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GEOTECHNICAL ENGINEERING
LAB MANUAL
DEPARTMENT OF CIVIL ENGINEERING
NAME: ………………………………………………….
ROLL No: ……..…....................................
YEAR: ……………….………………………….………
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CONTENTS
SL NO EXPERIMENT PAGE NO
1 SPECIFIC GRAVITY OF THE SOIL USING PYCNOMETER 9
2 GRAIN SIZE DISTRIBUTION OF THE SOILS BY SIEVE
ANALYSIS 13
3 ATTERBERG LIMITS AND INDICES 19
5
DETERMINATION OF COEFFICIENT OF PERMEABILITY OF
THE SOIL BY
A) CONSTANT HEAD METHOD
B) FALLING HEAD METHOD
29
6
DETERMINATION OF FIELD DENSITY OF SOILS BY
A) CORE CUTTER METHOD
B) SAND REPLACEMENT METHOD
37
7 COMPACTION TEST 47
8 UNCONFINED COMPRESSIVE STRENGTH OF SOIL 53
9 DIRECT SHEAR TEST 59
10 TRIAXIAL SHEAR TEST 65
11 IMPACT TEST 73
12 LOS ANGELES ABRASION TEST 79
13 SHAPE TEST( Flakiness Index) 83
14 SHAPE TEST( Elongation Index) 87
15 PENETRATION TEST 91
16 SPECIFIC GRAVITY TEST FOR BITUMEN 95
17 SOFTENING POINT OF BITUMEN 99
18 DUCTILITY TEST 103
19 CALIFORNIA BEARING TEST 107
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SL.NO NAME OF EXPERIMENT RESULT
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SL.
NO. EXPERIMENTS PAGE NO DATE MARK SIGN
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DETERMINATION OF SPECIFIC GRAVITY OF SOIL
AIM
To determine the specific gravity of soil fraction passing 4.75 mm I.S sieve by Pycnometer.
NEED AND SCOPE
The knowledge of specific gravity is needed in calculation of soil properties like void ratio,
degree of saturation etc.
DEFINITION
Specific gravity G is defined as the ratio of the weight of an equal volume of distilled water at
that temperature both weights taken in air.
APPARATUS
1. Pycnometer
2. Balance to weigh the materials (accuracy 10gm).
3. Wash bottle with distilled water.
4. Alcohol and ether.
PROCEDURE
1. Clean and dry the pycnometer
a. Wash the pycnometer with water and allow it to drain.
b. Wash it with alcohol and drain it to remove water.
c. Wash it with ether, to remove alcohol and drain ether.
2. Weigh the pycnometer (W1)
3. Take about 200 gm of oven-dried soil sample which is cooled in a desiccator. Transfer it to
the pycnometer. Find the weight of the pycnometer and soil (W2).
4. Put 10ml of distilled water in the pycnometer to allow the soil to soak completely. Leave it
for about 2 hours.
5. Again fill the pycnometer completely with distilled water put the stopper and keep the
pycnometer under constant temperature water baths (Tx0).
6. Take the pycnometer outside and wipe it clean and dry it. Now determine the weight of the
pycnometer and the contents (W3).
7. Now empty the pycnometer and thoroughly clean it. Fill the pycnometer with only distilled
water and weigh it. Let it be W4 at temperature (Tx0 C).
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OBSERVATIONS
S. No. Observation Number 1 2 3
1 Weight of pycnometer (W1 g)
2 Weight of pycnometer + dry soil
(W2 g)
3 Weight of pycnometer + dry soil + water
at temperature T x 0
C (W3 g)
4 Weight of pycnometer + water at temperature
Tx 0 C (W4 g)
5 Specific gravity G at Tx0 C
Average specific gravity at Tx 0 C
CALCULATIONS
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8. Repeat the same process for 2 to 3 times, to take the average reading of it.
RESULT
Specific Gravity of given soil =
INFERENCE
QUESTIONS
1. If entrapped air is not removed completely, how will it affect the value of specific
gravity of solids?
2. Specify the range over which the average specific gravity of soil solids will lie.
3. How is specific gravity of solids for fine grained soil (Clay) found in laboratory?
4. Mention the practical application of specific gravity of soil solids.
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GRAIN SIZE DISTRIBUTION OF SOIL BY SIEVE ANALYSIS
AIM
To determine the percentage of various size particles in a soil sample, and to classify the soil.
APPARATUS
i. 1st set of sieves of size 300 mm, 80 mm, 40 mm, 20 mm, 10 mm, and 4.75 mm.
ii. 2nd set of sieves of sizes 2mm, 850 micron, 425 micron, 150 micron, and 75 micron.
iii. Balances of 0.1 g sensitivity, along with weights and weight box.
iv. Brush.
THEORY
Soils having particle larger than 0.075mm size are termed as coarse grained soils. In these soils
more than 50% of the total material by mass is larger 75 micron. Coarse grained soil may have
boulder, cobble, gravel and sand.
The following particle classification names are given depending on the size of the particle:
i. BOULDER: particle size is more than 300mm.
ii. COBBLE: particle size in range 80mm to 300mm.
iii. GRAVEL (G): particle size in range 4.75mm to 80mm.
a. Coarse Gravel: 20 to 80mm.
b. Fine Gravel: 4.75mm to 20mm.
iv. SAND (S): particle size in range 0.075mm to 4.75mm.
a. Coarse sand: 2.0mm to 4.75mm.
b. Medium Sand: 0.425mm to 2.0mm.
c. Fine Sand: 0.075mm to o.425mm.
Dry sieve is performed for cohesion less soils if fines are less than 5%. Wet sieve analysis is
carried out if fines are more than 5% and of cohesive nature.
In simpler way the particle size distribution curve for coarse grain soil as follows,
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Gravels and sands may be either poorly graded (Uniformly graded) or well graded depending
on the value of coefficient of curvature and uniformity coefficient.
Coefficient of curvature (Cc) may be estimated as:
Coefficient of curvature (Cc) should lie between 1 and 3 for well grade gravel and sand.
Uniformity coefficient (Cu) is given by:
Its value should be more than 4 for well graded gravel and more than 6 for well graded sand.
Were, D60 = particle size at 60% finer.
D30 = particle size at 30% finer.
D10 = particle size at 10% finer.
PROCEDURE:
i. Weight accurately about 200gms of oven dried soil sample. If the soil has a large fraction
greater than 4.75mm size, then greater quantity of soil, that is, about 5.0 Kg should be taken.
For soil containing some particle greater than 4.75 mm size, the weight of the soil sample for
grain size analysis should be taken as 0.5 Kg to 1.0 Kg.
ii. Clean the sieves and pan with brush and weigh them upto 0.1 gm accuracy. Arrange the
sieves in the increasing order of size from top to bottom. The first set shall consist of sieves of
size 300 mm, 80mm, 40mm, 20mm, 10mm, and 4.75 mm. While the second set shall consist of
sieves of sizes 2mm, 850 micron, 425 micron, 150 micron, and 75 micron.
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OBSERVATION AND CALCULATION TABLE:
Mass of soil Sample taken for Analysis =
Coefficient of curvature (Cc) may be estimated as:
Uniformity coefficient (Cu) is given by:
% of soil
passing (%)
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iii. Keep the required quantity of soil sample on the top sieve and shake it with mechanical
sieve shaker for about 5 to 10 minutes. Care should be taken to tightly fit the lid cover on the
top sieve.
iv. After shaking the soil on the sieve shaker, weigh the soil retained on each sieve. The sum of
the retained soil must tally with the original weight of soil taken.
PRECAUTIONS:
i. During shaking the lid on the topmost sieve should be kept tight to prevent escape of soils.
ii. While drying the soil, the temperature of the oven should not be more than 1050C because
higher temperature may cause some permanent change in the 75µ fraction.
RESULT:
1. The given soil is................................
2. Coefficient of curvature (Cc) =
3. Uniformity coefficient (Cu) =
Questions:
i. What do you understand by well graded, poorly graded and uniformly graded soils?
ii. What do you understand by dry sieve and wet sieve analysis? Which once did you
perform and why?
iii. What is the grain size distribution curve? Why do you use a semi-long graph paper for
plotting it?
iv. What do you understand by GW,GP,GM,GC,SW,SP,SM,SC,SW-SM,GP-SC?
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ATTERBERG LIMITS TEST
AIM:
To determine the liquid limit, plastic limit, shrinkage limit of the given soil sample.
THEORY:
The definitions of the consistency limits proposed by Atterberg are not, by themselves, adequate
for the determination of their numerical values in the laboratory, especially in view of the
arbitrary nature of these definitions. In view of this, Arthur Casagrande and others suggested
more practical definitions with special reference to the laboratory devices and methods
developed for the purpose of the determination of the consistency limits. In this sub-section, the
laboratory methods for determination of the liquid limit, plastic limit, shrinkage limit, and other
related concepts and indices will be studied, as standardized and accepted by the Indian
Standard Institution and incorporated in the codes or practice.
APPARATUS:
1. Casagrande’s liquid limit device and grooving tool
2. Spatula
3. Balance
4. Glass plate
5. Hot air oven maintained at 105 ± 10C
6. Moisture Containers
STANDARD REFERENCE:
FOR LIQUID LIMIT:
IS: 2720(Part V)–1985.
FOR PLASTIC LIMIT:
IS: 2720, Part V–1985.
TERMS:
Shrinkage limit:
The shrinkage limit (SL) is the water content where further loss of moisture will not result in
any more volume reduction. The shrinkage limit is much less commonly used than the liquid
limit and the plastic limit.
Plastic limit:
The plastic limit (PL or wP) is the water content where soil starts to exhibit plastic behaviour. A
thread of soil is at its plastic limit when it is rolled to a diameter of 3 mm or begins to crumble.
To improve consistency, a 3 mm diameter rod is often used to gauge the thickness of the thread
when conducting the test. (AKA Soil Snake Test).
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Liquid limit:
Liquid limit (LL or wL) is defined as the arbitrary limit of water content at which the soil is just
about to pass from the plastic state into the liquid state. At this limit, the soil possesses a small
value of shear strength, losing its ability to flow as a liquid. In other words, the liquid limit is
the minimum moisture content at which the soil tends to flow as a liquid.
