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SOIL MECHANICS

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Page 1: Soil Laboratory Testing

VILNIUS GEDIMINAS TECHNICAL UNIVERSITY

GEOTECHNICAL DEPARTMENT

SOIL MECHANICS

STGT B 06104

LABORATORY TESTING MANUAL

PREPARED BY: J. MEDZVIECKAS, D. SLIŽYTĖ, V. STRAGYS

VILNIUS „Technika“ 2004

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Soil mechanics. Laboratory testing manual.

Prepared by J. Medzvieckas, D. Sližytė, V. Stragys.

Vilnius: Technika, 2004. 79 p. (anglų k.)

The manual includes soil mechanics laboratory testing procedures and calculation of soil parameters.

Leidinyje pateikiama gruntų mechanikos laboratorinių darbų atlikimo metodika, aprašomi prietaisai bei

rezultatų pateikimo reikalavimai.

Leidinys skirtas anglų kalba studijuojantiems Statybos programos studentams.

Rekomendavo VGTU Statybos fakulteto studijų komitetas

Recenzavo prof. habil. dr. G. Kaklauskas,

doc. dr. A. Krutinis

VGTU leidyklos “Technika” 679 mokomosios metodinės literatūros knyga

ISBN 9986-05-748-5

Sudarytojai J. Medzvieckas, D. Sližytė, V. Stragys, 2004

VGTU leidykla „Technika“, 2004

CONTENTS

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LABORATORY EXPERIMENT No. 1................................................................................................................................... 4 SOIL PARTICLE SIZE DISTRIBUTION (SIEVING) ....................................................................................................... 4

LABORATORY EXPERIMENT No. 2................................................................................................................................... 8 SOIL PARTICLE SIZE DISTRIBUTION (HYDROMETER TEST)................................................................................. 8

LABORATORY EXPERIMENT No.3.................................................................................................................................. 13 SOIL MOISTURE CONTENT .......................................................................................................................................... 13

LABORATORY EXPERIMENT No. 4................................................................................................................................. 16 SOIL DENSITY ................................................................................................................................................................. 16

LABORATORY EXPERIMENT No.5.................................................................................................................................. 22 SOIL PARTICLE DENSITY ............................................................................................................................................. 22

LABORATORY EXPERIMENT No. 6................................................................................................................................. 27 SOIL ATTEBERG LIMITS ............................................................................................................................................... 27

LABORATORY EXPERIMENT No. 7................................................................................................................................. 34 SOIL PERMEABILITY ..................................................................................................................................................... 34

LABORATORY EXPERIMENT No. 8................................................................................................................................. 40 SOIL ONE DIMENSIONAL CONSOLIDATION PROPERTIES................................................................................... 40

LABORATORY EXPERIMENT No.9.................................................................................................................................. 48 SOIL COMPACTION........................................................................................................................................................ 48

LABORATORY EXPERIMENT No. 10............................................................................................................................... 53 CALIFORNIA BEARING RATIO (C B R) ...................................................................................................................... 53

LABORATORY EXPERIMENT No. 11............................................................................................................................... 62 SOIL DIRECT SHEAR TEST ........................................................................................................................................... 62

LABORATORY EXPERIMENT No. 12............................................................................................................................... 69 SOIL UNCONFINED COMPRESSIVE STRENGTH...................................................................................................... 69

LABORATORY EXPERIMENT No. 13............................................................................................................................... 74 SOIL UNDRAINED TRIAXIAL COMPRESSION TEST............................................................................................... 74

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LABORATORY EXPERIMENT No. 1

SOIL PARTICLE SIZE DISTRIBUTION (SIEVING)

OBJECT:

To find the quantitative distribution of the particles in a cohesionless soil down to the fine-sound size.

APPARATUS:

Test sieves, sieve shaker, balances, rifle box, a drying oven, an evaporation dish, tray, a scoop, brush,

chemicals.

