Civil Engineering Reference
In-Depth Information
Example 1.3:
Consistency limits tests
A BS cone penetrometer test was carried out on a sample of clay with the following
results:
Cone penetration (mm)
16.1
17.6
19.3
21.3
22.6
Water content (%)
50.0
52.1
54.1
57.0
58.2
The results from the plastic limit test were:
Mass of tin
(g)
Mass of tin wet soil
+
tin
(g)
Mass of dry soil
+
tin
(g)
Test no.
1
8.1
20.7
18.7
2
8.4
19.6
17.8
Determine the liquid limit, plastic limit and the plasticity index of the soil.
Solution:
The plot of cone penetration to water content is shown in Fig.
1.6.
The liquid limit is
the water content corresponding to 20 mm penetration, i.e. w
L
=
55%.
The plastic limit is determined thus:
20 7 8 7
18 7 8 1
.
−
−
.
w
P
( )
1
=
×
100
=
18 9
.
.
.
19 6 17 8
17 8 8 4
.
−
−
.
w
P
(
2
)
=
×
100
=
19 1
.
.
.
Average w
P
=
19%
The plasticity index is the difference between w
L
and w
P
, i.e.
I
P
= − =
55 19
36%
Fig. 1.6
Example
1.3
.
