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"D" Seam Longwall Subsidence <br />"When considering workings with <br />• virgin area the prediction from <br />derived from cases of multi-seas <br />reduced by a multiplying factor <br />Page 31 August 17, 1998 <br />any w/h value in a <br />Fig. 3 (which was <br />n workings) should be <br />of 0.9." <br />The predicted maximum vertical subsidence (Sm,x) of the ground <br />surface above individual panels was calculated at each of the cross <br />section locations described above by multiplying the local seam <br />thickness, the assumed longwall mining height, by the virgin ground <br />correction, if appropriate, and by the panel width/depth correction <br />factor. The panel width/depth correction factor graph is included <br />as Graph 1 in Appendix B. <br />Predicted single panel maximum vertical surface subsidence <br />values were evaluated along cross sections perpendicular to the <br />center of each 640-foot wide final recovery room and starter room. <br />The profiles were constructed using Graph 3, Appendix B. The <br />predicted single panel vertical subsidence at the final and starter <br />room locations is assumed not to be affected by the mining of <br />adjacent panels, i.e. not affected by the planned crushing of <br />adjacent gateroad pillars because they are adjacent to the final <br />barrier pillars. The following example for locating the 6-foot <br />subsidence contour along the vertical cross section perpendicular <br />to the center of 640-foot wide Panel #1 final shield recovery room <br />(width/depth ratio equals 640/1010 = 0.634, the first line on Table <br />• 5) demonstrates the calculations, as follows: <br />1) Sm,x (7.609-ft, the first line on Table 5) along the subsidence <br />profile is predicted to occur 320 feet out from the center of <br />the final room and at the center of the panel, where it is <br />equidistant from the sides and end of the 640-ft wide Panel #1. <br />2) The 6-ft partial subsidence depth represents 0.79 of Sm,x. <br />3) Following the 0.639 panel width/depth ratio (Graph 3, Appendix <br />B) for the 0.639 profile line from the Y-axis to 0.795maxi <br />interpolated between the 0.75m,x and 0.8Sm,x lines on Graph 3 the <br />distance from the panel center to the 6-ft subsidence contour is at <br />approximately 0.139 times the 1010-ft depth on the X-axis from the <br />center of the panel (135-ft), or approximately 185-ft inside the <br />panel from the final shield recovery room barrier pillar. <br />Maximum individual panel tensile (+E) and compressive (-E) <br />strains were calculated by multiplying the Sm,x/depth ratio for each <br />profile line by the multipliers taken from the maximum ground <br />surface strain prediction graph for the local panel width/depth <br />factors. The width/depth strain factor graph is included as Graph <br />2 in Appendix B. <br /> <br />31 <br />