Various Lab Test On Soil
1) Water Content – There are two tests which can be done to determine
the water content of the soil. These are
a) Calcium
Carbide Method
b) Oven
Drying Method
Other tests on soil are :
2) Free
Swell Index Of Soil
3) Plastic
Limit Of Soil
4) Liquid
Limit Of Soil
5) Particle
Size Distribution Of Soil
6) The
Specific Gravity Of Soil
7) The
In-Situ Dry Density Of Soil By Sand Replacement Method
8 ) The
In-Situ Dry Density Of Soil By Core Cutter Method
9) The
Maximum Dry Density And The Optimum Moisture Content Of Soil
1. Water
Content
(a) Calcium
Carbide Method
This test is done to determine the water content in soil by
calcium carbide method as per IS 2720 (Part II) – 1973. It is a method for the rapid determination of water content from the gas pressure developed by the reaction of calcium carbide with the free water of the soil. From the calibrated scale of the pressure gauge, the percentage of water on the total mass of
wet soil is obtained and the same is converted to water content on the dry mass of
soil.
Apparatus required:-
i) Metallic pressure vessel, with a clamp for sealing the
cup, along with a gauge calibrated in percentage water content
ii) Counterpoised balance, for weighing the sample
iii) Scoop, for measuring the absorbent (Calcium Carbide)
iv) Steel balls – 3 steel balls of about 12.5mm dia. and 1 a steel ball of 25mm dia.
v) One bottle of the absorbent (Calcium Carbide)
PREPARATION OF SAMPLE
Sand – No special preparation. Coarse powders may be ground
and pulverized. Cohesive and plastic soil – Soil is tested with the addition of
steel ball in the pressure vessels. The test requires about 6g of the sample.
i) Set up the balance, place the sample in the pan till the mark on the balance
arm matches with the index mark.
ii) Check that the cup and the body are clean.
iii) Hold the body horizontally and gently deposit the
levelled, scoop-full of the absorbent (Calcium Carbide) inside the chamber.
iv) Transfer the weighed soil from the pan to the cup.
v) Hold cup and chamber horizontally, bringing them
together without disturbing the sample and the absorbent.
vi) Clamp the cup tightly into place. If the sample is
bulky, reverse the above placement, that is, put the sample in the chamber and
the absorbent in the cup.
vii) In case of clayey soils, place all the 4 steel balls
(3 smaller and 1 bigger) in the body along with the absorbent.
viii) Shake the unit up and down vigorously in this
position for about 15 seconds.
ix) Hold the unit horizontally, rotating it for 10 seconds,
so that the balls roll around the inner circumference of the body.
x) Rest for 20 seconds.
xi) Repeat the above cycle until the pressure gauge reading
is constant and note the reading. Usually it takes 4 to 8 minutes to achieve
constant reading. This is the water content (m) obtained on wet mass basis.
xii) Finally, release the pressure slowly by opening the
clamp screw and taking the cup out, empty the contents and clean the instrument
with a brush.
REPORTING OF RESULTS
The water content on dry mass basis,
w=m/[100-m] * 100%
Water
Content
b) Oven
Drying Method
This test
is done to determine the water content in soil by oven drying method as per IS:
2720 (Part II) – 1973. The water content (w) of a soil sample is equal to the
mass of water divided by the mass of solids.
Apparatus
required :-
i)
Thermostatically controlled oven maintained at a temperature of 110 ± 5oC
ii)
Weighing balance, with an accuracy of 0.04% of the weight of the soil taken
iii)
Air-tight container made of non-corrodible material with lid
iv) Tongs
PREPARATION
OF SAMPLE
The soil
specimen should be representative of the soil mass. The quantity of the
specimen taken would depend upon the gradation and the maximum size of
particles as under:
Procedure
to determine Water Content In Soil By Oven Drying Method
i) Clean
the container, dry it and weigh it with the lid (Weight ‘W1‘).
ii) Take
the required quantity of the wet soil specimen in the container and weigh it
with the lid (Weight ‘W2‘).
iii)
Place the container, with its lid removed, in the oven till its weight becomes
constant (Normally for 24hrs.).
iv) When
the soil has dried, remove the container from the oven, using tongs.
v) Find
the weight ‘W3‘ of the container with the lid and the dry soil
sample.
