Practice Question: Shallow foundation Settlement

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Solution

Answer: B) 0.9 inch

Refer to the PE Civil Reference Handbook Section 3.5.2:

\(\delta_v=C_{d} \Delta p B_{f} \frac{((1-\upsilon^2 ))}{E_{m}}\)

\(\Delta p = Change\ in\ stress\ at \ foundation\ depth \\\)

\(E_m = elastic\ modulus\ of\ soil\ layer\ = \ 250\ TSF = \ 250 \times 2000\ = \ 5 \times 10^5\ PSF\)

refer to reference table range between 200 and 300 TSF.

\(C_{d} = \text{Shape and rigidity }\)

Based on a continuous wall, where the length-to-width ratio is greater than 10,000:

\(C_{d} = 6.9\)

\(\upsilon =\text{possion ratio of soil = refer for reference table =0.25} \\\)

\(p_{o} = \text{effective in situ overburden stress at the foundation depth} \\\)

\(p_{0} = \gamma h_{1} = 8 \times 130 = 1040\ PSF \\\)

\(p= 2000\ PSF \\\)

\(\Delta p=p-p_{0}=2000-1040 =960\ PSF \\\)

\(\delta_v=C_{d} \Delta P B_{f} \frac{((1-\upsilon^2 ))}{E_{m}} = 6.9 \times 960 \times 6 \times \frac{(1-0.25^2)}{(250 \times 2000)} = 0.07452\ ft = 0.894\ inch. \\\)

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