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The influence of the non-liquefied crust that overlies a liquefied deposit on the severity of surficial liquefaction manifestations has been noted for several decades. In 1985, Ishihara proposed a generalize relationship relating the thicknesses of the non-liquefied crust and of the liquefied stratum to the severity of surficial liquefaction manifestations. Although subsequent studies using data from multiple earthquakes give credence to Ishihara’s relationship, the implementation of the procedure is tenuous for all but the simplest of profiles. In an effort to overcome issues with implementing the Ishihara relationship, new procedures have been proposed for predicting the severity of surficial liquefaction manifestations. The efficacies of two of these procedures are currently being assessed in a study using unique case history data from the 2016, Mw5.7 Valentine’s Day earthquake that impacted Christchurch, New Zealand. Preliminary results from this study show that both procedures yield predictions that are in accord with field observations. However, the final results from the ongoing study are expected to more fully assess the efficacies of these procedures.
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State-based assessment of cyclic liquefaction manifestation
This study assesses the robustness of a framework based on critical state soil mechanics (CSSM) principles in evaluating earthquake-induced liquefaction manifestation. The assessment is motivated by the contrasting procedures in evaluating static and cyclic liquefaction, where mechanical properties commonly inform the former, whereas the latter often relies on semiempirical-based methods. The framework discussed in this study considers as ingredients (1) laboratory-based mechanical properties that are an average representation of soil’s microstructure, (2) state inversion, (3) the link of state with cyclic resistance ratio (CRR), and (4) the seismic demand, represented by the cyclic stress ratio (CSR). The framework is assessed using ~5000 cone penetration tests (CPTus) conducted after the Canterbury earthquake sequence, where each CPTu is associated with liquefaction manifestation levels. The discussed framework is used to estimate safety factors, which are then combined with several liquefaction severity indexes (LSIs) to evaluate liquefaction manifestation in the context of a classification problem (i.e., “Yes” and “No”). The framework’s performance is assessed using machine learning by estimating receiver operating characteristic curves (ROC). Different state inversion procedures are also considered, and recommendations based on their performance are provided. In particular, a calibrated cavity expansion-based inversion for New Zealand is proposed. We find that the discussed framework offers comparable performance to state-of-practice procedures, even when general considerations for mechanical properties based on CSSM are made, which is encouraging. Moreover, by including mechanical properties, it can better inform extrapolations for regions without significant data and non-typical soils as long as adequate properties are considered. In this context, it shares conceptual similarities with non-ergodic approaches in earthquake engineering.
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- Award ID(s):
- 2145092
- PAR ID:
- 10520870
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Soil Dynamics and Earthquake Engineering
- Volume:
- 179
- Issue:
- C
- ISSN:
- 0267-7261
- Page Range / eLocation ID:
- 108520
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.soildyn.2024.108520
