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<br /> POWDERHORN COAL COMPANY <br /> FIGURE 2.05.6 B <br /> FACTORS OF SAFETY FOR RETREAT PILLARS <br /> PI LLAR SIZE (FEET) <br />DEPTH <br />(FEET) 10 x 80 12 x 80 14 x 80 ]5 x 80 18 x 80 20 x 80 <br />200 1.15 1.40 1.65 1.77 2.15 2.39 <br />300 0.95 1.16 1.38 1.48 1.80 2.01 <br />400 0.85 1.04 1.24 1.33 1.62 1.81 <br />500 0.79 0.97 1.15 1.24 1.51 1.69 <br />600 0.74 0.92 1.09 1.18 1.43 1.62 <br />800 0.68 0.85 1.01 1.09 1.34 1.50 <br />1,000 0.65 0.80 0.96 1.04 1.28 1.44 <br />1,200 0.62 0.77 0.93 1.02 1.23 1.39 <br />1,500 0.60 0.74 0.89 0.96 1.19 1.34 <br />