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Subsidence Evaluation for the <br />Exhibit 60E Southern Panels, Apache Rocks West, & Sunset Trail Mining Areas Page 12 <br />5.3.1 Vertical Displacement, Tilt, and Horizontal Strain <br />Differential vertical lowering of the continuous deformation and near surface zones causes vertical <br />displacement (S), tilt (M), and horizontal strain (E). In flat or gently sloping terrain (slopes less <br />than about 30 percent), surface profiles of subsidence depressions are similar to flexure of fixed - <br />end, laterally constrained beams. Tensile stresses are present in areas of positive curvature, which <br />become zero downward at the neutral surface, then reverse to compressive stresses below the <br />neutral surface. <br />In flat or gently sloping terrain, vertical displacement typically increases inward from the limit of <br />the subsidence depression, is half the maximum value at the point of inflection, and is maximum <br />in the middle of the depression (also called subsidence basin or subsidence trough). Tilt increases <br />inward from the margin of the depression to a maximum at the point of inflection and become zero <br />again at the point of maximum vertical displacement (Figure 3). Maximum values of tilt, <br />curvature, and strain, discussed herein, apply only to slopes less than about 30 percent; values may <br />be greater on slopes steeper than 30 percent. <br />Positive curvature (convex upward) and horizontal tensile strain increase inward from the margin <br />of the depression to a maximum about midway between the depression margin and the point of <br />inflection and decrease to zero again at the point of inflection. Negative curvature (concave <br />upward) and compressive horizontal strain increase inward from the point of inflection to a <br />maximum about midway between the point of inflection and the point of maximum vertical <br />displacement and decrease to zero again at the point of maximum vertical displacement. <br />5.3.1.1 Maximum Vertical Displacement (Subsidence) <br />The following range of vertical displacements (subsidence values) are projected for the Southern <br />Panels, Apache Rocks West, and Sunset Trail mining areas, based on the baseline data obtained <br />from subsidence measurements above the B -seam longwall panels 1NW, 2NW, and 3NW (Figure <br />4, Table 1) and E -seam longwall panels E 1 to E3 at West Elk Mine. <br />Southern Panels Mining Area: As noted above, the E -Seam longwall panels E1 to E8 were <br />originally approved as part of the South of Divide mining area, and subsequently panels E2 to E7 <br />were approved to extend into the Dry Fork mining area. To simplify the discussion of subsidence <br />projections, the full length panels will be addressed as the Southern Panels E1 to E8. Similarly, <br />the proposed B -seam panels in this area will be referred to as the Southern Panels B26 to B29. <br />Overburden depth above the projected E -seam longwall centers ranges from 800 to 1,800 feet. <br />With a projected longwall panel width of 1,120 feet, and assuming that the chain pillars (gate road <br />pillars) are similar to those in longwall panel 17 of the Apache Rocks mining area, maximum <br />subsidence (vertical displacement S, = a - t) is predicted as follows (Table 2) for the Southern <br />Panels mining area of panels E1 to E9 and E14: <br />• Panels El to E9 and E14: These panels range in width from subcritical to supercritical <br />(width -to depth ratio (W/d) ranges from 0.79 to 2.80). <br />831-032.816 Wright Water Engineers, Inc. <br />October 2018 <br />