Civil Engineering Reference
In-Depth Information
Fig. 7.6
Point of application of total active thrust (Rankine theory).
Example 7.2:
Rankine active thrust; more than one soil
Details of the soil retained behind a smooth wall are given in Fig.
7.7.
Draw the diagram
of the pressure distribution on the back of the wall and determine the total horizontal
active thrust acting on the back of the wall by the Rankine theory.
Solution:
Active pressure at the top of the wall,
P
a
0
=
.
For
P
a
3
:
Consider the upper soil layer:
1
−
sin
sin
30
°
K
a
=
°
=
0 33
.
1
+
30
p
=
0 33 16 3
.
× × =
16
kPa
a
3
Consider the lower soil layer:
1
−
sin
sin
20
°
K
a
=
0 49
.
°
=
1
20
+
p
=
0 49 16 3
.
× × =
23 5
.
kPa
a
3
The active pressure jumps from 16 to 23.5 kPa at a depth of 3 m.
Fig. 7.7
Example
7.2.