REPORTING OF RESULTS
The water
content
w = [W2-W3]
/ [W3 -W1]*100%
An
average of three determinations should be taken. A sample calculation is shown
below
2. Determine
Free Swell Index Of Soil
To
determine the free swell index of soil as per IS: 2720 (Part XL) – 1977. Free
swell or differential free swell, also termed as free swell index, is the
increase in volume of soil without any external constraint when subjected to
submergence in water. The apparatus used :
i) IS
Sieve of size 425µm
ii) Oven
iii)
Balance, with an accuracy of 0.01g
iv)
Graduated glass cylinder- 2 nos., each of 100ml capacity
Procedure to determine Free Swell Index Of Soil
i) Take
two specimens of 10g each of pulverised soil passing through 425µm IS Sieve and
oven-dry.
ii) Pour
each soil specimen into a graduated glass cylinder of 100ml capacity.
iii) Pour
distilled water in one and kerosene oil in the other cylinder upto 100ml mark.
iv)
Remove entrapped air by gently shaking or stirring with a glass rod.
v) Allow
the suspension to attain the state of equilibrium (for not less than 24hours).
vi) Final
volume of soil in each of the cylinder should be read out.
REPORTING OF RESULTS
Free
swell index = [Vd – Vk] / Vk x 100%
where,
Vd =
volume of soil specimen read from the graduated cylinder containing distilled
water.
Vk =
volume of soil specimen read from the graduated cylinder containing kerosene.
Free
Swell
Index
|
Degree
of
expansiveness
|
LL
|
PL
|
SL
|
<20
|
Low
|
0.50
|
0-35%
|
>17%
|
20-35
|
Moderate
|
40-60%
|
25-50%
|
8-18%
|
35-50
|
High
|
50-75%
|
35-65%
|
6-12%
|
>50
|
Very
high
|
>60%
|
>45%
|
<10%
|
We are
thankful to Er Jithesh for submitting the table to us
3. Determine The Plastic Limit Of Soil
This test
is done to determine the plastic limit of soil as per IS: 2720 (Part 5) –
1985.The plastic limit of fine-grained soil is the water content of the soil
below which it ceases to be plastic. It begins to crumble when rolled into
threads of 3mm dia. The apparatus used:
i)
Porcelain evaporating dish about 120mm dia.
ii)
Spatula
iii)
Container to determine moisture content
iv)
Balance, with an accuracy of 0.01g
v) Oven
vi)
Ground glass plate – 20cm x 15cm
vii) Rod
– 3mm dia. and about 10cm long
PREPARATION OF SAMPLE
Take out
30g of air-dried soil from a thoroughly mixed sample of the soil passing
through 425µm IS Sieve. Mix the soil with distilled water in an evaporating
dish and leave the soil mass for naturing. This period may be upto 24hrs.
Procedure
to determine The Plastic Limit Of Soil
i) Take
about 8g of the soil and roll it with fingers on a glass plate. The rate of
rolling should be between 80 to 90 strokes per minute to form a 3mm dia.
ii) If
the dia. of the threads can be reduced to less than 3mm, without any cracks
appearing, it means that the water content is more than its plastic limit.
Knead the soil to reduce the water content and roll it into a thread again.
iii)
Repeat the process of alternate rolling and kneading until the thread crumbles.
iv)
Collect and keep the pieces of crumbled soil thread in the container used to
determine the moisture content.
v) Repeat
the process at least twice more with fresh samples of plastic soil each time.
