Geoscience Reference
In-Depth Information
•
It is most useful in alluvial areas.
•
The table shows simplified interpretative approach. The actual classification and
strength is based on the combination of both the friction ratio and the measured
cone resistance, and cross checked with pore pressure parameters.
•
Applies to electric cone and different values apply for mechanical cones. Refer to
Figures 5.3 and 5.4 for different interpretations of the CPT results.
5.13 Soil type from friction ratios
•
The likely soil types based on friction ratios only are presented in the table below.
•
This is a preliminary assessment only and the relative values with the cone
resistance, needs to be also considered in the final analysis.
Table 5.13
Soil type based on friction ratios.
Friction ratio (%)
Soil type
1
Coarse to medium sand
<
1-2
Fine sand, silty to clayey sands
2-5
Sandy clays. Silty clays, clays, organic clays
5
Peat
>
5.14 Clay parameters from cone penetration tests
•
The cone factor conversion can have significant influence on the interpretation of
results.
•
For critical conditions and realistic designs, there is a need to calibrate this testing
with a laboratory strength testing.
Table 5.14
Clay parameters from cone penetration test.
Parameter
Relationship
Comments
Undrained strength (C
u
- kPa)
C
u
q
c
/N
k
Cone factor (N
k
)
17 to 20
=
=
C
u
=
u/N
u
17-18 for normally consolidated clays
20 for over-consolidated clays
Cone factor (N
u
)
=
2to8
Undrained strength (C
u
- kPa),
C
u
(q
c
P
o
)
/N
k
Cone factor (N
k
)
15 to 19
=
−
=
corrected for overburden
15-16 for normally consolidated clays
18-19 for over-consolidated clays
Coefficient of horizontal
c
h
300/t
50
t
50
- minutes (time for 50% dissipation)
=
consolidation (c
h
- sq m/year)
Coefficient of vertical
c
h
2c
v
Value may vary from 1 to 10
=
consolidation (c
v
- sq m/year)
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