Civil Engineering Reference
In-Depth Information
TABLE 4.16
Relation between Subgrade Reaction, Angle of Internal Friction
and Relative Density for Sand below Water Table
Angle of Internal
Friction,
Subgrade Reaction,
kN/m
3
Soil Type
ϕ′
Relative Density, %
Very loose
<
29
20
265.7
Loose sand
25
426.3
30
553.6
35
744.6
29
-
30
40
996.4
Medium dense
45
1356.3
50
1716.1
55
2026.1
30
-
36
60
2491.1
Dense
65
2850.9
70
3293.8
75
3792.0
36
-
40
80
4262.6
For piles driven through clay, the skin friction, f, is equal to or less than,
but should not exceed, the undrained shear strength of the clay c
u
, as deter-
mined by unconsolidated-undrained (UU) tri-axial tests and miniature vane
shear tests.
Unless test data indicate otherwise, f should not exceed c
u
or the following
limits:
1. For highly plastic clays, f may be equal to c
u
for underconsolidated and nor-
mally consolidated clays. For overconsolidated clays, f should not exceed
48 kPa for shallow penetrations or the equivalent value of c
u
for a normally
consolidated clay for deeper penetrations, whichever is greater.
2. For other types of clay:
=
c
u
for c
u
<
f
24 kPa
(4.27)
f
=
c
u/2
for c
u
<
72 kPa
(4.28)
f varies linearly for values of c
u
between the above limits.
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