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2.2.1.2 Stability Modeling <br />Both two - dimensional (213) and three - dimensional (313) slope stability models were executed as part <br />of the slope stability analyses. <br />2D Modeling <br />The 2D slope stability analyses were conducted using SLOPE /W, a computer - modeling program <br />developed by GEO -SLOPE International, Ltd. SLOPE /W uses limit equilibrium theory to compute a <br />factor of safety for earth and rock slopes. It is capable of using a variety of methods to compute the <br />factor of safety of a slope while analyzing complex geometry, stratigraphy, and loading conditions. <br />As previously mentioned, SLOPE /W allows the user to import the groundwater head file from the <br />seepage analysis to compute effective stresses. <br />Spencer's method was used as the search technique to determine the factor of safety of the dikes in <br />this stability analysis. This method is considered the most adequate because it satisfies all conditions <br />of static equilibrium and provides a factor of safety based on both force and moment equilibrium. <br />3D Modeling <br />Analysis of the refuse pile was also performed using the deformation analysis approach. The <br />deformation analyses were conducted using FLAOD (Fast Lagrangian Analysis of Continua), a <br />computer- modeling program for engineering mechanics computation. FLAOD simulates the <br />behavior of structures built out of soil, rock or other geotechnical materials that may undergo plastic <br />flow when their yield limits are reached. Materials are represented by element or zones, which form <br />a grid to fit the shape of the geometry modeled. Each element behaves according to a prescribed <br />linear or nonlinear stress - strain law in response to the applied forces or boundary restraints. The <br />material can yield and flow, and the grid can deform (in large- strain mode) and move with the <br />material that is represented. <br />FLAOD is capable of modeling deformations and computing the factor of safety of a slope while <br />analyzing complex geometry, stratigraphy, and loading conditions. FLAOD also models the <br />groundwater flow through soil. The flow modeling may be done by itself, independent of the <br />mechanical calculation of FLAC313, or it may be done in parallel with the mechanical modeling to <br />capture the effects of fluid /soil interaction. <br />PAS <br />Revised July 21, 2011 Z6 J Ljyv <br />P. \Mpls \06 CO',26 \06261003 RPE E Permit Mod Support \WorkFiles \Permit Apphcahon \Text \Exhibit 82 RPEE design 2011 -07 -21 TR 127 doc <br />