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Slope Stability Case Analyses <br /> Each portal area has its own geometry for the slope cases , which <br /> are titled - Mine #3 Stability of Reclaimed Slope , etc . <br /> From the CTL residual strength tests , the cohesions , angles of <br /> friction and dry densities for each test are listed below : <br /> Cohesion F . Angle Density <br /> Sample _ lb/sq . ft Degrees lb cu . ft . <br /> #1 and #2 Mine 700 39 . 0` 117 <br /> #3 Mine 860 37 . 0° 108 <br /> #4 Mine 1040 31 . 0 ° 117 <br /> #5 Mine 400 38 . 0 ' 115 <br /> All results above denote residual strength parameters , not peak . <br /> Using the above parameters , the slope geometries of each portal <br /> area and different pore pressure ratios , various cases of slope <br /> stability have been modelled using the REAME program developed by <br /> Dr . Yang Huang of the University of Kentucky for rotational <br /> failures . The program uses the Bishop ' s method of slices to <br /> determine the minimum factor of safety for a given set of <br /> conditions . Rotational failure is the most likely method of failure <br /> because it has the most mass per unit surface area for this <br /> geometry . Translational or plane failures generally occur on long <br /> slopes where there may be a division between two soil types . <br /> From standard seismic zone charts of the United States , it is <br /> determined that the seismic coefficient for central Colorado is <br /> 0 . 04 . <br /> The highwalI rocks in the Bowie Shale and the bench base in the <br /> Rollins Sandstone do constitute a stiff base in which no failure <br /> circles should pass . <br /> The results of the various cases are shown in the following tables : <br />