PLATICITY INDEX:
Plasticity index (PI or Ip ) is the range of water content within which the soil exhibits plastic
properties; that is, it is the difference between liquid and plastic limits.
PI (or Ip ) = (LL - PL) = (wL - wP )
When the plastic limit cannot be determined, the material is said to be non-plastic (NP).
Plasticity index for sands is zero.
For proper evaluation of the plasticity properties of a soil, it has been found desirable to use
both the liquid limit and the plasticity index values.
SHRINKAGE INDEX:
Shrinkage index (SI OR Is) is defined as the difference between the plastic and shrinkage limits
of a soil; in other words, it is the range of water content within which a soil is in a semisolid
state of consistency.
CONSISTENCY INDEX:
Consistency index or Relative consistency (CI OR IC ) is defined as the ratio of the difference
between liquid limit and the natural water content to the plasticity index of a soil:
Where w = natural water content of the soil (water content of a soil in the undisturbed condition
in the ground).
If IC= 0, w = LL
IC = 1, w = PL
IC > 1, the soil is in semi-solid state and is stiff.
IC < 0, the natural water content is greater than LL, and the soil behaves like a liquid.
LIQUIDITY INDEX:
Liquidity index (LI OR IL) or Water-plasticity ratio is the ratio of the difference between the
natural water content and the plastic limit to the plasticity index:
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Obviously, CI + LI = 1
PROCEDURE:
1. FOR DETERMINATION OF LIQUID LIMIT:
1. About 120 gm of air-dried soil from thoroughly mixed portion of material passing 425
micron I.S sieve is to be obtained.
2. Distilled water is mixed to the soil thus obtained in a mixing disc to form uniform paste. The
paste shall have a consistency that would require 30 to 35 drops of cup to cause closer of
standard groove for sufficient length.
3. A portion of the paste is placed in the cup of Casagrande apparatus and spread into portion
with few strokes of spatula.
4. Trim it to a depth of 1cm at the point of maximum thickness and return excess of soil to the
dish.
5. The soil in the cup shall be divided by the firm strokes of the grooving tool along the
diameter through the centre line of the follower so that clean sharp groove of proper
dimension is formed.
6. Lift and drop the cup by turning crank at the rate of two revolutions per second until the two
halves of soil cake come in contact with each other for a length of about 1 cm by flow only.
7. The number of blows required to cause the groove close for about 1 cm shall be recorded.
8. A representative portion of soil is taken from the cup for water content determination.
9. Repeat the test with different moisture contents at least three more times for blows between
10 and 40.
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Atterberg Limits Determination
Natural water content of given soil =
Liquid Limit Determination
Can No.
Mass of can (g)
Mass of wet soil + can (g)
Mass of dry soil + can (g)
Mass of dry soil (g)
Mass of water (g)
Water content, (%)
No. of drops
Plastic Limit Determination
Can No.
Mass of can (g)
Mass of wet soil + can (g)
Mass of dry soil + can (g)
Mass of dry soil (g)
Mass of water (g)
Water content, (%)
CALCULATIONS:
1. Plasticity index =
2. Shrinkage index =
3. Consistency index =
4. Liquidity index=
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2. FOR DETERMINATION OF PLASTIC LIMIT:
1. Take about 20gm of thoroughly mixed portion of the material passing through 425 micron
I.S. sieve obtained in accordance with I.S. 2720 (part 1).
2. Mix it thoroughly with distilled water in the evaporating dish till the soil mass becomes
plastic enough to be easily moulded with fingers.
3. Allow it to season for sufficient time (for 24 hrs) to allow water to permeate throughout the
soil mass
4. Take about 10gms of this plastic soil mass and roll it between fingers and glass plate with
just sufficient pressure to roll the mass into a threaded of uniform diameter throughout its
length. The rate of rolling shall be between 60 and 90 strokes per minute.
5. Continue rolling till you get a threaded of 3 mm diameter.
6. Kneed the soil together to a uniform mass and re-roll.
7. Continue the process until the thread crumbles when the diameter is 3 mm.
8. Collect the pieces of the crumbled thread in air tight container for moisture content
determination.
9. Repeat the test to atleast 3 times and take the average of the results calculated to the nearest
whole number.
3. FOR DETERMINATION OF SHRINKAGE LIMIT
Preparation of soil paste
1. Take about 100 gm of soil sample from a thoroughly mixed portion of the material passing
through 425-micron I.S. sieve.
2. Place about 30 gm of the above soil sample in the evaporating dish and thoroughly mix it
with distilled water and make a creamy paste. Use water content somewhere around the liquid
limit.
Filling the shrinkage dish
3. Coat the inside of the shrinkage dish with a thin layer of Vaseline to prevent the soil sticking
to the dish.
4. Fill the dish in three layers by placing approximately 1/3 rd of the amount of wet soil with the
help of spatula. Tap the dish gently on a firm base until the soil flows over the edges and no
apparent air bubbles exist. Repeat this process for 2nd and 3rd layers also till the dish is
completely filled with the wet soil. Strike off the excess soil and make the top of the dish
smooth. Wipe off all the soil adhering to the outside of the dish.
5. Weigh immediately, the dish with wet soil and record the weight.
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Shrinkage Limit Determination
CALCULATION
S.No
Determination No. 1 2 3
1 Wt. of container in gm,W1
2 Wt. of container + wet soil pat in gm,W2
3 Wt. of container + dry soil pat in gm,W3
4 Wt. of oven dry soil pat, W0 in gm
5 Wt. of water in gm
6 Moisture content (%), W
7 Volume of wet soil pat (V), in cm
8 Volume of dry soil pat (V0) in cm3
9 By mercury displacement method
a. Weight of displaced mercury
b. Specific gravity of the mercury
10 Shrinkage limit (WS)
11 Shrinkage ratio (R)
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6. Air-dry the wet soil cake for 6 to 8hrs, until the colour of the pat turns from dark to light.
Then oven-dry the soil to constant weight at 1050C to 110
0C say about 12 to 16 hrs.
7. Remove the dried disk of the soil from oven. Cool it in a desiccator. Then obtain the weight
of the dish with dry sample.
8. Determine the weight of the empty dish and record.
9. Determine the volume of shrinkage dish which is evidently equal to volume of the wet soil as
follows. Place the shrinkage dish in an evaporating dish and fill the dish with mercury till it
overflows slightly. Press it with plain glass plate firmly on its top to remove excess mercury.
Pour the mercury from the shrinkage dish into a measuring jar and find the volume of the
shrinkage dish directly. Record this volume as the volume of the wet soil pat.
Volume of the Dry Soil Pat
10. Determine the volume of dry soil pat by removing the pat from the shrinkage dish and
immersing it in the glass cup full of mercury in the following manner.
11. Place the glass cup in a larger one and fill the glass cup to overflowing with mercury.
Remove the excess mercury by covering the cup with glass plate with prongs and pressing it.
See that no air bubbles are entrapped. Wipe out the outside of the glass cup to remove the
adhering mercury. Then, place it in another larger dish, which is, clean and empty carefully.
12. Place the dry soil pat on the mercury. It floats submerge it with the pronged glass plate
which is again made flush with top of the cup. The mercury spills over into the larger plate.
Pour the mercury that is displayed by the soil pat into the measuring jar and find the volume of
the soil pat directly.
RESULT:
For given soil:
1. Liquid limit =
2. Plastic limit =
3. Plasticity index =
4. Shrinkage index =
5. Consistency index =
6. Liquidity index=
7. Shrinkage limit =
Questions:
1. What is liquid limit?
2. What is plastic limit?
3. What apparatus is used to measure the liquid limit of a given soil sample.
4. What number of blows is taken for consideration while determining the liquid limit of a
given soil sample.
5. What is plasticity index?
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PERMEABILITY TEST
AIM:
To determine the coefficient of permeability of a given soil sample by
i) Constant head method
ii) Variable head method
APPARATUS REQUIRED:
i) Permeameter with all accessories for constant head
ii) Compaction equipment
iii) Stop watch
iv) Balance
v) Measuring cylinder
vi) Scale
THEORY:-
Permeability is defined as the property of porous material which permits the passage or seepage
of water through its interconnected voids. The coefficient of permeability is finding out
following method.
a) Laboratory method:
i. Variable head test.
ii. Constant head test.
b) Field method:
i. Pumping out test.
ii. Pumping in test.
c) Indirect test:
i. Computation from grain size or specific surface.
ii. Horizontal capillarity test.
iii. Consolidation test data.
The derivation of the coefficient of permeability is based on the assumption of the validity of
the Darcy’s law to the flow of water in soil. The term coefficient of permeability implies the
velocity of flow of water through the soil under unit hydraulic gradient, and consequently has
the same units as that of velocity.
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A. Variable head test:
The variable head test is used for fine grained soils like silts and silty clays.
For the Variable head test the following formula is applicable:
Where, k = Coefficient of permeability at To C (cm/sec).
a = Cross Sectional area of stand pipe (cm2).
L = Length of soil specimen (cm)
A = Cross-sectional area of soil sample inside the mould (cm2)
t = (t1 – t2) = Time interval for the head to fall from h1 to h2.
h1 = Initial head of water at time t1 in the pipe, measured above the outlet.
h2 = Final head of water at time t2 in the pipe, measured above the outlet.
B. Constant head test:
The Constant head test is suitable for coarse grained soils like sands, sandy silts.
If Q is the total quantity of flow in a time interval t, we have from Darcy’s law,
K = QL / (hAT)
Where, k = Coefficient of permeability at To
C (cm/sec).
L = Length of soil specimen (cm)
A = Total cross-sectional area of soil sample (cm2)
Q = Quantity of water collected in measuring jar.
t = total time required for collecting ‘Q’ quantity of water.
h = Difference in the water levels of the overhead and bottom tank.
APPLICATION:
Water flowing through soil exerts considerable seepage force which has direct effect on the
safety of hydraulic structures.
The rate of settlement of compressible clay layer under load depends on its permeability. The
quantity of water escaping through and beneath the earthen dam depends on the permeability of
the embankments and its foundations respectively. The rate of discharge through wells and
excavated foundation pits depends on the coefficient of permeability of the soils. Shear strength
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of soils also depends indirectly on its permeability, because dissipation of pore pressure is
controlled by its permeability.
