Handout20 - The University of Texas Department of Civil...

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Unformatted text preview: The University of Texas Department of Civil Engineering CE 357 - SETTLEMENT OF FOOTINGS ON SAND (Ref.: Foundation Engineering, by Peck, Hansen, and Thornburn, John Wiley and Sons.) 1. When Standard Penetration Test (SPT) N-values are determined at depths where the effective overburden pressure is significantly different from 1 tons/sq ft, the N-values should be corrected. The corrected N-value (N corr ) is calculated from the uncorrected N-value and the vertical effective stress at a given depth as follows (0 is in units of tsf): N corr = CNN where C N = 0.77log 10 (20/0) for 0 ;::: 1/4 tsf C N = 2.00 - 2.16'0 for 0 < 1/4 tsf Note: N values must be corrected before any of the steps below are performed. 2. When N-values vary with depth, average the corrected N-values from the base of the footing to a depth, 8 (8 = width of footing) below the base of the footing and use the average corrected N-value for calculating settlement. When the average corrected N-values so determined vary from boring-to-for calculating settlement....
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