Laserfiche WebLink
• TABLE 13 <br />Probability of Chimney Collapse Through Overlying Rock <br />(data from Gray etal, 1977) <br />is <br />• <br />127 cases of chimney collapse to surface over Pittsburgh Seam, <br />documented in the field. <br />Height <br />Number of <br />Cumulative <br />Cumulative <br />Class <br />Documented <br />Number of <br />Percent of <br />Interval <br />Chimney <br />Chimney <br />Chimney <br />(feet) <br />Collapses <br />Collapses <br />Collapses <br />200 - 210 <br />1 <br />1 <br />0.8 <br />190 - 200 <br />0 <br />1 <br />0.8 <br />180 - 190 <br />0 <br />1 <br />0.8 <br />170 - 180 <br />0 <br />1 <br />0.8 <br />160 - 170 <br />0 <br />1 <br />0.8 <br />150 - 160 <br />1 <br />2 <br />1.6 <br />140 - 150 <br />3 <br />5 <br />3.9 <br />130 - 140 <br />1 <br />6 <br />4.7 <br />120 - 130 <br />0 <br />6 <br />4.7 <br />110 - 120 <br />0 <br />6 <br />4.7 <br />100 - 110 <br />2 <br />8 <br />6.3 <br />90 - 100 <br />2 <br />10 <br />7.9 <br />80 - 90 <br />3 <br />13 <br />10.2 <br />70 - 80 <br />5 <br />18 <br />14.2 <br />60 - 70 <br />2 <br />20 <br />15.7 <br />50 - 60 <br />8 <br />28 <br />22.0 <br />40 - 50 <br />15 <br />43 <br />33.9 <br />30 - 40 <br />21 <br />64 <br />50.4 <br />20 - 30 <br />29 <br />93 <br />73.2 <br />10 - 20 <br />29 <br />122 <br />96.1 <br />0 - 10 <br />5 <br />127 <br />100.0 <br />2.05 -64 Rev. 11 -30 -93 <br />