Bearing capacity problem example 7

A rectangular footing of size 10 x 20 ft is founded at a depth of 6 ft below the ground level in a cohesive soil (0 = 0) which fails by general shear. Given: ysal =114 lb/ft3, c = 945 lb/ft2. The water table is close to the ground surface.
Determine q , q and qna by
(a) Terzaghi’s method, and
(b) Skempton’s method. Use Fv = 3.
Solution
(a) Terzaghi’s method

 
(b) Skempton’s method
From Eqs. (12.22a) and (12.22d) we may write
 

 
Note: Terzaghi’s and Skempton’s values are in close agreement for cohesive soils