Geoscience Reference
In-Depth Information
•
K
D
2 or less then the soil is normally consolidated. A useful indicator in deter-
mining the slip zones in clays.
∼
•
Parameter
o
used in the formulae shown.
β
7.16 Over consolidation ratio from undrained strength ratio
and friction angles
•
The friction angle of the soil influences the OCR of the soil.
•
Sensitive CH clays are likely to have a lower friction angle.
•
CL sandy clays are likely to have the 30 degree friction angles.
•
Clayey sands are likely to have the higher friction angles.
Table 7.16
Over consolidation from undrained strength ratio (after Mayne et al., 2001).
C
u
/
σ
v
0.2
0.22
0.3
0.4
0.5
0.7
1.0
1.25
1.5
2.0
Friction angle
Over consolidation ratio
20
◦
1.5
1.7
2.3
3.1
3.8
5
8
10
11
15
30
◦
1.0
1.0
1.4
1.9
2.4
3.3
5
6
7
10
40
◦
1.0
1.0
1.0
1.4
1.7
2.4
3.5
4
5
7
•
Applies for unstructured and uncemented clays.
•
Value of 0.22 highlighted in the table as this is the most common value typically
adopted.
7.17 Overconsolidation ratio from undrained strength ratio
•
The undrained strength ratio is dependent on the degree of over consolidation.
Table 7.17
Overconsolidation from undrained strength ratio (after Ladd et al., 1977).
Overconsolidation
C
u
/σ
v
ratio
OH Clays
CH Clays
CL Clays/silts
1
0.25 to 0.35
0.2 to 0.3
0.15 to 0.20
2
0.45 to 0.55
0.4 to 0.5
0.25 to 0.35
4
0.8 to 0.9
0.7 to 0.8
0.4 to 0.6
8
1.2 to 1.5
0.9 to 1.2
0.7 to 1.0
10
1.5 to 1.7
1.3 to 1.5
0.8 to 1.2
7.18 Sign posts along the soil suction pF scale
•
Soil suction occurs in the unsaturated state. It represents the state of the soil's
ability to attract water.
•
=
+
Units are pF or KPa (negative pore pressure). PF
1
Log S (kPa).
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