Geology Reference
In-Depth Information
Figure 7-1
Atterberg Limits [2]
standard manner. The liquid limit is identified in the laboratory as
that water content at which the groove is closed a distance of
1
⁄
2
in.
when the soil sample is jarred in the standard manner by exactly
25 drops (or blows) from a height of 1 cm in a standardized liquid limit
device.
In addition to being useful in identifying and classifying soils, the
liquid limit can also be used to compute an approximate value of the
compression index,
C
c
, for normally consolidated clays by equation [3, 4]
C
c
0.009
LL
10
(7-1)
1
2
where
LL
, the liquid limit, is expressed as a percentage. The compres-
sion index is used in determining expected consolidation settlement of
load on clay.
Liquid limit device (see Figure 7-2)
Flat grooving tool (see Figure 7-3)
Drop gage—a metal block for adjusting the height of drop of the cup
(see Figure 7-4)
Balance (with accuracy to 0.01 g)
Evaporating dish
Spatula
Containers
Oven
No. 40 sieve
APPARATUS
AND SUPPLIES
The liquid limit device and flat grooving tool are special equipment
designed and built solely for determining liquid limits of soils. In simple
terms, the liquid limit device consists of a brass cup that is alternately
raised and dropped as a handle is turned. Figures 7-2 and 7-3 illustrate
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