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Januarv 15. 2008 Page 30 <br />5.0 GEOTECH\ICAL ISSUES FOR MINim. K-PIT AM) G-PIT <br />5.1 Failure llechanisms <br />There are two types of failure that have been observed in this area of the mine: local <br />highwall tailure and global slope failure. The highwall failure that occurred in G-Test pit in <br />2001 was a local failure initiated by unfavorable orientation ofthe geologic structures. A view <br />of that failure is shown in Figure 22. The bedding planes were dipping into the pit and sub- <br />vertical jointing in the sandstones were overturned. This structure was unfavorable for highwall <br />stability. <br />-71 <br />Via. ?. 7.1- • --? ` • ?i'i ,:. a ?„ <br />Ail <br />Air <br />Y ? <br />Figure 22. Highwall Stability Failure at G-Test Pit in 2001 <br />The failures that occurred in G-Strike Pit were a combination of local and global <br />instability. Aller the August 2004 failure. the highwall lost stability at the immediate lace. A <br />view of' that failure is shown in Figure 23. After the September 2005 highwall failure. the <br />mechanism controlling failure was thought related to global instability ofthe slope. Measurable <br />displacements were further f-orn the highwall face than expected. A view of that failure is shown <br />in Figure 24. <br />Agapito Associates, Inc.