Determining the Liquid Limit of Soil - Soil Properties: Testing, Measurement, and Evaluation - page 83

Table 7-1 Factors for Obtaining Liquid Limit from Water
Content and Number of Drops Causing Closure of Groove [5]

N (Number of Drops) k (Factor for Liquid Limit)

20 0.973

21 0.979

22 0.985

23 0.990

24 0.995

25 1.000

26 1.005

27 1.009

28 1.014

29 1.018

30 1.022

Mass of container, M c
Mass of container plus moist soil, M cws
Mass of container plus oven-dried soil, M cs

As indicated previously, the liquid limit is that water content of the soil
at which the standard groove is closed a distance of 1 ⁄ 2 in. by exactly 25
drops. This is determined for Method A (Multipoint Liquid Limit) by plot-
ting, on semilogarithmic graph paper, water content along the ordinate
(arithmetical scale) versus number of drops along the abscissa (logarith-
mic scale) and drawing the best straight line through the plotted points.
The resulting graph is referred to as a flow curve . From the flow curve,
the liquid limit can be read as the water content at 25 drops.
For Method B (One-Point Liquid Limit), the liquid limit for each
water content specimen can be determined using one of the following
equations [5]:

CALCULATIONS

b 0.121 a N

25

LL w (7-2)

or

LL kw (7-3)

where:
N number of blows causing closure of the groove for given trial
w water content for given trial, %
k factor given in Table 7-1

The liquid limit is the average of the two trial liquid limit values. If the
difference between the two trial liquid limit values is greater than one
percentage point, repeat the test.

A laboratory test was conducted according to the previous procedure
(Method A). The following data were obtained:

NUMERICAL
EXAMPLE