Civil Engineering Reference
In-Depth Information
FIGURE 8.8
Bearing capacity factor
N
c
for two layer soil conditions.
(
Reproduced from NAVFAC DM-7.2, 1982.
)
unliquefiable cohesive soil layer overlying a soil layer that is expected to liquefy during the
design earthquake. In Fig. 8.8, the terms are defined as follows:
Layer 1
upper cohesive soil layer that has a uniform undrained shear strength,
lb/ft
2
or kPa, or
s
u
c
c
1
Layer 2
lower soil layer that will liquefy during the design earthquake. The usual
assumption is that the liquefied soil does not possess any shear strength, or
c
2
0.
T
vertical distance from the bottom of the footing to top of the liquefied soil
layer, ft or m
B
width of footing, ft or m
Since the liquefied soil layer (i.e., layer 2) has zero shear strength (i.e.,
c
2
0), the ratio
of
c
2
/
c
1
will also be equal to zero. By entering Fig. 8.8 with
c
2
/
c
1
0 and intersecting the
