Laboratory Procedure for mechanical sieve Analysis
Mechanical in laboratory 1) Dry sieve Analysis 2) Wet sieve analysis
Apparatus required for test –
i) Weighing balance accurate to 1g and 0.1g
ii) Set of I C sieves – 80 mm, 40mm, 20 mm, 10 mm & 4.75 mm for gravels and for sand set of sieves 4.75 mm, 2.36mm, 2mm, 1.7mm, 1.18mm 600µ, 300µ, 150µ, and 75µ size
iii) Thermostatically controlled oven
iv) Water tight trays v) Seive brushes and a wire brush
vi) Mechanical sieve shaker vii) Riffler
a) Dry sieve analysis
i) The soil sample is taken in suitable quantity. The large the particle size the more is the quantity of soil required.
ii) The soil sample is first oven dried and it should be pulverized. It matters; it can be used air dry instead of oven dry.
iii) The sieves are arranged in chronological descending order and sample is sieved through set of sieves. The portion retained on 4.75 mm sieve is called gravel fraction and the portion passed through 4.75 mm and retained on 75 micron sieve is sand fraction.
iv) The weight of the soil portion retained on each sieve and pan is obtained to the nearest 0.1 gm and percentages weight retained is calculated for each sieve size and then % finer or % passing is obtained for each sieve size.
Dry sieve analysis is suitable for cohessionless soils with little or no fine particles
b) Wet sieve analysis
i) If soil contains substantial quantity about more than 5% of fine particles a wet sieve analysis is done. All lumps are broken into individual particles.
ii) A representative sample is taken using riffler and dried in an oven. The dried sample is taken in a tray and soaked in the water.
iii) The slurry is sieved through 4.75 mm sieve. The portion retained on 4.75mm sieve is gravel fraction. The material passing through 4.75 mm sieve is sieved through a 75 micron sieve. The material is washed until the wash water becomes clear.
iii) The material retained on 75µ sieve is collected and dried in an oven. Then it is sieved through the set of sieves. The material retained on each sieve is weighed and analysed