REPORTING
OF RESULTS
The plastic limit should be determined for at least three portions of the soil
passing through 425µm IS Sieve. The average water content to the nearest whole the number should be reported.
4. Determine
The Liquid Limit Of Soil
This test is done to determine the liquid limit of soil as
per IS: 2720 (Part 5) – 1985. The liquid limit of fine-grained soil is the
water content at which soil behaves practically like a liquid, but has small
shear
strength. It’s flow closes the groove in just 25 blows in
Casagrande’s liquid limit device. The apparatus used :-
i) Casagrande’s liquid limit device
ii) Grooving tools of both standard and ASTM types
iii) Oven
iv) Evaporating dish
v) Spatula
vi) IS Sieve of size 425µm
vii) Weighing balance, with 0.01g accuracy
viii) Wash bottle
ix) Air-tight and non-corrodible container for
determination of moisture content
PREPARATION
OF SAMPLE
i)
Air-dry the soil sample and break the clods. Remove the organic matter like
tree roots, pieces of bark, etc.
ii) About
100g of the specimen passing through 425µm IS Sieve is mixed thoroughly with distilled
water in the evaporating dish and left for 24hrs. for soaking.
Procedure to Determine The Liquid Limit Of Soil
i) Place a portion of the paste in the cup of the liquid
limit device.
ii) Level the mix so as to have a maximum depth of 1cm.
iii) Draw the grooving tool through the sample along the
symmetrical axis of the cup, holding the tool perpendicular to the cup.
iv) For normal fine grained soil: The Casagrande’s tool is
used to cut a groove 2mm wide at the bottom, 11mm wide at the top and 8mm deep.
v) For sandy soil: The ASTM tool is used to cut a groove
2mm wide at the bottom, 13.6mm wide at the top and 10mm deep.
vi) After the soil pat has been cut by a proper grooving
tool, the handle is rotated at the rate of about 2 revolutions per second and
the no. of blows counted, till the two parts of the soil sample come into
contact for about 10mm length.
vii) Take about 10g of soil near the closed groove and
determine its water content
viii) The soil of the cup is transferred to the dish
containing the soil paste and mixed thoroughly after adding a little more
water. Repeat the test.
ix) By altering the water content of the soil and repeating
the foregoing operations, obtain at least 5 readings in the range of 15 to 35
blows. Don’t mix dry soil to change its consistency.
x) Liquid limit is determined by plotting a ‘flow curve’ on
a semi-log graph, with no. of blows as abscissa (log scale) and the water
content as ordinate and drawing the best straight line through the plotted
points.
REPORTING OF RESULTS
Report the water content corresponding to 25 blows, read
from the ‘flow curve’ as the liquid limit.
A sample ‘flow curve’ is given as
5. Determine
Particle Size Distribution Of Soil
This test is done to determine the particle size
distribution of soil as per IS: 2720 (Part 4) – 1985. The appratus required to
do this test :-
i) A set of fine IS Sieves of sizes – 2mm, 600µm, 425µm,
212µm and 75µm
ii) A set of coarse IS Sieves of sizes – 20mm, 10mm and
4.75mm
iii) Weighing balance, with an accuracy of 0.1% of the
weight of sample
iv) Oven
v) Mechanical shaker
vi) Mortar with rubber pestle
vii) Brushes
viii) Trays
PREPARATION OF SAMPLE
i) Soil sample, as received from the field, should be dried
in air or in the sun. In wet weather, the drying apparatus may be used in which
case the temperature of the sample should not exceed 60oC. The clod
may be broken with wooden mallet to hasten drying. Tree roots and pieces of
bark should be removed from the sample.
ii) The big clods may be broken with the help of wooden
mallet. Care should be taken not to break the individual soil particles.
iii) A representative soil sample of required quantity as
given below is taken and dried in the oven at 105 to 120oC.