PROCEDURE:
a) Preparation of remoulded soil specimen:
i. Weight the required quantity of oven dried soil sample. Evenly sprinkle the calculated
quantity of water corresponding to the OMC. Mix the soil sample thoroughly.
ii. Clean the mould and apply a small portion of grease inside the mould and around the porous
stones in the base plate. Weight the mould and attach the collar to it. Fix the mould on the
compaction base plate. Keep the apparatus on solid base.
iii. The soil sample is placed inside the mould, and is compacted by the standard Proctor
compaction tools, to achieve a dry density equal to the pre-determine3d MDD. Weight the
mould along with the compacted soil.
iv. Saturate the porous stones. Place the filter papers on both ends of the soil specimen in the
mould. Attach the mould with the drainage base and cap having saturated porous stones.
b) Saturation of soil specimen:
i. Connect the water reservoir to the outlet at the bottom of the mould and allow the water to
flow in the soil. Wait till the water has been able to travel up and saturate the sample. Allow
about 1 cm depth of free water to collect on the top of the sample.
ii. Fill the remaining portion of cylinder with de-aired water without disturbing the surface of
soil.
iii. Fix the cover plate over the collar and tighten the nuts in the rods.
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OBSERVATION AND CALCULATION TABLE FOR CONSTANT HEAD
PERMIABILITY TEST:
OBSERVATION AND CALCULATION TABLE FOR FALLING HEAD
PERMIABILITY TEST:
Table 1:
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c) Constant head test:
i. Place the mould assembly in the bottom tank and fill the bottom tank with water up to the
outlet.
ii. Connect the outlet tube with constant head tank to the inlet nozzle of the permeameter, after
removing the air in flexible rubber tubing connecting the tube.
iii. Adjust the hydraulic head by either adjusting the relative height of the permeameter mould
and constant head tank or by raising or lowering the air intake tube with in the head tank.
iv. Start the stop watch and at the same time put a bucket under the outlet of the bottom tank,
run the test for same convenient time interval and measure.
v. Repeat the test twice more, under the same head and for the same time interval.
d) Variable head permeability test method:
i. Disconnect the water reservoir from the outlet at the bottom and connect the stand pipe to the
inlet at the top plate.
ii. Fill the stand pipe with water. Open the stop cock at the top and allow water to flow out so
that all the air in the cylinder is removed.
iii. Fix the height h1 and h2 on the stand pipe from the centre of the outlet such that (h1 – h2) is
about 30 cm to 40 cm.
iv. When all the air has escaped, close the stop clock and allow the water from the pipe to flow
through the soil and establish a steady flow.
v. Record the time interval, t, for the head to drop from h1 to h2.
vi. Take about five such observations by changing the values of h1 and h2.
vii. Measure the temperature of water.
RESULTS
Coefficient of permeability of given soil
By Constant head method =.................................
By Variable head method =..................................
QUESTIONS
i. What is Darcy’s law of flow velocity through soils? What are its Limitations?
ii. What are the steady and unsteady flows of water? What type of flow is assumed to
occur in soils?
iii. What are the laboratory methods of determination of coefficient of permeability of
soil? State their suitability.
iv. What is the effect of entrapped air on the coefficient of permeability of soil?
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FIELD DENSITY TEST
A. SAND REPLACEMENT METHOD
OBJECTIVE
Determine the in situ density of natural or compacted soils using sand pouring cylinders.
NEED AND SCOPE
The in situ density of natural soil is needed for the determination of bearing capacity of soils,
for the purpose of stability analysis of slopes, for the determination of pressures on underlying
strata for the calculation of settlement and the design of underground structures.
It is very quality control test, where compaction is required, in the cases like embankment and
pavement construction.
APPARATUS REQUIRED
1. Sand pouring cylinder of 3 litre/16.5 litre capacity mounted above a pouring come and
separated by a shutter cover plate.
2. Tools for excavating holes; suitable tools such as scraper tool to make a level surface.
3. Cylindrical calibrating container with an internal diameter of 100 mm/200 mm and an
internal depth of 150 mm/250 mm fitted with a flange 50 mm/75 mm wide and about 5 mm
surrounding the open end.
4. Balance to weigh unto an accuracy of 1g.
5. Metal containers to collect excavated soil.
6. Metal tray with 300 mm/450 mm square and 40 mm/50 mm deep with a 100 mm/200 mm
diameter hole in the centre.
7. Glass plate about 450 mm/600 mm square and 10mm thick.
8. Clean, uniformly graded natural sand passing through 1.00 mm I.S. sieve and retained on the
600micron I.S. sieve. It shall be free from organic matter and shall have been oven dried and
exposed to atmospheric humidity.
9. Suitable non-corrodible airtight containers.
10. Thermostatically controlled oven with interior on non-corroding material to maintain the
temperature between 1050C to 110
0C.
11. A dessicator with any desiccating agent other than sulphuric acid.
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OBSERVATIONS AND CALCULATIONS
S. No. Sample Details
Calibration 1 2 3
1 Weight of sand in cone (of pouring cylinder) W2 gm
2 Volume of calibrating container (V) in cc
3 Weight of sand + cylinder before pouring W3 gm
4 Weight of sand + cylinder after pouring W3 gm
5 Weight of sand to fill calibrating containers
Wa = (W1-W3-W2) gm
6 Bulk density of sand γγγγs = Wa / V gm/cc
S. No Measurement of Soil Density 1 2 3
1 Weight of wet soil from hole Ww gm
2 Weight of sand + cylinder before pouring W1 gm
3 Weight of sand + cylinder after pouring W4 gm
4 Weight of sand in hole Wb = (W1-W2-W4) gm
5 Bulk density γb = (Ww /Wb)x γs gm/cc
Water content determination
1 Container number
2 Weight of wet soil
3 Weight of dry soil
4 Moisture content (%)
5 Dry density γd = γb / (1+w) gm/cc
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THEORY
By conducting this test it is possible to determine the field density of the soil. The moisture
content is likely to vary from time and hence the field density also. So it is required to report the
test result in terms of dry density. The relationship that can be established between the dry
density with known moisture content is as follows:
PROCEDURE
Calibration of the Cylinder
1. Fill the sand pouring cylinder with clean sand so that the level of the sand in the cylinder is
within about 10 mm from the top. Find out the initial weight of the cylinder plus sand (W1) and
this weight should be maintained constant throughout the test for which the calibration is used.
2. Allow the sand of volume equal to that of the calibrating container to run out of the cylinder
by opening the shutter, close the shutter and place the cylinder on the glass sand takes place in
the cylinder close the shutter and remove the cylinder carefully. Weigh the sand collected on the
glass plate. Its weight (W2) gives the weight of sand filling the cone portion of the sand pouring
cylinder. Repeat this step at least three times and take the mean weight (W2) Put the sand back
into the sand pouring cylinder to have the same initial constant weight (W1)
Determination of Bulk Density of Soil
3. Determine the volume (V) of the container be filling it with water to the brim. Check this
volume by calculating from the measured internal dimensions of the container.
4. Place the sand poring cylinder centrally on the top of the calibrating container making sure
that constant weight (W1) is maintained. Open the shutter and permit the sand to run into the
container. When no further movement of sand is seen close the shutter, remove the pouring
cylinder and find its weight (W3).
Determination of Dry Density of Soil in Place
5. Approximately 60 sq.cm of area of soil to be tested should be trimmed down to a level
surface, approximately of the size of the container. Keep the metal tray on the level surface and
excavate a circular hole of volume equal to that of the calibrating container. Collect all the
excavated soil in the tray and find out the weight of the excavated soil (Ww). Remove the tray,
and place the sand pouring cylinder filled to constant weight so that the base of the cylinder
covers the hole concentrically. Open the shutter and permit the sand to run into the hole. Close
the shutter when no further movement of the sand is seen. Remove the cylinder and determine
its weight (W3).
6. Keep a representative sample of the excavated sample of the soil for water content
determination.
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OBSERVATION AND CALCULATION TABLE:
Internal diameter of cutter (cm): _ _ _ _ _ _ _ _
Height of the cutter (cm): _ _ _ _ _ _ _ _
Cross sectional area of the cutter (cm2): _ _ _ _ _ _ _ _
Volume of the cutter, V (cm3): _ _ _ _ _ _ _ _
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B. CORE CUTTER METHOD
AIM
To determine the field or in-situ density or unit weight of soil by core cutter method
APPARATUS
a) Special:
i. Cylindrical core cutter
ii. Steel rammer
iii. Steel dolly
b) General:
i. Balance of capacity5 Kg and sensitivity 1 gm.
ii. Balance of capacity 200gms and sensitivity 0.01 gms.
iii. Scale
iv. Spade or pickaxe or crowbar
v. Trimming Knife
vi. Oven
vii. Water content containers
viii. Desiccator.
THEORY:
Field density is defined as weight of unit volume of soil present in site. That is
� =�
�
Where, γ= Density of soil, W = Total weight of soil, V = Total volume of soil
The soil weight consists of three phase system that is solids, water and air. The voids may be
filled up with both water and air, or only with air, or only with water. Consequently the soil may
be dry, saturated or partially saturated. In soils, mass of air is considered to be negligible, and
therefore the saturated density is maximum, dry density is minimum and wet density is in
between the two.
Dry density of the soil is calculated by using equation,
�� =��
1 +
Where, γd=dry density of soil, γb=Wet density of soil,w = moisture content of soil.
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PROCEDURE:
i. Measure the height and internal diameter of the core cutter.
ii. Weight the clean core cutter.
iii. Clean and level the ground where the density is to be determined.
iv. Press the cylindrical cutter into the soil to its full depth with the help of steel rammer.
v. Remove the soil around the cutter by spade.
vi. Lift up the cutter.
vii. Trim the top and bottom surfaces of the sample carefully.
viii. Clean the outside surface of the cutter.
ix. Weight the core cutter with the soil.
x. Remove the soil core from the cutter and take the representative sample in the water content
containers to determine the moisture content
PRECAUTIONS:
i. Steel dolly should be placed on the top of the cutter before ramming it down into the ground.
ii. Core cutter should not be used for gravels, boulders or any hard ground.
iii. Before removing the cutter, soil should be removed around the cutter to minimize the
disturbances.
iv. While lifting the cutter, no soil should drop down
RESULT:
a. Bulk Density of soil:
By Sand Replacement method =....................................
