EGL Ref: 8983 8 October 2021 Page 5 File: TSF3 Stability Analysis Appendix Summary.docx.doc The following stability analyses have been run. TABLE B6: DOWNSTREAM STABILITY ANALYSES – SECTION 1 (PALEO GULLY SECTION) Stability Analyses Strength Parameters Figure Slide Surface Result Comment Static construction/ operation – peak undrained strength conditions Main embankment and foundation Combination of drained and undrained parameters applied using effective stresses based on excess porewater pressures due to fill placement. Tailings Residual undrained strengths applied using effective stresses based on hydrostatic porewater pressure profile. B1a B1b Foundation FOS=3.11 FOS=2.73 Above FOS=1.5 recommended by NZDSG B2a B2b Zone A FOS=2.90 FOS=3.69 Above FOS=1.5 recommended by NZDSG B3 Embankment FOS=2.38 Above FOS=1.5 recommended by NZDSG Static construction/ operation – peak drained strength conditions Main embankment and foundation Drained strength parameters applied using effective stresses based on excess porewater pressures due to fill placement. Tailings Drained strength parameters applied using effective stresses based on hydrostatic porewater pressure profile. B4a B4b Foundation FOS=2.82 FOS=3.22 Above FOS=1.5 recommended by NZDSG B5 Zone A FOS=2.62 Above FOS=1.5 recommended by NZDSG B6a B6b Embankment FOS=3.24 FOS=2.85 Above FOS=1.5 recommended by NZDSG Static long term – closure drains fail - peak undrained strength conditions Main embankment and foundation Combination of drained and undrained parameters applied using effective stresses based on long term porewater pressure profile Tailings Residual undrained strengths applied using effective stresses based on hydrostatic porewater pressure profile B7a B7b Foundation FOS=3.15 FOS=2.62 Above FOS=1.5 recommended by NZDSG B8a B8b Zone A FOS=2.77 FOS=3.66 Above FOS=1.5 recommended by NZDSG B9 Embankment FOS=2.37 Above FOS=1.5 recommended by NZDSG Static long term – closure drains fail - peak drained strength conditions Main embankment and foundation Drained strength parameters applied using effective stresses based on long term porewater pressure profile Tailings Drained strength parameters applied using effective stresses based on hydrostatic porewater pressure profile B10a B10b Foundation FOS=2.68 FOS=3.22 Above FOS=1.5 recommended by NZDSG B11 Zone A FOS=2.68 Above FOS=1.5 recommended by NZDSG B12a B12b Embankment FOS=3.31 FOS=2.68 Above FOS=1.5 recommended by NZDSG Post-earthquake – Undrained Main embankment fill Combination of drained and undrained parameters applied using effective stresses based on excess porewater pressures due to fill placement. Tailings Residual undrained strengths applied using effective stresses based on hydrostatic porewater pressure profile B13a B13b Foundation FOS=3.07 FOS=2.49 Above FOS=1.2 recommended by NZDSG B14a B14b Zone A FOS=2.35 FOS=3.62 Above FOS=1.2 recommended by NZDSG B15 Embankment FOS=2.83 Above FOS=1.2 recommended by NZDSG OBE embankment response Main embankment and foundation Combination of drained and undrained parameters applied using effective stresses based on excess porewater pressures due to fill placement. Tailings Residual undrained strengths applied using effective stresses based on hydrostatic porewater pressure profile B16 Top 1/3rd of embankment ky = 0.69 g < 0.5 cm See Table B15 for seismic parameters used for determining co-seismic deformations B17 Top 2/3rds of embankment ky = 0.44 g < 0.5 cm B18 Full embankment ky = 0.25 g < 0.5 cm SEE (CME + aftershock) B16 Top 1/3rd of embankment ky = 0.69 g < 1.0 to 1.1 cm B17 Top 2/3rds of embankment ky = 0.44 g < 1.0 to 3.2 cm B18 Full embankment ky = 0.25 g < 1.0 to 4.0 cm SEE (1 in 10,000 year EQ + aftershock) B16 Top 1/3rd of embankment ky = 0.69 g < 1.0 to 4.6 cm B17 Top 2/3rds of embankment ky = 0.44 g < 1.0 to 5.7 cm B18 Full embankment ky = 0.25 g 2.4 to 10.8 cm
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