The percentage of various size of particles in a dry soil sample is determined by particle size analysis or mechanical analysis.The mechanical analysis is carried out in two stage:

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1)Sieve analysis

2)Sedimentation analysis or wet mechanical analysis

Sieve analysis is carried out for coarse grained soil only,While sedimentation analysis is carried out for fine grained soils.

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**Sieve Analysis:- **

Sieve analysis is carried out by using a set of stander sieves are designated by the size of the mesh in mm.

Sieving is performed by arranging the various sieves one over the other in the order of their
mesh openings. The largest opening sieve is kept the top and the smallest opening sieve is kept the bottom. A
receiver is kept at
the bottom and a cover is kept at the top of the whole assembly.

The soil
sample is put on the top sieve. Then shaking is given to the whole assembly for at
least 10 minutes with the help of a shaking machine or
by hand The portion of the soil sample retained on each sieve is weighed. The
percentage of soil retained on each sieve is
calculated. From these results, percentage passing through each sieve is
calculated.

The results may be plotted on a semi-log graph paper with the
percentage finer on the arithmetic scale and particle diameter on the log scale. A
smooth curve can be drawn through them. This curve can indicate the type of soil.

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**Sedimentation analysis or wet
mechanical
analysis:-**

Wet mechanical analysis is used for analysis of soil finer
than 75 micron in size. The analysis is based on Stoke's
law. The sedimentation analysis can be done either by a hydrometer or by a pipette. Both the methods are based on the
following assumption

a) The particles are perfect sphere.

b) The liquid through
which the particles fall must be of indefinite extent .

c) The particle reaches
constant terminal velocity within a few seconds and is maintained indefinitely.

Pipette Method

Pipette Method

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