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1. Evaluating Liquefaction Triggering Potential Using Seismic Input Parameters that Are Consistent with ASCE 7-16

   https://doi.org/10.1061/9780784482810.010  

   Green, R.A. and (February 2020, Geo-Congress 2020: Geotechnical Earthquake Engineering and Special Topics)

   J.P. Hambleton, R. Makhnenko (Ed.)

   ASCE 7-16 details how the peak ground acceleration (PGA) should be determined for evaluating liquefaction triggering, with this PGA reflecting the influence of a range of earthquake magnitudes on a site’s seismic hazard. Similarly, the Finn and Wightman magnitude-weighting scheme can be used to account for the full range of magnitudes influencing the seismic hazard at a site, where the weights are derived from a site’s seismic hazard deaggregation data. However, the deaggregation data for the seismic hazard maps for the Central/Eastern U.S. are only available for rock motions and not motions at the surface of the soil profile. The authors explore this issue by comparing the weighted average magnitude scaling factors (MSF) and depth-stress weighting factor (rd) values for multiple sites in the Western U.S. developed using deaggregation data for rock motions and for motions at the surface of the soil profiles. Based on these comparisons, the authors found that using the PGA deaggregation data for rock conditions yield similar weighted averages for MSF and rd as those computed using deaggregation data for the PGA at the surface of the soil profile. 

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2. Evaluating Liquefaction Triggering Potential at Sites Impacted by the 2016 Mw5.8 Pawnee, Oklahoma, Induced Earthquake

   Quick, T. (February 2020, Geo-Congress 2020: Geotechnical Earthquake Engineering and Special Topics)

   J.P. Hambleton, R. Makhnenko (Ed.)

   Deep wastewater injection-induced seismicity has led to over a thousand Mw>3 earthquakes and four Mw>5 earthquakes in Oklahoma over the last ten years. The 3 September 2016, Mw5.8 Pawnee, Oklahoma, earthquake was the first induced seismic event worldwide, that the authors are aware of, where liquefaction was observed and documented, raising concerns regarding the liquefaction risk posed by future induced earthquakes. Determining the suitability of current variants of the simplified procedure for evaluating the regional liquefaction hazard caused by induced earthquakes is part of an ongoing study. A detailed site characterization campaign examining profiles where liquefaction was and was not observed following the 2016 Mw5.8 Pawnee, Oklahoma, earthquake is part of this study. The purpose of this paper is to present an overview of the sites targeted as part of this testing, a summary of preliminary results from the site characterization campaign, and a description of planned future testing. 

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3. Insights into the Liquefaction Hazard in Napier and Hastings Based on the Assessment of Data from the 1931 Hawke’s Bay, New Zealand, Earthquake

   El Kortbawi, M. (April 2019, Proceedings - Australia-New Zealand Conference on Geomechanics)

   Hawke’s Bay is situated on the east coast of the North Island of New Zealand and has experienced several earthquakes in the past during which triggered liquefaction. The 1931 Hawke’s Bay earthquake is particularly interesting because it was one of the most damaging earthquakes and the deadliest earthquake in New Zealand’s history. This study provides insights into the actual versus predicted liquefaction hazard in Napier and Hastings. Towards this end, the simplified Cone Penetration Test (CPT)-based liquefaction triggering evaluation procedure proposed by Boulanger & Idriss (2014) (BI14) is used in conjunction with Liquefaction Severity Number (LSN) framework to predict severity of surficial liquefaction manifestations across the region for the 1931 MS7.8 Hawke’s Bay event. A comparison of the results with post-event observations suggests that the liquefaction hazard is being over-predicted. One possible cause for this over-prediction includes the shortcomings liquefaction damage potential frameworks to predict the severity of surficial liquefaction manifestations in silty soil deposits. This study demonstrates how historical earthquake accounts in a region can be used to assess the risk of the region from future earthquakes. 

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4. Selecting Factor of Safety against Liquefaction for Design Based on Cost Considerations

   Upadhyaya, S. (June 2019, Proc. 7th International Conference on Earthquake Geotechnical Engineering (7ICEGE))

   The stress-based simplified procedure is the most widely used approach for evaluating liquefaction triggering-potential of sandy soils. In deterministic liquefaction evaluations, “rules of thumb” are typically used to select the minimum acceptable factor of safety (FS) against liquefaction triggering, sometimes guided by the strain potential of the soil once liquefied. This approach does not fully consider the value of the infrastructure that will potentially be impacted by the liquefaction response of the soil. Accordingly, in lieu of selecting FS based solely on precedent, Receiver Operator Characteristic (ROC) analyses are used herein to analyze the Standard Penetration Test (SPT) liquefaction case-history database of Boulanger & Idriss (2014) to relate FS to the relative consequences of misprediction. These consequences can be expressed as a ratio of the cost of a false-positive prediction to the cost of a false-negative prediction, such that decreasing cost-ratios indicate greater consequences of liquefaction, all else being equal. It is shown that FS = 1 determined using the Boulanger & Idriss (2014) procedure inherently corresponds to a cost ratio of ~0.1 for loose soils and ~0.7 for denser soils. Moreover, the relationship between FS and cost ratio provides a simple and rational approach by which the project-specific consequences of misprediction can be used to select an appropriate FS for decision making. 

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5. ASSESSING LIQUEFACTION IN GRAVELLY SOILS BASED ON FIELD CASE HISTORIES [ASSESSING LIQUEFACTION IN GRAVELLY SOILS BASED ON FIELD CASE HISTORIES]

   https://doi.org/10.5592/CO/2CroCEE.2023.141  

   Rollins, Kyle; Roy, Jashod (March 2023, Proceedings of the 2nd Croatian Conference on Earthquake Engineering)

   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. 

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