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0 <br /> doll � <br /> 0.2 <br /> 0e4 Mi nce <br /> 0.5 <br /> o.6 West Elk MA ne <br /> r-I 0.7 <br /> � O <br /> � ®e8 <br /> �77) O <br /> C�O o.9 NCB, 1975 <br /> 1.0 <br /> ® 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 <br /> V V /d <br /> Figure 4. Graph showing subsidence factors (a= S./t)versus mining panel width to depth ratios <br /> (W/d) for the West Elk longwall 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 />