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To. DRMS Den Page 3 of 5 2017-07-12 22 12 51 (GMT) 13032008630 From Greg Lewicki <br /> Geotechnical Stability Exhibit <br /> 'rho permanent slopes in place at White River City will be 3ft:1 V or shallower as shown on Map <br /> 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(311: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= -Tan eat of Internal Angle of Friction __ RECEIVED <br /> Tangent of Actual Angle of Failure Surface <br /> JUt 14 2017 <br /> 'fan 341 0.6745 (`Reclamation, <br /> FOS= 2.02 1>j&Safety <br /> Tan 18.4° 0.3326 <br /> The permanent slopes at the White River City Pit will he stable,and not risk aay neighboring; <br /> structures. <br /> �1)� ,Ji-!•ill.� . <br /> u <br /> 7 )n- <br /> ;W ' % <br /> AL <br /> 1 Original source:Houk and Rmy 1977 <br /> White River City GS-1 <br />