Some Important Limitations of Simplified Liquefaction Assessment Procedures

Abstract

AbstractA subset of a recently compiled database of CPT-based liquefaction case histories from Canterbury, New Zealand, is used to scrutinize the performance of simplified liquefaction assessment procedures, for different soil types and ground conditions. In general terms, simplified procedures are shown to perform well (i.e. correctly predict severe manifestation of liquefaction at the ground surface) for deposits that have a critical zone of vertically continuous low-resistance liquefiable soils at shallow depth (true-positive sites), and also (correctly predict the absence of liquefaction manifestation) for relatively uniform high-resistance clean sand or fine sand deposits (true-negative sites). In contrast, the severity of liquefaction manifestation in intermediate-resistance clean sand to silty sand deposits is generally underpredicted by the simplified procedures (false-negative sites). Lastly, systematic overprediction of liquefaction manifestation is observed in deposits with interbedded non-liquefiable soils and liquefiable soils of low-resistance (false-positive sites). The poor performance of the simplified procedures for the false-negative and the false-positive sites can be attributed to the neglect in the evaluation of important system response effects which, on the one hand, intensify the severity of liquefaction manifestation for the false-negative sites and, on the other hand, mitigate liquefaction manifestation for the false-positive sites.KeywordsCase historyLiquefactionSimplified methodSystem response