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' These plots were then analyzed in order to identify significant <br />potential failure modes involving failures along structural <br />discontinuities within the competent rock. <br />t A review of the structural data has indicated a generally <br />favorable joint and fracture orientation. Characteristics of the <br />bedding were poorly exposed in the highwall outcrop. However, <br />mine personnel have established that the bedding typically dips <br />' from two to four degrees into the slope. Joints are typically <br />' high angle. <br />' Evaluation of the potential failure modes in the highwall area <br />has determined that several different failure modes are possible. <br />' One failure mode investigated involved a more or less circular <br />failure mode through intact and/or weathered rock, which will be <br />' influenced, but not controlled, by structural discontinuities. <br />' This type of failure is expected to pose a significant threat <br />only where a zone of colluvial soil and weathered rock is thick. <br />The majority of the highwall area contains only a thin layer of <br />this material. Although signs of some instability may be found <br />' in this weathered rock and soil zone along the top of the entire <br />' highwall, .the area appears to have been sufficiently reinforced <br />by the more competent rock only a short distance below. Any <br />' significant problem with instability in the area has been <br />avoided. An analysis of the overall stability of the entire <br />' highwall area, assuming circular failure through intact rock, has <br />been conducted as part of this study. Specific results are found <br />in the stability/sensitivity section of this report and <br />' graphically presented on Figures 3 and 5. <br />I $ <br />