RL values, suggesting that the RL could supplement the LPI as a valuable proxy for liquefaction hazard assessments. Probabilistic liquefaction hazard assessments could be estimated using a logistic regression of the LPI and/or RL values.