Description : A subsidence estimation methodology to predict subsidence troughs due to flat and inclined coal seam exploitation is described. The foundations of the procedure are the correct definition of the rock mass behaviour model, its adequate characterization, and its implementation in the code ``FLAC'' (Fast Lagrangian Analysis of Continua was written by P.A. Cundall and is marketed by ITASCA Cons. Group Inc. of Minneapolis, MN, USA), which is based on the ``Finite Dierence Method'' or FDM numerical modelling technique. The method is first validated for flat coal seam longwall mining with caving in British basins - because of the large number of data from this area- which includes subsidence measurements and characterization parameters. The method is then applied to gently inclined seams, and the results are seen to fit empirical observations. Finally, for steeply inclined and sub-vertical seams the proposed methodology allows observation of two dierent movement trends in the overlying strata; the former is perpendicular to the strata direction, in the same way as the one observed in flat seam subsidence; and the latter, which becomes the most important one in seams dipping by more than 75oC, is parallel to the strata. These two dierent trends produce subsidence troughs presenting two relative subsidence maxima and extending along large surface areas. Thus, it would be unlikely to predict and assess these troughs, this may be a possible reason why so little coherent data about this kind of subsidence exists. These numerical observations of steeply inclined coal seams need to be validated empirically.
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