Question

A 450 mm wide, square in section concrete pile, 15 m long , is driven in a deep deposit of uniform clay. Laboratory unconfined compression tests on undisturbed samples indicate an average $q_u$ value of 75 $kN/m^2$. The ultimate load carrying capacity of the pile is ? $(\alpha =0.8)$.

• A. 810 kN
• B. 880 kN
• C. 760 kN
• D. 845 kN

Answer 1

The correct option is B 880 kN

For an unconfined compressive strength
$q_u=75kN/m^2$

$C_U=\frac{4_u}{2}=\frac{75}{2}=37.5kN/m^2$

$\therefore Q_u=C_{ub}.N_c.A_b+\alpha .C_u.A_s$

$Q_u=37.5\times 9\times 0.45\times 0.45+0.8\times 37.5\times 4\times 0.45\times 15$

= 68.34 + 810

$Q_u=878.34kN\simeq 880kN$