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<br />Table 1. Soil Properties <br /> <br />Description Moist Unit <br />Weight (pcf) Saturated Unit <br />Weight (pcf) Cohesion <br />(psf) Internal <br />Friction Angle <br />Overburden 108.5 119.6 1483 25 <br />Bedrock 135.0 139 2000 18 <br />Native Sand and Gravel 112.0 122.9 10 35 <br />Design Analysis and Criteria <br />The proposed mining and reclamation slopes were analyzed using the XSTABLE V5.208 DOS <br />computer program. XSTABLE was designed to analyze the slope stability of an earth <br />embankment subjected to several critical situations that may occur during the life of the <br />embankment. For the mining conditions, the scenario of maximum highwall dewatering was the <br />only scenario analyzed. <br />Methodology <br />The Bishop method was used in the computer analysis for determining the safety factors. The <br />procedure utilizes a critical failure surface searching method to generate circular surfaces. The <br />program automatically searches for the lowest factor of safety. 600-1200 separate failure <br />surfaces were analyzed for each case. The same process was used in determining the safety <br />factor for each case. For the given soil parameters, the factor of safety was determined. <br />The mining embankment configuration shown in the computer analysis represents the estimated <br />conditions for this site. If the mining conditions differ significantly from the estimated <br />conditions, the slope stability will need to be reevaluated on a case by case basis. The mining <br />highwall was found to be stable and well above the factor of safety. <br />The reclamation embankment analysis illustrates the slope failures consist of minor sloughing <br />failures indicative of erosion and maintenance requirements. The attached results show the <br />failure slopes and the associated property values and safety factor. The resulting property values <br />are conservative for anticipated site conditions. <br />Slope Stability Results <br />The minimum safety factors required are 1.5 for steady state. This design criteria was used to <br />establish the desired minimum safety factors for this project and should be considered <br />conservative for evaluating reclaimed slopes against alluvial mining high walls. The calculated <br />factors of safety are within the design criteria specified for this project and can be considered <br />indicators of high wall performances under the various conditions.