PROCEDURE:

1. Prepare soil sample. The soil should be dried in oven or air and should be subdivided using rifle box. Mass of

sample required for each test depends on soil group (fine, medium or coarse).

2. Clean the sieves to be used in the analysis and obtain the weight of each.

Use BS sieves 2 mm, 1.18 mm, 600 µm, 425 µm, and 63 µm (Sieve sizes depend on the soil group).

3. Arrange the order of the sieves to have the largest at the top of the stack and screw down the lid.

4. Vibrate the sample for 10 minutes before removing the stack and reveighting each sieve with the part of the

sample retaining on it.

5. Put the sample back in the container and clean the sieves with the brush.

CALCULATIONS, PLOTTING AND QUESTIONS:

1. Calculate particle size distribution curve and tabulate it in to the form 1.1.

2. Plot the grain size distribution. Use form 1.2. Is the sample well graded, gap graded or uniform? Explain.

3. Calculate Cc and Cu and classify the soil according to the Unified Classification System.

4. Would you expect the particle size distribution to be affected by the treatment given to the soil prior to sieving?

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5. What are the uses of the analysis?

6. Why do you use logarithmic plot for the distribution?

7. Why is sieve analysis confined to coarse grained soils?

References:

1. K.H. Head. Manual of Soil Laboratory Testing. Vol.1. pp. 159-175.

2. B.S. 1377: Part 2. pp. 30-34.

3. R.F. Craig. Soil Mechanics. pp. 5-7, 22

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LABORATORY EXPERIMENT No. 2

SOIL PARTICLE SIZE DISTRIBUTION (HYDROMETER TEST)

OBJECT:

To find the particle-size distribution in a soil from the coarse sand to the clay size.

APPARATUS:

Soil hydrometer (see fig. 2.1), two 1000 ml glass measuring cylinders, constant temperature bath, stop-clock,

glass rod, thermometer, mechanical shaker, chemical reagents.

PROCEDURE:

1. Prepare soil sample. The dry mass of soil required depends on the type of soil. Appropriate quantities are

about 100 g for a sandy soil and 50 g for a clay or silt.

2. Weight the sample to 0.01g and obtain it's initial mass. Prepare standard dispersant and prepare suspension

adding 100ml of the dispersant. Use sodium hexametaphosphate as the dispersing agent. Shake the mixture

thoroughly. Transfer it to 1000ml cylinder.

3. Shake the cylinder rigorously using end-over-end shaker and immediately replace upright.

4. Immerse the hydrometer in the suspension and take hydrometer readings on the upper rim of the meniscus

and after periods of 0.5min, 1min, 2min, 4min, 8min, 15min, 30min, 1h, 2h, 4h, 8h and 24h. Insert and withdraw

the hydrometer before and after taking each reading. Observe and record the temperature of the suspension.

CALCULATIONS, PLOTTING AND QUESTIONS:

1. Calculate true hydrometer readings by adding meniscus correction. Typical value of meniscus correction is

equal 0.5 and this value could be used for the academic reasons.

2. Calibrate hydrometer. For the academic reasons use example of calibration graph (see fig. 2.2) and calculate

effective depth, in mm.

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3. Use datum of hydrometer reading Rl0 = 0 and calculate the equivalent particle diameter D and percentage by

mass of particles less than D. Tabulate results into form 2.1.

4. Present results by plotting percentages against the particle diameter. Use form 2.2.

5. Which law governs the sedimentation of particles? Describe the main assumptions of that law.

References

1. K.H. Head. Manual of Soil Laboratory Testing. Vol.1. pp. 201-234.

2. B.S. 1377:Part 2. pp. 39-45.

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Temperature

(°C)

Dynamic viscosity, η

(mPas)

Density, ρw

(Mg/m3)

0 1.7865 0.999 84

5 1.5138 0.999 95

10 1.3037 0.999 70

15 1.1369 0.999 09

20 1.0019 0.998 20

25 0.8909 0.997 04

30 0.7982 0.995 65

40 0.6540 0.992 22

Fig. 2.3 Viscosity and density of water

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LABORATORY EXPERIMENT No.3

SOIL MOISTURE CONTENT

OBJECT:

Determination of moisture content of fine-, medium-, or coarse-grained soils.

