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August 1984 2 843-2044 <br /> occur. Further , consistent with the consolidation of the collu- <br /> vial soils , an increase in shear strength characteristics will <br /> occur. In order to fully analyze the stability of the pile at <br /> intermediate stages of construction , numerous physical char- <br /> acteristics of the colluvial soils must be known including the <br /> consolidation characteristics , the drained shear strength <br /> parameters , and the pore pressure response parameters. The <br /> laboratory testing program carried out on the samples from <br /> borehole W-1 did not address these questions. <br /> As an alternative to carrying out effective stress analyses for <br /> the intermediate cases , with the laboratory test data available , <br /> it is possible to carry out a worst case total stress analysis. <br /> This analysis is based on the assumption that the 5-year final <br /> waste pile configuration is instantaneously constructed at the <br /> site. <br /> Based on the laboratory test data previously submitted , the <br /> following total stress undrained parameters can be computed : <br /> a) Ccu = 1000 psf Ocu = 190 <br /> b) Ccu = 1900 psf Ocu = 11° <br /> Stability analyses of the overall waste pile geometry were <br /> carried out using simplified Bishop method with the above total <br /> stress parameters for the colluvial soils. <br /> Parameters for the waste materials and underlying Mancos Shale <br /> were the same as previously used. Both static and pseudostatic <br /> analyses were carried out to assess the performance of the waste <br /> pile under normal (gravity) loading and when subjected to <br /> earthquake forces. <br /> The minimum factors of safety computed based on the parameters <br /> outlined in a) above were 1.7 under gravity loading and 1 .5 under <br /> dynamic loading. For parameters outlined in b) above, the static <br /> factor of safety computed was 1.6 and the factor of safety under <br /> dynamic loading was computed to be 1.4. <br /> Based on the above "worst-case" analyses , the stability of the <br /> waste pile in the short-term (during the construction schedule) <br /> is considered to be acceptable. It is considered imperative <br /> that , during construction of the pile , the waste material be <br /> uniformly spread and compacted over the entire waste disposal <br /> area. <br /> Golder Associates <br />