Geoscience Reference
In-Depth Information
Table 19.4
Variation of (K
o
) with OCR.
Material type
Parameter
Value
K
o
for varying overconsolidation ratio (OCR)
OCR
1
(N.C.)
2
3
5
10
20
=
Sands and
Friction
25
0.58
0.77
0.92
1.14
1.53
2.05
gravels
angle
30
0.50
0.71
0.87
1.12
1.58
2.24
35
0.43
0.63
0.80
1.07
1.60
2.38
40
0.36
0.56
0.72
1.01
1.57
2.45
45
0.29
0.48
0.64
0.91
1.49
2.44
Clays
Friction
10
0.78
1.10
1.35
1.74
2.46
3.47
angle
15
0.69
0.98
1.20
1.55
2.19
3.09
20
0.61
0.86
1.05
1.36
1.92
2.72
25
0.53
0.75
0.91
1.18
1.67
2.36
30
0.45
0.64
0.78
1.01
1.42
2.01
Clays
Plasticity
0 (33)*
0.40
0.57
0.69
0.89
1.27
1.79
index
10 (29)
0.47
0.67
0.81
1.05
1.49
2.10
20 (24)
0.54
0.76
0.94
1.21
1.71
2.42
30 (20)
0.61
0.86
1.06
1.36
1.93
2.73
40 (16)
0.68
0.96
1.18
1.52
2.15
3.04
50 (15)
0.69
0.98
1.20
1.54
2.18
3.09
60 (14.5)
0.70
0.99
1.21
1.57
2.21
3.13
70 (14)
0.71
1.00
1.23
1.59
2.25
3.18
80 (13)
0.72
1.02
1.25
1.61
2.28
3.22
19.5 Variation of at rest earth pressure with OCR using
the elastic at rest coefficient
•
The at rest earth pressure for overconsolidated soils varies from K
o
OCR
sin
φ
to
K
o
OCR
1
/
2
for granular to cohesive soil respectively.
•
These formulae are applied below using the K
o
derived from elastic parameters,
then subsequently using the formulae but an “equivalent'' friction angle for the
case of sands, gravels and rocks.
•
Both formulae are used in the tabulation below to show an inconsistency at low
Poisson ratio/high friction angle materials.
Table 19.5
Variation of (K
o
) with OCR.
Material type
Poisson
Formulae used
K
o
for varying overconsolidation ratio (OCR)
ratio
for OCR
OCR
1 (N.C.)
235 0 0
=
Rocks
0.1 (63)*
K
o (OC)
0.11
0.21
0.30
0.46
0.86
1.59
Rock/Gravels
0.2 (49)
K
o (NC)
OCR
sin
φ
0.25
0.42
0.57
0.84
1.41
2.37
=
Gravel/Sand
0.3 (35)
0.43
0.64
0.80
1.07
1.60
2.37
Sands
0.4 (20)
0.67
0.84
0.96
1.14
1.44
1.81
Rocks
0.1 (63)*
K
o (OC)
0.11
0.16
0.19
0.25
0.35
0.50
K
o (NC)
OCR
1
/
2
Rock/Gravels
0.2 (49)
=
0.25
0.35
0.43
0.56
0.79
1.12
Gravel/Sand
0.3 (35)
0.43
0.61
0.74
0.96
1.36
1.92
Sands
0.4 (20)
0.67
0.94
1.16
1.49
2.11 2.98
(
Continued
)
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