APPARATUS:

Slightly different apparatus is used for fine-, medium-, and coarse grained soils.

For all types of soils:

A drying oven, capable of maintaining a temperature of 1050 to 1100 C is used.

For fine-grained soils:

A glass weighting bottle, or a suitable airtight corrosion resistant container, a balance readable to 0.01g, a

desiccator containing anhydrous silica gel.

For medium-grained soils:

An air tight corrosion-resistant container of about 500g capacity, a balance readable to 0.1g, a scoop of suitable

size.

For coarse grained soils:

An air tight corrosion-resistant container of about 4 kg capacity, a balance readable to 1g, a scoop of suitable

size.

PROCEDURE:

Slightly different procedures are used for fine-, medium-, or coarse-grained soils.

For fine-grained soils:

1. Clean and dry the weighting bottle or metal container and weight to the nearest 0.01g. Take a sample of at

least 30g of soil, crumble and place it in the container. Then weight the container and contents to the nearest

0.01g.

2. Place the container with itls contents in the oven and dry.

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3. After drying, remove the container from the oven and place in the desiccator to cool.

4. Weight the container and contents to the nearest 0.01g.

For medium-grained soils:

1. Use container of about 500g capacity.

2. Use the same procedure as for the fine-grained soils.

3. Find all masses to the nearest of 0.1g.

4. Allow sample to cool in air.

For coarse grained soils:

1. Use container of about 4 kg capacity.

2. Use the same procedure as for fine-grained soils.

3. Find all masses to the nearest 1g.

4. Allow sample to cool in air.

CALCULATIONS AND QUESTIONS:

1. Tabulate results into the form 3.1.

2. Calculate moisture content for at least 3 samples of the same soil. Find average.

3. Give definition of moisture content.

4. Give definitions of: adsorbed water, hygroscopic moisture, capillary water, gravitational water, chemically

combined water.

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References:

1. K. H. Head. Manual of Soil Laboratory Testing. Vol. 1. Pp. 71-78.

2. B.S. 1377: Part 2. Pp. 2-3.

3. R.F. Craig. Soil Mechanics. P. 23.

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LABORATORY EXPERIMENT No. 4

SOIL DENSITY

OBJECT:

Determination of soil density (Bulk density)

TYPES OF TEST:

Three methods are specified. The first method is called linear measurement method. It applies to soils that can

be calculated from linear measurements (see fig 4.1, a). The samples used are normally in the form either

rectangular prisms or right cylinders. In the second method, which is called immersion in water method, the

volume of the specimen is determined by weighting it in water (see fig. 4.1, b). In the third method, which is

called water displacement method, the volume of the specimen is measured by displacement of water (see fig.

4.1, c).

APPARATUS (COMMON FOR ALL THREE METHODS):

A trimming knife, a scalpel, a spatula, a two wire-saws, a metal straight-edge trimmer, straight edge, a steel tray,

square, vernier callipers, a flat glass plate.

APPARATUS FOR LINEAR MEASUREMENT METHOD:

The apparatus required is as specified for all three methods, with the addition of a balance readable 0.01g.

PROCEDURE FOR LINEAR MEASUREMENT METHOD

1. Form a soil specimen into a regular geometric shape.

2. Measure itls dimensions to an accuracy of 0.1 mm and calculate volume of specimen.

3. Weight specimen using balance readable 0.01g.

4. Express soil density (bulk density) dividing mass by volume (in MG/m3).

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APPARATUS FOR IMMERSION IN WATER METHOD:

Apparatus common to all procedures, apparatus for determination of specimen volume by immersion in water,

balance readable to 1g, equipment for melting paraffin wax, plasticity or putty, paraffin wax.

