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SUBSIDENCE PROFILES FOR MAXWELL MINE <br /> OVER FIRST NORTH ENTRIES <br /> Elevation Elevation Depth Seam <br /> Drill Hole No. of Surface of Seam of Cover Thickness (ft) <br /> 228 7265 6757 508 6.5 <br /> 217 7200 6761 439 7.9 <br /> 221 7103 6742 361 7.8 <br /> 206 7121 6734 387 7.9 <br /> 220 7040 6706 334 6.1 <br /> Average 406 7.25 <br /> Average Dept (H) 406 ft <br /> Average Seam Thickness (M) 7 ft <br /> Average Opening Width 18 ft <br /> Subsidence Facter (a)* 0.01 <br /> *Subsidence Factor (a) is interpolated from Fig. 9.4.2 Coal Mine Ground <br /> Control by Syd S. Peng, Ph.D. <br /> S max = ma (Maximum Subsidence Formula, Page 284, Coal Mine Ground Control) <br /> S max = (71) (0.01) = 0.07' = 0.84" (over single entry) <br /> Width to Height Ration: W/H = 181/406/ = 0.044 <br /> NOTE: The conservative W/H of 0.20 was used in calculating the various <br /> points on a subsidence profile. Ref. Page 301, Coal Mine Ground <br /> Control. <br /> PCP 11/7/81 <br />