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• size distribution used to determine the general gradation <br />range and variation in moisture content observed in the <br />pile. <br />• Strength tests, including staged triaxial tests used to <br />determine the strength characteristics of the refuse re- <br />quired for stability analysis. <br />Staged triaxial tests were run on remolded samples of a three- <br />coarse to one-fine mixture of coal processing wastes. This is <br />the expected minimum percentage of mixing that will be conducted <br />at the site prior to compaction. The actual production mixture <br />is however, expected to have a somewhat greater percentage of <br />coarse material which will enhance the properties of the fill. <br />Results of these tests are presented in Appendix A. <br />The angle of internal friction (d) varied from 28.5 degrees under <br />• total stress conditions to 35 degrees under effective stress <br />conditions. The cohesion intercept was essentially zero and was <br />neglected for conservatism. <br />The results of these laboratory tests were utilized for input to <br />the computerized stability analysis. <br />STORAGE OPTIMIZATION ENI2 STABILITY ANALYSIS <br />To determine the optimal storage height for the refuse pile, a <br />sensitivity analysis was performed relating pile height to <br />minimum factor of safety. <br />Three different slope heights were selected using a constant 2 <br />horizontal to 1 vertical pile slope. The heights selected were <br />• 48, 75 and 90 feet. <br />5 <br />