Civil Engineering Reference
In-Depth Information
Figure 22.1
Types of foundation.
Figure 22.2
Loads and stresses on a foundation.
for parking cars, in which case the weight
W
is relatively small. It is a good idea to
consider the weight
W
of the foundation separately from the loads from the structure
above the ground.
Outside the foundation the total vertical stress at depth
D
is
σ
=
p
0
, where
z
p
0
=
γ
D
(22.2)
and the net bearing pressure
q
n
is given by
q
n
=
q
−
p
0
(22.3)
The net bearing pressure is the change of total stress at the base of the foundation
and it is this stress which causes ground movements. Notice that
q
n
could be either
positive or negative depending on the magnitudes of
V
and
W
, both of which would
