Civil Engineering Reference
In-Depth Information
Values of
φ
′
(degrees)
10°
20°
30°
40°
Values of
δ
Values of c
w
/c
Values of K
p
0
All
1.42
2.04
3.00
4.60
values
1.55
2.51
4.46
9.10
φ
′
/2
φ
′
1.63
2.86
5.67
14.10
Values of K
pc
0
0
2.38
2.86
3.46
4.29
0
2.49
3.17
4.22
6.03
φ
′
/2
φ
0
2.55
3.38
4.76
7.51
0
0.5
2.92
3.50
4.24
5.25
0.5
3.05
3.88
5.17
7.39
φ
′
/2
φ
0.5
3.13
4.14
5.83
9.20
0
1.0
3.37
4.04
4.90
6.07
1.0
3.52
4.48
5.97
8.53
φ
′
/2
1.0
3.61
4.78
6.73
10.62
φ
′
The following design parameters are recommended for
δ
and c
w
:
For timber, steel and precast concrete:
=
φ
′
/2
For cast
in situ
concrete:
=
2
φ
′
/3
Generally, c
w
should be assumed to be half of the value for the active pressure conditions.
7.8 Surcharges
The extra loading carried by a retaining wall is known as a surcharge and can be a uniform load (roadway,
stacked goods, etc.), a line load (trains running parallel to a wall), an isolated load (column footing), or a
dynamic load (traffic).
7.8.1 Uniform load
Soil surface horizontal
When the surface of the soil behind the wall is horizontal, the pressure acting on the back of the wall due
Soil surface sloping at angle
β
to horizontal
When the surface of the soil is not horizontal, the surcharge can be considered as equivalent to an extra
height of soil, h
e
placed on top of the soil.
sin
sin(
q
ψ
h
e
=
γ
ψ
β
+
)
