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SECTIONSIX Soil-Bentonite Cutoff wall <br />excess slurry above the filter cake was cazefully poured off and the permeant of interest <br />added to the cylinder. The permeant was forced through the filter cake, and the rate of <br />flow was monitored. <br />1 Particle-Size Analysis of the Composite Soil Samples <br />The particle-size analysis testing was performed on each composite soil sample using the <br />sieve method as described in ASTM D422 [1]. <br />' ^ Slump of the Backfill Mix (Mini Slump Cone Procedure) <br />The slump of each soil-bentonite mix was measured using a lab size slump cone that has <br />' been calibrated to a standard slump cone used in ASTM Method C-143. The lab size <br />slump cone test method is described in an unpublished paper from the Civil Engineering <br />Department of Bucknell University by J.C. Evans et al, 1999. <br />^ Moisture Content on the Backfill Mix <br />Moisture content was determined in accordance with ASTM Method D-2216 [1] by <br />drying the sample in a 110°C oven to a constant weight. Moisture contents are expressed <br />as the percentage of water weight to the dry weight of the specimen soil. <br />^ Total Unit Weight of Soil-Bentonite Mixture <br />The initial specimen total unit weights were calculated based on sample dimensions and <br />weights. As-tested unit weights were based on measured height and volume changes that <br />occurred during specimen consolidation and the final specimen weight and water content <br />taken after completion of the hydraulic conductivity test. <br />^ Hydraulic Conductivity Tests on the Backfill Mixes <br />The hydraulic conductivity of each backfill mix was determined in accordance with <br />ASTM Method D-5084- Flow Pump Method. After specimen preparation, the specimen <br />was saturated with 'site groundwater and consolidated under a confining pressure of <br />approximately 2 psi. Flow through the sample was then induced under a gradient of <br />approximately 20. <br />Test Results and Discussion <br />Backfill Material Index Testing <br />The field samples were mixed to create composite samples of soil which are likely to be <br />representative of the site materials expected to be used in the soil-bentonite backfill mix. Three <br />composite samples were prepared for testing. <br />The gradations for the composite samples are shown in Figure D-1 in Appendix D. <br />Slurry Testing <br />An approximate 40 marsh-second viscosity slurry was prepazed using Wyo-Ben Hydroge190 <br />bentonite with the site surface water. The bentonite slurry was prepared by mixing a known <br />quantity of the mix-water in afive-gallon bucket with the required quantity of bentonite to create <br />a 6% (by dry weight) bentonite to water ratio. This slurry was then mixed until a uniform <br />consistency was obtained. <br />N~aP}RO~JEC~i$¢2238240_PLATiE_SAND_GRAVER$UB_OOU2.0_WORD_PROCWLA7TE SANO&GRAVEL GEO7ECHNICAL DESIGN REPORT 4.O.DOCl75-NOV-05i1 6-2 <br />V i47 <br />