Laserfiche WebLink
.Icrnuurv 15, 2008 pgge 38 <br /> .i <br /> <br /> <br /> <br /> <br /> <br /> Ilk *W. <br /> <br /> <br /> <br /> <br /> fr <br /> <br /> <br /> <br /> <br /> <br />Figure 24. 1-ligh-wall Slope Stability Failure at G-Strike Pit After September 2005 Failure <br />fay October 2006, sufficient mining had been pertormed in the new G-Dip Pit cut that the <br />hillside had been opened on two sides: on the east from G-Dip mining and on the north from <br />previous 6-Strike mining. The downdip face had been buttressed with spoils to stabilize the <br />tailed region. Global instability of the hillside was not anticipated because local failures had <br />never occurred on that scale and the monitoring data was not indicating global instability. <br />After excessive rain in late September, the entire hillside above the old G-Strike Pit <br />became unstable and slid. A view of the landslide is shown in f=igure 20. Characterization <br />activities have shown that the landslide had slid on a single, continuous, thin, weak saturated <br />layer which as discussed previously is referred to as the I.-Roof mudstone laver. <br />The slide plane mechanism leading to global slope failure has been simulated using three- <br />dimensional (31)) slope stability analyses.` Complex combinations of groundwater, mining <br />geometry, and rock behavior were simulated in these analyses in order to get the hillside to be <br />unstable. The model, illustrated in Figure 26, accounted fir the fiollowing key features. <br />Agapito Associates, Inc.