By Core Cutter Method =...............................................
b. Dry Density of soil:
By Sand Replacement method =....................................
By Core Cutter Method =...............................................
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QUESTIONS
i. Out of wet density, dry density, and saturated density, which one of them is
maximum and minimum? Explain.
ii. What are the main factors which affect in-situ density of soil? Explain.
iii. Beside the density what other properties do you need to calculate the void ratio and
degree of saturation of soils?
iv. What are the other methods to calculate the field density of soil?
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COMPACTION TEST
AIM OF THE EXPERIMENT:
To determine the Optimum moisture content and maximum dry density of a soil by standard
proctor compaction test.
APPARATUS REQUIRED:
a) Special:
i. Proctor mould (capacity 1000.0 cc, internal diameter 100mm, and effective
height 127.3 mm.
ii. Rammer for light compaction (2.6Kg, with free drop of 310 mm).
iii. Mould accessories including detachable base plate, removable
Collar.
iv. I.S. sieve 4.75 mm.
b) General:
i. Balance of capacity 10 kg, and sensitivity of 1 gm.
ii. Balance of capacity 200 gms and sensitivity of 0.01 gm.
iii. Drying oven.
iv. Desiccators.
v. Containers for water content.
vi. Graduated Jar.
vii. Trimming knife.
viii. Large mixing tray.
THEORY:
Compaction is the process of densification of soil mass by reducing air voids. The purpose of
laboratory compaction test is so determine the proper amount of water at which the weight of
the soil grains in a unit volume of the compacted is maximum, the amount of water is thus
called the Optimum Moisture Content (OMC). In the laboratory different values of moisture
contents and the resulting dry densities, obtained after compaction are plotted both to
arithmetic scale, the former as abscissa and the latter as ordinate. The points thus obtained are
joined together as a curve. The maximum dry density and the corresponding OMC are read
from the curve.
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The wet density of the compacted soil is c
Where, w1 = Weight of mould with
w2 = Weight of empty mould.
V = Volume of mould.
The dry density of the soil shall be
Where, t = wet density of the compa
w = moisture content
APPLICATION:
Compaction of soil increases the
the voids, settlement and permea
field problems like earthen dams,
the field is controlled by the
compaction test. The compac
controlled by the maximum dry d
laboratory compaction tests resul
compaction of the soil.
PROCEDURE:
i. Take about 20 kg of soil and si
ii. A 100 mm diameter Proctor
4.75 mm sieve is greater th
iii. Take about 2.25 kg of the
round 8%. Leave the mix to
iv. Clean and grease gently the
v. Take the weight of empty
vi. Fir the collar and place the
ted soil is calculated as below,
ht of mould with moist compacted soil.
ould.
shall be calculated as follows,
mpacted soil.
the density, shear strength, bearing capacity, thus
eability. The results of this are useful in the stabili
ms, embankments, roads and airfield. In such compa
the value of the OMC determined by
ction energy to be given by a compaction unit
y density determined in the laboratory. In other w
sults are used to write the compaction specification f
nd sieve it through 20 mm and 4.75 mm.
tor mould is to be used if the soil fraction that
han 80% by weight.
soil sample and add water to get the moisture co
to mature for few minutes.
he inside surface of the mould, and the base plate
mould with the base plate.
he mould on a solid base.
49
thus reducing
stability of
mpacted in
laboratory
unit is also
words, the
on for field
that passes
ontent
e.
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OBSERVATION AND CALCULATION TABLE:
i. Diameter of mould, D (cm): _ _ _ _ _ _
ii. Height of mould, h (cm) : _ _ _ _ _ _ _ _
iii. Volume of mould, V (cc) : _ _ _ _ _ _ _ _
Weight of empty mould + Base plate
(w1) ,kg
Weight of compacted soil + Base plate
(w2) ,kg
Bulk unit weight of compacted soil
γ (gm/cc)
Water content
(w)
Dry unit weight
γd = γ / (1 + w), (gm/cc)
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vii. Place first batch of soil inside the mould and apply 25 blows of
Standard rammer, so that the compacted layer thickness is about one-third height of
the mould Scratch the top of the compacted soil before the second layer is placed
Place the second batch of wet soil and follow the same procedure In all the soil is
compacted in three layers, each given 25 blows of the standard rammer weighing 2.6
Kg and having a drop of 310 mm.
viii. Remove the collar, and trim of the excess soil with trimming knife.
Clean the mould, and weight the mould with the compacted soil and the base plate. ix.
Take a representative sample from the mould and determine its water content.
ix. Repeat the above procedure for water content values of 13%, 17%, 20%, 22% and
25%.
RESULT
Maximum dry density =
Optimum moisture content =
QUESTIONNAIRE:
i. What is meant by dry side and wet side of optimum? Which side is preferred in the
field compaction? Explain.
ii. Explain how the gravel content in the soil mass affects the laboratory compaction specifications.
iii. What is the energy imparted by the standard and modified compaction test?
iv. What are the approximate values of OMC and MDD for coarse grained and fine grained soils?
v. What are the field methods of compaction the soils?
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OBSERVATION AND CALCULATION
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UNCONFINED COMPRESSION (UCC) TEST
AIM:
To determine the unconfined compressive strength, this is then used to calculate the
unconsolidated undrained shear strength of the clay under unconfined conditions.
THEORY:
According to the ASTM standard, the unconfined compressive strength (qu) is defined as the
compressive stress at which an unconfined cylindrical specimen of soil will fail in a simple
compression test. In addition, in this test method, the unconfined compressive strength is taken
as the maximum load attained per unit area, or the load per unit area at 15% axial strain,
whichever occurs first during the performance of a test.
For soils, the undrained shear strength (Su) is necessary for the determination of the
bearing capacity of foundations, dams, etc. The undrained shear strength (Su) of clays is
commonly determined from an unconfined compression test. The undrained shear strength (Su)
of a cohesive soil is equal to one-half the unconfined compressive strength (qu) when the soil is
under the f = 0 condition (f = the angle of internal friction). The most critical condition for the
soil usually occurs immediately after construction, which represents undrained conditions,
when the undrained shear strength is basically equal to the cohesion
(c).This is expressed as:
Then, as time passes, the pore water in the soil slowly dissipates, and the intergranular stress
increases, so that the drained shear strength (s), given by s = c + s‘tan f, must be used. Where
s‘= intergranular pressure acting perpendicular to the shear plane; and s‘= (s - u), s = total
pressure, and u = pore water pressure; c’ and j’ are drained shear strength parameters.
EQUIPMENT:
Compression device, Load and deformation dial gauges, Sample trimming equipment, Balance,
Moisture can.
PROCEDURE:
(1) Extrude the soil sample from Shelby tube sampler. Cut a soil specimen so that the ratio
(L/d) is approximately between 2 and 2.5, where L and d are the length and diameter of soil
specimen, respectively.
(2) Measure the exact diameter of the top of the specimen at three locations 120° apart, and then
make the same measurements on the bottom of the specimen. Average the measurements and
record the average as the diameter on the data sheet.
(3) Measure the exact length of the specimen at three locations 120° apart, and then average the
measurements and record the average as the length on the data sheet.
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Unconfined Compression Test Data
Deformation Dial: 1 unit = .......................mm; Proving Ring No: ......................
Load Dial: 1 unit =........................
Deformation
Dial Reading
Load Dial
Reading
Sample
Deformation
∆∆∆∆L (mm)
Strain
(e)
%
Strain
Corrected
Area A'
Load
Load
(KN)
Stress
(kPa)
0
20
40
60
80
100
120
140
160
180
200
250
300
350
400
450
500
550
600
650
700
750
800
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(4) Weigh the sample and record the mass on the data sheet.
(5) Calculate the deformation (DL) corresponding to 15% strain (e).
Where L0 = Original specimen length (as measured in step 3).
(6) Carefully place the specimen in the compression device and centre it on the bottom plate.
Adjust the device so that the upper plate just makes contact with the specimen and set the load
and deformation dials to zero.
(7) Apply the load so that the device produces an axial strain at a rate of 0.5% to 2.0% per
minute, and then record the load and deformation dial readings on the data sheet at every 20 to
50 divisions on deformation the dial.
(8) Keep applying the load until (1) the load (load dial) decreases on the specimen significantly,
(2) the load holds constant for at least four deformation dial readings, or (3) the deformation is
significantly past the 15% strain that was determined in step 5.
(9) Draw a sketch to depict the sample failure.
(10) Remove the sample from the compression device and obtain a sample for water content
determination.
RESULT
From the stress-strain curve and Mohr’s circle:
Unconfined compressive strength (qu) =
Cohesion (c) =
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850
900
950
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
2200
2400
2600
2800
3000
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AIM:
To determine shear strength para
APPARATUS REQUIRED:
a) Special:
i. Shear test frame housing the motor, lo
ii. Shear box of intern
iii. Water jacket for sh
iv. Metallic Grid plate
v. Base plate.
vi. Porous stones.
vii. Loading pad.
viii. Proving ring of cap
ix. Slotted weights to i
b) General:
i. Balance of capacity
ii. Scale.
iii. Dial Gauge of sensit
THEORY:
Shear strength of a soil is the ma
plane. Shear strength is compose
i. Internal friction whi
individual particles at their
interlocking strength is ind
ii. Cohesion which resistan
together in a soil mass. The
Coulomb has represented the
DIRECT SHEAR TEST
ameters of the given soil sample by Direct Shear
me housing the motor, loading yoke, etc.
nal dimension 60 mm x 60 mm x 25 mm.
r shear box.
es.
pacity 200 Kgf.
o impart appropriate normal stress on soil sample.
y 1 Kg and sensitivity 0.1 gms.
sensitivity 0.01 mm.
maximum resistance to shearing stress at failure
ed of:
which is the resistance due to fricti
t their contact points and interlocking of p
s indicated through parameter φ.
nce due to inter-particle force which tend hold
ss. The indicative parameter is called Cohesion interce
nted the shear strength of soil by the equation:
59
r Test.
