Geoscience Reference
In-Depth Information
Table 10.2
Variability of soils (Kulhawy,1992).
Property
Test
Mean COV without outliers
Index
Natural moisture content, w
n
17.7
Liquid limit, LL
11.1
Plastic limit, PL
11.3
Initial void ratio, e
o
19.8
Unit weight,
γ
7.1
Performance
Rock uniaxial compressive strength, qu
23.0
Effective stress friction angle,
φ
12.6
Tangent of
φ
11.3
Undrained shear strength C
u
33.8
Compression index C
c
37.0
10.3 Variability of in-situ tests
•
The limitations of in-situ test equipment needs to be understood.
•
The likely measurement error needs to be considered with the inherent soil
variability.
•
The SPT is a highly variable in-situ test.
•
Electric cone penetrometer and Dilatometer has the least variability.
•
The table shows cumulative effect of equipment, procedure, random.
Table 10.3
Variability of in - situ tests (From Poon and Kulhawy, 1999).
Test
Coefficient of variation (%)
Standard penetration test
15-45
Mechanical come penetration test
15-25
Self boring pressure meter test
15-25
Vane shear test
10-20
Pressure meter test, prebored
10-20
Electric cone penetration test
5-15
Dilatometer test
5-15
Figure 10.1
Normal distribution of properties.
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