PROCEDURE FOR IMMERSION IN WATER METHOD:

1. Adjust apparatus according to figure 4.1,b.

2. Fill the container with water to within 80mm of the top.

3. Trim and weight specimen to nearest 1g.

4. Fill all the surface air voids of the specimen with plasticine or putty and weight again.

5. Coat specimen by dipping in molten paraffin.

6. Place the waxed specimen in the cradle and measure the apparent mass of the specimen while suspended in

water.

CALCULATIONS:

Calculations and expression of results according to requirements of form 4.1.

APPARATUS FOR WATER DISPLACEMENT METHOD:

Cylindrical metal container with siphon tube, watertight container, paraffin wax, equipment for melting paraffin

wax, balance readable for 1g.

PROCEDURE FOR WATER DISPLACEMENT METHOD:

1. Prepare sample in the same way as for immersion in water method.

2. Weight the container for receiving water to the nearest 1g.

3. Lower specimen into the container.

4. Weight the receiver and water to the nearest 1g.

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5. Remove the specimen.

CALCULATIONS:

Calculate and express results

according to the requirements of form 4.2.

References:

1. K.H. HEAD. Manual of Soil Laboratory Testing. Vol. 1. Pp. 130-140.

2. B.S. 1377:Part 2. Pp.22-26.

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LABORATORY EXPERIMENT No.5

SOIL PARTICLE DENSITY

OBJECT:

Determination of soil particle density.

TYPES OF TEST:

Two methods are described. The first is a gas jar method suitable for most soils including those containing

gravel-sized particles. The second is the small pycnometer method, which is the definitive method for soils

consisting of clay, silt and sand-sized particles.

GAS JAR METHOD

Method is suitable for soil containing up to 10% of particles retaining on a 37.5 mm test sieve.

APPARATUS:

Two gas jars 1 l capacity, mechanical end-over-end shaker, balance 5 kg capacity, readable to 0.1g,

thermometer readable to 10 C, drying oven.

PROCEDURE:

1. Prepare representative soil sample of about 1 kg. Break down soil particles retained on 37.5 mm sieve. Obtain

2 test specimens from the prepared sample. Each should be of about 200g for fine-grained soil. Dry in oven.

2. Weight gas jars to the nearest 0.2g.

3. Place each prepared specimen into gas jar and weight.

4. Add 500 ml water and shake for in shaking apparatus for 20-30 min.

5. Fill the gas jar to the brim of water and place the ground glass plate on top of the jar.

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6. Weight jar contents and plate.

7. Empty gas jar, wash, fill to the brim with water, slid on ground-glass plate, dry and weight.

8. Repeat procedure on the other specimen.

CALCULATIONS:

Calculate and express results according to the requirements of form 5.1.

SMALL PYCNOMETER METHOD

This method is used for soils consisting of particles finer than 2 mm.

APPARATUS:

Density bottles (50 ml), at 250 + 0.20C, vacuum desiccator, drying oven, analytical balance reading to 0.001g,

source of vacuum, spatula 150x3mm, wash bottle, containing de-aired density fluid.

PROCEDURE:

1. Wash, dry and weight density bottles to the nearest 0.001g.

2. Prepare representative soil sample of about 30g, oven dry and cool in the desiccator.

3. Divide the dried specimen into three equal parts and place each into density bottle. Weight each bottle with

soil to 0.001g.

4. Add the de-aired liquid to each bottle so that soil is just covered, place the bottles in the vacuum desiccator

and reduce pressure gradually to about 20 mm mercury and leave under vacuum for at least 1 hour.

5. Release the vacuum, remove desiccator lid, stir the soil and transfer to temperature bath. Leave for 1 hour at

least.

6. Remove the stoppered bottle from the bath, wipe it, dry and weight (bottle+stopper+liquid) to 0.001g.

7. Clean out each bottle, fill with de-aired liquid, immerse in the constant-temperature bath and after weight

(bottle+stopper+liquid) to 0.001g.

