2008-04-15_REVISION - M1980244 (210)

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C~ .~ J SMITH WILLIAMS CONSULTANTS, INC. Project: CCBV Phase S YLF Job No. 1125 Calculation Title: PSSA Embankment Settlement Pre ared B : JF~ Date: March 14 2008 Checked B : DTW Date: March 19 2008 OBJECTIVE: Assess the settlement and potential strain of geomembrane along the Phase 5 PSSA embankmnet under the design ore loads. METHOD: Use PLAXIS, atwo-dimensional finite element program to assess stress and strains Tong the embankment section and upstream face. Apply the model to across-section that cuts through the PSSA embankment. ASSUMPTIONS: • Since the focus of the analysis is the strain and deformation of the PSSA embankment only. Model only needs to consider the embakment material and foundation (bedrock). Ore loads can be simulated using distributed forces along embankment face. • Given the scale of the model, the geomembrane liner on the PSSA face cannot be modeled explicitly; however the liner strains can be estimated using the strains along the slope surface of interest (e.g. the geomembrane liner does not contribute to the strength). • The embankment will be constructed using structural fill. The structural fill is modeled as a linear-elastic soil. The parameters of the soil were based on test data, and have the following properties: Fra a Value Unit Wt. 120 cf Elastic Modulus 835,000 psf (This represents a stiff soil based on data presented in Bowles, 1982. Actual test data indicates that the elastic modulus ranges from 700,750 sf to 960,300 s . Friction An le 32 de ees Cohesion 0 sf conservative • The bedrock is modeled as aMohr-Coulomb material with a friction angle of 40 degrees and zero cohesion. The unit weight of the bedrock is 140 pounds per cubic foot. • The ore over the liner was modelled as an equivalent distributed force, with zero force at the embankment crest and a maximum force equal to 50 feet of ore at the toe of the embankment.