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Experiment No. 5 : To determine the grain size distributionby sieving.

Object:The object of the test is to determine the grain size distribution of coarse grained soil by

sieving.

Theory:The representative soil sample is separated into two fractions by sieving through

4.75 mm IS sieve. The fraction retained on the sieve is called the gravel fraction which is

subjected to coarse sieve analysis. For coarse sieve analysis, the fraction is sieved through

a set of IS sieves of size 100 mm, 80 mm, 40 mm, 20 mm, 10 mm and 4.75 mm. The

material passing 4.75 mm sieve is subjected to fine sieve analysis and is sieved through aset of IS sieves of size 2 mm, 1mm, 600 , 425 , 300 , 212 , 150 and 75 .

Mass of material retained on each sieve is determined. Then the percentage of material

retained on any sieve is given by

where, Mn = mass of soil retained on sieve n

M = total mass of soil taken for analysis.

The cumulative percentage of material retained,

where, p, p2, are % retained on sieves , 2, which are

coarser than sieve n

Finally, percentage finer than sieve n is

However, we shall conduct Fine sieve analysis only using sand sample.

Equipment :1. Set of fine sieves of size 2mm, 1 mm, 600, 425, 300, 212, 150 and 75 with

pan and cover,

2. Weighing balance of accuracy 0.1 g,3. Sieve shaking machine.

Procedure:1. Take 500 g of dry representative soil.2. Arrange the sieves one over the other in the order of their mesh openings the

largest aperture sieve kept at the top and the smallest aperture sieve at the

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bottom. A receiving pan is kept at the bottom. The soil sample is put on the top

sieve and the sieve is closed with a cover or lid.

3. The whole assembly with soil sample, cover and pan is then fitted on a sieveshaking machine and the machine is operated for atleast 10 minutes.

4. The portion of soil sample retained on each sieve is weighed.5.

The percentage of soil retained on each sieve is calculated on the basis of totalmass of soil sample taken and from these results, percentage passing through each

sieve is calculated.

6. The results of sieve analysis are plotted on a semi-log graph sheet to get a grain-size distribution curve with the percentage finer N as the ordinate and the

particle diameter as the abscissa.

7. From the grain-size distribution cuve, find out nature of the soil sample i.e.,whether it is well graded or poorly graded soil. Also calculate uniformity

coefficient Cu and coefficient of curvature Cc.

Data and observation sheetMass of dry soil taken for analysis : 500 g

Sl.

No. ISSieve Particle sizeD (mm) Mass retained(g) %retained Cumulative% retained % finer(N)1. 2 mm 2mm

2. 1 mm 1 mm

3. 600 0.600 mm

4. 425 0.425 mm

5. 300 0.300 mm6. 212 0.212 mm

7. 150 0.150 mm

8. 75 0.075 mm

9. Pan

Result:Soil is well / poorly graded.

Uniformity coefficient Cu =Coefficient of curvature Cc =