CALCULATIONS AND QUESTIONS:

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1. Calculate and tabulate results according to the requirement of form 5.2. The average of the three values

obtained is calculated. If any one value differs from the average value by more than 0.03 Mg/m3, the test should

be repeated.

2. Determine soil dry density, void ratio, porosity, degree of saturation, air content and unit weight. For

calculations use values of soil density, soil particle density and moisture content, which have been obtained in

laboratory tests No. 3 and No. 4.

References:

1. K.H. Head. Manual of Soil Laboratory Testing. Vol.1. Pp.140-149.

2. B.S. 1377: Part 2. Pp. 26-29.

3. R.F. Craig. Soil Mechanics. Pp. 23-27.

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LABORATORY EXPERIMENT No. 6

SOIL ATTEBERG LIMITS

OBJECT:

Determination of the liquid and plastic limit of a soil.

L I Q U I D L I M I T T E S T

Two main types of test are specified: a) Casagrande apparatus method, which has been used for many years as

a basis for soil classification and b) Cone penetrometer method, which is more satisfactory.

CASAGRANDE APPARATUS METHOD

Method is used for determination of liquid limit of a sample of natural soil or of sample of soil from which material

retained on a 425 m test sieve has been removed.

APPARATUS:

Liquid limit device and grooving tools (see fig. 6.1.a), apparatus for moisture content determination, two palette

knives, a flat glass plate, a wash bottle, a corrosion-resistant air-tight containers.

PROCEDURE:

1. Take a sample from material passing 0.425 m test sieve of 300 g.

2. Place it in the blow as it is shown in fig. 6.1, a.

3. Cut a groove in through the sample from back to front, dividing it into two equal halves.

4. Turn the crank handle of the machine at a steady rate of two revolutions per second so that the blow is lifted

and dropped. Continue turning until the groove is closed along a distance of 13 mm. Record the number of blows

to reach this condition.

5. Take s small quantity (about 10 g) of soil for the moisture content determination.

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6. Repeat stages 2-5 adding a little more water each time. The moisture content should be such that the number

of blows is roughly evenly spaced over the range from about 50 to 10.

CALCULATIONS AND PLOTTING:

1. Calculate moisture content for each blow count. Plot the moisture content against the corresponding number

of blows.

2. Use form 6.1 and draw the best straight line. Draw the ordinate representing 25 blows. Find the moisture

content at the intersection point with straight line.

3. The moisture content read at the intersection point is called as the liquid limit. The plastic limit is usually

reported at the same time.

CONE PENETROMETER METHOD

Method is based on the measurement of penetration into the soil of a standardised cone of specified mass. At

the liquid limit the cone penetration is 20 mm.

APPARATUS:

Penetrometer apparatus (see fig. 6.1, b and c), metal cups, moisture content apparatus, metal straight edge, two

palette knives.

PROCEDURE:

1. Take a sample from material passing the o.425 mm BS test sieve of 200 g.

2. Place the sample on the porcelain mixing dish and mix thoroughly with water (50-70 ml) until the mass

becomes a thick homogenous paste (uniform colour).

3. Push the mixed soil in the metal cup with a palette knife, taking care not to trap air. The excess soil shall be

struck off, to give a smooth surface.

4. Place the cup under the penetrometer and lower the cone so that it just touches the soil surface. `Note the dial

gauge readings.

5. Release the cone for a period of 5s and note again the dial gauge reading. The difference between the two

readings shall be recorded as a cone penetration.

6. If necessary add water so that the first reading is approximately 15 mm.

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7. Take a representative of sample (about 10 g) from the cup and put it on the dish. Weight this and dry the soil

in an oven for one day and weight again.

8. Take the rest of the soil back in the porcelain mixing dish, add water and mix again thoroughly. Put the soil in

a clean cup.

