Civil Engineering Reference
In-Depth Information
Fig. 3.10
Influence factors for the vertical stress beneath the corner of a rectangular foundation (after
Fadum,
1948
).
Example 3.5:
Vertical stress increments beneath a foundation
A 4.5 m square foundation exerts a uniform pressure of 200 kPa on a soil. Determine (i)
the vertical stress increments due to the foundation load to a depth of 10 m below its
centre and (ii) the vertical stress increment at a point 3 m below the foundation and 4 m
from its centre along one of the axes of symmetry.
Solution:
(i) The square foundation can be divided into four squares whose corners meet at the
centre O (Fig.
3.11a
).
B
z
L
z
z (m)
m
=
n
=
I
σ
4I
σ
σ
z
(kPa)
2.5
0.9
0.9
0.163
0.652
130
5.0
0.45
0.45
0.074
0.296
59
7.5
0.3
0.3
0.04
0.16
32
10.0
0.23
0.23
0.025
0.1
20
