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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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Assessing Liquefaction Susceptibility Using the CPT Soil Behavior Type Index
Cone Penetration Test (CPT) based simplified liquefaction evaluation procedures offer significant advantages over variants based on alternative in-situ test indices. However, the main drawback of CPT-based variants is that soil samples are typically not recovered during CPT sounding, and as a result, soils are often not characterized directly or tested further in the laboratory. The need thus arises to infer soil properties from CPT indices without physical confirmation. Utilizing an unprecedented database of field and laboratory test data from Christchurch, New Zealand, this study proposes deterministic and probabilistic correlations relating the soil behavior type index (Ic) to liquefaction susceptibility as defined by published criteria. The findings show that Ic can be used with reasonable accuracy as a proxy for laboratory index-test based criteria for assessing liquefaction susceptibility. Additionally, to assess liquefaction hazards in a fully probabilistic manner, the uncertainty of Ic for defining liquefaction susceptibility can be accounted for using an approach similar to that used to create fragility functions for performance-based earthquake engineering. The approaches used herein to develop deterministic and probabilistic Ic relationships for liquefaction susceptibility are not limited to soils from New Zealand, but rather, can be applied worldwide.
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- Award ID(s):
- 1724575
- PAR ID:
- 10051372
- Date Published:
- Journal Name:
- Proc. 3rd Intern. Conf. on Performance-Based Design in Earthquake Geotechnical Engineering (PBDIII)
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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