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- 2 0 - <br />of safety significantly. The increase is on the <br />order of IO to IS percent. <br /> <br />1 <br /> <br /> <br />1 <br /> <br /> <br /> <br /> <br />1 <br /> <br /> <br />5. Location of the waste rock pile on the surface of <br />the upper bench causes a decrease of the factors <br />of safety. The decrease is, however, very small. <br />If dry conditions are assumed and the waste pile <br />is placed so that its toe coincides with the crest <br />of the bench, our analyses indicate that the factor <br />of safety decreases by about 4 percent. If the waste <br />pile is located 100 feet from the crest, the factor <br />of safety decreases only by about 1 percent. If the <br />area of the bench has ground water in one of the <br />coal seams, the decrease of factors of safety, result- <br />ing from the loading by the waste pile, is higher <br />(12 percent if the pile reaches to the crest, 4 per- <br />cent if the pile is located 100 feet from the crest). <br />However, it should be recognized that some of these <br />changes in safety factor are very small in comparison <br />to the accuracy of the stability analysis, the auto- <br />matic search option used, and the shear strength <br />parameters used. They should therefore be considered <br />as being preliminary estimates only. <br />6. The stability conditions or factors of safety of the <br />slope are of the same order for a `allure developing <br />through the E-seam. This assumes the same hydrological <br />conditions in both seams. <br />7. Loading of the slope with the waste pile influences <br />only a potential failure through the F seam. It has <br />a negligible effect on a potential failure through <br />the lower E seam. <br />ccaNroao ca+svimw, ~HC. <br />