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<br /> <br /> ~ <br /> ~ <br /> <br /> ,_~ <br />r <br /> ~ <br /> <br />~ r <br />~ <br />\~ 'D,~ <br />~~ <br />~~ <br />~ <br />~ <br />~ <br /> <br />~ <br />~=~ .~ <br />~ <br />~ ~_ <br /> <br />_. . <br />, <br />i <br />~'- ~~Lnl v~~~'J~'4 ~L 1V1~'i1^_~ ~ <br /> <br />f~ J3 ~.. <br />~ <br /> <br />a 'I.~.J C - ~n'~P ~~ IG U~ 1'~~1il7'~~ ~~ <br /> ~ ~ <br />:~ <br />• '~ <br />-" <br />~~.~ ~ <br />~ ~` <br /> <br />_`i <br />~ <br />~ <br />~~ <br />'-- -a <br />~; rJ.J ~ <br />a n <br />c.r ~, . <br />L <br />~ ~T1C~ <br />1~~~ ~ <br /> _ <br />~ , <br /> „I <br />_,~ <br />G ~e~ <br /> <br />G.~ ~L~.c Gam ~.© fl.~ 1.4 Il.~ a.~ <br /> `, ` ~~~ <br />Figure 3. Graph showing subsidence factors (a = Sm/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 Boazd (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 azea). <br />