Aquaculture Engineering

Practical - 12
Experiment No 1 - Distribution of grain size in coarse grained soil

Aim
To find out the grain size distribution of coarse grained soil by sieving.

Apparatus
IS sieves, Pans, Vibrating machine, Weighing machine, Weights etc.

Procedure

• Collect some quantity of soil sample received from the field and dry it in the oven.
• Take 5 kg oven dried soil sample, keep it in a tray and soak it with water.
• Puddle the sample thoroughly in water and transfer the slurry to a 4.75 mm sieve which separates the sample into gravel and sand fractions. Collect the materials in separate containers.
• Sieve the dried sample retained in 4.75 mm sieve through 63 mm 20mm, 10mm and 4.75 mm by hand sieving. The mass of the material retained on each sieve should be recorded.
• Wash the material passed through 4.75 mm sieve through a 75 micron sieve to separate the silt and clay particles from the sand fraction. Collect the material retained on 75 micron sieve in container and keep it in the oven.
• The dried material retained on 75 micron sieve is carefully placed on top of the sieve pan of 2 mm size followed by 1mm, 600, 425, 300, 212, 150 and 75 micron size respectively.
• After pouring the soil into the top most sieve it is closed tightly by a lid and the whole set of sieve is kept in a vibrating machine. It is allowed to vibrate for 10-15 minutes.
• The weight of soil retained in each pan is found out by weighing.
• Cummulative weight of soil retained, its percentage weight and the percentage of finer is calculated.
• The material passing through 75 micron sieve may be used for sedimentation analysis.
• A graph is plotted on a semi-logarithms graph sheet taking sieve size or particle size as abscissa percentage finers as the ordinate.

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