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Sanborn Creek Subsidence Paqe 21 September 2, 1997 <br />B. Maximum individual panel tensile (+E) and compressive (-E) <br />strains were calculated by multiplying Ste./depth for each profile <br />• line by the multipliers taken from the prediction graph included in <br />Appendix B. <br />The subsidence contours plotted on Plate la for panel #1 and <br />on Plate 2a for Panel #2 were predicted from the subsidence profile <br />graph, Figure 5. Figure 6 provides the predicted worst-case <br />horizontal strain profile graph used to locate the maximum strain <br />contours on Plate lb for Panel #1 and for Plate 2b for Panel #2 as <br />a single separate panel. Panel #2 is the first panel to be <br />longwall panel mined in the first group of three panels. <br />The vertical subsidence and horizontal strain profile graphs <br />were modified for a 25° angle of draw. It was necessary to make <br />this modification from the NCB subsidence and horizontal strain <br />profile graphs for the NCB 35° angle of draw measured in Great <br />Britain. Appendix B contains the NCB 35 angle of draw profile <br />prediction graphs. Angles of draw measured adjacent to western <br />U.S. coal mines (Pendleton, 1985; Gentry and Abel, 1978; Abel and <br />Lee, 1984) are consistently smaller than the 35° NCB angle of draw. <br />Subsidence contour depths were located along each panel <br />_ ribside and profiles constructed using Figure 5. The following <br />example for the 6-ft subsidence contour at the center of the <br />starter room of 560-ft wide Panel #1, Plate la, demonstrates the <br />calculations at a depth of 500-ft, as follows: <br />1) Six (8.86-f t, the second line on Table 9) along the subsidence <br />profile occurs at the center of the panel, equidistant from the <br />sides and end of the 560-ft wide Panel #1, i.e. 280-ft inside <br />Panel #1 <br />2) The 6-ft partial subsidence depth represents 0.68 of Ste. <br />3) Following the 1.12 panel width/depth ratio (Table 4) of 1.12 <br />profile line from the Y-axis to 0.685„ interpolated between <br />the 0.6S~x and 0.7S~x lines on Figure 5 the distance from the <br />panel center to the 6-ft subsidence contour is at 0.92 times <br />the 500-ft depth on the X-axis from the center of the panel <br />l (210-ft), or approximately 70-ft inside the panel from the <br />Ii starter room chain pillars. <br />`J Locations for all the predicted subsidence contour values were <br />calculated and the predicted subsidence contours plotted on Plate <br />la. This process was repeated for Panel #2, Plate 2a to <br />L demonstrate the difference between the predicted subsidence for the <br />individual Panel #2 and the predicted subsidence for the initial <br />group of panels; Panel #2 plus Panel #3 and Panel #4. Predicted <br />maximum subsidence over Panel #2 when it is mined and before Panel <br />#3 is mined is 3.90-ft (Table 9). The predicted worst-case <br />. subsidence over Panel #2 following mining of Panel #3 and Panel #4 <br />~ 21 <br />