Sieve analysis

test is conducted to determine the grading or the particle size distribution of

a given aggregate. Through the test procedures and the obtain results we can

construct the particle distribution curve. Where it gives us important

parameters which can be used to determine the grading of the soil.

D10,

D30 and D60

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Ø

D10 (Effective Size) – The size of

soil when the passing percent is 10.

D10

= 0.126mm

Ø

D30 – The size of soil when the

passing percent is 30.

D30

= 0.591mm

Ø

D60 – The size of soil when the

passing percent is 60.

D60

= 1.366mm

We can determine

above values from the Particle distribution curve.

Determining

the gradation of soil through above values

1. Coefficient

of Uniformity (Cu) – Coefficient of Uniformity is an indication of

the range of particle sizes of the soil.

From the

calculation we find out the Cu value as 10.818.

Cu > 5

indicates a well-graded soil, i.e. a soil which has a distribution of particles

over a wide size range. (Nptel.ac.in, 2018). Therefore, we can determine this

soil sample is well-graded. And also it has a wide size range.

2. Coefficient

of Curvature (Cc) – This is a measure of the shape of curve

between D60 and D10 grain sizes.

Cc is

another parameter to determine the soil gradation. From the calculation we

found that the Cc value for the tested soil sample is 2.026.

Cc between 1 and

3 also indicates a well-graded soil. (Nptel.ac.in, 2018). Therefore, with that

reference it proves that the soil sample is well-graded.

3. Fineness

modulus – Fineness modulus of (fine aggregate) is an index number which

represents the mean size of the particles in sand. The cumulative percentage

retained on each sieve is added and subtracted by 100 gives the value of fine

aggregate. (The Constructor, 2018).

The calculations

from the obtained results gave the fineness modulus as 3.01.

Fineness modulus

of fine aggregate varies from 2.0 to 3.5. Fine aggregate having fineness

modulus more than 3.2 should not considered as fine aggregate. (The

Constructor, 2018).

Therefore, the

fineness modulus of the soil sample is within the required range. Where it

shows that the soil sample is well-graded.

Determining

the soil gradation by the shape of the PSD curve

As stated above, we can also

determine the soil grading by the shape of the particle distribution curve constructed

through the obtained results.

By comparing the

PSD curve of the test (figure 1) and curves shown in figure 2, we can see that

curve II is similar to the PSD curve of the test. Which proves that the soil

sample is well-graded through the shape of the curves.

As

it mentioned in the procedure, 500g of soil sample was used to conduct the

test. But in the results table, the summation of the soil retained in each

sieve is 497g. It is due to wastage of some sand particle through the process

of the test. And also sieve no. 200 was damaged when the practical was

conducted. That could also be a major influence for the loss of mass of the

soil sample.