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3) The dip of the failure plane must be greater than the angle of friction of the <br />plane. <br />4) Release surtaces, which provide reduced resistance to sliding, must be <br />present in the rock mass to define the lateral boundaries of the slide. <br />6.2.1 East Wall <br />Historically, the east wall has had no major instability issues. The stereonet plot <br />for the east wall using the entire dataset (Figure 10) indicates two plunges of <br />lines of intersection less than the angle of the slope face, indicating that the <br />potential for sliding exists along these intersections. However, both of the <br />wedges indicate that sliding will not occur unless friction angles are less than <br />33°, therefore indicating that they are stable for the 45° slope angle. The <br />stereonet plot also show that F-1 and F-2 intersect resulting in a plunge of line of <br />intersection less than the angle of the slope face and indicating the potential for <br />sliding. The emergence of F-2 as a definitive discontinuity set has been <br />identified only over the past two years as a result of the 2003 geotechnical <br />investigation and the 2004 field mapping effort. To date, not enough data have <br />been collected to define the extent of the F-2 discontinuity set or to delineate if <br />both the F-1 and F-2 discontinuities occur in the same location simultaneously. <br />One explanation would imply that localized faulting within the quarry has resulted <br />in "structural blocks". or regions where F-1 or F-2 occur seoarately. although <br />' more data is required to fully support this hypothesis. Until further data are <br />collected, the intersection of the F-1 and F-2 planes will not be evaluated in the <br />' wedge stability analyses presented herein. <br />' For the near vertical bench face (prior to reclamation), additional potential <br />wedges may exist. These wedge failures have been observed occasionally on <br />' the east wall and are localized in extent. The development and size of these <br />wedge failures will be controlled by the discontinuous nature of the overall planar <br />features of the quarry. <br />' -15- <br />