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Worksheet 3 (cont) <br /> --------------------------- - _� <br /> - --------------------------------------- <br /> Worksheet #3 -- Slope Stability Analysis, Factor of Safety <br /> --------------------------------------------------------------------- <br /> Limit equilibrium analysis method, see attached sheets for derivation <br /> and equations. <br /> reference: Stability Analysis of Earth Slopes, Y.H. Huang, Van <br /> ' Nostrand Reinhold Publ., 71-78, 1983, ISBN 0-442-23689-1. <br /> --------------------------------------------------------------------- <br /> ***** INPUT BLOCK ***** <br /> ** SECTION ANALYZED: XS-8 (smallest area, excluding xs1) <br /> Geometric Variables Soil Properties <br /> ------- ------- --------------- <br /> L1 = 24.8 ft effective cohesion c = 0.1 tsf <br /> L2 = 61.1 ft effect. frict. angle, f = 30 deg <br /> alpha, a = 25.8 deg unit weight of waste,Gs = 125 lb/ft3 <br /> area Al = 103 s ft pore press. ratio ru = 0.25 <br /> -area,A2-= -----227_sq-ft W1, W2 - weight of each block <br /> ---------------------------------------------- <br /> ***** COMPUTE QUADRATIC COEFFICIENTS ***** <br /> W1 = 12875 al = 12349.7 = 12349.71 <br /> W2 = 28375 a2 = 4465.6 16081.3 12220.0 = 32766.91 <br /> a3 = 1246.4 1400.9 - 2647.3 <br /> Quadratic eq_ forfactorofsafety, F_ a1*F^2 + a2*F + a3 =0 <br /> - - - - - - .---. _- - - - _ __ <br /> ***** TRIAL AND ERROR SOLUTION TO QUADRATIC ***** <br /> F RHS __-_-- F- RHS <br /> -------------------- --------- <br /> 2 -18782.3 2.7 -1088.6 <br /> 2.2 -14961.9 2.71 -748.2 <br /> 2.4 -10153.6 2.72 -405.3 <br /> 2.6 -4357.3 2.73 -59.9 <br /> 2.8 2427.0 <--- 2.74 288.0 <---- Solution <br /> 3 10199.3 2.75 638.3 <br /> 3.2 18959.5 2.76 991.1 <br /> -------------------------------------------------------------------- <br /> FACTOR OF SAFETY = - -2.74 ***** Section 8 <br /> ------------------ --------------------------------------------� <br /> Construction <br /> The waste pile will be constructed in stages, progressively <br /> extending up the drainage as needed. Prior to development of a new <br /> stage, the topsoil will be removed and stockpiled at the existing <br /> topsoil storage site. All vegetation will be removed prior to <br /> stripping of the topsoil. <br /> The mine waste material shall be put in place in lifts which <br /> optimally should be between 12-18 inches and in no case shall <br /> exceed 24 inches. Each lift will be compacted to attain 90% of the <br /> maximum dry density. The AASHTO specification T99-74 outlines the <br /> procedure determining the required density. <br /> 10 <br />