2020-11-05_REVISION - M1973021 (12)

Home Browse Search

Sillimanitic Gneiss was considered for the global condition, FOSs reported ranging from 1.85 to 2.17 and 1.46 to 1.97 for SLOPE/W and FLAC/Slope, respectively. These results indicate global stability is adequate for the various bench configurations as all global analyses meet the minimum State required FOS of 1.25. Considering smaller segments of the highwall with applied local strength conditions, the resulting FOSs presented in Table 7-4 vary from 1.21 to 1.58 and from 1.21 to 1.35 for the SLOPE/W and FLAC/Slope results, respectively. As indicated by the red shading in Table 7- 4, a 30-foot wide mid-slope bench at El. 6,650 feet (i.e., no change in highwall width) does not meet the minimum State required FOS of 1.25 for the both analysis methods, and a 50- foot wide mid-slope bench at El. 6,650 feet does not meet the minimum State required FOS of 1.25 for the FLAC/Slope analysis. Based on these results, an intermediate bench width of 60 feet at El. 6,650 feet results in a FOS of 1.26 or greater, which satisfies State minimum FOS criteria of 1.25. Table 7-3. Slope Stability Analyses Results: South Quarry Global Stability 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? 1-1a No 2.00 1.56 30 1-1 b Yes 1.85 1.69 1-2a No 2.10 1.75 30 50 1-2b Yes 1.93 1.69 1-3a No 2.34 Note 3 100 1-3b Yes 2.12 1.86 2-1 a No 2.03 1.58 30 2-1 b Yes 1.85 1.64 2-2a No 2.11 1.62 40 50 2-2b Yes 1.94 1.50 2-3a No 2.34 1.87 100 2-3b Yes 2.14 1.91 3-1 a No 2.04 1.75 30 3-1 b Yes 1.86 1.60 3-2a No 2.12 1.71 50 50 3-2b Yes 1.95 1.62 3-3a No 2.35 1.99 100 3-3b Yes 2.15 1.87 37 Aggregate Industries-Morrison Quarry GEI Consultants, Inc AM-07 Geotechnical Stability Exhibit November 2020