Qassim University

College of Engineering

Civil Engineering Department

CE 354

Geotechnical Engineering Lab

Dr. Sherif M. ElKholy

Particle Size Analysis of Soil

(Sieve Analysis Method)

Particle Size Analysis of Soil (Sieve Analysis Method)

Importance of the test:

Particle-size is one of the design criteria of soils used for

road projects, runways, dams, earth embankments,etc.

Information obtained from particle-size analysis can be

used to predict soil-water movement.

The test results may be used in designing filters that are

used in Earth Embankments works.

What is Particle-size Analysis?

The particle-size analysis is an attempt to determine the relative properties of the different grain sizes that make up the soil sample (Soil Particles gradation).

It is not possible to determine the individual particle sizes, however the test can only determine the approximate size range between two sieves.

The particle-size analysis does not provide any information on the shape of the particles, whether they are rounded or angular.

Particle Size Analysis of Soil (Sieve Analysis Method)

Important Features:

All Soil classification systems uses the No. 200 sieve as the

dividing point between Cohessive Soil (Silt & Clay) and

Cohessionless Soil (Sand & Gravel).

For soil particles smaller than No. 200 sieve, the

Hydrometer Test is used to determine the gradation of

the soil particles.

Particle Size Analysis of Soil (Sieve Analysis Method)

Important Features:

No. 4 sieve (and sometimes No. 10 sieve) is the division point between Sand & Gravel soil.

Oven-dry soil samples are commonly used for this test in order to start from a known soil mass. Using air-dry soil samples cause some errors in calculations.

Particle Size Analysis of Soil (Sieve Analysis Method)

Test Objectives:

To make a mechanical particle-size analysis of a

cohessionless soil sample.

To learn how to present the resulting data and to determine

the classification of such a soil sample.

Particle Size Analysis of Soil (Sieve Analysis Method)

Test Equipment:

A Set of Standard Sieves.

Mortar and Pestle or a

Mechanical Pulverizer (Crusher).

Balance Sensitive to 0.1 g.

Supply of Thoroughly Oven-Dried

(Or Air-Dried) Soil Sample.

Particle Size Analysis of Soil (Sieve Analysis Method)

Standard Sieve Sizes Sieve

No.

Opening

(mm)

Sieve

No.

Opening

(mm)

4 4.75 35 0.500

5 4.00 40 0.425

6 3.35 45 0.355

7 2.80 50 0.300

8 2.36 60 0.250

10 2.00 70 0.212

12 1.70 80 0.180

14 1.40 100 0.150

16 1.18 120 0.125

18 1.00 140 0.106

20 0.85 200 0.075

25 0.71 270 0.053

30 0.60 400 0.038

Standard Sieve Sizes

All US sieves are available in two diameter sizes, 200 mm and 305 mm.

The US sieve sizes starts from 100 mm opening down to 0.083 mm opening.

Starting from No. 4 sieve (4.75 mm opening) up to No. 18 sieve (1.0 mm opening), the sieve opening is reported in mm.

From No. 20 sieve to No. 400, the mesh opening is in micrometers (1 m = 0.001 mm).

Standard Sieve Sizes

From No. 20 sieve to No. 400, the mesh opening is in micrometers (1 m = 0.001 mm).

The No. 200 sieve has an opening of 850 m or 0.850 mm.

Starting from No. 4 sieve and smaller, the size opening is reported in numbers such as Sieve No. 4, sieve No. 5, and sieve No. 200etc.

Common Sieve Sizes

Data Obtained from Sieve Analysis

The results are plotted on a Semilog curve for the particle sizes to give both small an large diameters as nearly equal weight as possible.

Particle-size Distribution Curve

Data Obtained from Sieve Analysis

From the particle-size distribution curve, grain sizes D10, D30, and D60 are obtained.

The D refers to the size or apparent diameter of the soil particles while the subscript (10, 30, 60) denotes the percent that is smaller than that diameter, e.g. D10 = 0.16 mm means that 10% of the sample grains have diameter smaller than 0.16 mm.

Data Obtained from Sieve Analysis

Effective Size: The size D10 of the soil.

Coefficient of Uniformity, Cu: defined as an indication of the spread (range) of particle sizes.

Cu = (D60 / D10)

A large value of Cu indicates that the D10 and D60 sizes

differ appreciably.

Data Obtained from Sieve Analysis

Coefficient of Curvature, Cc: defined as a Measure of the shape of the curve between D60 and D10 grain sizes.

Cc = D2

30 / (D10 D60)

A value of Cc greatly different from 1.0 indicates particle sizes missing between D60 and D10 sizes differ appreciably.

The sizes D15 and D85 may be used in determining the suitability of the soil used for filter design in Earth Structures such as dams and embankments.

GENERAL PROCCEDURE

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.

NB: This step is not necessary if the amount of soil retained on the

No. 200 sieve is too small.

Determine the mass of the dry soil retained on the No. 200

sieve. The difference between this mass and that retained on

the No. 200 sieve determined in step 9 is the mass of soil that

has washed through.

GENERAL PROCCEDURE

1. Collect a representative oven dry sample. Samples having

largest particles of the size of No.4 sieve openings (4.75 mm)

should be about 500 grams. For soils having largest particles of

size greater than 4.75 mm, larger weights are needed.

GENERAL PROCCEDURE

2. Break the soil sample into individual particles using a mortar

and a rubber-tipped pestle. (The idea is to break up the soil

into individual particles, not to break the particles

themselves.).

3. Determine the mass of the sample accurately to 0.1 g (W).

4. Prepare 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.

GENERAL PROCCEDURE

5. Pour the soil prepared in Step 2 into the stack of sieves from

the top.

6. Place the cover on the top of the stack of sieves.

7. Run the stack of sieves through a sieve shaker for about 10 to

15 minutes.

GENERAL PROCCEDURE

8. Stop the sieve shaker and remove the stack of sieves.

GENERAL PROCCEDURE 9. Weigh the amount of soil retained on each sieve and the

bottom pan.

10. 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.

CALCULATION

SAMPLE CALCULATION

SAMPLE CALCULATION

Alternative Method:

SAMPLE CALCULATION

CONCLUSIONS

The conclusion should answer the following questions:

1. Of what significance is the sieve analysis to a geotechnical

engineer?

2. How much soil mass was lost in the analysis? What are some

possible sources for error?

3. What do D10, D85, D60 signify?

4. What do the coefficient of uniformity, Cu, and the coefficient

of concavity, Cc indicate about the test soil?

But What are Filters? And What do they do??

Very fine soil particles are easily carried in suspension by percolating soil water in drainage systems unless they are protected using properly designed filters which depends on the results of particle-size analysis.

Particle-size of this filters material must be larger than the protected soil particles in order to allow for water seeping through while trapping (catching) the finer soil particles.

Particle Size Analysis of Soil (Sieve Analysis Method)