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Evaluations of Liquefaction Potential Index (LPI) in the 2010-2011 Canterbury earthquake sequence (CES) in New Zealand have shown that the severity of surficial liquefaction manifestations is significantly over-predicted for a large subset of sites. While the potential cause for such over-predictions has been generally identified as the presence of thick, non-liquefiable crusts and/or interbedded non-liquefiable layers in a soil profile, the severity of surficial liquefaction manifestations at sites that do not have such characteristics are also often significantly over-predicted, particularly for the Mw 6.2, February 2011 Christchurch earthquake. The over-predictions at this latter group of sites may be related to the peak ground accelerations (PGAs) used in the liquefaction triggering evaluations. In past studies, the PGAs at the case history sites were estimated using a procedure that is conditioned on the recorded PGAs at nearby strong motion stations (SMSs). Some of the soil profiles on which these SMSs were installed experienced severe liquefaction, often with an absence of surface manifestation, and the recorded PGAs are inferred to be associated with high-frequency dilation spikes after liquefaction was triggered. Herein the influence of using revised PGAs at these SMSs that are in accord with pre-liquefaction motions on the predicted severity of surficial liquefaction at nearby sites is investigated. It is shown that revising the PGAs improved these predictions, particularly at case history sites where the severity of the surface manifestations was previously over-predicted and could not be explained by other mechanisms.
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Vs-based Evaluation of Select Liquefaction Case Histories from the 2010-2011 Canterbury Earthquake Sequence
The 2010–2011 Canterbury earthquake sequence included a number of events that triggered recurrent soil liquefaction at many locations in Christchurch, New Zealand. However, the most severe liquefaction was induced by the Mw7.1 September 4, 2010, Darfield and Mw6.2 February 22, 2011, Christchurch earthquakes. The combination of well-documented liquefaction surface manifestations during multiple events, densely recorded ground motions during these events, and detailed subsurface characterization information at the selected sites provides an unprecedented opportunity to add quality case histories to the empirical soil liquefaction database. The authors have already documented and published 50 high-quality liquefaction case histories from these earthquakes using cone penetration test (CPT) data. This paper examines 46 of these case histories using shear-wave velocity (Vs) profiles derived from surface wave (SW) methods and a Christchurch-specific Vs correlation based on CPT tip resistance. The Vs profiles have been used to evaluate the two most commonly used Vs-based simplified liquefaction evaluation procedures (i.e., Andrus and Stokoe and Kayen et al.). An error index (EI ) has been used to quantify the overall performance of these two procedures in relation to liquefaction observations. Although the two procedures are essentially equivalent for sites with normalized Vs (i.e., Vs1) <180 m=s, the Kayen et al. procedure, with 15% probability of liquefaction, provides better predictions of liquefaction triggering for sites with Vs1 greater than 180 m=s. Additionally, total EI values obtained using Vs profiles from surface wave testing in conjunction with the Kayen et al. procedure are lower than two other CPT-based triggering procedures but higher than the total EI value obtained using the Idriss and Boulanger CPT-based procedure.
