Question

For the strip footing on a saturated clay, for the given failure surface (fig. 3. 12), the bearing capacity equation takes the form

where
$C_u$ =undrained shear strength
${\varphi }_u$ = angle of internal friction
B = width of strip footing
$q_c$ ultimate bearing capacity of soil

• A.
  $$5.7C_u$$
• B.
  $$5.14C_u$$
• C.
  $$4\pi C_u$$
• D.
  $$2\pi C_u$$

Answer 1

The correct option is D

$$2\pi C_u$$
Taking moment about A.
$M_A=0$$$(q_u\times B\times 1)\frac{B}{2}-\left({\sigma }_{z}B\right)\frac{B}{2}-\left(\pi B{C}_u\right)B=0$$$$q_u=2\pi C_u+{\sigma }_z$$$${\sigma }_z=0$$Hence:

$$q_u=2\pi C_u$$