Geotechnical Engineering

DHARM

INDEX PROPERTIES AND CLASSIFICATION TESTS 87

Shrinkage ratio =

()

()

VV

V

Ld

d

−

100/(wL – ws)

=

136.VV

V

dd

d

F −

HG

I

KJ

100/(45 – 9) = 36%/36% = 1.00.

0.36 Vd

0.24 Vd

VL

Vp

Vd

L

P

S

D

C

B

O

ws w (33%)p w (45%)L

Water content

Volume

A

Fig. 3.26 Water content vs volume of soil (Example 3.22)

Example 3.23: The liquid limit and plastic limit of a clay are 100% and 25%, respectively.

From a hydrometer analysis it has been found that the clay soil consists of 50% of particles

smaller than 0.002 mm. Indicate the activity classification of this clay and the probable type of

clay mineral.

Liquid limit, wL = 100%

Plastic limit, wp = 25%

Plasticity Index, Ip = (wL – wp)

= (100 – 25)% = 75%

Percentage of clay-size particles = 50

Activity, A =

I

c

p ...(Eq. 3.62)

where c is the percentage of clay-size particles.

∴ A = 75/50 = 1.50

Since the activity is greater than 1.25, the clay may be classified as being active.

The probable clay mineral is montmorillonite.

Example 3.24: A clay soil sample has been obtained and tested in its undisturbed condition.
The unconfined compression strength has been obtained as 200 kN/m^2. It is later remoulded
and again tested for its unconfined compression strength, which has been obtained as