A reinforced concrete pile 30 ft long and 15 in. in diameter is embedded in a saturated clay of very stiff consistency. Laboratory tests on samples of undisturbed soil gave an average undrained cohesive strength cu = 2500 lb/ft^2. Determine the net pullout capacity and the allowable pullout load

Question

A reinforced concrete pile 30 ft long and 15 in. in diameter is embedded in a saturated clay of very stiff consistency. Laboratory tests on samples of undisturbed soil gave an average undrained cohesive strength [latex]c_{u}=2500 lb / ft ^{2}[/latex]. Determine the net pullout capacity and the allowable pullout load with [latex]F_{s}=3[/latex].

Accepted Answer

Given: L = 30 ft, d = 15 in. diameter, [latex]c_{u}=2500 lb / ft ^{2}, F_{s}=3[/latex].

From Fig. 15.23 [latex]c_{a} / c_{u}=0.41 ext { for } c_{u}=2500 imes 0.0479 \approx 120 kN / m ^{2}[/latex] for concrete pile.

From Eq. (15.66)

[latex]P_{u l}=W_{p}+A_{s} \alpha \bar{c}_{u}[/latex] (15.66)

[latex]P_{u l}( ext { net })=\alpha \bar{c}_{u} A_{s}[/latex]

where [latex]\alpha=c_{a} / c_{u}=0.41, c_{u}=2500 lb / ft ^{2}[/latex]

[latex]A_{s}=3.14 imes \frac{15}{12} imes 30=117.75 ft ^{2}[/latex]

Substituting

[latex]P_{u l}( ext { net })=\frac{0.41 imes 2500 imes 117.75}{1000}=120.69 kips[/latex]

[latex]P_{u l} ext { (allowed) }=\frac{120.69}{3} \approx 40 ext { kips }[/latex]

Question 15.23: A reinforced concrete pile 30 ft long and 15 in. in diameter...

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