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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />II <br />I <br />I <br />I <br /> <br />002655 <br /> <br />determined as discussed above. Pore pressure values along the <br /> <br />failure surface required in the effective stress analysis were <br /> <br />derived assuming steady state flow conditions and a phreatic line <br /> <br />in the zone 1 at the normal water surface elevation, and a phreatic <br /> <br /> <br />line in the zone 2 and underlying foundation at the contact line <br /> <br />between the foundation and embankment. These assumptions should <br /> <br />give conservative factor of safety values. The unit weight values <br /> <br />for. the various materials were 130 p.c.f. for zone land 140 p.c.f. <br /> <br />for zone 2. These values were derived by applying optimum moisture <br />to the standard proctor maximum dry density. <br /> <br />The slope stability analysis method used was that which is <br /> <br />presented in "Design Standards No. 2 -- Treatise on Darns" published <br />by the Bureau of Reclamation, employing the "Daehn's Modified <br /> <br />Slip-Circle Graphical" analysis. By this method, the weight of <br /> <br />the dam embankment is resolved into components normal and tangen- <br /> <br />tial to the assumed slip circle. By such a resolution at a series <br /> <br />of locations along the slip circle, the total normal and tangential <br /> <br />force on the slip surface can be represented graphically by an area <br /> <br />above the slip circle. The pore pressure forces are similarly <br /> <br />represented as an area. <br /> <br />The factor of .safety is then: <br /> <br />= CL + TAN0 (N-P.P.) <br />T <br /> <br />S.F. <br /> <br />Where: <br /> <br />C = Cohesion Intercept <br />L = Length of slip surface <br />o = Angle of Internal Friction <br />N = Normal Forces <br />P.P. = Pore Pressure Forces <br />T = Tangential Forces <br /> <br />-4- <br />