Exp.3 Sieve Analysis Test

3.
GRAIN SIZE DISTRIBUTION

In order to classify a soil for engineering purposes, we need to know the distribution of the
size of grains in a given soil mass. There are two methods:
1-Sieve analysis: is a method used to determine the grain size distribution of soils. Sieves are
made of woven wires with square openings. Table below gives a partial list of the U.S
standard sieve numbers with their corresponding size of openings. Note that.as the sieve
number increases the size of the openings decreases. For all practical purposes, the No. 200
sieve is the sieve with the smallest opening that should be used for the test.
The method of sieve analysis described here is applicable for soils that are mostly Granular
with some or no fines.
Sieve No. Opening (mm)
4 4.75
8 2.36
10 2.00
16 1.18
30 0.600
40 0.425
50 0.300
100 0.150
200 0.075
2- Hydrometer analysis: is the procedure generally adopted for determination of the particle-
size distribution in a soil for the fraction that is finer than No. 200 sieve size (0.075 mm). The
lower limit of the particle-size determined by this procedure is about 0.001 mm.
SIEVE ANALYSIS:
OBJECTIVE:
a) Select sieves as per I.S specifications and perform sieving.
b) Obtain percentage of soil retained on each sieve.
c) Draw graph between log grain size of soil and % finer.
NEED AND SCOPE OF EXPERIMEN:
The grain size analysis is widely used in classification of soils. The data obtained from grain
size distribution curves is used in the design of filters for earth dams and to determine
suitability of soil for road construction, air field etc. Information obtained from grain size
analysis can be used to predict soil water movement although permeability tests are more
generally used.
Apparatus:
1-A balance sensitive up to 0.1g
2-Set of sieves (The sieves for soil tests: 4.75 mm to 75 microns).
3- Mechanical sieve shaker.

PROCEDURE:
1. Collect a representative oven dry soil sample.
2. Determine the mass of the sample accurately to 0.1 g (W).
3. Make a stack of sieves. A sieve with larger openings is placed above a sieve with smaller
openings. The sieve at the bottom should be No. 200. A bottom pan should be placed
under sieve No. 200. As mentioned before, the sieves that are generally used in a stack are
Nos. 4, 10,20,40,60, 140, and 200; however, more sieves can be placed in between.
4. Pour the soil prepared in Step 2 into the stack of sieves from the top.
5. Place the cover on the top of the stack of sieves.
6. Run the stack of sieves through a sieve shaker for about 10 to 15 minutes.
7. Stop the sieve shaker and remove the stack of sieves.
8. Weigh the amount of soil retained on each sieve and the bottom pan.
9. If a considerable amount of soil with silty and clayey fractions is retained on the No.200
sieve, it has to be washed. Washing is done by taking the No. 200 sieve with the Soil
retained on it and pouring water through the sieve from a tap in the laboratory.
When the water passing through the sieve is clean, stop the flow of water. Transfer the soil
retained on the sieve at the end of washing to a porcelain evaporating dish by back washing. Put
it in the oven to dry to a constant weight. (Note: This step is not necessary
If the amount of soil retained on the No. 200 sieve is small.) Determine the mass of the dry soil
retained on. No. 200 sieve. The difference between this mass and that retained on No. 200 sieve
determined in Step 9 is the mass of soil that has washed through.
OBSERVATIONS AND RECORDING:
Weight of soil sample, W=
Sieve opening Weight of empty Weight of sieve + Weight of soil

(mm) sieve retained soil retained on each
(g) (g) sieve
(g)
CALCULATION:
1- Calculate the percent of soil retained on the n th sieve ( counting from the top)
2- Calculate the cumulative percent of soil retained on the nth sieve
3- Calculate the cumulative percent passing through the nth sieve

Sieve opening Weight retained Percent Cumulative Percent
(mm) on each sieve (g) weight on percent finer
each sieve retained
Sample of calculation:
GRAPH:
Draw graph between log sieve size vs % finer. The graph is known as grading curve. Corresponding
to 10%, 30% and 60% finer, obtain diameters from graph are designated as D10, D30, D60.
100 10 1 0.1 0.01 0.001 0.0001

Other Calculations:
Determine D 10, D 30, and D60 (from graph) which are, respectively, the diameters corresponding to
percent's finer of 10%, 30%, and 60%.
Calculate the uniformity coefficient (Cu) and the coefficient of gradation (Cc) using this equation:
General Comments
The diameter, D10 is generally referred to as effective size. The effective size is used for several
empirical correlations, such as coefficient of permeability. The uniformity coefficient, Cu, is a
parameter which indicates the range of distribution of grain sizes in a given soil specimen. If Cu is
relatively large, it indicates a well graded soil. If Cu is nearly equal to one, it means that the soil
grains are of approximately equal size, and the soil may be referred to as a poorly graded soil.
Figure below shows the general nature of the grain-size distribution curves for a well graded and a
poorly graded soil. In some instances, a soil may have a combination of two or more uniformly
graded fractions, and this soil is referred to as gap graded. The grain-size distribution curve for a gap
graded soil is also shown in Fig. below.
The parameter Cc is also referred to as the coefficient of curvature. For sand, if Cu is greater than 6
and Cc is between I and 3, it is considered well graded. However, for a gravel to be well-graded Cu
should be greater than 4 and Cc must be between I and 3.
Classify the soil to poorly or gap graded
Discuss your result.

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3.

GRAIN SIZE DISTRIBUTION

NEED AND SCOPE OF EXPERIMEN:

2-Set of sieves (The sieves for soil tests: 4.75 mm to 75 microns).

3- Mechanical sieve shaker.

Weight of soil sample, W=

Sieve opening Weight of empty Weight of sieve + Weight of soil

2- Calculate the cumulative percent of soil retained on the nth sieve

3- Calculate the cumulative percent passing through the nth sieve

100 10 1 0.1 0.01 0.001 0.0001

Classify the soil to poorly or gap graded

Discuss your result.

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