.
on the failure
ion between
particles. This
hold the particles
cept (c).
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Where, shear str
= Cohesion
Tota
Angle
The graphical representation of the
The parameters c and are not const
saturation, drainage conditions and the
In direct shear test, the sample is sh
plane is horizontal. The normal
the corrected area of the soil samp
by the corrected of soil sample.
APPLICATION:
The purpose of direct shear test
cohesion, angle of shearing resi
parameters are used in the des
calculating the bearing capacity of
the earth pressures behind the re
checking the stability to natural slop
PROCEDURE:
i. Prepare a soil speci
undisturbed soil sample or
also be directly prepared
ii. Fix the upper part of the
to the lower part.
iii. Place the porous stone in
iv. Transfer the soil specime
v. Place the upper grid, po
vi. Place the box inside the
vii. Bring the upper half of
Contact is observed by the sl
viii. Mount the loading yoke
ix. Put the weight on the lo
intensity. Add the weight of the
intensity.
r strength of soil = shear stress at failure.
sion intercepts
al normal stress on the failure plane
le of internal friction or shearing resistance
the above equation gives a straight line called Fai
onstant for a given type of soil but depends
ions and the condition of laboratory testing.
sheared along the horizontal plane. This indicates
stress, on this plane is the external vertical
mple. The shear stress at failure is the external lat
is to get the ultimate shear resistance, peak
sistance and stress-strain characteristics of the
sign of earthen dams and embankments. The
y of soil-foundation systems. These parameters he
etaining walls. The values of these parameters
opes, cuts and fills.
imen of size 60 mm * 60mm* 25 mm
e or from compacted or remoulded sample. Soil
d in the box by compaction.
the box to the lower box by fixing screws. Attac
in the box.
men prepared into the box.
id, porous stone and loading pad in the order on soil sp
the container and mount it on loading frame.
the box in contact with the proving ring assemb
the slight movement of proving ring dial gauge n
oke on the ball placed on the loading pad.
oading yoke to apply a given value of normal str
ht of the yoke also in the estimation of normal str
61
ilure envelope.
in its degree of
tes that the failure
load divided by
l lateral load divided
shear resistance,
s of the soils. Shear
ese are used in
elp in estimating
are also used in
mm either from
oil specimen may
ch the base plate
r on soil specimen.
ssembly.
needle.
stress
mal stress
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OBSERVATION AND
1. Size of Soil sample
2. Weight of yoke, w1=
3. Weight of Loading p
4. Lever Ratio = 1:5
5. Proving ring Numbe
6. Proving ring Consta
7. Rate of strain for Ho
Load on yoke (w) (kg)
Normal load on soil sample
(kg)=(W+w1)x5+w2
Normal stress (kg/cm
= N/(6x6)
Proving ring division at failur
Shear force at failure (S) =D x
Shear resistance at failure (
=S/(6x6)
ND CALCULATION TABLE:
= Internal Dimensions of the Box
=0.775 Kg.
pad, w2=0.620 Kg.
er=
ant (K): 1 Division = Kg.
Horizontal Shear = 1.25 mm/min.
mal load on soil sample(N)
m2)
re (D)
D x k
( )
62
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63
x. Remove the fixing screws from the box and raise slightly the upper box with the
help of the spacing screws. Remove the spacing screws also.
xi. Adjust the entire dial gauge to read zero.
xii. Shear load is applied at constant rate of strain.
xiii. Record the readings of proving ring and dial readings at a fixed interval.
xiv. Continue the observations till the specimen fails.
xv. Repeat the test on the identical specimen under increasing normal stress and
record the corresponding reading.
PRECAUTIONS:
i. Before starting the test, the upper half of the box should be brought in proper contact
with the proving ring.
ii. Before subjecting the specimen to shear, the fixing screws should take out.
iii. Spacing screws should also be removed before shearing the specimen. iv.
No vibrations should be transmitted to the specimen during the test.
v. Do not forget to add the self weight of the loading yoke in the vertical loads.
RESULT
The angle of internal friction of the given sample of sand (ϕ) =
INFERENCE
QUESTIONNAIRE:
i. Differentiate between the angle of repose and angle of shearing resistance of soils
ii. What are the advantages and disadvantages of direct shear test?
iii. What are other laboratory tests to determine the shear strength of soils?
iv. Why do you put the grids keeping the serration at right angles to the direction of
shear?
v. Are you using stress or strain controlled device?
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TRIAXIAL TEST
AIM:
To find the shear strength of the soil by Undrained Triaxial Test.
APPARATUS:
a) Special:
i. A constant rate of strain compression machine of which the following is a
brief description of one in common use.
• A loading frame in which the load is applied by yoke acting through an
elastic dynamometer, more commonly called a proving ring which
used to measure the load. The frame is operated at a constant rate by a
geared screw jack. It is preferable for the machine to be motor driven, by a
small electric motor.
• A hydraulic pressure apparatus including an air compressor and water
reservoir in which air under pressure acting on the water raises it to the
required pressure, together with the necessary control valves and pressure
dials.
ii. A triaxial cell to take 3.8 cm dia and 7.6 cm long samples, in which the sample can
be subjected to an all round hydrostatic pressure, together with a vertical
compression load acting through a piston. The vertical load from the piston
acts on a pressure cap. The cell is usually designed with a non-ferrous metal top
and base connected by tension rods and with walls formed of Perspex.
b) General:
i. 3.8 cm (1.5 inch) internal diameter 12.5 cm (5 inches) long sample tubes.
ii. Rubber ring.
iii. An open ended cylindrical section former, 3.8 cm inside dia, fitted with
a small rubber tube in its side.
iv. Stop clock.
v. Moisture content test apparatus.
vi. A balance of 250 gm capacity and accurate to 0.01 gm.
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THEORY:
Triaxial test is more reliable because we can measure both drained and untrained shear strength.
Generally 1.4” diameter (3” tall) or 2.8” diameter (6” tall) specimen is used. Specimen is encased
by a thin rubber membrane and set into a plastic cylindrical chamber. Cell pressure is applied in
the chamber (which represents σ3’) by pressurizing the cell fluid (generally water).
Vertical stress is increased by loading the specimen (by raising the platen in strain controlled test
and by adding loads directly in stress controlled test, but strain controlled test is more common)
until shear failure occurs. Total vertical stress, which is σ1’ is equal to the sum of σ3’ and
deviator stress (σd). Measurement of σd, axial deformation, pore pressure, and sample
volume change are recorded.
Depending on the nature of loading and drainage condition, triaxial tests are conducted in three
different ways.
i. UU Triaxial test
ii. CU Triaxial test
iii. CD Triaxial test
APPLICATION:
UU triaxial test gives shear strength of soil at different confining stresses. Shear strength is
important in all types of geotechnical designs and analyses.
PROCEDURE:
i. The sample is placed in the compression machine and a pressure plate is placed on the top.
Care must be taken to prevent any part of the machine or cell from jogging the sample
while it is being setup, for example, by knocking against this bottom of the loading piston.
The probable strength of the sample is estimated and a suitable proving ring
selected and fitted to the machine.
ii. The cell must be properly set up and uniformly clamped down to prevent leakage of
pressure during the test, making sure first that the sample is properly sealed with its end
caps and rings (rubber) in position and that the sealing rings for the cell are also correctly
placed.
iii. When the sample is setup water is admitted and the cell is fitted under water escapes
from the beed valve, at the top, which is closed. If the sample is to be tested at zero lateral
pressure water is not required.
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OBSERVATION AND CALCULATION TABLE:
Size of specimen:
Length:
Proving ring constant:
Diameter: 3.81 cm
Initial area L:
Initial Volume:
Strain dial least count (const):
Sample
No.
Wet bulk
density
(gm/cc)
Cell
pressure (kg/cm
2)
Compressive stress at failure
Strain
at
failure
Moisture
content
Shear
strength
(kg/cm2)
Angle of
shearing
resistance
1
2
3
Cell pressure kg/cm
2
Strain dial Proving ring
reading
Load on sample kg
Corrected area cm
2
Deviator
stress
0.5
0
50
100
150
200
250
300
350
400
450
0.5
0
50
100
150
200
250
300
350
400
450
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iv. The air pressure in the reservoir is then increased to raise the hydrostatic pressure in the
required amount. The pressure gauge must be watched during the test and any necessary
adjustments must be made to keep the pressure constant.
v. The handle wheel of the screw jack is rotated until the underside of the hemispherical
seating of the proving ring, through which the loading is applied, just touches the cell
piston.
vi. The piston is then removed down by handle until it is just in touch with the pressure
plate on the top of the sample, and the proving ring seating is again brought into contact
for the begging of the test.
vii. The machine is set in motion (or if hand operated the hand wheel is turned at a constant
rate) to give a rate of strain 2% per minute. The strain dial gauge reading is then taken
and the corresponding proving ring reading is taken the corresponding proving ring chart.
The load applied is known. The experiment is stopped at the strain dial gauge reading
for 15% length of the sample or 15% strain.
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0.5
0
50
100
150
200
250
300
350
400
450
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GENERAL REMARKS:
i. It is assumed that the volume of the sample remains constant and that the area of the
sample increases uniformly as the length decreases. The calculation of the stress is
based on this new area at failure, by direct calculation, using the proving ring constant
and the new area of the sample. By constructing a chart relating strains readings, from
the proving ring, directly to the corresponding stress.
ii. The strain and corresponding stress is plotted with stress abscissa and curve is drawn.
The maximum compressive stress at failure and the corresponding strain and cell
pressure are found out.
iii. The stress results of the series of triaxial tests at increasing cell pressure are plotted on
a Mohr stress diagram. In this diagram a semicircle is plotted with normal stress as
abscissa shear stress as ordinate.
iv. The condition of the failure of the sample is generally approximated to by a straight
line drawn as a tangent to the circles, the equation of which is t = C + a tan f. The
value of cohesion ‘C’ is read of the shear stress axis, where it is cut by the tangent to
the Mohr circles, and the angle of shearing resistance (f) is angle between the tangent
and a line parallel to the shear stress.
