EGL Ref: 8983 8 October 2021 Page 15 File: TSF3 Stability Analysis Appendix Summary.docx.doc Two empirical relationships for shearwave velocity based on the Pacific Earthquake Engineering Research (PEER) Centre Report 2012/08 (Ref. 4) were applied. The relationships are the result of a review on a wide range of empirical correlations for shearwave velocity including gravels. One is for Holocene age gravels and the other is for Pleistocene age gravels. The empirical curves are plotted for reference in Figure B10 using the site specific parameters for unit weight and relative density. Density is considered through the Standard Penetration Test – N Value, SPT-N, not corrected for overburden (i.e. N60). The target (N1)60 value is determined using the common relationship below with a Cd value of 46 (Ref. 5): The equivalent (N1)60 value is 33 for a relative density of 0.85. Using equation 39 in Idriss and Boulanger (2008) (Ref. 5) for overburden correction, the equivalent N60 profile was developed to then estimate shearwave velocity, Vs. No limit to the maximum value of CN was applied at shallow depth. The N60 profile developed and applied to the Vs reference curves is shown in Figure B10. A third reference curve for dense gravels (relative density of 0.95) was applied as per Lin et al. (2014) using a shearwave velocity of 312m/s (Ref. 6) with an exponent ns = 0.331. This is shown in Figure B10. This reference curve was used to estimate the Vs profile for embankment in a stepped profile up to a maximum Vs = 600m/s, which was limited as the Vs30 for the underlying rock for the seismic hazard study was 600m/s and the PEER equation 4.102 for Pleistocene Gravels indicates values less than 600m/s. The estimated Vs values with depth are indicated in Table B13.
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