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- Award ID(s):
- 1724575
- PAR ID:
- 10051373
- Date Published:
- Journal Name:
- Journal of geotechnical and geoenvironmental engineering
- Volume:
- 143
- Issue:
- 9
- ISSN:
- 1090-0241
- Page Range / eLocation ID:
- 04017066-1
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Evaluations of Liquefaction Potential Index (LPI) in the 2010-2011 Canterbury earthquake sequence (CES) in New Zealand have shown that the severity of surficial liquefaction manifestations is significantly over-predicted for a large subset of sites. While the potential cause for such over-predictions has been generally identified as the presence of thick, non-liquefiable crusts and/or interbedded non-liquefiable layers in a soil profile, the severity of surficial liquefaction manifestations at sites that do not have such characteristics are also often significantly over-predicted, particularly for the Mw 6.2, February 2011 Christchurch earthquake. The over-predictions at this latter group of sites may be related to the peak ground accelerations (PGAs) used in the liquefaction triggering evaluations. In past studies, the PGAs at the case history sites were estimated using a procedure that is conditioned on the recorded PGAs at nearby strong motion stations (SMSs). Some of the soil profiles on which these SMSs were installed experienced severe liquefaction, often with an absence of surface manifestation, and the recorded PGAs are inferred to be associated with high-frequency dilation spikes after liquefaction was triggered. Herein the influence of using revised PGAs at these SMSs that are in accord with pre-liquefaction motions on the predicted severity of surficial liquefaction at nearby sites is investigated. It is shown that revising the PGAs improved these predictions, particularly at case history sites where the severity of the surface manifestations was previously over-predicted and could not be explained by other mechanisms.more » « less
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null (Ed.)Data from 58 high-quality liquefaction case histories from the Darfield and Christchurch earthquakes are utilized to investigate the efficacy of current liquefaction aging correction procedures. Toward this end, liquefaction case histories are analyzed in which aging corrections are and are not applied, and the resulting predictions are compared to the actual liquefaction response of the deposits. An error index is calculated to quantify the efficacy of aging corrections. While all the sites located in the Christchurch area are classified as Holocene, based on their geological age, their liquefaction response is influenced more by the geotechnical age of the soil deposits. Aging correction was determined to be beneficial for the liquefaction assessment of soils that experienced recurrent liquefaction (i.e., geotechnical young deposits). However, aging corrections were determined to exacerbate the liquefaction assessment of relatively old (greater than ∼62–580 years) soil deposits.more » « less
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Gravelly soils have liquefied at multiple sites in at least 27 earthquakes over the past 130 years. These gravels typically contain more than 25% sand which lowers the permeability and makes them susceptible to liquefaction. Developing a reliable, cost-effective liquefaction triggering procedure for gravelly soils has been a challenge for geotechnical engineers. Typical SPT- or CPT-based correlations can be affected by large-size gravel particles and can lead to erroneous results. To deal with these problems, we have developed liquefaction triggering curves for gravelly soils based on (1) shear wave velocity (Vs) and (2) a large diameter cone penetrometer. With a cone diameter of 74 mm, the Chinese Dynamic Cone Penetration Test (DPT) is superior to smaller penetrometers and can be economically performed with conventional drilling equipment. Using logistic regression analysis, the DPT has been directly correlated to liquefaction resistance at sites where gravels did and did not liquefy in past earthquakes. Probabilistic liquefaction resistance curves were developed based on 137 data points from 10 different earthquakes in seven countries. Using a similar data set, probabilistic liquefaction triggering curves were also developed based on Vs measurements in gravelly soils. The Vs-based liquefaction triggering curves for gravels shift to the right relative to similar curves based on sands. New magnitude scaling factor (MSF) curves have also been developed specifically for gravel liquefaction which were found to be reasonably consistent with previous curves for sand.more » « less
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This dataset contains 332 CPT-based liquefaction case histories from 25 globally distributed earthquakes. These data, or subsets of these data, have been analyzed in the literature and are provided here to replicate published results. These cases are sourced from existing studies, to include observations of manifestation severity, CPT soundings, and estimation of GWT depth and ground-motion IMs, as generally reported by original investigators. When available, recent refinements were adopted from the literature. Of the 332 global cases, ~55% are “Manifestation” and ~45% are “No Manifestation.” The compiled, post-processed data is presented in a structure array (a single file), allowing researchers to easily access and analyze information pertinent to free-field liquefaction response (i.e., triggering and surface manifestation). Research opportunities using this data include, but are not limited to, the training or testing of new and existing liquefaction-prediction models. Information describing the contents and structure of the case-history data are provided in a ReadME document. Note: This database substantially augments, and thus supersedes, that of Geyin and Maurer (2021). Geyin, M., B. Maurer (2021). "CPT-Based Liquefaction Case Histories from Global Earthquakes: A Digital Dataset (Version 1)", in CPT-Based Liquefaction Case Histories from Global Earthquakes: A Digital Dataset (Version 1). DesignSafe-CI. https://doi.org/10.17603/ds2-wftt-mv37more » « less
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