RESULT
Shear strength of the soil =
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IMPACT TEST
Aim
To determine the aggregate impact value of given aggregate as per IS-2386 Part IV.
Apparatus
The apparatus consists of an
• Impact testing machine: The machine consists of a metal base, a detachable
cylindrical steel cup of internal diameter 10.2 cm and depth 5cm, a metal hammer of
weight between 13.5 to 14 Kg, 10cm in diameter and 5 cm long and an arrangement
for raising the hammer and allow it to fall freely between vertical guides from a
height of 38 cm on the test sample in the cup.
• A cylindrical metal measure having 7.5 cm and depth of 5 cm for measuring
aggregates.
• A tamping rod of circular cross section, 1cm in diameter and 23cm long, rounded at
one end.
• I.S. sieve of sizes 12.5 mm, 10 mm and 2.36 mm.
• Balance of capacity not less than 500 g to weigh accurate up to 0.01 g.
Principle
Toughness is the property of a material to easiest impact. Due to moving loads the aggregates are
subjected to pounding action or impact and there is possibility of stones breaking into smaller
pieces. Therefore a test designed to evaluate the toughness of stones i.e., the resistance of the
stones to fracture under repeated impacts may be called Impact test on aggregates. The test can
also be carried on cylindrical stone specimen known as Page Impact test. The aggregate Impact
test has been standardized by Indian Standard Institution. The aggregate impact test is conducted
as per IS-2386 Part IV.
The aggregate Impact value indicates a relative measure of the resistance of aggregate to a sudden
shock or an Impact, which in some aggregates differs from its resistance to a slope compressive
load in crushing test. A modified Impact test is also often carried out in the case of soft
aggregates to find the wet Impact value after soaking the test sample.
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Aggregate Impact Testing Machine
Observation and Calculation
Sl. No. Details of sample Trail 1 Trail 2 Average
1 Total weight of aggregate sample filling the
cylindrical measure = W1 g
2 Weight of the aggregate passing 2.36 mm
sieve after the test = W2 g
3 Weight of aggregate retained on 2.36 mm
sieve after the test = W3 g
4 Difference in weight = W1 – (W2 + W3) g
5
Aggregate Impact value = percent fines =
��∗ �
� %
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Aggregate Impact Value = ��∗ �
� %
Various agencies have specified the maximum permissible aggregate Impact values for the
different types of pavements. IRC has specified the following values.
The maximum allowable aggregate Impact value for water bound Macadam; Sub-Base coarse
50% where as cement concrete used in base course is 45%. WBM base course with Bitumen
surface in should be 40%. Bituminous Macadam base course should have A.I.V of 35%. All the
surface courses should possess an A.I.V below 30%.
Procedure
• The test sample consists of aggregates passing 12.5 mm sieve and retained on 10 mm
sieve and dried in an oven for 4 hours at a temperature of 100 0C to 110
0C.
• The aggregates are filled upto about 1/3 full in the cylindrical measure and tamped 25
times with rounded end of the tamping rod.
• The rest of the cylindrical measure is filled by two layers and each layer being tamped
25 times.
• The overflow of aggregates in cylindrical measure is cut off by tamping rod using it
as a straight edge.
• Then the entire aggregate sample in a measuring cylinder is weighted nearing to
0.01g.
• The aggregates from the cylindrical measure are carefully transferred into the cup
which is firmly fixed in position on the base plate of machine. Then it is tamped 25
times.
• The hammer is raised until its lower face is 38cm above the upper surface of
aggregates in the cup and allowed to fall freely on the aggregates. The test sample is
subjected to a total of 15 such blows each being delivered at an interval of not less
than one second. The crushed aggregate is then removed from the cup and the whole
of it is sieved on 2.36 mm sieve until no further significant amount passes. The
fraction passing this sieve is weighed accurate to 0.1g. Repeat the above steps with
other fresh sample.
• Let the original weight of the oven dry sample be W1g and the weight of fraction
passing 2.36 mm I.S sieve be W2g. Then aggregate Impact value is expressed as the %
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of fines formed in terms of the total weight of the sample.
Result
The mean Aggregate Impact Value is ______________________%.
Inference
Viva voce
1. How is aggregate Impact expressed?
2. What do you understand by dry and wet Impact value?
3. Aggregate Impact value of material A is 15 and that of B is 35. Which one is better for
surface course?
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LOS ANGELES ABRASION TEST
Aim
To determine the abrasion value of given aggregate sample by conducting Los Angeles
abrasion test.
Apparatus
• Los Angeles machine with inside diameter 70 cm and inside length of 50 cm and
abrasive charges.
• I.S Sieve with 1.7 mm opening.
• Weighting Balance of 0.1g accuracy.
Principle
Abrasion is a measure of resistance to wear or hardness. It is an essentially property for road
aggregates especially when used in wearing coarse. Due to the movements of traffic, the road
stones used in the surfacing course are subjected to wearing actions at the top. When traffic
moves on the road the soil particle (sand) which comes between the wheel and road surface
causes abrasion on the road stone. The abrasion test on aggregate is found as per I.S.-2386
part-IV.
The principle of Los Angeles abrasion test is to find the percentage wear due to the relative
rubbing action between the aggregates and steel balls used as abrasive charge pounding
action of these balls also exist while conducting the test. Maximum Allowable Los Angeles
Abrasion Values of Aggregates in Different types of pavement layers as per Indian Road
Congress (IRC) are:-
For sub-base course a value of 60%. For base course such as WBM, Bituminous Macadam
(B.M.), Built – Up spray grout base course and etc. value of 50%.
For surface course such as WBM, BM, Bituminous Penetration Macadam, Built-Up spray
grout binder course and etc. a value of 40%.
If aggregates are used in surface course as Bituminous carpet, Bituminous surface dressing,
single or two coats, cement concrete surface coarse and etc. a value of 35%. If aggregates are
used for Bituminous concrete, Cement concrete pavement as surface coarse than aggregate
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Schematic diagram of Los Angeles abrasion testing machine
Observation and Calculation
Sl. No. Details of sample Trail 1 Trail 2 Average
1 Weight of specimen, W1 g
2 Weight of specimen after abrasion test,
retained on 1.70 mm test sieve, W2 g
3
Los Angeles Abrasion value = Percentage
wear = � �� ��
��100
Specifications for conducting Los Angeles abrasion test
Gra
din
g
Weight of test sample in grams for different gradings, in the size range, mm (passing and retained
on aggregate test sieves) Abrasive charge
80-63 63-50 50-40 40-25 25-20 20-12.5 12.5-10 10-6.3 6.3-4.75 4.75-2.36 No. of
spheres
Weight of
charge ,g
A - - - 1250 1250 1250 1250 - - - 12 5000 ± 25
B - - - - - 2500 2500 - - - 11 4584 ± 25
C - - - - - - - 2500 2500 - 8 3330 ± 20
D - - - - - - - - - 5000 6 2500 ± 15
E 2500* 2500* 5000* - - - - - - - 12 5000 ± 25
F - - 5000* 5000* - - - - - - 12 5000 ± 25
G - - - 5000* 5000* - - - - - 12 5000 ± 25
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abrasion value of 30% maximum.
Procedure
• Clean and dry aggregate sample confirming to one of the grading A to G is used for
the test. (Refer table no. 1)
• Aggregates weighing 5 Kg for grading A, B, C or D and 10Kg for gradings E, F or G
may be taken as test specimen and placed in the cylinder.
• The abrasive charge is also chosen in accordance with table no.1 and placed in the
cylinder of the machine, and cover is fixed to make dust tight.
• The machine is rotated at a speed of 30 to 33 revolutions per minute.
• The machine is rotated for 500 revolutions for gradings A, B, C and D, for gradings E,
F and G, it shall be rotated for 1000 revolutions.
• After the desired number of revolutions, the machine is stopped and the material is
discharged from the machine taking care to take out entire stone dust.
• Using a sieve of size larger than 1.70 mm I.S sieve, the material is first separated into
two parts and the finer position is taken out and sieved further on a 1.70 mm I.S sieve.
• Let the original weight of aggregate be W1 g, weight of aggregate retained on 1.70
mm I.S sieve after the test be W2 g.
Los Angeles abrasion value, % = � �� ��
��100
Result
The average value of two Los Angeles abrasion test is --------------%
Inference
Viva voce
1. The abrasion value found from Los Angeles test for two aggregates A and B are 50% and
38% respectively. Which aggregate is harder? Why? For what types of constructions are
these suitable?
2. Why Los Angeles abrasion test is considered superior to the other form of tests which are
used to determine the hardness of aggregates?
3. Two materials have abrasion values 3 and 10 respectively. Which one is harder and why?
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SHAPE TEST (Flakiness Index)
Aim
To determine the flakiness Index of a given aggregates sample.
Apparatus
The apparatus consists of a standard thickness gauge, I.S. sieves of sizes 63, 50, 40, 31.5, 25,
20, 16, 12.5, 10 and 6.3mm and a balance to weigh the samples.
Principle
The particle shape of aggregate is determined by the percentages of flaky and elongated
particles contained in it. In case of gravel it is determined by its Angularity Number.
Flakiness and Elongation tests are conducted on coarse aggregates to assess the shape of
aggregates. Aggregates which are flaky or elongated are detrimental to the higher workability
and stability of mixes. They are not conducive to good interlocking and hence the mixes with
an excess of such particles are difficult to compact to the required degree. For base coarse
and construction of bituminous and cement concrete types, the presence of flaky and
elongated particles are considered undesirable as they may cause inherent weakness with
probabilities of breaking down under heavy loads. Rounded aggregates are preferred in
cement concrete road construction as the workability of concrete improves. Angular shape of
particles are desirable for granular base coarse due to increased stability derived from the
better interlocking when the shape of aggregates deviates more from the spherical shape, as
in the case of angular, flaky and elongated aggregates, the void content in an aggregate of any
specified size increases and hence the grain size distribution of the graded aggregates has to
be suitably altered in order to obtain minimum voids in the dry mix or the highest dry density.
It is determined according to the procedure laid down in IS-2386 (PART- I).
