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-14- <br />• <br />to the underlying clay soils and there will have been little or <br />no time for consolidation. The consolidation of the underlying <br />Foundation materials can be accelerated by decreasing the thick- <br />ness of the soft zone by excavation and removal of a portion of <br />these soils. If this procedure is selected, the time of consolidation <br />will decrease roughly proportional to the square of the thickness <br />of material removed. <br />Numerous trial failure surfaces were investigated for stability <br />at the proposed maximum dam section. The embankment is planned for <br />construction with cohesive soils and for purposes of our analysis <br />a cohesion of 2500 psf and angle of internal friction 0 of 0 degrees <br />was used. These values correspond with results from triaxial tests <br />• on proposed embankment materials. In addition, a number of trials <br />were run assuming the embankment material to be similar to the spoil <br />from the mine area. For these analyses the unit weight was assumed <br />to be 103 pcf, C = 0, and the angle of internal friction was assumed <br />to be 37 degrees. The computed factors of safety varied considerably <br />between the various methods of analysis. For the cohesive fill, the <br />lowest computed factor of safety was 2.96 using the graphical method <br />of slices and 3.1 using a computer solution and the modified Spencer <br />method. When the fill was assumed to have only frictional properties, <br />the lowest computed factor of safety was 1.63, using the method of <br />slices. Slightly higher values were computed if the failure was <br />assumed to occur in a wedge-like manner. In our opinion, the critical <br /> <br />