Particle Size Distribution of Soil by Sieve Analysis.

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Determination of Particle Size Distribution by Sieve Analysis;

Object and scope.

The object of this experiment is to determine the particle size distribution of coarse-grained soil by sieving.

The test covers both coarse sieve analysis (for gravel fraction) as well as fine sieve analysis (for the sand fraction).

Material and equipment.

(i) Balances accurate to 1 g and 0.1 g.

(ii) Set of IS sieves: 100 mm, 75 mm. 22 mm, 10 mm, 4.75 mm. 2 mm, 1 mm, 600 microns, 425 microns, 300 microns, 212 microns, 150 microns, and 75-microns sizes.

(iii) Thermostatically controlled oven.

(iv) Two or more large metal or plastic water tight trays.

(v) Sieve brushes and a wire brush.

(vi) Mortar with a rubber covered pestle.

(vii) Mechanical sieve-shaker.

(viii) Riffles.

Test Procedure.

1. Using riffles, take a representative sample of soil received from the field and dry it in the oven.

2. Weigh the required quantity of dried soil, keep it in a tray and soak it with water.

Depending on the maximum size of material present in substantial taken for analysis may be as follows [IS: 2720 (Part-IV)-1985]

3. Puddle the sample thoroughly in water and transfer the slurry to the 4.75 mm sieve which divides the gravel fraction from the sand fraction.

Wash the slurry with a jet of water.

Collect the materials retained on 4.75 mm sieve and the material passing through it in separate containers.

Keep the material retained on 4.75 mm sieve in the oven.

4. Wash the material passing through the 4.75 mm sieve through a 75-microns sieve so that silt and day particles are separated from the sand fraction.

Collect the material passing through 75-micron sieve and the material retained on it in separate containers, and keep them in the oven.

5. Sieve the dried material, retained on 4.75 mm sieve (step 3), through the following set of sieves: 100 mm, 19 mm, 10 mm and 4.75 mm by hand sieving.

While sieving through each sieve, the sieve shall be agitated so that the sample rolls in irregular motion over the sieve.

The material from the sieve may be rubbed, if necessary, with the rubber pestle in the mortar taking care to see those individual soil particles are not broken;

and re-sieved to make sure that only individual particles are retained.

The mass of material retained on each sieve should be recorded.

6. Sieve the dried material, retained on a 75-microns sieve (step 4), through the following set of sieves;

2 mm, 1 mm, 603 microns, 425 microns, 300 microns, 212 microns, 150 microns, and 75-microns size.

The set of sieves should be arranged one above the other and fitted to a mechanical sieve shaker such that the 2 mm sieve is at the top and the 75-microns sieve is at the bottom.

A cover should be placed on the top of the 2 mm sieve, and a receiver should be placed below the 75-microns sieve.

A minimum of 10 minutes sieving should be used.

The soil fraction retained on each sieve should be carefully collected in containers, and the mass of each fraction determined and recorded.

Alternatively, the material retained on 75-microns sieve (step 4), may not be dried;

but should be washed through a nest of sieves specified in step 6, nested in order of their fineness with the finest (75-microns) at the bottom.

Washing should be continued until the water passing through each sieve is substantially clean.

The fraction retained on each sieve should be emptied carefully without loss of material in separate containers and oven-dried.

The oven-dried fraction should be weighed separately, and their mass should be recorded.

7. The material passing 75-microns sieve (step 4) may be used for sedimentation analysis.

Tabulation of observations.

The test observations and results are recorded as illustrated in the following Table.

Calculations.

The percentage of soil retained on each sieve is calculated on the basis of the total mass of soil sample taken,
and from these results, the percent passing through each of the sieves is calculated as illustrated in the following Table.

Data and Observation Sheet for Sieve Analysis.

Sample No. 108

Mass retained on 4.75 mm sieve = 167 gm.

Mass of dry soil sample = 1000 gm.

Mass passing through a 75-microns sieve = 77 gm.

Note 1: Dry Sieve Analysis.

If the soil sample contains little or no fines (passing 75-microns sieve), dry sieve analysis may be carried out.

The gravel fraction and sand fraction are first separated by dry sieving through 4.75 mm sieve.

The material retained on 4.75 mm size is further sieved through the following set of sieves: 100 mm, 75 mm, 19 mm, 10 mm, and 4.75 mm sieves.

The material passing 4.75 mm sieve is sieved through the following set of sieves: 2 mm, 1 mm, 600 microns, 425 microns, 300 microns, 212 microns, 150 microns, and 75-microns sizes.

Note 2:

The permissible maximum mass of sample on the 200 mm diameter sieves should be as follows:

Note 3:

If the soil contains a greater amount of fines (finer than 75-microns size),

the dried soil fraction passing through 4.75 mm sieve (step 6) should be soaked in water containing two grants of sodium hexa-metaphosphate (or one gram of sodium hydroxide and one gram of sodium carbonate) per liter of water.

The soaked specimen should then be washed thoroughly over the nest of sieves specified in step 6.

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