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• -22- <br />the interaction of forces between segments. Solution is achieved by <br />iteration until forces at segment interfaces balance. Both analysis <br />methods have been modified for our use on in -house computers. A nominal <br />cohesion value must be entered when using the Bishop method in order to <br />determine a factor of safety for deep - seated failures. Without some <br />cohesion, the problem degenerates to an infinite or shallow failure case. <br />We used a cohesion value of 100 psf in our analysis whenever the Bishop <br />method was utilized. The results of Bishop and Spencer analysis is <br />presented in Appendix C. <br />In the case of a totally cohesionless material, calculation of the <br />factor of safety can be simplified to a ratio of the tangent of the slope <br />angle divided by the tangent of the materials angle of internal friction. <br />• This method is only applicable for dry slope situations. Chart methods <br />proposed by Janbu can be used to evaluate relatively simple slope topo- <br />graphy with ground water conditions. Both of these methods were also <br />utilized in our analysis. <br />Evaluation of Existing Spoil Configurations <br />The existing slope face has been exposed for a period of about 3 <br />years with no evidence of failure apparent at this time. Most of the <br />spoil slope from Sta. 0 +00 to about Sta. 8 +50 were formed by dozing ma- <br />terial over the crest. We believe that these slopes are at their angles <br />of repose. At the angle of repose the factor of safety is equal to 1 <br />and incipient failure is implied. The type of failure suggested by this <br />r 1 <br />LJ <br />