Geoscience Reference
In-Depth Information
Figure 5.2
Indicative variation of clay strength with changing granular content.
5.8 Critical state angles in sands
•
The critical state angle of soil (
φ
crit
)
=
30
+
A
+
B.
•
This is the constant volume friction angle. The density of the soil provides an
additional frictional value but may change depending on its strain level.
Table 5.8
Critical state angle.
Particle distribution
Critical state angle of soil (
crit
)
30
A
B
φ
=
+
+
Angularity
Rounded
Sub - Angular
Angular
Grading
B
A
0
A
2
A
4
=
=
=
Uniform soil (D
60
/D
10
<
2)
B
=
0
30
32
34
Moderate grading (2
D
60
/D
10
6)
B
2
32
34
36
≤
≤
=
Well graded (D
60
/D
10
6)
B
4
34
36
38
>
=
5.9 Peak and critical state angles in sands
•
The table applies for siliceous sands and gravels.
•
Using above Table for A and B, the peak friction angle (
φ
peak
)
=
30
+
A
+
B
+
C.
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