9. Repeat the described operation at least three times using the same sample to which further increments of

water are added. The amount of water added must be chosen so that the range of penetration values of

approximately 15mm to 25mm is covered.

CALCULATIONS:

1. Calculate moisture content for each penetration reading. Use form 6.2 for calculations and plotting.

2. Plot each cone penetration reading (in mm) against the corresponding moisture content. Draw the best

straight line.

3. The moisture content corresponding to a cone penetration of 20 mm is read. The result is reported as a liquid

limit.

The plastic limit and plasticity index are usually reported with the liquid limit.

P L A S T I C L I M I T T E S T

This method covers the determination of the plastic limit of soil, i.e. the lowest moisture content at which the soil

is plastic.

APPARATUS:

A flat glass plate on which soil is mixed, a flat glass plate on which treads are rolled, two palette knives,

apparatus for moisture content determination.

PROCEDURE:

1. Take sample from material passing 0.425 mm BS test sieve of 20g.

2. Add water so that a ball can be rolled, without clinging to the hand. Take 8g of it and make again a ball.

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3. Roll the ball on the glass plate using the palm of the hand until a tread of 3 mm diameter is formed. If the tread

does not show any cracks, turn it into a ball again and reroll.

4. If the cracks do not show the thread, take the crumbled soil and determine the moisture content.

CALCULATIONS, PLOTTING AND QUESTIONS:

1. Calculate the moisture content of both samples tested. Forms 6.1 or 6.2 may be used.

2. Calculate the plasticity index and liquidity index of the soil. For calculations use moisture content value, which

was determined during the laboratory test No.3.

3. After filling up the test result sheet draw the locations of the plastic and liquid limit on a water content scale.

Indicate significant values and the three phases of the soil.

4. What is the engineering significance of the consistency limits and for which soils it is especially important?

5. Why are the tests only carried out on material passing through a 0.425 mm BS test sieve?

6. Classify the soil according to the Unified Classification System. What problems (if there are any) do you

expect when using this engineering practice?

References:

1. K.H. Head. Manual of Soil Laboratory Testing. Vol.1 Pp. 78-99.

2. B.S. 1377: Part 2. Pp. 5-14.

3. R.F. Craig. Soil Mechanics. Pp. 7-10.

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LABORATORY EXPERIMENT No. 7

SOIL PERMEABILITY

OBJECT:

Determination of the coefficient of permeability of granular soil.

TYPE OF TEST:

The test procedure described in this laboratory experiment covers the determination of the coefficient of

permeability using the constant head permeability apparatus (see fig. 7.1, a and b). This procedure is suitable for

soils having coefficients of permeability in the range

10-2 to 10-5 m/s.

APPARATUS:

A permeameter cell. Cells of 75mm and 100mm diameter are generally suitable; glass piezometer tubes,

constant head reservoir, constant head discharge reservoir, small tools, i.e. funnel, tamping rod, scoop, etc.;

thermometer, stop clock, measuring cylinders.

PROCEDURE:

1. Prepare auxilary apparatus and permeameter cell. Ensure that all joints are air-tight. Measure internal

dimensions of cell, distances between centres of each manometer and fill required results into data sheet (form

7.1).

2. Select, prepare and place soil sample in cell. The sample may be placed in the permeameter by one of three

methods, i.e. compacting by rodding, dry pouring (see fig. 7.2,a) or by pouring through water (see fig. 7.2,b).

3. Assemble and connect up cell.

4. Saturate and de-air sample.

5. Run test. Adjust the height of inlet receiver. Open the control valve at the base to produce flow through the

sample under the hydraulic gradient appreciably less than unity. Place measuring cylinder and start the timer.

Measure the quantity of water collected in the cylinder during the given interval of time (use form 7.1) and record

the time. Record the levels of water in the manometer tubes, record the temperature of water.

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6. Raise the level of constant head tank and repeat the stage 5 at a greater hydraulic gradient.

