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~~ ~ 82298/2 <br />shear tests provided an effective angle of internal friction <br />of 36.2 degrees for a relative density of 50 percent, and 40.5 <br />degrees for a relative density of 70 percent. The direct shear <br />test results are included in this report. <br />The computer analysis employed a Modified Bishop's Method <br />of analysis in order to determine the stability of the slope. <br />Three trial shear circles varying in size and location were <br />utilized in the computer analysis. The circles are indicated <br />on Figures 4 and 5 included in this report. Trial Circle A <br />was chosen to model a situation of a large failure along the <br />downstream face of the embankment. Trial Circle B was chosen <br />to model a sma:Ll failure along the downstream face of the <br />embankment. Trial Circle C was chosen to model a failure where <br />a portion of tl~e top of the embankment, as well as a portion of <br />the downstream face, undergoes a slope failure. A uniform <br />soil condition was evaluated to model homogeneous soil conditions <br />throughout the embankment. A two layer soil embankment model <br />was chosen to analyze a situation where more dense soils are <br />located on the lower layer and less dense soils are located on <br />the upper layer. In addition, an earthquake situation was <br />modeled. A do~mstream slope of 2 to 1 for the embankment and ~.-. <br />an embankment Yieight of 150 feet were used in the analysis. <br />The bedrock surface was located directly beneath the embankment <br />and was considered a rigid foundation. The bedrock foundation <br />material of they existing tailings pond and the proposed exten- <br />sion ponds con~•ists of San Juan tuff, a volcanic andesite bed- <br />rock containing very few fractures. The embankment and bedrock <br />parameters are in accordance with information provided to us by <br />Mr. Charles Ponchak of Camp Bird Colorado, Inc. <br />