Laserfiche WebLink
E <br />GEOTECHNICAL STABILITY EXHIBIT <br />There are no buildings or any structures outside the permit area which could be affected by the <br />excavation. A minimum 30 foot buffer will be maintained from the property boundary line to all new <br />excavations. The final reclamation plan will shift to involve backfilling and the creating slopes no <br />steeper than 3 H:I V. <br />From Table 2.5 in the SME Mining Reference Handbook', the backfill is best classified as sand and <br />gravel, mixed grain size. This material has an internal angle of friction of approximately 45 degrees <br />and no cohesion. <br />The Factor of Safety (FOS) for sand and gravel with a (3H: IV) 18.4 degree slope in Ioose sand <br />material with an assumed internal angle of friction of 45 degrees can be approximated by ignoring <br />the cohesion component of the stability and simply evaluating the internal angle of friction as <br />follows: <br />FOS = _ Tangent of Internal Angle of Friction <br />Tangent of Actual Angle of Failure Surface <br />FOS = Tan 45° _ 1 = 3.0 <br />Tan 18.40 0.3326 <br />2. Conclusion <br />The factor of safety is 3.0, well above the minimum of 1.5 for permanent conditions. <br />' Original source: Houk and Bray 1977 <br />Ben Langenfeld, P.E. <br />A.E.# 0047151 <br />Fairplay Au Pit March 2017 GEO-1 <br />Gres [swW and Aaeocistm PLLC <br />