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qq 0q, <br /> Geotechnical Stability Exhibit <br /> The permanent slopes in place at the Hayden Gravel Pit will be 311:1 V or shallower as shown on <br /> Map F of the approved permit. <br /> From Table 2.5 in the SME Mining Reference Handbook', the backfill is best classified as loose <br /> sand, mixed grain size. This material has an internal angle of friction of approximately 34 degrees <br /> and no cohesion. <br /> The Factor of Safety(FOS) for sand and gravel with a(3H:IV) 18.4 degree slope in loose sand <br /> material with an assumed internal angle of friction of 34 degrees can be approximated by <br /> ignoring the cohesion component of the stability and simply evaluating the internal angle of <br /> friction as follows: <br /> FOS = Tangent of Internal Angle of Friction <br /> Tangent of Actual Angle of Failure Surface <br /> FOS = <br /> Tan 34' 0.6745 <br /> Tan 18.40 0.3326 <br /> The permanent slopes at the White River City Pit will be stable, and not risk any neighboring <br /> structures. <br /> RECEIVED <br /> t.S <br /> JUL 182017 <br /> � 6 • <br /> ®-a e ( of Reclamati0tl, <br /> L�� 'H <br /> o4 R- > Mining&Safety <br /> ���fl®P��46gq4}}ppyQ9944r'QA4•`v8��Y <br /> V�P�R9 Ti'f✓� .f� <br /> 'Original source:Houk and Bray 1977 <br /> Hayden Gravel GS-1 <br />