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Elk Creek Mine Subsidence Page 34 February 26, 2003 <br />LONGWALL PANEL GROUP SUBSIDENCE PREDICTION <br />• <br />'• <br />• <br />Ultimate subsidence over gateroads between adjacent panels <br />will increase if the interior gateroad pillars fail. Such gateroad <br />pillar failure may occur when the second panel face passes and the <br />protective support provided by the adjacent coal block before it is <br />mined past. Gateroad pillar failure may occur later as the result <br />of pillar deterioration over time. Gateroad pillars along the <br />ribsides of outer panels of a panel group should not fail because <br />they will be protected by either adjacent barrier pillars or <br />unmined coal. Ultimate subsidence at the east and west ends of an <br />individual panel in a panel group should not exceed subsidence at <br />the ends of the individual panel alone because immediately adjacent <br />barrier pillars will support any additional load transfer from over <br />the individual panels. <br />The maximum predicted vertical surface subsidence from mining <br />adjacent panels. For example, Panel #1 and Panel #2 in Panel Group <br />1, will increase over and near the gateroads between the panels if <br />the two rows of 120-ft wide, 180-ft long and 9.5-ft high gateroad <br />pillars between the panels yield and then crush out. The gateroad <br />pillars are bounded by a 20-ft wide entry (center of the three <br />gateroad entries) and by 20-ft wide crosscuts. Similarly, the <br />maximum predicted vertical surface subsidence from mining adjacent <br />panels in all panel groups will increase over and near the <br />gateroads between the panels if the gateroad pillars between them <br />crush out. The planned gateroad pillars between panels in Panel <br />Group 2 will be 50-ft wide, 180-ft long and 9.5-ft high. The <br />planned gateroad pillars between panels in Panel Group 3 will be <br />80-ft wide, 180-ft long and 9.5-ft high. It is unlikely that the <br />gateroad pillars between adjacent panels will completely crush out <br />because the pillars will yield to shed excess load, initially <br />arched across the two adjacent panels onto the caved roof rock in <br />the longwall mined panels. The caved roof rock will also restrain <br />the gateroad pillar ribside facing the caved panel rubble. <br />Failure of gateroad pillars should not increase subsidence <br />around the outer panel boundaries. Gateroad pillars on the south <br />side of Panel #1 of Panel Group 1, Panel #5 of Panel Group 2 and <br />Panel #19 of Panel Group 3 should not yield or crush because they <br />will be protected by either unmined coal or adjacent barrier <br />pillars. Similarly, gateroad pillars on the north side of Panel #4 <br />of Panel Group 1, Panel #11 of Panel Group 2 and Panel #12 of Panel <br />Group 3 should not yield or crush because they will be protected by <br />either unmined coal or adjacent barrier pillars. The barrier <br />pillars west of the set-up rooms in all panels will protect the <br />set-up pillars. The barrier pillars east of all recovery rooms <br />will be protected from yield or crush by barrier pillars. <br />The planned Panel Group 1 gateroad pillars are 120-ft wide on <br />140-ft centers by 180-ft long on 200-ft centers. Gateroads and <br />crosscuts will be 20 feet wide. Table 5 presents the average <br />-34- <br />