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Januarv 1 5. ?OOZY Pee ijc 36 <br />5.0 GEOTECHNICAL ISSUES FOR MINING K-PIT AND G-Pn <br />5.1 Failure Mechanisms <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 of the 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 tier highwall <br />stability. <br />Moil iiii-MbEft'", <br /> <br />. qffl <br />xi? V, <br />r _ <br />-••t ?'!• „? .-i~ Z4•r• ? ..?? ?, ??^'=•-•".171" ';? - •r- <br />4';,{ ?= t `% • + r ,?• 1J71c? ? . ice. ? - ' ... ? ? ` ?'?. <br />? ?1 • <br />ow: <br />Figure 22. Hgghwall Stability Failure at GTest Pit in 2001 <br />The failures that occurred in G-Strike Pit were a combination of local and global <br />instability. Auer the August 2004 failure, the highwall lost stability at the immediate face. A <br />view of that tailure is shown in Figure 23. After the September 2005 highwall failure, the <br />mechanism controlling failure was thought related to global instability of the slope. Measurable <br />displacements were further from the highwall tare than expected. A view, of that failure is shown <br />in Figure 24. <br />Agap ito Associates, Inc.