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5.3 South Quarry Global Stability Analysis <br /> The results for the SLOPE/W and FLAC/Slope modeling are listed in Table 6 and Table 8. <br /> Table 6 and Table 8 also presents a summary of the bench configurations analyzed for the <br /> two cases described in Section 4.2. The column titled"Number of Benches above <br /> Intermediate Bench" describes the number of smaller benches, defined by the columns titled <br /> "Bench Height" and"Bench Face Angle", between the intermediate benches. Analysis result <br /> figures are presented in Appendices B and C and critical failure surfaces along with factors <br /> of safety are shown for each analysis case. <br /> Due to the inherent uncertainty in spatial variability of materials on site, additional global <br /> stability analyses were performed with lower material strengths. The strength reduction <br /> method, as used in FLAC/Slope and described in Section 4.2.2, was used to estimate strength <br /> properties that would still meet stability criteria for both cases. A targeted factor of safety of <br /> 1.40 was used to estimate cohesion and friction angles by modifying the strength reduction <br /> equations: <br /> Ctrial _ 1.40 C <br /> Fglobal <br /> trial 1.40 <br /> (P = al'Ctail(F,9lobal tan(p) <br /> where Fglobal is the factor of safety from the global analysis as presented in Table 6 and Table <br /> 8. These lower strength material properties provide a basis for assessment of the margin of <br /> stability for the global model. The results of these analyses are shown in Table 7 and in <br /> Figures B-17 through B-26 and C-19 through C-28. <br /> 5.3.1 SLOPEW <br /> In general, SLOPE/W estimated higher factors of safety than FLAC/Slope. This was likely <br /> due to the constraints put on the slip surface entry and exit locations. In SLOPE/W, the slip <br /> surfaces were defined to enter from the top of the slope and exit through the bottom, going <br /> through the entire height of the highwall or considered region. When the entire highwall was <br /> analyzed with global properties,the factors of safety were consistently above 4.20 for all <br /> bench configurations presented in Table 6. For the regional models with weaker global <br /> properties, the factors of safety ranged from 1.29 to 1.54 for the presented bench <br /> configurations. <br /> For analyses where failure was considered below El. 7000 through the 70-foot tall highwalls <br /> using the global properties, SLOPE/W was unable to calculate realistic factors of safety. <br /> Using the material properties derived from shear strength testing and considering three <br /> benches below El. 7000, the calculated factor of safety was well above stability criteria and <br /> greater than 3.60. For analyses that considered a stability bench at El. 6650 (Cases 15 <br /> through 18), SLOPE/W estimated factors of safety that were adequate for stability for both <br /> global and weaker regional properties used. <br /> Aggregate Industries Morrison Quarry GEI Consultants, Inc. <br /> AM-06 Geotechnical Stability Exhibit 31 August 2018 <br />