Laserfiche WebLink
The Factor of Safety (FOS) for gravel with an 13 degree slope in GC classified material with an <br />assumed internal angle of friction of 34 degrees can be approximated by ignoring the cohesion <br />component of the stability and simply evaluating the internal angle of friction as follows: <br />FOS = <br />Tangent of Internal Angle of Friction <br />Tangent of Actual Angle of Failure Surface <br />Tan 34° .6745 <br />FOS = _ = 2.9 <br />Tan 13° .2308 <br />This factor of safety far exceed the normal long term safety factor of 1.3, therefore, the plan of <br />extraction, as presented in Figure U-1, is acceptable. In addition, the exposed 1.5H:1V gravel <br />slopes will only be present for a short period of time, since the mine will be conducting <br />contemporaneous reclamation. These slopes are at a slope of 3H:1 V. <br />Craig Ranch Pit, March 2011 U-2