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<br />• <br />• <br />4.0 RESULTS AND CONCLUSIONS <br />The stability of the proposed mining geometry <br />overburden depths from 200 ft to 900 ft. The <br />the barrier pillar is specified for the same <br />4.1 Pillar Sizes in Floor Coal Mining Zone <br />is evaluated for <br />minimum width of <br />overburden range. <br />Table 1 summarizes the safety factors for the proposed mining <br />geometry for overburden depths ranging from 200 ft to 900 ft. <br />The pillar design model indicates that the proposed mining <br />geometry provides for a factor of safety greater than 2.0 for a <br />range of overburden depths up to 600 ft and greater than 1.5 for <br />a range of overburden depths from 600 ft to 900 ft. <br />4.2 Barrier Pillar <br />A barrier pillar must be left between Panel C and adjacent mine <br />workings. Where Panel C is adjacent to caved areas, the minimum <br />required width of the barrier pillar is 140 ft. Where Panel C is <br />adjacent to panel entries that have not be caved, the minimum <br />required width of the barrier pillar is 100 ft. <br />Cyprus Orchard Valley Mine <br />Panel C Pillar Analysis <br />March 72, 1992 <br />page 6 <br />