Procedure to determine Particle Size Distribution Of Soil
i) The dried sample is taken in a tray, soaked in water and
mixed with either 2g of sodium hexametaphosphate or 1g of sodium hydroxide and
1g of sodium carbonate per litre of water, which is added as a dispersive
agent. The soaking of soil is continued for 10 to 12hrs.
ii) The sample is washed through 4.75mm IS Sieve with water
till substantially clean water comes out. Retained sample on 4.75mm IS Sieve
should be oven-dried for 24hrs. This dried sample is sieved through 20mm and
10mm IS Sieves.
iii) The portion passing through 4.75mm IS Sieve should be
oven-dried for 24hrs. This oven-dried material is riffled and about 200g taken.
iv) This sample of about 200g is washed through 75µm IS
Sieve with half litre distilled water, till substantially clear water comes
out.
v) The material retained on 75µm IS Sieve is collected and
dried in oven at a temperature of 105 to 120oC for 24hrs. The dried
soil sample is sieved through 2mm, 600µm, 425µm
and 212µm IS Sieves. Soil retained on each sieve is
weighed.
vi) If the soil passing 75µm is 10% or more, hydrometer
method is used to analyse soil particle size.
HYDROMETER ANALYSIS
i) Particles passed through 75µm IS Sieve along with water
are collected and put into a 1000ml jar for hydrometer analysis. More water, if
required, is added to make the soil water suspension just 1000ml. The
suspension in the jar is vigorously shaken horizontally by keeping the jar
in-between the palms of the two hands. The jar is put on the table.
ii) A graduated hydrometer is carefully inserted into the
suspension with minimum disturbance.
iii) At different time intervals, the density of the
suspension at the centre of gravity of the hydrometer is noted by seeing the
depth of sinking of the stem. The temperature of the suspension is noted for
each recording of the hydrometer reading.
iv) Hydrometer readings are taken at a time interval of 0.5
minute, 1.0 minute, 2.0 minutes, 4.0 minutes, 15.0 minutes, 45.0 minutes, 90.0
minutes, 3hrs., 6hrs., 24hrs. and 48hrs.
v) By using the nomogram given in IS: 2720 (Part 4) – 1985,
the diameter of the particles for different hydrometer readings is found out.
REPORTING OF RESULTS
After completing mechanical analysis and hydrometer
analysis, the results are plotted on a semi-log graph with particle size as
abscissa (log scale) and the percentage smaller than the specified diameter as
ordinate
6. Determine
The Specific Gravity Of Soil
This test is done to determine the specific gravity of
fine-grained soil by density bottle method as per IS: 2720 (Part III/Sec 1) – 1980.
Specific gravity is the ratio of the weight in air of a given volume
of a material at a standard temperature to the weight in
air of an equal volume of distilled water at the same stated temperature.
The apparatus used:
i) Two density bottles of approximately 50ml capacity along
with stoppers
ii) Constant temperature water bath (27.0 + 0.2oC)
iii) Vacuum desiccator
iv) Oven, capable of maintaining a temperature of 105 to
110oC
v) Weighing balance, with an accuracy of 0.001g
vi) Spatula
PREPARATION OF SAMPLE
The soil sample (50g) should if necessary be ground to pass
through a 2mm IS Sieve. A 5 to 10g sub-sample should be obtained by riffling
and oven-dried at a temperature of 105 to 110oC.
Procedure to Determine the Specific Gravity of Fine-Grained
Soil
i) The density bottle along with the stopper, should be
dried at a temperature of 105 to 110oC, cooled in the desiccator and
weighed to the nearest 0.001g (W1).
ii) The sub-sample, which had been oven-dried should be
transferred to the density bottle directly from the desiccator in which it was
cooled. The bottles and contents together with the stopper should be weighed to
the nearest 0.001g (W2).
iii) Cover the soil with air-free distilled water from the
glass wash bottle and leave for a period of 2 to 3hrs. for soaking. Add water
to fill the bottle to about half.
