2014-09-26_REPORT - C1980007 - Laserfiche WebLink

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Subsidence Prediction Based on Measurements endix A at West Elk Mine [ol 8 feet; from 0.007 to 0.027 (0.7 to 2.7 percent) where the extraction thickness equals 12 feet; and from 0.007 to 0.030 (0.7 to 3.9 percent) where the extraction thickness equals 14 feet. Horizontal compressive strain ges from -0.004 to -0.024 (44 to -2.4 percent) where the extraction thickness uals 8 feet; -0.007 to -0.029 (47 to -2.9 percent) where the thickness equals 12 fe�t; and -0.007 to -0.042 (47 to -4.2 percent) where it equals 14 feet (Table 2). • Panel E9: Predicted horizontal t nsile strain in this single panel ranges from 0.018 to 0.027 (1.8 to 2.7 percent) where a coal extraction thickness equals 12 feet and 0.021 to 0.031 (2.1 to 3.1 percent) whe a the extraction thickness equals 14 feet. Compressive strain this panel is predicted to range from -0.018 to -0.029 ( -1.8 to -2.9 percent) where the extraction t ickness equals 12 feet and -0.021 to -0.034 ( -2.1 to -3.4 percent) where it equals 14 et (Table 2). Maximum Projected Depths of Surface racks Curvature, or differential tilt (curvature is respect to horizontal distance) of subsided calculated curvature values and horizontal measurements, therefore, provides a mean: hence the maximum depth of tension crs boundary between tensile and compressive In terrains with slopes less than about 2 estimated by dividing the maximum horizc given location. The calculated depth of t] between tension above and compression t monitoring network at West Elk Mine. Ci 100 foot range of maximum values becai slopes exceeding 30 percent. An unpubli International) indicated that surface crack d less extensive or terminate where shale and he second derivative of vertical displacement with Dck layers causes horizontal strain. Comparison of :ensile strain derived from horizontal displacement of calculating the depth of the neutral surface, and :ks from the surface. The neutral surface is the percent, the depth of the neutral surface can be it strain values by those of maximum curvature at a tension zone to the neutral surface —the boundary ►w— ranges from 50 to 100 feet in the subsidence c depth may be much less than this projected 50 to most of the monitoring network was located on d study for the U. S. Bureau of Mines (Engineers th rarely is greater than 50 feet. Cracks will also be iystone layers occur. Based on annual field subsidence observatiojns, maximum crack depth in bedrock in the South of Divide mining area is estimated to be 1) 5 15 feet in terrain sloping less than, or equal to, 30 percent, 2) 10 to 35 feet in terrain sloping ore than 30 percent, and 3) 40 to 50 feet in thick, brittle sandstones in ridges. Crack depth will likely be at a maximum lue above massive coal barriers. Crack depth may therefore be greatest above the 700-foot-wide protective barrier system projected between longwall panels E4 and E5. The crack depth is projected to be less (probably 10 to 20 percent less) above the panel chain pillars, where even the rigid pillars are predicted to yield 10 to 30 percent of the coal extraction thickness. 831 - 032.690 Wright Water Engineers, Inc.