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<br />• <br />• <br />-zz- <br />or the sliding wedge method and then checked using the conventional <br />method of slices and the modified Spencer technique. The modified <br />Spencer technique will generally yield a factor of safety slightly <br />higher than indicated by the conventional method of slices because <br />of the more accurate type of computation. In our opinion, the <br />mathematical technique used to analyze these sites is not a criti- <br />cal parameter. The method of slices or the modified Spencer tech- <br />nique both are satisfactory analytical procedures, however, the <br />procedures are totally dependent upon the quality of data input. <br />The numerical value selected for strength of the various materials <br />and the pore pressure assumptions essentially control the computed <br />factor of safety <br />conservative. <br />The design values selected were judged to be <br />Summary of Stability Analysis <br />Stability analyses of the proposed spoil areas are summarized <br />on Figs. 4, 5, 6, 7, 12 and 13. In Area I a layer of relatively 1 <br />I r~~~ <br />soft clay at the base of the proposed spoil fill controls the sta- ~ <br />bility. The overall stability of the slope was investigated using <br />a 3 trial surfaces as indent ified on Fig. 4. Various other con- <br />figurations were considered, however, these trial surfaces yielded <br />the lowest factors of safety. The summary presented on Fig. 4 pre- <br />sents the factor of safety for various trial surfaces with no buttress <br />fill at the toe of the slope. The lowest computed factor of safety <br />was 1.51 which does exceed the minimum factor of safety required by <br />the Office of Surface Mining regulations. Figure 5 is an analysis <br />r <br />