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H4.0 Analyses of Corrective Measures <br />This section is an update of Section 4.0 of the "1997/98 Landslide Corrective Measures Report". This <br />section provides updated analysis of corrective measures implemented in 1998 and 1999, and their effects <br />on the landslide. <br />!n accordance with the observational approach, the overall stability of the landslide was analyzed <br />accounting for corrective measures made to June of 1999. The overall landslide stability was reanalyzed <br />using slope stability limit equilibrium models. <br />The analyses of corrective measures were based upon aback-calculation of 1997 conditions and the <br />increase in stability with the corrective measures installed in 1998 and early 1999. Geotechnical <br />parameters were taken from Table 1 of the "1997/98 Landslide Corrective Measures Report". Figwe H3 <br />shows an updated figure of piezometric levels used in the analysis. This information was used to model <br />[he groundwater and the slope stability of the landslide. <br />• 4.1 Groundwater Analyses <br />See the "1997/98 Landslide Corrective Measures Report" for a discussion on groundwater analysis. <br />Two groundwater models were used established to simulate groundwater conditions in 1997/98 and in <br />1998/99. Dewatering measures previously described were constructed th 1997 and 1998. Illustrations of <br />these models are shown in Appendix H 1. <br />4.2 Limit Equilibrium Slope Stability Analyses <br />A limit equilibrium analyses was used to predict the factors of safety under 1997, 1998, and 1999 <br />conditions. Spencer's Procedure of Slices using the computer program SLOPE/W was used because it <br />satisfies all conditions of equilibrium and allows for noncircular failure planes. A newer version of this <br />sohware was used in 1999. in the limit equilibrium model, the pins are assigned an effective strength <br />based upon the number of rows, spacing, and strength of the pins. Three models were run: <br />• Barr Engineering Company July 37, 1999 <br />PCOOCS1208220ICAK 14 Appendix H <br />1999 Addendum to <br />7997198 Landslide Cortective Measures Report <br />