Soil Classification and Atterbergs Limits - Lab Notes

This article contains lab notes on Soil Classification and Atterbergs Limits for Construction Technology 1 (Civil) course at Western Sydney University. It covers topics such as particle size, grading curve, plasticity index, shrinkage limit tests and more. The article also includes tables, graphs and figures to help understand the concepts better.

Soil Classification. 1
300720 CONSTRUCTION TECHNOLOGY 1 (Civil)
LAB 1 Notes Autumn 2017.
WESTERN SYDNEY UNIVERSITY
SCHOOL OF COMPUTING, ENGINEERING & MATHEMATICS.

Soil Classification. 2
Experiment 1:
1. Hand in your completed results and plot the results on the Grading Curve as found on page 5 of
the Soil Assignment 1.
Part A: Results.
Table 1 Calculation of Percentages Passing.
Size of Sieve
(microns)
Sieve + Sample
(g)
Mass of Sieve (g) Mass of Sample
(g)
% Passing
2.36 mm 476.18 474.55 1.63 99.37
1.18 mm 418.31 391.85 26.46 89.08
600 microns 381.59 347.49 34.1 75.81
425 microns 358.61 336.89 21.72 67.37
300 microns 400.28 317.69 82.59 35.24
150 microns 375.46 302.38 73.08 6.82
75 microns 306.34 294.60 11.74 2.26
Passing 256.66 250.86 5.8 0
TOTAL 257.12
Predominant Particle Size, if found, as calculated above (Pg. 3), to be recorded here:-
34.1 g of 257.12g sample is retained by the 300 micron sieve, the sample is mainly silt and clay i.e.
greater than 20% of the sample retained in one pan.
% (300 micron sieve) = 82.59/257.12 x 100 = 32.12%

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N.B. Silt and clay ranges from 0.002 mm to 0.06 mm in dia.
Figure 2 Grading Curve.
Graph showing percentage passing

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Graph showing percentage retained
1. Is there a predominant soil fraction?
Silt and clay is the predominant soil fraction in the soil sample. 34.1 g of 257.12g sample is retained by
the 300 micron sieve, the sample is mainly silt and clay i.e. greater than 20% of the sample retained in
one pan.
% (300 micron sieve) = 82.59/257.12 x 100 = 32.12%
N.B. Silt and clay ranges from 0.002 mm to 0.06 mm in dia.

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2. How will the particle size affect the properties of the soil examined? If so, in what way?
The soil particles in the examined soil will affect water drainage of the soil. Water drainage of
the soil is structured by soil smoothness or roughness and organic matter. Silt and clay contain greater
surface area than those with bigger sand particles, and a large surface area permits a soil to grasp more
water. Furthermore, a soil with a high proportion of silt and clay constituents, which describes fine
soil, has a greater water-holding ability.
3. Comment on the shape of the grading curve plotted.
The shape of the curves shows that the soil examined is a fine grained soil. The steep curve
indicates that the soil has a narrow range of particle sizes and hence poorly graded soils.
4. Would this soil sample be able to be well compacted?
The soil can be compacted very well because of the small particle sizes that are densely distributed.
5. Could this soil be used as a backfill behind a retaining wall i.e. water can easily drain through
this sample?
The soil cannot be used as a backfill behind a retaining wall since it has poor characteristics of
water drainage. Silt and clay contain greater surface area than those with bigger sand particles, and a
large surface area permits a soil to grasp more water.

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Part B Atterbergs Limits.
Part B: Results.
Table 3 Plasticity Calculations.
Test Mass of
Crucible (g)
Wet Mass +
crucible (g)
Dry mass +
crucible (g)
Moisture
Content %
Liquid Limit 23.63 51.46 41.56 55.21
Plastic Limit 27.47 47.96 41.24 48.80
Plasticity Index 6.41
Plasticity Index calculated and recorded here:-
W L . L. = M 2 − M 3
M 3 − M1
× 100
(9.9/17.93)*100=55.21%
(6.72/13.77)*100=48.80%
P. I . = W L . L . − W P . L .
P.I=55.21- 48.80%

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Figure 5 Casagrande’s plasticity chart.
Soil type determined from Fig 5, noted below:-
From the above plot (55, 6.4), the soil sample is an inorganic silts of high compressibility and
organic clays.
Table 4 Moisture calculations for Shrinkage Limit.
Test Mass of Trough
(g)
Wet mass +
trough (g)
Dry mass +
trough (g)
Moisture Content
%
Sample 1 209.72 302.4 295.58 7.94
Sample 2 205.74 299.29 289.63 11.52

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Sample 3 206.76 337.81 313.02 23.33
W P . L. = M 8 − M 9
M 9 − M 7
× 100
Sample 1
(6.82/85.86)*100=7.94%
Sample 2
(9.66/83.89)*100=11.52%
Sample 3
(24.79/106.26)*100=23.33%
Table 5 Shrinkage calculations for Shrinkage Limit.
Test Length of Trough (mm) Shrinkage of Sample
(mm)
% Shrinkage
Sample 1 250 0 0
Sample 2 250 1.2 0.48
Sample 3 250 10.6 4.24
S L. = LS X 100
L
Where: L is the length of the mould in millimetres
LS is the mean longitudinal shrinkage in millimetres
Sample 1
(0/250)*100=0%
Sample 2
(1.2/250)*100=0.48%

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Sample 3
(10.6/250)*100=0.48%
Figure 6 Graph of soil shrinkage.
1. What is the significance of the Plasticity Index? ((More explanation than just stating the
difference between the LL & PL!!!))
It is the amount of unified abilities of the binder brought about by the clay content.
Moreover, it provides some suggestion of the extent of bulging and contraction that will occur in
the dampening and desiccating of the soil sample tested. If soils lack adequate
mechanical interconnect they necessitate quantities of cohesive constituents to provide an
adequate performance. Insufficiency of clay binder may lead to ravelling of gravel wearisome
layers in the course of dry weather and extreme perviousness.

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2. Comment on the reactivity of the soil in relation to Figure 5, Casagrande’s Plasticity Chart. Is the
soil likely to provide a stable foundation material?
The soil is moderately reactive and can experience moderate ground movement due to
moisture changes. The soil tested cannot provide a stable foundation since it comprises of
moderately reactive silts and organic.
3. In relation to the Shrinkage Limit Tests, what remedial action (building or civil works)
could be introduced to minimise ground movement under a building?
a) Excavation done upto depth bigger than the depth of footing by almost 20-30 cm.
b) Free drainage solid such as a combination of sand & gravel is filled & compacted upto the
bottom level of foundation.
c) R.C.C footing is built at a level, over which the brick barricade may be elevated.
d) A R.C.C smock with light strengthening and of approximately 2m girth is done all along the
structure to avert the dampness from openly entering the footing.
e) The beanbag of granular soil under the footing will engross the influence of bulging, thereby
decreasing its harmful impacts on R.C.C footing.
f) Arrange for slotted footing so that this may decrease the swelling pressure.
g) Construction should be carried out during the dry spell when soil shrinks to its verge level

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