iv) Entrapped air can be removed by heating the density
bottle on a water bath or a sand bath.
v) Keep the bottle without the stopper in a vacuum
desiccator for about 1 to 2hrs. until there is no further loss of air.
vi) Gently stir the soil in the density bottle with a clean
glass rod, carefully wash off the adhering particles from the rod with some
drops of distilled water and see that no more soil particles are lost.
vii) Repeat the process till no more air bubbles are
observed in the soil-water mixture.
viii) Observe the constant temperature in the bottle and
record.
ix) Insert the stopper in the density bottle, wipe and
weigh(W3).
x) Now empty the bottle, clean thoroughly and fill the
density bottle with distilled water at the same temperature. Insert the stopper
in the bottle, wipe dry from the outside and weigh (W4 ).
xi) Take at least two such observations for the same soil.
REPORTING OF RESULTS
The specific gravity G of the soil = (W2 –
W1) / [(W4–1)-(W3-W2)]
The specific gravity should be calculated at a temperature
of 27oC and reported to the nearest 0.01. If the room temperature is
different from 27oC, the following correction should be done:-
G’ = kG
where,
G’ = Corrected specific gravity at 27oC
k = [Relative density of water at room temperature]/
Relative density of water at 27oC.
A sample proforma for the record of the test results is
given below. Relative density of water at various temperatures is taken from
table here. Relative
Density Water
7. Determine
The In-Situ Dry Density Of Soil By Sand Replacement Method
This test is done to determine the in-situ dry density of
soil by sand replacement method as per IS: 2720 (Part XXVIII) – 1974. The
apparatus needed is
i) Sand-pouring cylinder conforming to IS: 2720 (Part
XXVIII) -1974
ii) Cylindrical calibrating container conforming to IS:
2720 (Part XXVIII) – 1974
iii) Soil cutting and excavating tools such as a scraper
tool, bent spoon
iv) Glass plate – 450mm square and 9mm thick or larger
v) Metal containers to collect excavated soil
vi) Metal tray – 300mm square and 40mm deep with a 100mm
hole in the centre
vii) Balance, with an accuracy of 1g
Procedure To Determine The In-Situ Dry Density Of Soil By Sand Replacement Method
A. Calibration of apparatus
a) The method given below should be followed for the
determination of the weight of sand in the cone of the pouring cylinder:
i) The pouring cylinder should be filled so that the level
of the sand in the cylinder is within about 10mm of the top. Its total initial
weight (W1) should be maintained constant throughout the tests for
which the calibration is used. A volume of sand equivalent to that of the
excavated hole in the soil (or equal to that of the calibrating container)
should be allowed to runout of the cylinder under gravity. The shutter of the
pouring cylinder should then be closed and the cylinder placed on a plain
surface, such as a glass plate.
ii) The shutter of the pouring cylinder should be opened
and sand allowed to runout. When no further movement of sand takes place in the
cylinder, the shutter should be closed and the cylinder removed carefully.
iii) The sand that had filled the cone of the pouring
cylinder (that is, the sand that is left on the plain surface) should be
collected and weighed to the nearest gram.
iv) These measurements should be repeated at least thrice
and the mean weight (W2) taken.
b) The method described below should be followed for the
determination of the bulk density of the sand ( Ys ):
i) The internal volume (V) in ml of the calibrating
container should be determined from the weight of water contained in the
container when filled to the brim. The volume may also be calculated from the
measured internal dimensions of the container.
ii) The pouring cylinder should be placed concentrically on
the top of the calibrating container after being filled to the constant weight
(W1). The shutter of the pouring cylinder should be closed during
the operation. The shutter should be opened and sand allowed to runout. When no
further movement of sand takes place in the cylinder, the shutter should be
closed. The pouring cylinder should be removed and weighed to the nearest gram.
iii) These measurements should be repeated at least thrice
and the mean weight (W3) taken.
