2020-11-05_REVISION - M1973021 (12)

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6.3.2 SLOPE/W Limit equilibrium stability analyses were performed using SLOPE/W (v10.9) developed by GEO-SLOPE International, Ltd. The analyses were performed using Spencer's method. Spencer's method is the preferred method as it satisfies both moment and force equilibrium. For all SLOPE/W analyses, circular and non-circular"optimized" slip surfaces were considered and defined using the entry-and-exit method. The South and West Quarry highwall global analyses were evaluated using the Spencer analysis method. The intra-bench local analyses were evaluated using the Bishop Simplified method. 6.3.3 FLAC/Slope Additional stability analyses were performed using FLAC/Slope (v8.0), which is a simplified version of FLAC used for performing slope stability analyses using the finite difference method. The slope stability factor of safety (FOS) is obtained in FLAC/Slope using the strength reduction method to progressively reduce material shear strength until the slope reaches a limiting state of equilibrium. Using frictional strength parameters, this is defined according to the equations: trial = 1 Ftrial trial = arctan (Ft 1 tanqb) rial where Ft"al is the trial value factor of safety, ct"al is the resulting trial apparent cohesion, and 0trial is the resulting trial friction angle. Analyses are performed for various iterations of Ftrial until a limiting value of c`ial and 0"al that cause the slope to fail are obtained. The corresponding value of Ftrial is the resulting FOS, providing an alternative method to calculating the FOS. The Hoek-Brown criterion is approximated locally in FLAC/Slope using the Mohr-Coulomb criterion: r = Q'tan(kc + cc where apparent cohesion (cc) and friction angle ((kc) are given in terms of the local minor principal stress, 63 by: Oc = 2 tan-1 N(pc — 90' and 07UCS c` 2 o 2s Aggregate Industries—Morrison Quarry GEI Consultants, Inc. AM-07 Geotechnical Stability Exhibit November 2020