EGL Ref: 8983 8 October 2021 Page 6 File: TSF3 Stability Analysis Appendix Summary.docx.doc TABLE B7: DOWNSTREAM STABILITY ANALYSES – SECTION 2 (SHEAR KEY CUT) 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. B19a B19b Foundation FOS=2.93 FOS=2.28 Above FOS=1.5 recommended by NZDSG B20 Zone A FOS=3.03 Above FOS=1.5 recommended by NZDSG B21a B21b Embankment FOS=2.29 FOS=3.25 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. B22a B22b Foundation FOS=3.21 FOS=2.76 Above FOS=1.5 recommended by NZDSG B23 Zone A FOS=3.31 Above FOS=1.5 recommended by NZDSG B24a B24b Embankment FOS=2.64 FOS=3.23 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 B25a B25b Foundation FOS=2.96 FOS=2.20 Above FOS=1.5 recommended by NZDSG B26 Zone A FOS=3.23 Above FOS=1.5 recommended by NZDSG B27a B27b Embankment FOS=2.23 FOS=3.09 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 B28a B28b Foundation FOS=3.15 FOS=2.63 Above FOS=1.5 recommended by NZDSG B29 Zone A FOS=2.84 Above FOS=1.5 recommended by NZDSG B30a B30b Embankment FOS=2.55 FOS=3.26 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 B31a B31b Foundation FOS=2.41 FOS=1.88 Above FOS=1.2 recommended by NZDSG B32 Zone A FOS=2.81 Above FOS=1.2 recommended by NZDSG B33a B33b Embankment FOS=1.90 FOS=3.14 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 B34 Top 1/3rd of embankment ky = 0.69 g < 0.5 cm See Table B15 for seismic parameters used for determining co-seismic deformations B35 Top 2/3rds of embankment ky = 0.40 g < 0.5 cm B36 Full embankment ky = 0.18 g < 0.5 cm SEE (CME + aftershock) B34 Top 1/3rd of embankment ky = 0.69 g < 1.0 to 1.1 cm B35 Top 2/3rds of embankment ky = 0.40 g < 1.0 to 4.6 cm B36 Full embankment ky = 0.18 g 1.8 to 8.9 cm SEE (1 in 10,000 year EQ + aftershock) B34 Top 1/3rd of embankment ky = 0.69 g < 1.0 to 4.6 cm B35 Top 2/3rds of embankment ky = 0.40 g < 1.0 to 7.5 cm B36 Full embankment ky = 0.18 g 4.3 to 18.9 cm
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