B. Measurement of soil density
The following method should be followed for the measurement
of soil density:
i) A flat area, approximately 450sq.mm of the soil to be
tested should be exposed and trimmed down to a level surface, preferably with
the aid of the scraper tool.
ii) The metal tray with a central hole should be laid on
the prepared surface of the soil with the hole over the portion of the soil to
be tested. The hole in the soil should then be excavated using the hole in the
tray as a pattern, to the depth of the layer to be tested upto a maximum of
150mm. The excavated soil should be carefully collected, leaving no loose
material in the hole and weighed to the nearest gram(Ww). The metal
tray should be removed before the pouring cylinder is placed in position over
the excavated hole.
iii) The water content (w) of the excavated soil should be
determined as discussed in earlier posts. Alternatively, the whole of the
excavated soil should be dried and weighed (Wd).
iv) The pouring cylinder, filled to the constant weight (W1)
should be so placed that the base of the cylinder covers the hole
concentrically. The shutter should then be opened and sand allowed to runout
into the hole.The pouring cylinder and the surrounding area should not be
vibrated during this period. When no further movement of sand takes place, the
shutter should be closed. The cylinder should be removed and weighed to the
nearest gram (W4).
CALCULATIONS
REPORTING OF RESULTS
The following values should be reported:
i) dry density of soil in kg/m3 to the nearest whole
number; also to be calculated and reported in g/cc correct to the second place
of decimal
ii) water content of the soil in percent reported to two significant
figures.
A sample proforma for the record of the test results is
given below.
8. Determine
The In-Situ Dry Density Of Soil By Core Cutter Method
This test is done to determine the in-situ dry density of
soil by core cutter method as per IS: 2720 (Part XXIX) – 1975.The apparatus
needed for this test is
i) Cylindrical core cutter
ii) Steel dolley
iii) Steel rammer
iv) Balance, with an accuracy of 1g
v) Straightedge
vi) Square metal tray – 300mm x 300mm x 40mm
vii) Trowel
Procedure
Determine The In-Situ Dry Density Of Soil By Core Cutter Method
i) The
internal volume (V) of the core cutter in cc should be calculated from its
dimensions which should be measured to the nearest 0.25mm.
ii) The core cutter should be weighed to the nearest gram
(W1).
iii) A small area, approximately 30cm square of the soil
layer to be tested should be exposed and levelled. The steel dolly should be
placed on top of the cutter and the latter should be rammed down vertically
into the soil layer until only about 15mm of the dolly protrudes above the
surface, care being taken not to rock the cutter. The cutter should then be dug
out of the surrounding soil, care being taken to allow some soil to project
from the lower end of the cutter. The ends of the soil core should then be
trimmed flat in level with the ends of the cutter by means of the straightedge.
iv) The cutter containing the soil core should be weighed
to the nearest gram (W2).
v) The soil core should be removed from the cutter and a
representative sample should be placed in an air-tight container and its water
content (w)
REPORTING OF RESULTS
Bulk density of the soil g cc Y = [W2 –
W1]/ V g/cc
Dry density of the soil g cc Yd = 100Y/[100+w] g/cc
Average of at least three determinations should be reported
to the second place of decimal in g/cc.
A sample proforma for the record of the test results is
given below
9. Determine
The Maximum Dry Density And The Optimum Moisture Content Of Soil
This test is done to determine the maximum dry density and
the optimum moisture content of soil using heavy compaction as per IS: 2720
(Part 8 ) – 1983.The apparatus used is
i) Cylindrical metal mould – it should be either of 100mm
dia. and 1000cc volume or 150mm dia. and 2250cc volume and should conform to
IS: 10074 – 1982.
