Geotechnical Engineering

DHARM

74 GEOTECHNICAL ENGINEERING

=

9.80

9.80 (22.45 16.30)−−

=

9.80

(9.80 16.15)− = 2.685

∴ Specific gravity of the soil solids = 2.685.

Example 3.2: In a specific gravity test, the weight of the dry soil taken is 0.66 N. The weight
of the pyknometer filled with this soil and water is 6.756 N. The weight of the pyknometer full
of water is 6.3395 N. The temperature of the test is 30°C. Determine the grain specific gravity,
taking the specific gravity of water at 30°C as 0.99568.

Applying the necessary temperature correction, report the value of G which would be
obtained if the test were conducted at 4°C and also at 27°C. The specific gravity values of
water at 4°C and 27°C are respectively 1 and 0.99654.

Weight of dry soil taken, Ws = 0.66 N

Weight of pyknometer + soil + water (W 3 ) = 6.756 N

Weight of pyknometer + Water (W 4 ) = 6.3395 N

Temperature of the Test (T) = 30°C

Specific gravity of water at 30°C (GwT) = 0.99568

By Eq. 3.4,

G =

WG

WWW

sw

s

. T
−−() 34

=

0.66 0.99568

0.66 (6.756 6.3395)

×

−−

= 2.69876 ≈ 2.70

If the test were conducted at 4°C, GwT = 1

∴ G =

W

WWW

s

s

.

()

1

−− 34

= ×

−−

0.66 1

0.66 (6.756 6.3395) = 2.71

If the tests were conducted at 27°C, GwT = 0.99654

∴ G =

W

WWW

s

s

×

−−

=

×

−−

0.99654 0.66 0.99654

() 34 0.66 (6.756 6.3395)

= 2.7011 ≈ 2.70.

Example 3.3: In a specific gravity test in which a density bottle and kerosene were used, the
following observations were made:

Weight of empty density bottle = 0.6025 N

Weight of bottle + clay sample = 0.8160 N

Weight of bottle + clay + kerosene filling the remaining volume = 2.5734 N

Weight of bottle + kerosene = 2.4217 N

Temperature of the test = 27°C