CALCULATIONS, PLOTTING AND QUESTIONS:

1. Calculate the rate of flow (in L/s) during the period of each observation of flow from the equation

q1 = Q1/ t

2. Calculate the hydraulic gradient i between the uppermost and lowest manometer gland points from the

equation i = h/y, where h - is the difference between the two manometer levels, in mm (see fig 7.1, a) and y - is

the difference between the corresponding gland points, in mm.

3. Calculate the coefficient of permeability k (in m/s), for one set of readings from the equation which is given in

the data sheet (see form 7.1).

4. Find the temperature correction factor (use fig. 7.3,a) and calculate permeability at 20o C.

5. Plot diagrams rate of flow q (mm/min) against time from the start t (minutes and rate of flow q against 1/ t.

(See examples, fig. 7.3, b and c).

6. What is the effect of air bubbles in the water on the calculated k - value?

7. Describe briefly other methods of permeability tests.

8. Enumerate factors affecting permeability of soils.

References:

1. K.H. Head. Manual of Soil Laboratory Testing. Vol 2. Pp. 427-449.

2. B.S. 1377: Part 5. Pp. 10-14.

3. R.F. Craig. Soil Mechanics. Pp. 37-45.

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Form 7.1

Constant Head Permeability Test

Location ……………………………………..………… Sample No. ……………………………………………………...

Operator ..……………..……………………………… Date …………………………………………….………………...

Soil description ..…………..……………………………………………..……………………………………………..……..

Method of preparation ..………..……………………………………………..………………………………………………

Sample diameter ……………… mm area A ……………… mm2 dry mass ……………… g

length ……………… mm volume ……………… cm3 dry density ……………… Mg/m

3

S.G. assumed ……………………….. voids ratio = G0 / ρ0 – 1 = ……………………………..

Heights above datum: inlet ……………. mm manometer a ………………………. mm

outlet ……..……. mm b ………………………. mm

Temperature ……………………………..°C c ………………………. mm

Head difference .... a to c ............mm

Distance between . a to c ............mm

Flow downwards Hydraulic gradients i = ........................

Readings

Time from

start, min

Time interval

t, min

Measured flow

Q, ml

Rate of flow q,

ml/min t

1

Remarks

2 2

4 2

6 2

8 2

10 2

15 5

20 5

25 5

30 5

35 5 Steady state rate of flow

45 10 (from graph ) q = ml/min

Permeability k = q / (Ai x 60) = ………………………………………………………………m/s

Temperature correction Dry density …………………………Mg / m3

Voids ratio …………………………………..

Permeability (20 °C) ……………… m/s

Fig. Typical data from constant head permeability test

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LABORATORY EXPERIMENT No. 8

SOIL ONE DIMENSIONAL CONSOLIDATION PROPERTIES

OBJECT:

Determination of the one - dimensional consolidation properties of naturally deposited, undisturbed soil samples.

APPARATUS:

Consolidation apparatus, known as odometer (see fig. 8.1), consists of consolidation cell, loading device and dial

gauge; auxiliary items, including apparatus for moisture content determination, a timing device, thermometer,

balance readable to 0.1g.

PROCEDURE:

1. Prepare, calibrate and check apparatus (for the academic reasons calibration corrections y will be given by

the instructor).

2. Prepare soil specimen from the undisturbed soil, measure and calculate itls details and fill data into form 8.1.

3. Assemble specimen in consolidation cell, fit cell in load frame, set up loading yoke, adjust beam and set dial

gauge.

4. Fill consolidation cell with water, record the initial gauge reading and apply the pressure. A range of pressures

selected from the following sequence has been found to be satisfactory: 6, 12, 25, 50, 100, 200, 400, 800, 1600,

3200 kPa.

For choosing the appropriate pressures ask instructors advice.

5. Take readings of the compression gauge at suitable intervals of time. The following periods of elapsed time

from zero are convenient:

0, 10, 20, 30, 40, 50 s

1, 2, 4, 8, 15, 30 min

1, 2, 4, 8, 24 h

A suitable form for recording the readings is shown as form 8.2.