FLAKINESS INDEX
The flakiness index of aggregates is the percentage by particles whose least dimension
(thickness) is less than three-fifths or 0.6 times their mean dimension. The test is not
applicable to sizes smaller than 6.3mm.
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Thickness Gauge
Observation and calculation
Size of aggregate
Thickness
Gauge (0.6
times the mean
sieve), mm
Weight of the
fraction
consisting of
atleast 200
pieces, g
Weight of
aggregates in
each fraction
passing
thickness gauge,
g
Passing through
I.S. sieve , mm
Retained on I.S.
sieve , mm
63 50 33.90
50 40 27.00
40 31.5 21.50
31.5 25 16.95
25 20 13.50
20 16 10.80
16 12.5 8.55
12.5 10 6.75
10 6.3 4.89
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Procedure
• The sample is sieved with the sieves mentioned in the table.
• A minimum of 200 pieces of each fraction to be tested are taken and weighed (w1g).
• In order to separate flaky materials, each fraction is then gauged for thickness on
thickness gauge, or in bulk on sieve having elongated slots as specified in the table.
• Then the amount of flaky material passing the gauge is weighed to an accuracy of
atleast 0.1% of test sample.
• Let the weight of the flaky materials passing the gauge be w1 g. Similarly the weights
of the fractions passing and retained on the specified sieves be w1, w2, w3, etc. are
weighed and the total weight w1+w2+w3+………. = w g is found. Also the weights
of the materials passing each of the specified thickness gauge are found = W1, W2,
W3… and the total weight of the material passing the different thickness gauges =
W1+W2+W3+………. =W g is found.
• Then the flakiness index is the total weight of the flaky material passing the various
thickness gauges expressed as a percentage of the total weight of the sample gauged
Flakiness Index = ����������⋯ �
� �� �� ��⋯ ��100
= �
�100 %
Result
The flakiness index of the given sample of aggregates is _______________%.
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SHAPE TEST (Elongation Index)
Aim
To determine the Elongation Index of a given aggregate sample.
Apparatus
Length gauge, I.S-sieves as given in the table and a balance of accuracy 0.01 g.
Principle
The particle shape of aggregate is determined by the percentages of flaky and elongated
particles contained in it. In case of gravel it is determined by its Angularity Number.
Flakiness and Elongation tests are conducted on coarse aggregates to assess the shape of
aggregates. Aggregates which are flaky or elongated are detrimental to the higher workability
and stability of mixes. They are not conducive to good interlocking and hence the mixes with
an excess of such particles are difficult to compact to the required degree. For base coarse
and construction of bituminous and cement concrete types, the presence of flaky and
elongated particles are considered undesirable as they may cause inherent weakness with
probabilities of breaking down under heavy loads. Rounded aggregates are preferred in
cement concrete road construction as the workability of concrete improves. Angular shape of
particles are desirable for granular base coarse due to increased stability derived from the
better interlocking when the shape of aggregates deviates more from the spherical shape, as
in the case of angular, flaky and elongated aggregates, the void content in an aggregate of any
specified size increases and hence the grain size distribution of the graded aggregates has to
be suitably altered in order to obtain minimum voids in the dry mix or the highest dry density.
It is determined according to the procedure laid down in IS-2386 (PART- I).
Elongation index: The elongation index of an aggregate is the percentage by weight of
particles whose greatest dimension (length) is greater than one and four fifth times or 1.8
times their mean dimensions. The elongation test is not applicable to sizes smaller than 6.3
mm.
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Length Gauge
Observation and calculation
Size of aggregate
Length Gauge
(1.8 times the
mean sieve),
mm
Weight of the
fraction
consisting of
atleast 200
pieces, g
Weight of
aggregates in
each fraction
passing
thickness gauge,
g
Passing through
I.S. sieve , mm
Retained on I.S.
sieve , mm
63 50 -
50 40 81.0
40 31.5 64.4
31.5 25 -
25 20 40.5
20 16 32.4
16 12.5 25.6
12.5 10 20.2
10 6.3 14.7
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Procedure
• The sample is sieved through I.S-sieves specified in the table. A minimum of 200
aggregate pieces of each fraction is taken and weighed.
• Each fraction is thus gauged individually for length in a length gauge. The gauge
length is used should be those specified in the table for the appropriate material.
• The pieces of aggregates from each fraction tested which could not pass through the
specified gauge length with its long side are elongated particles and they are collected
separately to find the total weight of aggregate retained on the length gauge from each
fraction.
• The total amount of elongated material retained by the length gauge is weighed to an
accuracy of atleast 0.1% of the weight of the test sample.
• The weight of each fraction of aggregate passing and retained on specified sieves
sizes are found – W1, W2, W3, …………. And the total weight of sample determined
= W1+W2+W3+……………. = W g. Also the weights of material from each fraction
retained on the specified gauge length are found = x1, x2, x3… and the total weight
retained determined = x1+x2+x3+…… = x g.
• The elongation index is the total weight of the material retained on the various length
gauges, expressed as a percentage of the total weight of the sample gauged.
Elongation Index = �!��!��!��⋯ �
� �� �� ��⋯ ��100
= !
�100 %
Result
The elongation index of a given sample of aggregates is _______________%.
Viva voce
1. What are the applications of shape tests?
2. Explain what is meant by flaky particles?
3. What is the significance of shape factors of coarse aggregates in pavement
construction?
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PENETRATION TEST
Aim
To determine the grade of the given binder.
Apparatus
It consists of items like container, needle, water bath, penetrometer, stop watch etc. Container
is 55mm in diameter and 35mm to 57mm height. The needle is provided with a shank
approximately 3.0mm in diameter into which it is immovably fixed.
Principle
The consistencies of bituminous materials vary depending upon several factors such as
constituents, temperature, etc. As temperature ranges between 25º and 50ºC most of the
paving bitumen grades remain in semi solid or in plastic states and their viscosity is so high
that they do not flow as liquid.
Determination of absolute viscosity of bituminous material is not so simple. Therefore the
consistency of these materials is determined by indirect methods. The consistency of bitumen
is determined by penetration test which is a very simple test. Various types and grades of
bituminous materials are available depending on their origin and refining process. The
penetration test determines the consistency of these materials for the purpose of grading
them, by measuring the depth (in units of one tenth of a millimeter or one hundredth of a
centimeter) to which a standard needle will penetrate vertically under specified conditions of
standard load, duration and temperature. Thus the basic principle of the penetration test is the
measurement of the penetration (in units of one tenth of a mm) of a standard needle in a
bitumen sample maintained at 25C during five seconds, the total weight of the needle
assembly being 100gm. The softer the bitumen, the greater will be the penetration. The test is
conducted as per IS-1203 for paving bitumen.
Procedure
• The bitumen is softened to a paving consistency between 75º and 100ºC above the
approximate temperature at which bitumen softens.
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Penetration test concept
Observation and calculation
Test property Trails
Mean value 1 2 3
Penetrometer dial initial reading
Penetrometer dial initial reading
Penetration mean value
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• The sample material is thoroughly stirred to make it homogeneous and free from air
bubbles and water.
• The sample containers are cooled in atmosphere of temperature not lower than 13ºC
for one hour. Then they are placed in temperature controlled water bath at a temperature
of 25ºC for a period of one hour.
• The weight of needle, shaft and additional weight are checked. The total weight of this
assembly should be 100 g.
• Using the adjusting screw, the needle assembly is lowered and the tip of the needle is
made to just touch the top surface of the sample.
• The needle assembly is clamped in this position. The contact of the tip of the needle is
checked using the mirror placed on the rear of the needle.
• The initial reading of the Penetrometer dial is either adjusted to zero or the initial reading
is noted.
• Then the needle is released by pressing a button and a stop watch is started. The needle is
released exactly for a period of 5.0 seconds.
• At least 3 measurements are made on this sample by testing at distance of not less than
100 mm apart.
• The difference between the initial and final penetration readings are taken as the
penetration value.
Result
The average penetration value of a given bitumen sample is -------------- and the grade of
bitumen is --------------.
Inference
Viva Voce
1) What are the applications of penetration test?
2) What do you understand by the term 30/40 bitumen?
3) What are the precautions to be taken while conducting a penetration test?
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SPECIFIC GRAVITY TEST FOR BITUMEN
Aim
To determine the Specific gravity of given Bituminous material by Pycnometer method.
Apparatus
Specific gravity Bottle, Balance and Distilled water.
Principle
The density of a bitumen binder is a fundamental property frequently used as an aid in
classifying the binders for use in paving jobs. In most applications, the bitumen is weighed,
but finally in use with aggregate system, the bitumen content is converted on volume basis.
Thus an accurate density value is required for conversion of weight to volume. The specific
gravity is greatly influenced by the chemical composition of binder. Increased amount of
aromatic type compounds cause an increase in the specific gravity.
The specific gravity is defined by ISI as the ratio of the mass of a given volume of the
bituminous material to the mass of an equal volume of water, the temperature of both being
specified at 27ºC±0.1ºC.
The code of practice used to determine the specific gravity is IS: 1202.
Procedure
• The clean, dried specific gravity bottle is weighed let that be W1 g.
• Then it is filled with fresh distilled water and then kept in water bath for at least half
an hour at temperature 27ºC±0.1ºC.
• The bottle is then removed and cleaned from outside. The specific gravity bottle
containing distilled water is now weighed. Let this be W2 g.
• Then the specific gravity bottle is emptied and cleaned. The bituminous material is
heated to a pouring temperature and the material is poured half the bottle, by taking
care to prevent entry of air bubbles. Then it is weighed. Let this be W3 g.
• The remaining space in specific gravity bottle is filled with distilled water at 27ºC and
is weighed. Let this be W4 g. Then specific gravity of bituminous material is given by
formula, specific gravity=�"#�"$�
�"%�"$���"&�"#�
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Observation and calculation
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Result
The specific gravity of given bituminous binder is ___________________.
Viva Voce
1. Define specific gravity.
2. What is the use of finding specific gravity?
3. What are the factors affecting specific gravity test?
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SOFTENING POINT OF BITUMEN
Aim
To determine the softening point of given paving bitumen as per IS: 1205.
