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_1g_ <br />• circles and then used a specified shear surface method of analysis <br />to evaluate potential stability based on field observations of the <br />orientation of most probable weak planes within the sedimentary rock. <br />Slope Geometry <br />Any method of analysis requires that the ultimate geometry of the <br />slope be established before the actual mathematical analysis begins. <br />For purposes of this study we used a preliminary mining plan from Y,err <br />Coal which had an overa]1 slope angle of approximately 43 degrees <br />with intermediate benches 60 feet high sloping at 70 degrees and bench <br />widths of approximately 40 feet. A second general case of overall <br />slope angle of approximately 38 degrees with intermediate benches at <br />60-foot intervals sloping at 60 degrees was used for comparative <br />studies to evaluate the relative increase in stability available by <br />• flattening the overall and intermediate slope angles. The analysis <br />was conducted in two stages. We evaluated the stability of the entire <br />slope and the second phase was to consider stability of intermediate <br />benches. For intermediate bench determinations, the stability was <br />evaluated including surcharge load to represent a large mine truck. <br />For the overall slope no surcharge load was included. It is our <br />opinion, that the truck load is critical to the evaluation of the <br />individual intermediate slopes, however, the overall pit slope stability <br />wil] not be significantly influenced by the individual truck load. <br />The general pit configuration is one of excavation approximately <br />on the angle of dip for the sedimentary rack along the west wall and <br />at the overall angle described above for the east wall. The present <br />• <br />