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TECHNICAL MEMORANDUM <br /> Page 14 - <br /> June 3, 1992 Awft <br /> ® SAC31583.AC.ZZ <br /> A key:assumption used to estimate foundation settlement was that similar material types will <br /> exhibit similar consolidation properties throughout the landfill area. Data obtained during <br /> the subsurface exploration, however, indicated that the clay layers in which consolidation <br /> tests were performed exhibited wide variations in density. Accordingly, because the <br /> consolidation tests were performed on relatively compressible samples and relatively stiffer <br /> clay zones occur at various depths, the foundation settlement estimates presented are likely <br /> conservative. Also, since no geotechnical subsurface information (SPT blow-counts or shear <br /> strength) was available for depths greater than 178 feet, an approximate, order-of-magnitude <br /> settlement estimate was made using an elastic theory approach. Actual foundation <br /> settlement values measured in the field may therefore vary from the values reported in this <br /> technical memorandum. - <br /> Because of the anticipated landfill extension refuse loads, it is estimated that foundation <br /> settlement in the clay layers will consist of both recompression settlement and virgin <br /> compression settlement. A summary of the consolidation properties used in the analysis are <br /> presented in Table 3. <br /> Tabic 3 f <br /> ® Summary of Consolidation Test Results used in Foundation Settlement Analysis <br /> r� <br /> Sample Soil Slope of Slope of Pre consolidation Ovcrconsolidation <br /> Boring Dcpth 'Type Recompression Compression Pressure Ratio <br /> No. (ft) (USCS) Curve(Cr) Curve(Cj (ps() (OCR) <br /> BH-1 33.0-355 ML - 0.01 0.10 14000 3 <br /> BH-1 76.0-785 CL 0.02 0.14 16,000 1.7 <br /> BH-2 48.0-505 CL 0.03 0.13 81000 _ 1.4 <br /> The OCRs shown in Table 3 were determined based on the original groundsurface contour <br /> and estimated groundwater table elevation at the time of drilling. <br /> s <br /> Results of Analyses <br /> The greatest magnitude of total foundation settlement is anticipated to occur in the area of <br /> maximum refuse height, in the area near Boring BH-1. Total settlement at this.location is <br /> estimated to be up to 2 feet. Foundation settlement for interim fill conditions will be <br /> smaller than this estimated settlement. Subsurface material encountered during our <br /> exploration was typically very sandy, and the clay material that was encountered was <br />