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Normal Stress vs. Shear Stress <br /> 1.8 <br /> 1. <br /> 1.4 <br /> 1.2 <br /> GJ <br /> 1 <br /> L <br /> N <br /> 0.8 <br /> L <br /> °1 0.6 <br /> s , <br /> 0.4 <br /> 0.2 <br /> 0 <br /> -2 0 2 4 6 8 10 12 <br /> Normal stress(ksi) <br /> Figure 2. Normal vs. shear stresses <br /> • A typical interbench highwall region modeled to represent the rockmass at a more <br /> local scale with weaker structures (high angle joint sets, gneissic foliation, etc). The <br /> strengths used were developed from the direct shear laboratory test results performed <br /> on the structures within the core obtained during the 2017 field investigation. <br /> Average strength values were developed based on direct shear test results on samples <br /> taken at open fractures in the rock. The tests with the highest three strength <br /> properties were averaged to be representative of the stronger rock with weaker <br /> structures. The resulting properties were cohesion of 64.2 psi and angle of internal <br /> friction of 21.8'. <br /> The global highwall stability was modeled between El. 7550 and El. 6340. The bench <br /> configurations analyzed and presented in this report consisted of 40-foot high and 40-foot <br /> wide benches above El. 7000 (assumed existing with no reclamation), an intermediate <br /> stability bench at El. 7000, with various iterations of highwall/bench configurations between <br /> El. 7000 and the assumed bottom of the pit at El. 6340 aimed at optimizing South Quarry <br /> reserves while maintaining an acceptable slope stability. Our iterations ranged from <br /> 4011:40V up to 25H:70V. The intermediate bench, which increases the overall stability of <br /> the full height highwall, had a width that varied from 25 feet wide to 100 feet wide. <br /> For the global stability case,the entire highwall was considered as potential a failure surface <br /> for the critical slip surface in safety factor calculations. For the interbench highwall analysis <br /> case, the critical slip surface was limited to a range of three benches above the intermediate <br /> bench and three benches below the intermediate bench. <br /> Aggregate Industries Morrison Quarry GEI Consultants, Inc. <br /> South Quarry Highwall Design Technical Revision 17 August 2017 <br />