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'1, Effects on Surface Runoff and Streams Due to Subsidence <br />Features at the Mine <br />• Peng's Coal Mine Ground Control provides widely <br />accepted procedures for predicting subsidence over <br />coal mine excavations. These procedures are used here <br />to predict the amount of subsidence over the ranges of <br />cover to be encountered. <br />The maximum subsidence to be encountered is dependent upon <br />three parameters: the depth of the seam, the height of <br />the extracted coal and the width of the excavated area. <br />For the permit area, the depth of the seam ranges from <br />0 to 1100 feet. Planned retreat mining will occur at depths <br />ranging from 250 to 1000 feet, with an average of 500 feet. <br />The height of the extracted coal, or mining height, is ex- <br />pected to be 5.5 feet in the Lower Starkville seam. The <br />width of excavated area is dependent upon panel widths, <br />barrier pillars and pillars left for ventilation and other <br />• reasons. It is expected that the width of extraction <br />underground will be 350 feet for each panel. <br />Three cases of subsidence will be calculated: one for <br />minimum cover of 250 feet, one for maximum cover of 1000 <br />feet, and one for the average cover of 500 feet. <br />Case 1 - depth of cover = 250 feet. <br />first, a width of excavation to depth ratio is <br />calculated: <br />width = 350 ft. = 1.4 <br />depth 250 ft. <br /> <br />56~ D. H. EMLING COMPANY <br />