DETERMINATION OF SPECIFIC GRAVITY

DETERMINATION OF SPECIFIC GRAVITY

OBJECTIVE
Determine the specific gravity of soil fraction passing 4.75 mm I.S sieve by density bottle.

NEED AND SCOPE

The knowledge of specific gravity is needed in calculation of soil properties like void ratio, degree of saturation etc.

 DEFINITION

Specific gravity G is defined as the ratio of the weight of an equal volume of distilled water at that temperature both weights taken in air.

 APPARATUS REQUIRED

1. Pycnometer of 900 ml  .
2. Balance to weigh the materials (accuracy 10gm).
3. Wash bottle with distilled water.
4. Alcohol and ether.

  PROCEDURE

1. Clean and dry the density bottle  

1. wash the bottle with water and allow it to drain.
2. Wash it with alcohol and drain it to remove water.
3.  Wash it with ether, to remove alcohol and drain ether.

2. Weigh the empty bottle with stopper (W₁)

3. Take about 100 to 200 gm of oven soil sample which is cooled in a desiccator. Transfer it to the bottle. Find the weight of the bottle and soil (W₂).

4. Put 100ml of distilled water in the bottle to allow the soil to soak completely. Leave it for about 2 hours.

5. Again fill the bottle completely with distilled water put the stopper and keep the bottle  

    under constant temperature water baths (T_x⁰ ).

6. Take the bottle outside and wipe it clean and dry note. Now determine the weight of the bottle and the contents  (W₃).

7. Now empty the bottle and thoroughly clean it. Fill the bottle with only disttiled water and weigh it. Let it be W₄ at temperature (T_x⁰ C).

8. Repeat the same process for 2 to 3 times, to take the average reading of it.

  OBSERVATIONS 

S. No.	Observation Number	1	2	3
1 2 3 4	Weight of density bottle (W1 g) Weight of density Pycnometer + dry soil (W2 g) Weight Pycnometer + dry soil + water at temperature T x0 C (W3 g) Weight of Pycnometer + water (W4 g) at temperature Tx0 C
	Specific gravity G at  Tx0 C
	Average specific gravity at Tx0 C

CALCULATIONS




INTERPRETATION AND REPORTING

  Unless or otherwise specified specific gravity values reported shall be based on water at 27⁰C. So the specific gravity at 27⁰C = K�Sp. gravity at T_x⁰C.

       The specific gravity of the soil particles lie with in the range of 2.65 to 2.85. Soils containing organic matter and porous particles may have specific gravity values below 2.0. Soils having heavy substances may have values above 3.0.