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.
D30 and D60
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D10 (Effective Size) – The size of
soil when the passing percent is 10.
D30 – The size of soil when the
passing percent is 30.
D60 – The size of soil when the
passing percent is 60.
We can determine
above values from the Particle distribution curve.
the gradation of soil through above values
of Uniformity (Cu) – Coefficient of Uniformity is an indication of
the range of particle sizes of the soil.
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.
of Curvature (Cc) – This is a measure of the shape of curve
between D60 and D10 grain sizes.
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.
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).
from the obtained results gave the fineness modulus as 3.01.
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
fineness modulus of the soil sample is within the required range. Where it
shows that the soil sample is well-graded.
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.
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