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 c_{u}=2500 lb / ft ^{2}. Determine the net pullout capacity and the allowable pullout load with F_{s}=3.
Chapter 15
Q. 15.23
Step-by-Step
Verified Solution
Given: L = 30 ft, d = 15 in. diameter, c_{u}=2500 lb / ft ^{2}, F_{s}=3.
From Fig. 15.23 c_{a} / c_{u}=0.41 \text { for } c_{u}=2500 \times 0.0479 \approx 120 kN / m ^{2} for concrete pile.
From Eq. (15.66)
P_{u l}=W_{p}+A_{s} \alpha \bar{c}_{u} (15.66)
P_{u l}(\text { net })=\alpha \bar{c}_{u} A_{s}
where \alpha=c_{a} / c_{u}=0.41, c_{u}=2500 lb / ft ^{2}
A_{s}=3.14 \times \frac{15}{12} \times 30=117.75 ft ^{2}
Substituting
P_{u l}(\text { net })=\frac{0.41 \times 2500 \times 117.75}{1000}=120.69 kips
P_{u l} \text { (allowed) }=\frac{120.69}{3} \approx 40 \text { kips }
