Sieve Analysis
Objective:
To determine the particle size distribution of a soil by mechanical
sieving.
Theory:
Soil consists of an assemblage of discrete particles of various shapes and
sizes.
In this experiment the soil particles are grouped into separate size ranges
and to
determine the relative proportions of dry weight of each size range is
determined.
Two separate procedures that is, sieving and sedimentation are used for
grain size
analysis to span the very wide range of particle sizes. Sieving is used for
gravel and sand
size particles, which can be separated into different size ranges with a
series of sieves of
standard aperture openings. Sieving can not be used for silt and clay size
particles,
wherein sedimentation procedure is used (e.g. hydrometer).
From the grain size distribution curve, particle sizes such as D10, D30,
and D60 can be
obtained. The D10 is called as the effective particle size of the
soil.
Coefficient of Uniformity Cu: This is the indicator of the spread of the
range of the
particle sizes and defined as
Apparatus
1. Set of fine sieves -2 mm, 1 mm, 600Pm, 425Pm, 212Pm, 150Pm and
75Pm
2. Set of coarse sieves -100mm, 80mm, 40mm, 20mm, 10mm and
4.75mm
3. Weighing balance with an accuracy of 0.1 % mass of the
sample
4. Trays, brushes etc
Procedure
(a) Processing of soil
1. Pound the soil with a wooden mallet and mix the pounded soil
properly.
2. Weigh 1000g of soil separately in a tray. This is required for gravel
analysis.
3. Pass the remaining soil through 4.75mm sieve.
4. Keep 5 to 7kg of soil (passing through 4.75mm sieve) in a packet
supplied to you and
keep it in box. This soil will be required for subsequent
experiments.
(b) Gravel distribution
1. Soak 500g of deaired soil (from Step 3. above) in the
tray.
2. Add a pinch of Na2CO3 to aid dispersion and mix the mixture
thoroughly.
3. Keep the mixture for soaking for at least an hour.
4. Wash the mixture on 4.75 mm sieve under the current of water and
collect the
fraction retained on the sieve.
5. Transfer the fraction retained on the sieve to porcelain dish and
keeps it for drying it
in an oven for 24 hours.
6. Pass the dried soil through the set of sieves from 38mm to 4.75mm and
record the
weight of soil retained on each sieve in the record sheet.
7. Calculate the percent soil finer than the various sieve
sizes.
(c) Sand distribution
1. Take 200g of soil (soil sieved from 4.75mm sieve)
2. Soak the sample for an hour in water.
3. Wash the soaked soil sample on 75 Pm sieve.
4. Keep the soil retained on the 75 Pm sieve in oven for 24
hours.
5. Sieve the dried soil through the set of sieves from 2.39mm to 75 Pm
and record the
weight of the soil retained on each sieve in the record sheet.
