Question

please i need the correct answer for this queistion

because i found in the previous qustion the same question with two diffranet answers and i think there were incorrect

Problem 2 (25 points) An 8x8 ft square footing is embedded at depth 4 ft. The load from column consists of a normal load p- 200 Kips and V- 80 Kips. The soil in the site is a saturated clay with the following properties: undrained shear strength su 1.5 Kip/ft2Y 120pcf. The groundwater is at a great depth. Determine the factor of safety of the footing against bearing failure by only considering the vertical bearing pressure caused by the normal load p. There is no base or ground inclination. Unit weight of concrete yr-150 lb/ft). Saruraied clay

Answer 1

We have

c_u = 1.5 kip/ft² = 1500 lb/ft²

Y = 120 pcf

For UU condition of saturated clay

$\phi_{u} =0$

Ultimate Bearing Capacity of square footing given by Terzaghi is

q_u = 1.2cN_c + qN_q + 0.4YBN_y

where q = overburden = YD_f = 120 x 4 = 480 lb/ft²

For   $\phi_{u} =0$

N_c= 5.14 , N_q = 1 , N_y = 0

Putting values we have

q_u = 1.2x1500 x 5.14 + 480x1 + 0

= 9732 lb/ft²

q_nu = q_u - YD_f

= 9732 - 480

= 9252 lb/ft²

Bearing pressure caused by vertical load 'p' only is given by

q = P/A = (200x10³)/(8x8)

= 3125 lb/ft²

Factor of safety against bearing faliure is given by

F = q_nu/q

= 9252/3125

= 2.96