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Jcmaurt, l5. 200S <br />'_0 ft <br />120 f <br />Figure 15. Conceptual 3D Model of Z-Dip Cut #2 Pit Spoil Pile <br />Pofie '5 <br />The methodology used to calibrate the spoil strengths was to incrementally decrease the <br />spoil frictional strength from a peak of 55° until a failure surface developed in the spoil area of <br />the model similar to what was observed. Spoils were assumed to weaken with disturbance; that <br />is, any zone that reached its peak yield strength would soften to a residual strength of 10° less <br />after 5% inelastic strain (strain-softening relation). Thus, incrementally reducing peak strength <br />from 55° to 45° meant also reducing the residual strength from 45° to 35°. This would reproduce <br />the softening behavior of the spoils necessary to reproduce the localized slope failure <br />mechanism. <br />Results ofthe analysis indicate that the limit of equilibrium ofthe spoil is reached when <br />the spoil friction is about 40°. -Table 3 summarizes the results ofthe analysis. I:i4?ure 16 shows <br />Agapito Associates, Inc.