TABLE B8: GEOTECHNICAL STABILITY SUMMARY SECTION 2 – NORTH SLOPE Stability Analyses Strength Parameters Figure Slide Surface Result Comment Static max operation – peak drained strength conditions Stockpile and foundation Drained strength parameters applied using effective stresses based on excess porewater pressures due to fill placement. B21a Foundation – Circular FOS=1.88 Above FOS = 1.5. Criteria met. B21b Foundation – Base Slide FOS=2.16 Static max operation – peak undrained strength conditions Stockpile and foundation Combination of drained and undrained parameters applied using effective stresses based on excess porewater pressures due to fill placement. B22a Foundation – Circular FOS=1.61 Above FOS = 1.5. Criteria met. B22b Foundation – Base Slide FOS=1.50 Post-earthquake max operation – Undrained conditions Stockpile and foundation Combination of drained and post-earthquake softened undrained parameters applied using effective stresses based on excess porewater pressures due to fill placement. B23a Stockpile and Foundation – Circular FOS=1.54 Above FOS = 1.2. Criteria met. B23b Foundation – Base Slide FOS=1.25 B23c Stockpile – Base Slide FOS=1.24 EQ max operation 1 in 150 year embankment response Stockpile and foundation Combination of drained and post-earthquake softened undrained parameters applied using effective stresses based on excess porewater pressures due to fill placement. Post-earthquake strength applied from for assessment of yield acceleration B24 Full embankment ky = 0.05g < 0.5 to 3 cm See Table B11 for seismic parameters used for determining co-seismic deformations. Displacements estimates indicate acceptable performance with minor displacement in the 150 year return period case. For the 2500 return period case the displacements of 10 to 40cm for the maximum operation profile would result in minor damage to liners and drains however the risk is limited as the displacement reduce to minor for the depleted closure profile. EQ max operation 1 in 2500 year embankment response B25 Full embankment ky = 0.05g 10 to 40 cm EQ max closure 1 in 150 year embankment response B24 Full embankment ky = 0.19g < 0.5 cm EQ max closure 1 in 2500 year embankment response B25 Full embankment ky = 0.19g < 0.5 to 4 cm
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