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• <br />• <br />~• <br />Elk Creek Mine Subsidence Page 21 February 26, 2003 <br />longwall panels should not exceed 188-ft, but probably may equal <br />or exceed 126-ft. <br />A zone of downward deflected rock lies above the fractured <br />and fissured overburden to the ground surface. The permeability <br />of this rock should have increased because it will be subject to <br />compression by the downward deflection of the subsidence trough, <br />as indicated on Figure 5. Therefore, no water from Bear Creek <br />should enter the Elk Creek Mine through the 210-ft minimum <br />overburden thickness between Bear Creek and Panel #1 of longwall <br />Panel Group 1. <br />The drill hole interburden lithology data provided was <br />separated into the proportions of sandstone, shale and coal and <br />is presented in Table 3. The lithologic distribution in the <br />interburden is variable. However, sandstone is the predominant <br />lithology present. The interburden weighted average sandstone in <br />the interburden between the `b' Seam and the underlying `C" Seam <br />is 61$ of the total. The interburden weighted average sandstone <br />in the interburden between the `b' Seam and the underlying "B" <br />Seam is 58$. Sandstone is the most favorable lithology for <br />multiple seam mining. Sandstone is favorable because of its <br />generally higher strength which more rapidly distributes the <br />stress concentrated above the barrier pillars in underlying mine <br />workings (Chanda, 1989). As shown on Plate 2, all of Panel #1, <br />almost all of Panel #2 and most of Panel #3 have been undermined. <br />However, only a very small part of Panel #4 has been undermined. <br />~, <br />-Ll- <br />