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1 ' San Luis Mine Phase n, Raise 2 Design Report ' approximately 25 to 30 percent of the saturated tailings for which both dynamic and residual pore pressure data was available exhibited negative dynamic excess pore pressures (i.e. dynamic pressure is less than residual pressure) indicative of dilatent behavior during shear (Campanella, et. al., ' 1984). Figure 4 which presents the pore pressure dissipation data for CPT-lA at a depth of 80.9 fr (24.65 m) is a typical example of negative dynamic pore pressure data and dilatent behavior. 1 2.2.3 Material Types ' The CPT tip resistance, sleeve friction, and dynamic pore pressure data is utilized to determine material type as shown on the data profiles in Appendix B.2. The coarser grained tailings or ' "tailings sand" are interpreted to have exhibited soil behavior type classifications of sand, sand to silty sand, or silty sand to sandy silt. The fine grained tailings or "slimes" are interpreted to have exhibited soil behavior type classifications of clayey silt to silty clay, silty cloy to clay, clay or sensitive fine grained. Interlayered tailings sand and slimes or mixed tailings are interpreted to have exhibited a soil behavior type classification of sandy silt to clayey silt. ' The silty or clayey sand and gravel utilized as access ramp and Phase II Reise 1 fill material frequently contained sufficient fines to exhibit soil behavior types of clay, silty clay to clay, or ' clayey silt to silty clay based on the CPT classification procedure and did not reflect the granular nature of the material. However, unlike the tailings slimes, this material typically exhibited negative dynamic pore pressure response due to the dense dilative nature of the fill. 'I The data indicates a general trend for increased amounts of mixed tailings and slimes with increasing ' distance from the embankment as is expected for the type of deposition practiced at the facility. The data also indicates that the tailings are complexly layered with large lateral variations over short t distances and no distinct horizons or layers which extend across the area investigated. In many instances, CPT probes separated by a distance of as little as 5 ft frequently exhibited different material classification at the same horizon. In other instances, good correlation of material types was observed between adjacent probe sites. Figures 5 through 8 present cross-sections of the tailings encountered along each access ramp. ' 2.2.4 Material Properties ' The CPT tip resistance, sleeve friction, and dynamic pore pressure data is averaged over 25 cm intervals and used to compute an equivalent Standard Penetration Test (SPT) N~ value, relative ' density and friction angle for granular soil behavior types (tailings sand) and undrained shear strength for cohesive soil behavior types (mixed tailings or slimes). This date is included in the interpreted outputs contained in Appendix B.2. 1 n Y 2~ ro~ec[ o.