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!~~ <br />reviewed. The coal waste for this waste pile is generated off a screen as coal exits <br />the mine. The waste consists of material which does not break through the screen <br />and is judged to contain a high percentage of shale, sandstone, or siltstone. The <br />waste is generally more coarse and contains less fines than the washed waste <br />previously investigated. The following paragraphs summarize material properties. <br />Classification. The coal waste consists of coal, shale and sandstone <br />fragments. Gradation tests from this investigation indicate 65 to 72 percent gravel, <br />25 to 33 percent sand and 2 to 3 percent silt and clay sized particles. The fines were <br />generally non-plastic. Gradation test results are shown on Figs. 4 and 5. <br />Standard ProctorTesting. One standard Proctor moisture-density test (ASTM <br />D 698) was performed for this investigation on a sample of coal waste from a <br />composite sample of the bulk samples. The Proctor test indicates a maximum dry <br />density of 107.5 pcf with an optimum moisture content of 9,5 percent (Fig. 6). This <br />value is considered a reasonable estimate for "typical" coal waste and is consistent <br />with our previous investigations. Based upon 90 percent compaction and near <br />optimum moisture content, a unit weight of 105 pcf was used in the analysis. <br />Direct Shear Test Results. We performed a direct shear test on a sample of <br />the coal waste for this investigation. The test was performed on remolded samples <br />of the composite bulk samples at near optimum moisture contents. The results are <br />shown on Fig. 7 and provide a basis from which typical or minimum strength <br />estimates can be made. The normal strength value used in our stability analysis <br />(~ = 37 degrees and Cohesion = 200 psf) is shown on the plot. <br />STABILITY ANALYSIS <br />We performed a stability analysis of the existing coal processing waste pile <br />slope configurations. The analysis considered the results of the previous and <br />current field and laboratory investigations. The computer aided stability analysis was <br />performed using the program Slope/WTM developed by Geo-Slope international Ltd. <br />8?SIN RESOl1RCES, INC. <br />OTLT 2],793 5 <br />