Field sampling and testing - Geotechnical Investigation and Design Tables - page 48

4.14 Vane shear correction factor
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A correction factor should be applied to the vane shear test result for the value to
be meaningful.

Table 4.14 Vane shear correction factor (based on
Bjerrum, 1972).

Plasticity index (%) Vane correction factor ( ) µ

20% 1.0 <

30% 0.9

40% 0.85

50% 0.75

60% 0.70

70% 0.70

80% 0.65

90% 0.65

100% 0.65

- Rate of shear can influence the result.
- Embankments on soft ground using large equipment are usually associated

with 1 week construction time (loading) - 10,000 minutes. Chandler (1988).

4.15 Dynamic cone penetrometer tests
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This DCP test is measured in two ways as shown in the table.

•

There are different variations of the DCP in terms of its hammer weight and drop
height. Two variations with similar energy characteristics are shown in Figure 4.3.

•

The DCP is most useful as profiling tool, although it is used to determine the
strength properties and with correlations to the CBR. The blows/100mm is the
profiling approach, while the penetration/blow is the strength approach.

Table 4.15 Dynamic cone penetrometer tests.

Measurement Example Comments

Blows/100 mm 10 Blows/100 mm

Equivalent reading

Penetration (mm)/blow 10 mm/blow

4.16 Surface strength from site walk over
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The pressure exerted by a person walking on the ground is based on their mass
and foot size.

•

For the Table below:
- a heavy person is used as above 80 kg with small shoe size.

- a light is person is below 60 kg with a large shoe size.

•

All others are medium pressure