Geoscience Reference
In-Depth Information
Table 11.9
Coefficient of volume compressibility derived from SPT N-value (after Stroud and Butler,
1975).
Plasticity index (%)
Conversion factor (f
2
)
v
(10
−
3
kPa
−
1
) based on N-value: m
v
1/(f
2
N)
=
N
10
20
30
40
50
=
10
800
0.12
0.06
0.04
0.03
0.02
20
525
0.19
0.09
0.06
0.05
0.04
30
475
0.21
0.10
0.07
0.05
0.04
40
450
0.22
0.11
0.07
0.06
0.04
11.10 Deformation parameters from CPT results
•
The Coefficient of volume change and the constrained modulus (ie large strain
condition) values can be derived from the CPT results.
Table 11.10
Deformation parameters from CPT results (Fugro, 1996; Meigh, 1987).
Parameter
Relationship
Comments
Coefficient of volume change, m
v
m
v
1/(
q
c
)
For normally and lightly overconsolidated
soils
α =
=
α
5
for classifications CH, MH. ML
α =
6
for classifications CL, OL
5
for classifications OH with moisture
α =
1
.
100% for overconsolidated soils
α =
>
4
for classifications CH, MH. CL, ML
2
for classifications ML, CL with q
c
2 MPa
α =
>
Constrained modulus, M
M
=
3q
c
M
=
1/m
v
Elastic (Young's) modulus, E
E
2.5 q
c
Square pad footings - axisymetric
=
E
=
3.5 q
c
Strip footings - plane strain
11.11 Drained soil modulus from cone penetration tests
•
The approximate relationship between CPT value and drained elastic modulus for
sands is provided in the table.
Table 11.11
Preliminary drained elastic modulus of sands from cone penetration tests.
Relative density
Cone resistance, q
c
Typical drained elastic
(MPa)
modulus E
,MPa
V. loose
2.5
10
<
<
Loose
2.5-5.0
10-20
Med dense
5.0-10.0
20-30
Dense
10.0-20.0
30-60
V. dense
20.0
60
>
>
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