Environmental Engineering Reference
In-Depth Information
12.3.11 Passive Earth Pressure Distribution (Constant
Suction with Depth)
The horizontal pressure corresponding to the passive state
can be computed for various depths and plotted as shown in
Fig. 12.48a. For the passive case, conjugate planes are formed
at 45
The entire soil mass is in a state of compression for pas-
sive pressure conditions. The total horizontal pressure at
ground surface is a function of total cohesion:
2
c
N
φ
+
u
w
)
tan
φ
b
N
φ
p
p
=
2
(u
a
−
(12.55)
φ
/
2 to the horizontal, as shown in Fig. 12.48b. The
saturated soil case is designated using the effective cohesion
term
c
. The passive pressure is translated to the right as the
suction is increased since the total cohesion is assumed to be
constant with depth. Figure 12.49 shows a breakdown of the
passive pressure distribution into its three pressure distribu-
tion components.
−
12.3.12 Passive Earth Pressure Distribution (Linear
Decrease in Suction to Water Table)
It is possible to select various distributions for matric suction
with respect to depth. Let us assume that the matric suction
linearly decreases with depth to a value of zero at the water
table (Fig. 12.43). The matric suction at any depth can be
Figure 12.48
Rankine passive earth pressure distribution for saturated soil and soil with a
constant matric suction: (a) passive pressure distribution corresponding to passive pressure case;
(b) conjugate planes corresponding to passive pressure case.
Figure 12.49
Components of passive earth pressure distribution when matric suction is constant
with respect to depth.
Search WWH ::
Custom Search