Geoscience Reference
In-Depth Information
Table 8.13 Typical values of the coefficient of consolidation (Carter and Bentley, 1991).
Soil
Classification
Coefficient of consolidation, c v ,m 2 /yr
Boston blue clay
CL
12
6
±
Organic silt
OH
0.6-3
Glacial lake clays
CL
2.0-2.7
Chicago silty clays
CL
2.7
Swedish medium
CL-CH
0.1-1.2 (Laboratory)
Sensitive clays
0.2-1.0 (Field)
San francisco bay mud
CL
0.6-1.2
Mexico city clay
MH
0.3-0.5
8.14 Variation of coefficient of consolidation with liquid limit
The coefficient of consolidation is dependent on the liquid limit of the soil.
c v decreases with strength improvement, and with loss of structure in remoulding.
Table 8.14 Variation of coefficient of consolidation with liquid limit (NAVFAC, 1988).
Liquid limit, %
30
40
50
60
70
80
90
100
110
Coefficient of consolidation, c v ,m 2 /yr
Undisturbed - virgin
120
50
20
10
5
3
1.5
1.0
0.9
compression
Undisturbed - Recompression
20
10
5
3
2
1
0.8
0.6
0.5
Remoulded
4
2
1.5
1.0
0.6
0.4
0.35
0.3
0.25
LL
>
50% is associated with a high plasticity clay/silt.
LL
<
30% is associated with a low plasticity clay/silt.
8.15 Coefficient of consolidation from dissipation tests
The previous sections discussed the measurement of permeability and the dis-
sipation tests carried out with the piezocone. This also applies to testing for the
coefficient of consolidation. The measurement of in situ coefficient of permeability
by dissipation tests is more reliable than laboratory testing.
Laboratory testing does not account for minor sand lenses, which can have a
significant effect on permeability.
Table 8.15 Coefficient of consolidation from measured time to 50% dissipation (Mayne, 2002).
Coefficient of
cm 2 /min
0.001 to 0.01
0.01 to 0.1
0.1 to 1
1 to 10
10 to 200
consolidation,
m 2 /yr
0.05 to 0.5
0.5 to 5.3
5.3 to 53
53 to 525
525 to 10,500
C h
t 50 (mins)
400 to 20,000
40 to 2000
4 to 200
0.4 to 20
0.1 to 2
t 50 (hrs)
6.7 to 330 hrs
0.7 to 33 hrs
0.1 to 3.3 hrs
0.3 hrs
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