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An additional configuration was analyzed where the slope transitioned from 40HAOV to <br /> 25H:70V or 30H:70V benches at El. 7000, without an intermediate bench. The configuration <br /> was modeled for the two cases described above and two models considering only failure <br /> through the potion of the slope consisting of the taller benches. Of the models considering <br /> failure through the benches below El. 7000,one used the global material properties and <br /> considered all benches between El. 7000 and 6340. The second model considered three <br /> benches and used the properties derived from shear strength testing. A stability bench was <br /> also modeled at El. 6650 with a 100-foot width and a 50-foot width for configurations <br /> without an intermediate bench at El. 7000. <br /> 4.2.1 SLOPE-W <br /> SLOPE/W is a stability analysis software developed by GEO-SLOPE International, Ltd. that <br /> utilizes limit equilibrium methods. The South Quarry highwall was evaluated for stability <br /> using the Spencer analysis method and the Bishop Simplified analysis method in SLOPE/W. <br /> The Spencer method satisfies both moment and force equilibrium and was used to analyze <br /> the entire highwall. The Bishop Simplified method satisfies moment equilibrium and was <br /> used to analyze the smaller region of the highwall. The Bishop Simplified method was used <br /> for these analyses because the Spencer method was unable to calculate realistic slip surfaces <br /> for the regional extents specified. Although the Bishop Simplified method only satisfies <br /> moment equilibrium for the slip surfaces as opposed to both moment and force equilibrium <br /> satisfied by the Spencer method, it generally results in more conservative estimates of safety <br /> factors. For all SLOPE/W analyses, circular slip surfaces were evaluated and defined using <br /> the entry-and-exit method for both cases. <br /> 4.2.2 FLAC/Slope <br /> FLAC/Slope is a component of FLAC used for slope stability analysis. Unlike.SLOPE/W <br /> which uses limit equilibrium methods, FLAC/Slope uses finite differences for analyses. <br /> FLAC/Slope uses the strength reduction method to progressively reduce the shear strength of <br /> the material until the slope reaches a state of limiting equilibrium based on the Mohr- <br /> Coulomb failure criterion. The factor of safety F is defined according to the equations: <br /> trial _ 1 C <br /> Ftrial <br /> trial = arctan(F 1 <br /> trial tamp) <br /> Simulations are made by changing F"al until it results in a cohesion and friction angle that <br /> cause the slope to fail. The trial strengths are incrementally decreased, or increased if the <br /> initial slope is unstable(i.e., FS < 1.0), until the limiting conditions are found. This provides <br /> an alternative method from limit equilibrium methods in calculating the factor of safety. <br /> Aggregate Industries Morrison Quarry GEI Consultants,Inc. <br /> South Quarry Highwall Design Technical Revision 18 August 2017 <br />