Investigations of bedrock within subsided areas over abandoned coal mines in Illinois reveal little disturbance of the bedrock. In areas that have surface subsidence of 0. 3 to 1 m (1 to 3. 25 ft), examination of cores from exploration drilling and investigations of the boreholes by means of closed circuit television have shown that fractures are spaced at least 0. 9 to 3. 6 m (3 to 12 ft) apart. The amount of fracturing found in the collapsed area decreased as the amount of soft, weak materials increased in the immediate overburden of the mine.
|Original language||English (US)|
|Title of host publication||Transactions of the American Institute of Mining, Metallurgical, and Petroleum Engineers, Society|
|Number of pages||6|
|State||Published - Dec 1 1986|
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