ii) Balances – one of 10kg capacity, sensitive to 1g and
the other of 200g capacity, sensitive to 0.01g
iii) Oven – thermostatically controlled with an interior of
noncorroding material to maintain temperature between 105 and 110oC
iv) Steel straightedge – 30cm long
v) IS Sieves of sizes – 4.75mm, 19mm and 37.5mm
PREPARATION OF SAMPLE
A representative portion of air-dried soil material, large
enough to provide about 6kg of material passing through a 19mm IS Sieve (for
soils not susceptible to crushing during compaction) or about 15kg of material
passing through a 19mm IS Sieve (for soils susceptible to crushing during
compaction), should be taken. This portion should be sieved through a 19mm IS
Sieve and the coarse fraction rejected after its proportion of the total sample
has been recorded. Aggregations of particles should be broken down so that if
the sample was sieved through a 4.75mm IS Sieve, only separated individual
particles would be retained.
Procedure To Determine The Maximum Dry Density And The
Optimum Moisture Content Of Soil
A) Soil not susceptible to crushing during compaction –
i) A 5kg sample of air-dried soil passing through the 19mm
IS Sieve should be taken. The sample should be mixed thoroughly with a suitable
amount of water depending on the soil type (for sandy and gravelly soil – 3 to
5% and for cohesive soil – 12 to 16% below the plastic limit). The soil sample
should be stored in a sealed container for a minimum period of 16hrs.
ii) The mould of 1000cc capacity with base plate attached,
should be weighed to the nearest 1g (W1 ). The mould should be
placed on a solid base, such as a concrete floor or plinth and the moist soil
should be compacted into the mould, with the extension attached, in five layers
of approximately equal mass, each layer being given 25 blows from the 4.9kg
rammer dropped from a height of 450mm above the soil. The blows should be
distributed uniformly over the surface of each layer. The amount of soil used
should be sufficient to fill the mould, leaving not more than about 6mm to be
struck off when the extension is removed. The extension should be removed and
the compacted soil should be levelled off carefully to the top of the mould by
means of the straight edge. The mould and soil should then be weighed to the
nearest gram (W2).
iii) The compacted soil specimen should be removed from the
mould and placed onto the mixing tray. The water content (w) of a
representative sample of the specimen should be determined.
iv) The remaining soil specimen should be broken up, rubbed
through 19mm IS Sieve and then mixed with the remaining original sample.
Suitable increments of water should be added successively and mixed into the
sample, and the above operations i.e. ii) to iv) should be repeated for each
increment of water added. The total number of determinations made should be at
least five and the moisture contents should be such that the optimum moisture
content at which the maximum dry density occurs,
lies within that range.
B) Soil susceptible to crushing during compaction –
Five or more 2.5kg samples of air-dried soil passing
through the 19mm IS Sieve, should be taken. The samples should each be mixed
thoroughly with different amounts of water and stored in a sealed container as
mentioned in Part A)
C) Compaction in large size mould –
For compacting soil containing coarse material upto 37.5mm
size, the 2250cc mould should be used. A sample weighing about 30kg and passing
through the 37.5mm IS Sieve is used for the test. Soil is compacted in five
layers, each layer being given 55 blows of the 4.9kg rammer. The rest of the
procedure is same as above.
REPORTING OF RESULTS
Bulk density Y(gamma) in g/cc of each compacted specimen
should be
calculated from the equation,
Y(gamma) = (W2-W1)/ V
where, V = volume in cc of the mould.
The dry
density Yd in g/cc
Yd =
100Y/(100+w)
The dry densities, Yd obtained in a series of
determinations should be plotted against the corresponding moisture contents,w.
A smooth curve should be drawn through the resulting points and the position of
the maximum on the curve should be determined. A sample graph is shown below:
The dry density in g/cc corresponding to the maximum point on the moisture content/dry density curve should be reported as the maximum dry density to the nearest 0.01. The percentage moisture content corresponding to the maximum dry density on the moisture content/dry density curve should be reported as the optimum moisture content and quoted to the nearest 0.2 for values below 5 percent, to the nearest 0.5 for values from 5 to 10 percent and to the nearest whole number for values exceeding 10 percent.
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