2014-09-26_REPORT - C1980007 - Laserfiche WebLink

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Subsidence PredictioO Based on Measurements 4endix A at We t Elk Mine 4 the 1NW, 2NW, and 3NW longwall panels t West Elk Mine (Figure Q as summarized in Table 1, Exhibit 60B (included herein). The pro ected range of maximum vertical displacements, for the South of Divide mining area is shown in Table 2, Exhibit 60B (included herein). South of Divide Mining Area: Overburde depth above the projected E -Seam longwall centers ranges from 400 to 1,425 feet. With a projected longwall panel width of 1,080 feet, and assuming that the chain pillars (gate road pi lars) are similar to those in the Apache Rocks mining area, maximum subsidence is predicted as follows: • Panels El to E8: These panels, ich will trend roughly N80 °W, will range in width from subcritical to supercritical (with -to depth ratio (W /d) ranges from 0.76 to 2.7). 1. Maximum vertical displace ent above the chain pillars (SAP) is expected to range from 0.8 to 2.4 feet (0.1 to 0 3t) where the extraction thickness is 8 feet, 1.2 to 3.6 feet (0.1 to 0.3t), where the traction thickness is 12 feet, and from 1.4 to 4.2 feet (0.1 to 0.3t), where the extraction thickness is 14 feet. 2. Maximum vertical displacement above the center of the mined panels is projected to range from 4.8 to 6.4 feet) (0.6 to 0.8t) where the extraction thickness is 8 feet, from 7.2 to 9.6 feet, where the extraction thickness is 12 feet, and from 8.4 to 11.2 feet (0.6 to 0.8t), where the *traction thickness is 14 feet. • Panel E9: This panel trends about 10 °E and is of supercritical width. 1. Maximum vertical displac ment above the chain pillars in this shallow overburden is expected to range from 1.2 feet (0.1 t), where the extraction thickness is 12 feet and from 1.4 feet (0.1 t), where the extraction thickness is 14 feet. 2. Maximum subsidence is 1 where extraction thickness extraction thickness is 14 f Maximum Tilt Maximum tilt (Mn,) was calculated from dii monitoring network in terms of the ratio of (S,,, /d in dimensionless units L/L) (Figure D percent. Maximum calculated tilt ranges f West Elk Mine. Maximum tilt in the Soutt to 2.3 S,,,/d. Maximum tilt in four different Western United States ranges from 2.5 to 5• ected to range from 8.4 to 9.6 feet (0.7 to 0.8t), 12 feet, and 9.8 to 11.2 feet (0.7 to 0.8t), where the ferential vertical displacements at the West Elk Mine maximum vertical displacement to overburden depth ). Tilt values at West Elk Mine range from 1.4 to 2.1 •om about two to three times Sm /d (2 to 3•(Sm /d)) at of Divide mining area is projected to range from 2.2 mining areas studied by Dunrud (1984, p. 168) in the Sm /d). South of Divide Mining Area: As stated ear ier in this report tilt above the eight longwall panels (panels El to E8) and the single panel (E9) I s projected to range between 2.2 and 2.3 Sm /d for coal extraction thickness ranging between 8 and 14 feet. These values are based on subsidence 831 - 032.690 Wright Water Engineers, Inc.