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• 1.0 SUBSIDENCE PREDICTION <br />1.1 BACKGROUND OF PREDICTIONS <br />Most theories for predicting subsidence caused by coal extraction apply to wide <br />openings with total extraction and have been developed from observations above longwall <br />panels. If pillars are completely recovered in room-and-pillar mining, the result is total <br />extraction and the same theories should be applicable. Any room-and-pillar mining <br />practices planned at the Bowie #2 Mine will not result in total extraction. <br />Subsidence prediction methods can be divided into two categories: the empirical <br />and the phenomenological approaches (Hall and Dowding, 1981). Empirical methods <br />predict subsidence based on previous experience and observations under similar <br />geological and mining conditions. Phenomenological methods model the physical behavior <br />of the earth materials using physical or numerical methods in order to predict subsidence. <br />Empirical methods are generally used for the prediction of subsidence. With <br />phenomenological models, it is invariably difficult to accurately represent the complex <br />geologic conditions and rock mass characteristics which are inherent to underground coal <br />mines within the Mesaverde Formation. The models available are continually being refined <br />in research projects and find limited application in specialized problems. <br />In accordance with most subsidence investigations, empirical methods of prediction <br />have been used for this study. The two most commonly used empirical methods of <br />subsidence prediction are as follows: <br />Subsidence Engineer's Handbook (SEC): <br />The Subsidence Engineer's Handbook (1975) has been developed by Britain's <br />National Coal Board based on extensive monitoring of subsidence in Great Britain. It <br />comprises perhaps the most complete method to deal with all aspects of subsidence <br />engineering and it has been widely used in different parts of the world. The graphical <br />solutions presented in this handbook are reported to have an accuracy of +/-10% when <br />used in Great Britain. <br />C~ <br />- 1 - 10/00 <br />PR~oy <br />~~z~/~ ~ <br />