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Geotechnieal Evaluation of Mlne-Induced Seismicity on Monument Dam <br />Dorsey 3 Whitney, LLP <br />• TABLE 6.1 <br />MATERIAL PROPERTIES USED IN BACK-CALCULATION OF FAILURE ZONE <br />SHEAR STRENGTH <br /> Strength Parameters <br /> Used in Back- <br /> Saturated Calculation Anal sis <br /> Unit Cohesion Friction <br />Material Weight c' Angle m' <br /> (pct) s de rees <br />Upper Landslide 130 0 15' <br />Failure Zone 130 0 15* <br />Lower landslide 130 200 22 <br />Note: <br />' Stahiliry analysis procedure solved for this strength parameter. <br />6.2.4 Stability Analysis Results <br />The effective mobilized friction angle in the failure zone was back-calculated to be <br />15 degrees. A computer plot of the back-calculated stability analysis is shown on Figure 6.2. <br />• 6.3 Post-Failure Stability Analysis <br />6.3.1 Static Stability Analysis <br />• <br />A static stability analysis of the existing (post-failure) landslide was performed using the <br />same geometry as for the pre-failure analysis, as shown on Figure 6.1, and the same material <br />properties as obtained from the pre-failure analysis, see Table 6.1. The stability of the <br />existing landslide was evaluated for dry season conditions using lower measured water <br />levels, as measured in fall months, in the piezometers. <br />6.3.2 Results <br />The resulting factor of safety for the post-failure water pressure condition is 1.03. A <br />computer plot of the post-failure static analysis of the landslide is shown on Figure 6.3. <br />6.3.3 Pseudo-Static Analysis <br />The representative cross section for the pseudo-static stability analysis is the same as the one <br />used in the static stability analysis of the post-failure landslide, see Figure 6.1. Dry season <br />(lower) water levels were used For the pseudo-static analysis. The material properties used in <br />the pseudo-static analysis are the same as obtained from the pre-failure analysis, see Table <br />GEI~ 22 0603500603-16MOnwnmt DamGmndwcilEvil <br />March 2006 <br />