Geotechnical Engineering

DHARM

76 GEOTECHNICAL ENGINEERING

Percentage error = (2.694 2.500)

2.694

−

× 100 = 7.2.

Example 3.5: A pyknometer was used to determine the water content of a sandy soil. The
following observation were obtained:
Weight of empty pyknometer = 8 N
Weight of pyknometer + wet soil sample = 11.60 N
Weight of pyknometer + wet soil + water filling remaining volume = 20 N
Weight of pyknometer + water = 18 N
Specific gravity of soil solids (determined by a separate test) = 2.66
Compute the water content of the soil sample.
The weights may be designated W 1 through W 4 in that order,
By Eq. 3.6,

w =

()

()

WW

WW

G

G

21

34

1

1

−

−

F −

HG

I

KJ

−

L

N

M

O

Q

P × 100

Substituting the values,

w =

(11.60 8.00)

(20 18)

(2.66 1)

2.66

− 1

−

× − −

L

N

M

O

Q

P × 100

=

3.6

2.0

1.66

2.66

L ×− 1

NM

O

QP

× 100

= (1.1233 – 1) × 100 = 12.33

∴ Water content of the soil sample = 12.33%.

Example 3.6: A soil sample with a grain specific gravity of 2.67 was filled in a 1000 ml con-
tainer in the loosest possible state and the dry weight of the sample was found to be 14.75 N. It
was then filled at the densest state obtainable and the weight was found to be 17.70 N. The
void ratio of the soil in the natural state was 0.63. Determine the density index in the natural
state.

G = 2.67

Loosest state:

Weight of soil = 14.75 N

Volume of solids = 14.75

0.0267

cm^3 = 552.4 cm^3

Volume of voids = (1000 – 552.4) cm^3 = 447.6 cm^3

Void ratio, emax = 447.6/552.4 = 0.810

Densest state:

Weight of soil = 17.70 N

Volume of solids =

17.70

0.0267

cm^3 = 662.9 cm^3

Void ratio, emin =

337.1

662.9

= 0.508