2020-11-05_REVISION - M1973021 (12)

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Considering Factor of Safety (FOS) Bench Width Bench Width Presence of at El 7000 ft at El 6650 ft Case ID Sillimanitic ( ) ( ) SLOPE/W FLAC/Slope Gneiss? 4-1 a No 2.07 Note 3 30 - 4-1 b Yes 1.86 1.46 4-2a } No 2.15 1.87 100 50 4-2b Yes 1.95 1.66 4-3a No 2.40 1.94 100 4-3b Yes 2.17 1.97 Notes: 1.) All existing benches above El. 7,000 ft have been mined with a height of 40 ft,width of 65 ft,and a face angle of 90°(vertical). 2.) Proposed Highwall benches are modeled with a height of 70 ft,width of 30 ft,and a face angle of 90° (vertical)below El.7,000 ft. 3.) A FOS was not able to be computed for this case as FOS by inspection is greater than 1.25 Table 7-4. Slope Stability Analyses Results: South Quarry Local Stability Local Stability Factor of Safety (FOS) Condition Bench Width(ft) SLOPE/W FLAC/Slope 30 1.34 1.35 40 1.38 1.34 Bench at El. 7000 - 50 1.41 1.35 100 1.58 1.35 30 Note 4 Bench at El. 6650 50 1.30 100 1.54 1.35 Notes: 1.) All existing benches above El.7,000 ft have been mined with a height of 40 ft,width of 65 ft, and a face angle of 90' (vertical). 2.) Proposed highwall benches are modeled with a height of 70 ft,width of 30 ft,and a face angle of 90°(vertical). 3.) Local Stability not considering the presence of Sillimanitic Gneiss. 4.) A FOS using FLAC was not computed for this case as FOS by inspection is less than 1.25. 7.2.2 West Quarry Global Stability Analyses Results for the slope stability analyses of the West Quarry are provided in Table 7-5 for the SLOPE/W and FLAC/Slope models. Analysis result figures that depict the critical failure surfaces and resulting FOS for each analysis case are presented in Appendices E and F. 38 Aggregate Industries-Morrison Quarry GEI Consultants, Inc. AM-07 Geotechnical Stability Exhibit November 2020