Table 11-2. Design Parameters for Drilled Piers in Clay
Side Resistance
Tip
Limit on side
∝avg
shear - tsf
Nc
Remarks
Design Category
A. Straight-sided shafts in either homo-
geneous or layered soil with no soil
of exceptional stiffness below the
base
1. Shafts installed dry or by the
slurry displacement method
0.6
2.0
9
(a) aavg may be in-
2. Shafts installed with drilling
mud along some portion of the
creased to 0.6 and side
(a)
(a)
0.5
9
shear increased to 2.0
hole with possible mud entrapment
0.3
B. Belled shafts in either homogeneous
tsf for segments drilled
or layered clays with no soil of
dry
exceptional stiffness below the base
1. Shafts installed dry or by the
slurry displacement methods
0.3
0.5
9
2. Shafts installed with drilling
(b) aavg may be in-
mud along some portion of the
creased to 0.3 and side
(b)
(b)
0.3
9
shear increased to 0.5
hole with possible mud entrapment
0.15
tsf for segments drilled
C. Straight-sided shafts with basedry
resting on soil significantly
stiffer than soil around stem
0
0
9
D. Belled shafts with base resting
on soil significantly stiffer than
soil around stem
0
0
9
Note:
In calculating load capacity, exclude (1) top 5 ft of drilled shaft, (2) periphery of bell, and (3) bottom 5 ft of
straight shaft and bottom 5 ft of stem of shaft above bell.
U. S. Army Corps of Engineers
11-10
Previous Page
