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settlement from the loads placed upon it by the waste pile. Because <br />of this, the internal integrity of the proposed homogeneous pile is <br />the major concern with regard to the operational stability of the <br />embankment. It is expected that the critical areas for failure <br />will occur within the pile itself, and not through the foundation <br />strata. In the analysis, the foundation strata was given a high <br />strength value, so that the failure would occur through the pile. <br />Stability analyses in this report used a computerized <br />stability program called STBL2. STBL2 uses a modification of the <br />simplified Bishop method of slices in which overall horizontal <br />force equilibrium is satisfied instead of overall moment <br />equilibrium. In this manner, it is capable of analyzing both <br />circular and non-circular failure surfaces. This method is also <br />known as Janbu's simplified procedure which is the same expression <br />as that derived by Carter (Siegel, 1975). STBL2 has a routine <br />which searches 100 circular failure surfaces for the most critical <br />sections and a routine to calculate the safety factor for any <br />designated non-circular failure surface. <br />Initially, a potential failure plane along the interface <br />between the pile and foundation strata was analyzed for stability. <br />To supplement this, a random circle searching routine was used to <br />find the critical circle within the pile. As mentioned, the <br />channel is a drainageway for an ephemeral stream. Since all <br />• surface water will be diverted from the pile itself, excessive <br />positive water pressures are not likely to develop within the pile <br />(Wardwell, 1982). Because of this, the water table was initially <br />assumed to be no higher than the interface between the pile and the <br />foundation. <br />While it is unlikely that a high water table would form <br />within the pile, the stability of the embankment was also analyzed <br />with a water surface placed within the pile itself. The purpose of <br />this was to estimate <br />• ~ ~g)9~' <br />20591.626 2.05-41 revised 10/23/97 <br />