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TYPICAL SUBSIDENCE PROFILE OVER AVF <br />- AREA AT ALLEN MINE - 50% EXTRACTION <br />Average Depth (H) = 400 ft. <br />Average Seam Thickness (M) = 5.25 ft. <br />Average Opening Width = 30 ft. <br />Subsidence Factor (a)* = 0.01 <br />*Subsidence Factor (a) is interpolated from Fig. 9.4.2 Coal Mine <br />Ground Control by Syd S. Peng, Ph. D. <br />Smax = ma (Maximum Subsidence Formula, page 284, Coal Mine Ground <br />Control <br />Smax = (5.25') (0.01) = 0.0525' = 0.63" (over single entry) <br />Width to Height Ratio = ld/H = 30'/400' = 0.075 <br />• NOTE: The conservative W/H of 0.20 was used in calculating the <br />various points on a subsidence profile. Ref. Page 301, Coal Mine Ground <br />Control. <br /> <br />