Assume a site consists of an end-bearing pier founded on solid rock.
The diameter of the pier is 3 ft (0.9 m) and a 40 ft (12 m) long zone of the pier is embedded in
clay that is in the process of consolidating. Assuming the clay has a uniform undrained shear
strength su of 500 psf (24 kPa), calculate the downdrag load on the pier.
Solution Using a total stress analysis, therefore, su = cohesion (c). From Fig. 6.13, the value
of cA = 480 psf (23 kPa) for a concrete pier embedded in clay having c = 500 psf (24 kPa).
Using Eq. 6.22:
QD = 2pRL1cA = 2p (1.5 ft)(40 ft)(480 psf ) = 181,000 lb (800 kN)