2021-02-05_PERMIT FILE - C1980007A (5)

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Subsidence Evaluation for the Exhibit 60E Southern Panels, Apache Rocks West, & Sunset Trail Mining Areas Page 22 to the angle of draw (Figure 3), and is therefore also predicted to range from 10 to 20 degrees for both B-seam and E-seam panels. 5.7 Relation between Dynamic and Final Subsidence Deformations Maximum dynamic tilt (change of slope) and horizontal tensile and compressive strain are reportedly less above longwall mining panels than are the final tilt and strain values at panel boundaries. Dynamic tilt and strain decrease, relative to final tilt and strain, as the rate of face advance increases. Dynamic tilt and strain reportedly decrease with increasing speed of longwall coal extraction(Peng 1992,p. 20-21). Based on observations in a West Virginia coal mine: I. Maximum dynamic tilt decreased by an average of 42 percent (from 0.0024 to 0.0014) as the mining face rate of movement increased from 10 to 40 feet per day; dynamic tilt therefore decreased by 14 percent as the face rate of movement increased by 30 feet per day. 2. Maximum dynamic tensile strain decreased by an average of 22.5 percent (from 0.0031 to 0.0024) as the mining face velocity increased from 10 to 40 feet per day; dynamic horizontal tensile strain decreased by 7.5 percent as the face increased by 30 feet per day. 3. Maximum dynamic compressive strain decreased by an average of 48 percent (0.0062 to 0.0032) as the face velocity increased from 10 to 40 feet per day; dynamic horizontal compressive strain decreased by 16 percent as the face increased by 30 feet per day. 5.8 Critical Extraction Width of Mining Panels Critical extraction width (W x) is the width of mining panels necessary for maximum subsidence to occur at a given overburden depth (d). Values for Wcr/d typically range from about 1.0 to 1.4, with an average of about 1.2. Based on the subsidence development data for the 5th NW longwall panel, the critical extraction width may be closer to the average value of 1.2 than 1.4 in the Southern Panels, Apache Rocks West, and Sunset Trail mining areas (Figure 4). 5.9 Results of Computer Modeling A computer software package was used to model the results of subsidence measurements at West Elk Mine and to project subsidence in the Southern Panels, Apache Rocks West, and Sunset Trail mining areas. The package used is entitled: "Surface Deformation Prediction System (SDPS)", Version 6.2G developed by Department of Mining Engineering, University of Kentucky; Department of Mining and Minerals Engineering, Virginia Polytechnic Institute and State University. This program performed an influence function analysis and best fit of West Elk Mine subsidence data. The fit between the data points and the influence function output from the model is shown in Figure 6. Considering that there was some F-seam influence on the B-seam subsidence data, the actual subsidence measurements and subsidence profiles predicted by the influence function model compare favorably. 831-032.912 Wright Water Engineers, Inc. December 2020