geotechnical engineering lab - Ammini College of … 607(P)_ Geotechnical... · geotechnical engineering lab manual ... 3 atterberg limits and indices 19 5 determination of coefficient

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GEOTECHNICAL ENGINEERING

LAB MANUAL

DEPARTMENT OF CIVIL ENGINEERING

NAME: ………………………………………………….

ROLL No: ……..…....................................

YEAR: ……………….………………………….………

Downloaded from Official website of Ammini College of Engineering, Palakkad http://ammini.edu.in/content.aspx?pageid=362

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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

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DETERMINATION OF COEFFICIENT OF PERMEABILITY OF

THE SOIL BY

A) CONSTANT HEAD METHOD

B) FALLING HEAD METHOD

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DETERMINATION OF FIELD DENSITY OF SOILS BY

A) CORE CUTTER METHOD

B) SAND REPLACEMENT METHOD

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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.


40


Internal diameter of cutter (cm): _ _ _ _ _ _ _ _

Height of the cutter (cm): _ _ _ _ _ _ _ _

Cross sectional area of the cutter (cm2): _ _ _ _ _ _ _ _

Volume of the cutter, V (cm3): _ _ _ _ _ _ _ _


41

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.


42


43

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 =...............................................


44


45

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?


46


47

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.


48


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.


50


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)


51

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?


52

OBSERVATION AND CALCULATION


53

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.


54

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


55

(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) =


56

850

900

950

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2200

2400

2600

2800

3000


57


58


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).


60


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


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


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?


64


65

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.


66


67

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.


68


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


69

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.


70

0.5

0

50

100

150

200

250

300

350

400

450


71

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 =


72


73

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.


74

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 =

��∗ �

� %


75

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 %


76


77

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?


78


79

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


80

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


81

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?


82


83

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.


84

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


85

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 _______________%.


86


87

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.


88

Length Gauge


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


89

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?


90


91

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.


92

Penetration test concept


Test property Trails

Mean value 1 2 3

Penetrometer dial initial reading

Penetrometer dial initial reading

Penetration mean value


93

• 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?


94


95

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=�"#�"$�

�"%�"$��"&�"#�


96



97

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?


98


99

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.


100

Softening test concept



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


101

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?


102


103

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


104

Ductility test concept



Mean value 1 2 3

Ductility value


105

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?


106


107

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


108

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


109

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.


110

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 =


111

• 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.


112


113

LOS ANGELS ABRATION TEST

FLAKINESS AND ELONGATION TEST

CBR TEST


114

PENETRATION TEST


115

SOFTENING POINT OF BITUMEN

DUCTILITY TEST


116


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