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Elk Creek Mine Subsidence Page 25 February 26, 2003 INDIVIDUAL LONGWALL PANEL TROUGH SUBSIDENCE PREDICTION • Longwall panel subsidence was predicted using the NCB (1975) `Subsidence Engineers' Handbook". The NCB method was developed from measuring the surface subsidence over 187 longwall panels. These case histories were used to produce the four subsidence prediction graphs in Appendix C. Individual panel subsidence prediction probably represents the most conservative and accurate part of longwall subsidence prediction. The Handbook states, `Prediction of subsidence by the above method should be correct to 10~ in the great majority of cases." 1• Tables A1, A4, A7 and A10 in Appendix A present the .predicted maximum subsidence effects for the individual Panels #1 through #4 of-Pa:.el. Group 1. Tables A13, A16, A19, A22, A25, A28 and A31 in Appendix A present the predicted maximum subsidence effects for the individual Panels #5 through #11 of Panel Group 2. Tables A34, A37, A40, A43, A46, A99, A52 and A55 in Appendix A present the predicted maximum subsidence effects for the individual Panels #12 through #19 of Panel Group 3. Surface subsidence contour maps were initially constructed around each Elk Creek Mine longwall panel. The subsidence contours selected were 0, 1-ft, 2-ft, 9-ft, 6-ft, 8-ft and 10-ft. The selection was based on the local mining height. The maximum local mining height is 12-ft, the maximum shearer cutting height, where the thickness of the "D" Seam equals or exceeds 12-ft. The maximum vertical surface is predicted not to exceed 0.9 times the mining height, in this case 10.8-ft. This can be seen on the panel width/depth correction graph, C1 in Appendix C. The seam thickness controls the local mining height when less than 12-ft. In addition, vertical surface subsidence tails off slowly to zero outside the panel ribsides which requires closer contour intervals when approaching the limit of subsidence. '_ , e subsidehc ce ontour maps were constructed by compositing the distance from each selected panel ribside location to where ' the trough subsidence reaches each selected subsidence contour value. The single panel subsidence and strain predictions were made for vertical panel cross sections in planes perpendicular to ' the gateroad ribsides, the set-up room ribside and the shield recovery room ribside. Subsidence calculations were generally made at the intersection of selected overburden contours and where Bear Creek or Elk Creek crossed over panel ribsides. The first step in applying the NCB subsidence prediction ' method is to calculate the maximum vertical subsidence (Smax). This requires the local mining height, panel width in meters, overburden depth in meters and whether or not the local area has '• -25-