Apparatus
Ring and Ball apparatus, Water bath with stirrer, Thermometer, Glycerin, etc. Steel balls each
of diameter 9.5mm and weight of 2.5±0.05 g.
Principle
Bitumen does not suddenly change from solid to liquid state, but as the temperature increase,
it gradually becomes soften until it flows readily. The softening point is the temperature at
which the substance attains particular degree of softening under specified condition of test.
For bitumen it is usually determined by Ring and Ball apparatus. The test is conducted as per
IS: 1205.
Procedure
• Sample material is heated to a temperature between 75º and 100ºC above the
approximate softening point until it is completely fluid and is poured in heated rings
placed on the metal plate.
• To avoid sticking of the bitumen to metal plate, coating is done to this with a solution
of glycerin and dextrin.
• After cooling the rings in air for 30 minutes, the excess bitumen is trimmed and rings
are placed in the support.
• At this time the temperature of distilled water is kept at 5ºC. This temperature is
maintained for 15 minutes after which the balls are placed in position.
• Then the temperature of water is raised at uniform rate of 5ºC per minute with a
controlled heating unit, until the bitumen softens and touches the bottom plate by
sinking of balls. At least two observations are made. For material whose softening
point is above 80ºC, glycerine is used for heating medium and the starting
temperature is 35ºC instead of 5ºC.
• The temperature at the instant when each of the ball and sample touches the bottom
plate of support is recorded as softening point value.
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Softening test concept
Observation and calculation
Test property Trails
Mean value 1 2 3
Temperature (0C) at which I ball
touches the bottom plate
Temperature (0C) at which II ball
touches the bottom plate
Final softening point temperature
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Result
The softening point value of given bitumen sample is ___________________ºC and grade of
bitumen is _________________.
Viva Voce
1) What are the factors which affect the ring and ball test results?
2) What is softening point? If material A has softening point of 56 and B has 42 which
binder is good and why?
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DUCTILITY TEST
Aim
To conduct ductility test on given bitumen sample.
Apparatus
Briquette mould, (length – 75mm, distance between clips – 30mm, width at mouth of clips
20mm, distance between clips – 30mm, cross section at minimum width – 10mm x 10mm),
Ductility machine with water bath and a pulling device at a pre-calibrated rate, a putty knife,
thermometer.
Principle
A certain minimum ductility is necessary for a bitumen binder. This is because of the
temperature changes in bituminous mixes and the repeated deformations that occur in flexible
pavements due to the traffic loads. It is of significant importance that the binders form ductile
thin films around the aggregates. The binder material which does not possess sufficient
ductility would crack and thus provide previous pavement surface. This is in turn results in
damaging effect to the pavement structure. The ductility is expressed as the distance in
centimeters to which a standard briquette of bitumen can be stretched before the thread
breaks. The test is standardized by the IS: 1208. The test is conducted at 27º±0.5ºC and a rate
of pull of 50±2.5 mm per minute.
Procedure
• The bitumen sample is method to a pouring temperature (75ºC to 100ºC) and poured
into the mould assembly and placed on a brass plate, where a solution of glycerin or
soap solution is applied at all surfaces of briquette mould exposed to bitumen.
• After the sample is poured to the mould, thirty to forty minutes the entire assembly is
placed in a water bath at 27ºC.
• Then the sample is removed from the water bath maintained at 27ºC and excess
bitumen material is cutoff by leveling the surface using hot knife.
• After trimming the specimen, the mould assembly containing sample is replaced in
water
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Ductility test concept
Observation and calculation
Test property Trails
Mean value 1 2 3
Ductility value
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bath maintained at 27ºC for 85 to 95 minutes. Then the sides of mould are removed
and the clips are carefully booked on the machine without causing any initial strain.
Two or more specimens may be prepared in the moulds and clipped to the machine so
as to conduct these test simultaneously.
• The pointer is set to read zero. The machine is started and the two clips are thus pulled
apart horizontally.
• While the test is in operation, it is checked whether the sample is immersed in water
at depth of atleast 10mm. The distance at which the bitumen thread of each specimen
breaks is recorded (in cm) to report as ductility value.
Result
The ductility value of the given bitumen sample is _________________ cm.
Inference
Viva voce
1) List the factors that affect the results of a ductility test.
2) Explain the significance of ductility test.
3) What do you understand by the terms Repeatability and Reproducibility?
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CALIFORNIA BEARING RATIO TEST
Aim:
To determine California Baring Ratio (C.B.R.) value of a given soil sample.
Apparatus:
Loading machine which can be operated at a constant rate of 1.25mm per minute, cylindrical
moulds of 150mm diameter i.e., 175mm height provided with a collar of about 50mm length
and detachable perforated base are used for this purpose, Compaction Rammer.
Theory and Scope:
The California Bearing Ratio (C.B.R.) test was developed by California Division of Highway
as a method of classifying and evaluating soil subgrade and base course materials for flexible
pavements. The test is empirical and the results cannot be related accurately with any
fundamental property of the material.
The CBR is a measure of resistance of a material to penetration of standard plunger under
controlled density and moisture conditions. The CBR test may be conducted in re-moulded or
undisturbed specimen in the laboratory. The test is simple and has been extensively
investigated for field correlations of flexible pavement thickness requirement. The test is
conducted by causing a cylindrical plunger of some diameter to penetrate a pavement
component material at 1.25mm/minute. The loads, for 2.5mm and 5mm are recorded. This
load is expressed as a percentage of standard load value at a respective deformation level to
obtain C.B.R. value. The values are given in the table
As per IRC recommendation the minimum value of C.B.R. required for a subgrade should be
8%. The procedure is standardized by Indian Standards Institution in two different categories.
The first being Test of Soils in laboratory, determination of CBR, IS: 2720 part XVI. The
second
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For Penetration Test
1. Calibration factor of the proving ring 1 Div. = ...................kg
2. Surcharge weight used (kg) =
3. Least count of penetration dial, 1Div. = ................ mm
Penetration of
plunger,
mm
Load dial reading,
Divisions Load, kg
0.0
0.5
1.0
1.5
2.0
2.5
3.0
4.0
5.0
7.5
10.0
12.5
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being Methods of Test for soils, field determination of CBR, IS: 2720 XXXI.
Procedure:
• Each batch of soil is (of atleast 5.5kg for granular soils and 4.5 to 5kg weight for fine
grained soils) mixed with water upto the optimum moisture content or the field
moisture content if specified so.
• The spacer disc is placed at the bottom of the mould over the base plate and a coarse
filter paper is placed over the spacer disc.
• The moist soil sample is to be compacted over this in the mould by adopting either the
• I.S. light compaction or the I.S. heavy compaction.
• After compacting the last layer, the collar is removed and the excess soil above the
top of the mould is evenly trimmed off by means of straight edges.
• The clamps are removed and the mould with the compacted soil is lifted leaving
below the base plate and the spacer disc is removed.
• A filter paper is placed on the base plate, the mould with compacted soil is inverted
and placed in position over the base plate and clamps of the base plate are tightened.
• Weights of 2.5 to 5kg are placed over the soil sample in the mould. Then the whole
mould is placed in water tank for soaking.
• A swelling measuring device consisting of tripod and the dial gauge are placed on top
edge of the mould and the spindle of the dial gauge is placed touching the top of the
sample. The initial dial gauge reading is recorded and the test set up is kept
undisturbed in the water tank to allow soaking of the soil specimen for four full days
or 96 hours.
• After 96 hours of soaking, the mould with specimen is clamped over the base plate
and the same surcharge weights are placed on the specimen centrally such that the
penetration test can be conducted. The mould with base plate is placed under
penetration plunger of the loading machine.
• The penetration plunger is seated at the centre of the specimen and is brought in
contact with the top surface of the soil sample by applying a seating load of 4.0kg.
• The dial gauge for the measuring the penetration values of the plunger is fitted in
position. The dial gauge of the proving ring and the penetration dial gauge are set to
zero.
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Density Determination
Weight of mould + soil (g) =
Weight of mould (g) =
Weight of soil (g) =
Volume of sample (cm3) =
Bulk density (g/cc) =
Water content (%) =
Dry density (g/cc) =
Water Content Determination
Weight of container + wet soil (g) =
Weight of container + dry soil (g) =
Weight of water (g) =
Weight of container (g) =
Weight of dry soil (g) =
Water content (%) =
CBR Calculations
CBR for 2.5 mm penetration = '()* )+ ,.. // 0121+3)+4(2
5+)2*)3* 6()* *100
CBR for 5 mm penetration =
CBR of the soil =
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• The load is applied through the penetration plunger at a uniform rate of
1.25mm/minute. The load readings are recorded at penetration readings of 0.0, 0.5,
1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 7.5, 10.0, 12.5 mm penetration. The maximum load
value and the corresponding penetration value are recorded.
• After the final reading, the load is released and the mould is removed from the loading
machine. The proving ring calibration factor is noted so that the load dial values can
be converted into load in kg.
• The load values noted for each penetration level are divided by the area of the loading
plunger (19.635cm2) to obtain the pressure.
• A graph is plotted by penetration in mm on x-axis and the pressure in kg/cm2 on y-
axis. Then the unit pressure values corresponding to 2.5 and 5.0mm penetration
values are found from the graph. Then the CBR value is calculated from the formula:
CBR in % =
• The CBR values at 2.5mm and 5.0mm penetrations are calculated for each specimen
from the corresponding graphs. Generally the CBR value at 2.5mm penetration if
higher and the value are adopted. However if higher CBR value is obtained at 5.0mm
penetration, the test is to be repeated to verify the results. If the value at 5.0mm
penetration is again higher, this is adopted as the CBR value of the soil sample.
Result:
The CBR value of the given soil sample is _________________%.
Viva Voce:
1. What is the significance of surcharge load while soaking and testing the soil in CBR
test?
2. CBR value of soil A is 15 and of soil B is 4. Which one is a better soil? Why?
3. Discuss the limitations of CBR test.
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LOS ANGELS ABRATION TEST
FLAKINESS AND ELONGATION TEST
CBR TEST
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PENETRATION TEST
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SOFTENING POINT OF BITUMEN
DUCTILITY TEST
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