Geoscience Reference
In-Depth Information
5.19 Soil strength of sand from dilatometer test
•
Local relationships should always be developed to use with greater confidence.
Table 5.19
Soil strength of sand from dilatometer testing.
Description
Strength
K
D
V. Loose
D
r
15%
30
◦
1.5
<
φ
<
<
Loose
D
r
=
15-35%
φ =
30-35
◦
1.5-2.5
Med dense
D
r
35-65%
35-40
◦
2.5-4.5
=
φ =
Dense
D
r
65-85%
40-45
◦
4.5-9.0
=
φ =
V. Dense
D
r
>
85%
φ
>
45
◦
>
9.0
5.20 Clay strength from effective overburden
•
This relationship is also useful to determine degree of over consolidation based on
measured strength.
Table 5.20
Estimate of a normally consolidated clay shear strength from effective overburden
(adapted from Skempton, 1957).
Effective
Undrained shear strength of a normally consolidated clay
overburden
C
u
=
(0.11
+
0.0037PI)
σ
v
(kN/m
3
)
C
u
/
σ
v
=
0.18
0.26
0.30
0.33
0.41
0.48
Likely OCR
2
2-4
3-8
<
PI
20%
40%
50%
60%
80%
100%
=
10-50
Very soft to soft
2-9
3-13
3-15
3-17
4-20
5-24
50-100
Very soft to firm
9-18
13-26
15-30
17-33
20-41
24-48
150-200
Firm to Stiff
28-37
39-52
44-59
50-66
61-81
72-96
300
Stiff to very stiff
55
77
89
100
122
144
σ
v
-
For values of C
u
/
>
0.5, the soil is usually considered heavily overconsoli-
dated.
- Lightly overconsolidated has OCR 2-4
- OCR - Overconsolidation ratio
-
σ
v
Typically C
u
/
=
0.23 used for near normally consolidated clays (OCR
<
2)
-C
u
/
σ
v
is also dependent on the soil type and the friction angle (refer Chapter 7).
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