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PILE STABILITY ANALYSES <br />Stability analyses were performed for the pile using <br />the Simplified Bishop method. This included both static <br />analyses and pseudo-static analyses to simulate earthquake <br />loading by applying a horizontal force equal to 0.05 g to <br />each slice. <br />Material properties used in the stability analyses <br />were developed from triaxial testing of the coal waste and <br />rock tunnel waste, and from direct shear testing of the al- <br />luvial foundation material. Coal waste properties were taken <br />from the Morrison-Knudsen report "ENGINEERING EVALUATIONS, <br />COAL BASIN MINE". Properties of the alluvium and rock waste <br />were obtained from testing of the materials by Lincoln-Devore, <br />as presented in Vol. 2, Coal Basin Mine Permit Application. <br />All stability analyses were run assuming that the <br />foundation material was saturated, that is, with the piezo- <br />metric surface at the surface of the alluvium. This is a <br />reasonable assumption for worst-case conditions. It implies <br />complete drainage of the pile, but not of the foundation. The <br />possibility of a foundation failure with the failure surface <br />extending into the alluvium has been evaluated as part of the <br />stability analyses. <br />• <br />112 <br />