Civil Engineering Reference
In-Depth Information
Example 5.3: Atterberg limits and soil mineralogy
The Atterberg limits of a soil are
w
L
=
70 and
w
P
=
35 and it contains 80% by weight of clay. The water content of a
sample is 45%.
Plasticity index
I
P
=
w
L
−
w
P
=
70
−
35
=
35
w
−
w
P
45
−
35
Liquidity index
I
L
=
=
=
0.29
I
P
35
I
P
% clay
=
35
80
=
Activity
A
=
0.44
The clay is likely to be predominantly kaolinite.
Example 5.4: Calculation of the state of a soil
A 1.5 kg sample of dry sand is poured
into a Eureka can (see Fig. 5.7) and displaces 560 cm
3
of water. The volume of the
soil grains is equal to the volume of the water displaced from the can and so
10
3
560
weight of soil grains
volume of soil grains
=
1.5
×
specific gravity
G
s
=
=
2.68
A second 1.5 kg sample of the same dry sand is poured into an empty measuring
cylinder 55 mm in diameter and occupies 950 cm
3
(see Fig. 5.8(a)). Therefore,
volume of soil
volume of grains
=
950
560
=
specific volume
v
=
1.70
10
−
3
weight of dry soil
volume
1.5
×
9.81
×
15.5 kN/m
3
unit weight of dry soil
γ
d
=
=
=
950
×
10
−
6
10
−
6
volume
area
=
950
×
depth of dry sand
=
10
−
6
=
0.40 m
55
2
π
/4
×
×
Figure 5.7
Eureka can experiment.
