Introduction

Sieve analysis is a method used to determine the grain size distribution of a soil by passing it through a series of sieves. This method is applicable for soils that are mostly granular with some or no fines. The particle size analysis for the fines portion is done using the hydrometer analysis method. The data from the sieve analysis are used to characterize the soil and can be used to reject or accept material for specific engineering applications. Sieve analysis does not provide information about the shape of the particles.

Table 1 – Soil quantity as per ASTM D1140

Objective

• Understand the grain size distribution analysis of soils.
  § Classify the coarse-grained portion of the soil
  § Obtain a distribution of the fine-grained portion of a soil.

Apparatus (Refer to Figure 1)
1. Stack of sieves.
2. Mechanical shaker.
3. Balance. The balance has to be sensitive up to 0.1 g. 4. Mortar and a rubber-tipped pestle.

5. Brush.

Procedure

1. Prepare the soil sample. The approximate minimum mass of sample is defined according to the nominal diameter of the largest particles of the soil (refer to Table 1).
2. Take the sample by spooning it randomly. Collect the sample by braking the soil sample into individual particles using a mortar and a rubber-tipped pestle.
3. Determine the mass M of the sample accurately to 0.1 g.
4. Assemble a stack of sieves (Figure 2, a). A sieve with larger openings is placed above a sieve

with smaller openings. Place a pan under the smallest sieve.

1. Place the set of sieves on a mechanical shaker.
2. Pour the soil sample prepared in step 2 into the stack of sieves from the top.
3. Cover the top of the stack of sieves.
4. Run the mechanical shaker for 10 minutes.
5. Stop the mechanical shaker and remove the stack of sieves.
6. Weigh the amount of soil retained on each sieve and in the bottom pan.
7. 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. 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 10 is the mass of the soil that has washed through.

Calculations

1. Calculate the percent of soil retained on the n-th sieve,

(Mass retained, Mn) / (total mass, M [step 3]) × 100 = Rn

1. Calculate the cumulative percent of soil retained on the n-th sieve, ΣRn
2. Calculate the cumulative percent passing through the n-th sieve, Percent finer = 100 – ΣRn
3. If soil retained on the No. 200 sieve is washed, the dry unit weight determined after washing (step 11) should be used to calculate the percent finer than No. 200 sieve. The weight lost due to washing should also be added to the weight of the soil retained on the pan.
4. Make a semi-log plot of percent finer versus log of particle diameter (Figure 2, b).

6. Compute the coefficient of uniformity, Cu, and the coefficient of gradation, Cc. Cu = D60 / D10

Cc = D230 / (D10 × D60)

Where, D60 is the particle size in millimeter corresponding to 60% passing; D30 is the particle size in millimeter corresponding to 30% passing; D10 is the particle size in millimeter corresponding to 10% passing. The values can be obtained using the plot, see Figure 1 for reference.

Note: the mass loss during sieve analysis has to be smaller than 2%.

References

Das, M. “Soil Mechanics Laboratoyr Manual.” 2009 Oxford Press, NY, Seventh edition.