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<br />C~ <br />0 <br />O.Il <br />0.2 <br />IE <br />~ ®.3 <br />® ®.~ <br />~ 0.5 <br />~ 0.0 <br />~ ®.`~ <br />~ ®.F~ <br />~ 0.9 <br />Il.0 <br /> <br />~~- ~oasnerse4 P~/ili~e <br />,, O <br />~ ~fi1~s4 Cflk l~'[i ~e <br />~~_---p <br />I~TCIE$, fl9'~5 <br />1 tD.2 4).~ 6D.6 4).~ - <br /> <br />~ O <br />_ <br />1 1 1 <br />4 <br />2 4 <br />A 4 <br />A"n 3 <br />~~~ <br />Figure 4. Graph showing subsidence factors (a = Sm/t) versus mining panel width to depth ratios <br />(W/d) for the West Elk longwaq mine (squares), 1972 to 1976 Somerset room-and-pillar mine <br />(circles), and the York Canyon, New Mexico longwall mine (diamonds), along with the average <br />National Coal Board (NCB) longwall curve. Topographic effects on subsidence factors for the <br />York Canyon, New Mexico longwall mining area (upper point of measurement was in a deep <br />draw; middle point was on an isolated ridge; lower point is maximum for area). <br /> <br />