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2011-02-14_PERMIT FILE - C1980007A (3)
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2011-02-14_PERMIT FILE - C1980007A (3)
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Last modified
12/13/2018 7:01:03 AM
Creation date
4/14/2011 9:10:05 AM
Metadata
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Template:
DRMS Permit Index
Permit No
C1980007A
IBM Index Class Name
Permit File
Doc Date
2/14/2011
Doc Name
SUBSIDENCE EVALUATION
Section_Exhibit Name
Exhibit 60E Subsidence Evaluation for the South of Divide and Dry Fork Mining Areas
Media Type
D
Archive
Yes
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Subsidence Evaluation for the <br />• Exhibit 60E South of Divide and Dry Fork Mining Areas Page 17 <br />5.6 Angie of Major Influence <br />The angle of major influence, P, (also called angle of influence of the point of evaluation) is <br />defined by Peng (1992, p. 11) ". . . as the angle between the horizontal and the line connecting <br />the inflection point and the edge of the radius of major influence." The radius of major influence <br />(r) is therefore the horizontal distance from the vertical projection of the inflection point to the <br />point of maximum subsidence and the limit of subsidence (Figure 3). The angle of major <br />influence is used for computer modeling by the influence function method. In the B -seam <br />mining at West Elk Mine, the angle of major influence ranges (from a horizontal reference) from <br />about 70 to 80 degrees. <br />The angle of major influence may also be referenced to the vertical, as has been done for the <br />break angle and angle of draw. The angle of major influence (from a vertical reference) is <br />roughly equal to the angle of draw (Figure 3), and is therefore also predicted to range from 10 to <br />20 degrees. <br />5.7 Relation Between Dynamic and Final Subsidence Deformations <br />Maximum dynamic tilt (change of slope) and horizontal tensile and compressive strain are <br />reportedly less above longwall mining panels than are the final tilt and strain values at panel <br />boundaries. Dynamic tilt and strain decrease, relative to final tilt and strain, as the rate of face <br />advance increases. <br />. Dynamic tilt and strain reportedly decrease with increasing speed of longwall coal extraction <br />(Peng 1992, p. 20 -21). Based on observations in a West Virginia coal mine: <br />1. Maximum dynamic tilt decreased by an average of 42 percent (from 0.0024 to 0.0014) as <br />the mining face rate of movement increased from 10 to 40 feet per day; dynamic tilt <br />therefore decreased by 14 percent as the face rate of movement increased by 30 feet per <br />day. <br />2. Maximum dynamic tensile strain decreased by an average of 22.5 percent (from 0.0031 to <br />0.0024) as the mining face velocity increased from 10 to 40 feet per day; dynamic <br />horizontal tensile strain decreased by 7.5 percent as the face increased by 30 feet per day. <br />3. Maximum dynamic compressive strain decreased by an average of 48 percent (0.0062 to <br />0.0032) as the face velocity increased from 10 to 40 feet per day; dynamic horizontal <br />compressive strain decreased by 16 percent as the face increased by 30 feet per day. <br />5.8 Critical Extraction Width of Mining Panels <br />Critical extraction width (W�) is the width of mining panels necessary for maximum subsidence <br />to occur at a given overburden depth (d). Values for W,,,/d typically range from about 1.0 to 1.4, <br />with an average of about 1.2. Based on the subsidence development data for the 5th NW <br />longwall panel, the critical extraction width may be closer to the average value of 1.2 than 1.4 in <br />the South of Divide and Dry Fork mining areas (Figure 4). <br />0 <br />831 - 032.810 <br />Wright Water Engineers, Inc. <br />1i <br />
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