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• -23- <br />type of analysis would be relatively shallow and would probably not <br />involve a large volume of material. <br />Calculated values varied from 1.2 to 1.9 for deep seated failures <br />with essentially dry slope conditions when analyzed using circular <br />failure surfaces. Values of 1.2 to 1.8 were calculated with high water <br />table conditions. The lower factors of safety are computed for the con- <br />figurations at the angle of repose as depicted at Sta. 6 +00 with the <br />higher factors of safety computed for Sta. 1.0 +00 where a bench in the <br />slope exists. The lower bound factor of safety was calculated for failure <br />surfaces which passed partially through the fire clay zone. Failure sur- <br />faces which passed through the bedrock had calculated factors of safety <br />generally greater than 2.0. <br />• At least one non - circular failure plane was; analyzed for each slope <br />configuration. The failure surface dipped steeply from the ground surface <br />through the spoil and through the fire clay to the slope toe. The lowest <br />factors of safety were calculated for failure surfaces which follow <br />these types of paths. Under this failure mode, massive failure would re- <br />sult based upon our analysis. For the purpose of analysis, the strength <br />of the fire clay was varied to evaluate the affect various strengths of <br />the materials have on mass stability. Varying the strength of the ma- <br />terials within the range of values discussed previously resulted in many <br />calculated factors of safety less than 1.0 and some slightly greater than <br />1.0. Factors of safety less than 1.0 imply that failure has already oc- <br />curred which is not consistent with the current ; performance of the <br />slope observed. <br />