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Junuurv 15, 2008 1'gi?e 40 <br />Figure 26. FLAC3D Model Geometry Developed to Analyze Stability of G-Pit Landslide <br />compared to photographs of the actual failed region (Figure 28) the model results are considered <br />good. Ivey to this back-analysis calibration was utilizing higher than expected groundwater <br />pressures and weaker than expected L-Roof mudstone bedding strengths. <br />When those same properties and groundwater conditions were used to simulate the G-Dip <br />Pit mining, the back-analysis was able to reproduce the onset of failure and extent of failure fr)r <br />the October 2006 landslide. Figure 29 illustrates the failure predicted from displacements and <br />inelastic failure indicators. The extent of the failure agrees quit well with photographs of failed <br />region (Figure 30). The model was not able to reproduce the large displacements, but the onset <br />of instability was reproduced. <br />The conclusion about failure mechanisms from the stability analyses are that the model <br />was capable of reasonably reproducing the landslide and there is more understanding of <br />conditions leading to the landslide. These conditions are summarized as follows. <br />• Groundwater levels were likely higher than previously assumed. <br />• Some bedding strengths are weaker than previously assumed. <br />• The effects of the previous failure in G-Strike Pit include: <br />Bedding likely lost strength with time due to straining, and <br />The disturbed ground area extended further uphill than expected. <br />Agap ito Associates. Inc.