GRAIN SIZE ANALYSIS

(Detailed Procedure given in IS 2720 (Part-IV)

 

 

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/passing.

NEED AND SCOPE OF EXPERIMENT

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.Balance

2.I.S sieves

            3.Rubber pestle and mortar.

            4.mechanical Sieve Shaker

             The grain size analysis is an attempt to determine the relative proportions of different grain sizes which make up a given soil mass.

 

PROCEDURE

    Soil passing 4.75mm I.S. Sieve and retained on 75micron I.S. Sieve contains no fines.

 

1. Take 500gm of the soil sample after taking representative sample by quartering.

2. I.S sieves are selected and arranged in the order as shown in the data sheet.

3. The sieving may be done either by hand or by mechanical sieve shaker for 10 minutes.

4. The weight the material retained on each sieve is recorded.

5. The percentage retained on each sieve is calculated on the basis of the total weight of the soil sample taken.

6. From these results the percentage passing through each of the sieves is calculated.

7. The moisture content of soil if above 5% it is to be measured and recorded.

Note: No particle of soil sample shall be pushed through the sieves.

 

GRAPH

Draw graph between log sieve size vs % finer/passing. The graph is known as grading curve. Corresponding to 10%, 30% and 60% finer, obtain diameters from graph are designated as D_10, D_30, D_60.

 

CALCULATION

1. The percentage of soil retained on each sieve shall be calculated on the basis of total weight of soil sample taken.
2. Cumulative percentage of soil retained on successive sieve is found.

 

 

HYDROMETER ANALYSIS

           

OBJECTIVE

Grain size analysis of soils by hydrometer analysis test. 

SPECIFIC OBJECTIVE

1. To determine the grain size distribution of soil sample containing appreciable amount of fines.

2. To draw a grain size distribution curve.

NEED AND SCOPE OF THE EXPERIMENT

For determining the grain size distribution of soil sample, usually mechanical analysis (sieve analysis) is carried out in which the finer sieve used is 75 micron or the nearer opening. If a soil contains appreciable quantities of fine fractions in (less than 75 micron) wet analysis is done. One form of the analysis is hydrometer analysis. It is very much helpful to classify the soil as per ISI classification. The properties of the soil are very much influenced by the amount of clay and other fractions.

APPARATUS

1. Hydrometer
2. Glass measuring cylinder-Two of 1000 ml capacity with ground glass or rubber stoppers       about 7 cm diameter and 33 cm high marked at 1000 ml volume.
3. Thermometer- To cover the range 0 to 50^o C with an accuracy of   0.5 ^o C .
4. Water bath.
5. Stirring apparatus.
6. I.S sieves apparatus.
7. Balance-accurate to 0.01 gm.
8. Oven-105 to 110.
9. Stop watch.
10. Desiccators
11. Centimeter scale.
12. Porcelain evaporating dish.
13. Wide mouth conical flask or conical beaker of 1000 ml capacity.
14. Thick funnel-about 10 cm in diameter.
15. Filter flask-to take the funnel.
16. Measuring cylinder-100 ml capacity.
17. Wash bottle-containing distilled water.
18. Filter papers.
19. Glass rod-about 15 to 20 cm long and 4 to 5 mm in diameter.
20. Hydrogen peroxide-20 volume solution.
21. Hydrochloric acid N solution-89 ml of concentrated hydrochloric acid.(specific gravity 1.18) diluted with distilled water one litre of solution.
22. Sodium hexametaphosphate solution-dissolve 33 g of sodium hexametaphosphate and 7 gms of sodium carbonate in distilled water to make one litre of solution.

PROCEDURE

1. Take 40gm of the oven dry soil sample after removing soluble salts and organic matter if any.

2. Mix the soil sample with 4% solution of dispersing agent in water (Sodium hexametaphosphate solution) to get a known amount of suspension by volume and stirred well. This suspension should be made 24 hrs before testing.

3. In the measuring cylinder the suspension is turned end to end for even distribution of particles before the time ‘t’ begins to be measured.

4. The hydrometer readings are recorded at regular intervals as indicated in the data sheet.

5. From the data obtained the particle size distribution curve is plotted in the semi-logarithmic graph sheet.

 

Composite Correction for Dispersion Agent and Temperature, (C_t – C_d):

Insert the hydrometer in the comparison cylinder containing dispersant solution in distilled water with the same concentration as used for making the soil suspension. The Composite correction (C_t – C_d) is negative of the hydrometer reading corresponding to the top meniscus.

 

DATA SHEETS: