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• Kathy Welt <br />January 11, 1995 <br />Page 3 <br />Development Waste Rock - Cohesion 288 psf ,internal friction angle 30°, moist <br />unit weight 80 pcf, saturated unit weight 90 pcf. <br />Development Waste Coal -Cohesion 72 psf, internal fraction 41 degrees, moist <br />unit weight 45 pcf, saturated unit weight 50 pcf. <br />Slope stability was evaluated using PCSTABL5. This computer program was <br />developed at Purdue University and uses the simplified Janbu or simplified Bishop <br />method of slices. It compares the forces resisting slope failure to forces which cause <br />slope failure along a specified failure surface. The analysis utilizes a limit <br />equilibrium procedure to calculate the factor of safety against failure. The input <br />information for the analyses includes, but is not limited to, slope geometry, <br />• groundwater conditions, soil strengths, and loading conditions. <br />The slope stability analysis is summarized in the following table. <br />Mine Waste Development Pile <br />(cross action A•A) <br />Original: 2.88 <br />P~posea: 2.98 <br />The calculated factors of safety for the pile is above the minimum factor of <br />safety of 1.50, as required by the State of Colorado Mined Land Reclamation Board, <br />1981. <br />• <br />