1018 14TH ST 2023-02-09 - Laserfiche WebLink

SHANNON 6WILSON,INC. historical earthquakes to create a relationship between soil density and liquefaction potential. The ability of a soil to resist liquefaction is expressed as a cyclic resistance ratio (CRR). The demand placed on the soil deposit by seismic loading is expressed as the cyclic stress ratio (CSR). The FS against liquefaction is the ratio of the CRR to the CSR. The results of the liquefaction analysis are present in Appendix C for the IBC ground motion and the 200-year design ground motion. We estimated the FS against liquefaction of each soil SPT sample between the groundwater table (estimated at+11 feet) and elevation -12 feet (a total of 21 samples from all of the borings performed for this project) for a variety of earthquake ground motion levels using the empirical methods discussed above. A summary of our analyses is shown in the following table: Surface Earthquake Return Peak Ground Moment Percent of Samples Period(years) Acceleration (g) Magnitude that Liquefy 100 0.18 6.4 10 200 0.25 6.5 20 224 0.26 6.5 30 475 0.33 6.5 50 975 0.39 6.5 60 2475 0.48 6.5 70 Based on the above analyses, a 200-year return period ground motion selected by the Port for this project would represent a condition where about 20 percent of the samples within the fill and alluvium would liquefy. The results of the liquefaction analyses for the 200-year design ground motion are included in Appendix C. Based on these results, localized zones within the upper fill and alluvium deposits may liquefy during the 200-year design ground motion. Potential liquefaction in borings B-2, B-3C, and B-4 (Segments A. B. and C) is limited to one sample per boring for the 200-year design ground motion. Based on these results, the liquefaction would be localized and minimal and,therefore, can be neglected in our analyses, in our opinion. The relative density of the fill and alluvium soil sampled at boring B-1 B (Segment D) is less than that observed in Segments A, B, and C. Our analyses indicate that more liquefaction would occur in this area than along segments A, B and C. If bulkhead design for Segment D is pursued in the future, we recommend performing additional explorations along the Segment D alignment to confirm the relative density of the soils and evaluate the potential for liquefaction 21-i-?nv 1-ou 3-R i 1A10C./"J)rC q, 21-1-21761-003 9