Use Figure 1 and Table 1 for the following: Compute the vertical effective stress (σ'v) in kN/m2...

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Civil Engineering

  1. Use Figure 1 and Table 1 for the following:
    1. Compute the vertical effective stress (σ'v) inkN/m2 at the center of the clay layer prior to theconstruction of the footing.
    2. Assuming a load of 1150 kN, use the Boussinesq procedure todetermine increase in the vertical stress (Δσ) in kN/m2at the center of the clay layer below the center of thefooting.
    3. Assuming the values that you computed in (a) and (b) arerepresentative for the entire thickness of the clay layer,calculate the ultimate primary consolidation settlement(ΔHfinal) in mm that will occur in the clay layer fromplacement of the footing. Use an empirical relation to estimate thecompression index.
    4. A consolidation test was performed on a 25 mm thick,undisturbed sample taken from the center of the clay layer. Thetime and dial gauge readings obtained from an increase in pressureon the specimen from 200 to 400 kN/m2 are given in Table1. Use the \"logarithm of time\" method (i.e., Casagrande procedure)to determine the coefficient of consolidation (cv) inmm2/min.
    5. Using Terzaghi's 1D consolidation theorem, calculate and plotthe predicted settlement of the footing as a function of time(i.e., ΔH(t) vs. time), where ΔH(t) is in mm and time is in days.[Compute ΔH(t) at enough times so that you can reasonably constructthe requested plot. Also, compute ΔH(t) for times long enough thatΔHfinalis reached.]
    6. Based on the inherent assumptions in Terzaghi's 1Dconsolidation theorem and those made above versus actual fieldconditions, would you expect the footing in Figure 1 to settlefaster or slower than predicted in (e), why?

    7. Time (t) from the application of pressure increment (min)

      Dial gauge reading (mm)

      0

      4.995

      0.1

      5.010

      0.25

      5.033

      0.5

      5.053

      1

      5.107

      2

      5.153

      4

      5.211

      8

      5.287

      15

      5.351

      30

      5.379

      60

      5.400

      120

      5.418

      290

      5.434

      395

      5.440

      1230

      5.460

      Table 1. Time vs. deformation readings for astress increase from 200 to 400 N/m2.

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WhereTv Time factor for 50 consolidation 0197    See Answer
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