Evaluation of liquefaction potential at a silt site in providence, Rhode Island

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Recent geological, seismological and paleoseismological studies in the northeastern United States provide important clues regarding past occurrences of soil liquefaction in this region and, hence, highlight the future potential for liquefaction. Assessing liquefaction potential in the Providence, Rhode Island, area is complicated because of the uncertainty in the seismic ground motions as well as the uncertainty of the cyclic resistance of the silts that underlie the city. To provide insight on this issue, a deterministic evaluation of liquefaction potential at a study site in Providence using a cyclic stress-based approach was presented. The CSR was estimated for two earthquake scenarios. These scenarios corresponded to the two predominant modal events identified in the deaggragation matrices obtained from the USGS for the 2,500-year spectral accelerations for oscillator periods closest to the fundamental period of the site. The two scenarios considered were a small event (M5.4) occurring locally, and a large event (M7.4) originating from the Charlevoix Seismic Zone, Canada. The CRR of the silt at the study site was evaluated using empirical correlations based on SPT blow count, CPT tip resistance and in-situ shear wave velocity. The shear wave velocity correlation used in the analysis was developed from an extensive laboratory study 9 using the silt recovered from the study site. A comparison of the CRRs resulting from the three correlations suggests that the SPT-based method gave the lowest predictions, while the CPT-based method provided the highest resolution with depth. Comparing the CSR and CRR predictions indicate that there is a low potential for liquefaction at the study site. However, given that the results depend to a large extent on the site characteristics, this finding is only applicable to the study site. This narrow finding further reinforces the need to perform site-specific evaluations of liquefaction potential for a given project.

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Civil Engineering Practice





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