Civil Engineering Reference
In-Depth Information
Figure 5.6
Superposition of settlement profiles for group of piles.
interaction factor must also take account of how the presence of the second pile will
modify the deformation field imposed by the first pile.
The following sections describe how the stiffness of pile groups under axial and
lateral loading may be evaluated from the stiffness of single piles and the use of
appropriate interaction factors.
5.2.1 Axial loading
Randolph and Wroth (1979) describe how the solution for the axial load deformation
response for single piles may be extended to deal with pile groups. Theoretical inter-
action factors are deduced from the form of the deformation field around a single pile,
treating the pile shaft separately from the pile base. Under axial loading, the defor-
mation field around the pile shaft varies approximately logarithmically with radius,
r
,
according to
2
G
ln
r
m
/
r
=
τ
o
d
w
(5.9)
(see section 4.2.1). Thus the shaft interaction factor,
α
s
, for a pile a distance
s
from
the pile in question may be estimated as
ln
r
m
/
s
α
s
≈
(5.10)
ζ
