Laserfiche WebLink
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 100 foot buffer will be maintained from the permit boundary line to all new <br /> excavations. There will be no mining related disturbance within 30 feet of the property line. <br /> Since the permanent condition of the slopes will be backfilled 3H:1 V earth slopes,two scenarios are <br /> evaluated: <br /> 2.1 Scenario 1 —All Backfill is Gravel <br /> Figure U-1, from Huang, shows typical internal angles of friction for various materials. Assuming <br /> that the gravel is classified as GC (clayey gravels,poorly graded gravel-sand-clay),this material has <br /> an internal angle of friction of approximately 34 degrees. <br /> The Factor of Safety(FOS) for sand and gravel with a(3H:IV) 18.4 degree slope in GC classified <br /> material with an assumed internal angle of friction of 34 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 /> Tan 34' 0.6745 <br /> FOS — — = 2.0 <br /> Tan 18.40 0.3326 <br /> 2.2 Scenario 2—Backfill is Sand <br /> Figure U-1, from Huang, shows typical internal angles of friction for various materials. Assuming <br /> that the backfill is classified as SM(silty sands,poorly graded sand-silt mixture),this material has an <br /> internal angle of friction of approximately 34 degrees. <br /> 5 Mile Pit March 2016 GEO-3 <br />