6. Plot the compression gauge readings against logarithm of time while the test is in progress.

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7. Increase the pressure to the next value and repeat stages from 5 to 6.

8. Unload specimen, dismantle cell weight and dry specimen and weight again.

CALCULATIONS, PLOTTING AND QUESTIONS:

1. Calculate the void ratio e, at the end of each loading stage and coefficient of volume compressibility mv , for

the each loading increment (Use graph, form 8.3).

2. Plot void ratio of the specimen, e on a linear scale against the corresponding applied pressure, σ on a

logarithmic scale (Use graph, form 8.4).

3. Use square root time curve-fitting method (see fig. 8.2) for consolidation coefficient cv calculations. Calculate

values of coefficient of consolidation for each force increment applied to the specimen.

4. Explain log time curve-fitting method for determination coefficient of consolidation.

5. What is the civil engineering relevance of the consolidation test?

6. Explain the meaning of terms consolidation and settlement and the soil properties that affect them.

7. Explain what is meant by a normally consolidated and overconsolidated clay stratum.

8. Name assumptions of one-dimensional consolidation theory.

References:

1. K. H. Head. Manual of Soil Laboratory Testing. Vol.2. Pp. 651-730.

2. B.S. 1377: Part 5. Pp. 2-8.

3. R.F. Craig. Soil Mechanics. Pp. 244-295.

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LABORATORY EXPERIMENT No.9

SOIL COMPACTION

OBJECT:

To determine the dry density -moisture content relationship of a given soil sample using the CBR (California

Bearing Ratio) mould and 4.5 kg rammer.

APPARATUS:

CBR mould (see fig. 9.1, a), 4.5 kg rammer (see fig 9.1,b), a balance readable to 5g, metal or plastic tray, large

metal scoop, palette knife, apparatus for determination of moisture content.

PROCEDURE:

1. Take 25 kg of air-dried soil passing 37.5 mm B.S. sieve and mix this thoroughly with a suitable amount of

water depending on the type of soil.

2. Weight the mould with base plate attached to 5g. Place the mould on a solid base with the extension attached.

3. Place a quantity of moist soil in the mould such that when compacted it occupies a little over one fifth of the

height of the mould body.

4. Apply 62 blows using B.S. "heavy" rammer. Distribute the blows according to recommendations shown on fig.

9.1, c.

5. Repeat stages 4 and 5 for the 2-5 layers. The amount of soil should be sufficient to fill the mould body, with

the surface not more than 6 mm proud of the upper edge of the mould body.

6. Remove the extension and stuck off the excess soil carefully with the straight edge, weight the soil and mould

with baseplate to 5g.

7. Remove the compacted soil from the mould and take a representative sample for the moisture content

determination.

8. Add a suitable increment of water and mix thoroughly into the soil.

9. Repeat stages 3 to 8 to give a total of at least five determinations.

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CALCULATIONS, PLOTTING AND QUESTIONS:

1. Calculate the bulk density, ρ (Mg/m3) of each compacted specimen (Use form. 9.1).

2. Calculate moisture content w and dry density ρd of each compacted specimen.

3. Plot the dry densities obtained from a series of determinations as ordinates against the corresponding

moisture contents as abscise. Read off the values of maximum dry density and optimum moisture content (see

fig. 9.2).

4. On the same graph, plot the curves corresponding to 0%, 5% and 10% air voids, calculated from the equation

1 - Va/100

ρd = −−−−−−−−−−−−

1/ρs + W/100ρw

where

ρd is dry density (in Mg/m3)

ρs is the particle density (in Mg/m3)

ρw is density of water (assumed 1 Mg/m3)

W is moisture content (in %)

Va is volume of air voids (in %).

5. Give definition of "optimum moisture content (OMC)", "maximum dry density", "relative compaction",

"percentage of air voids".

6. Enumerate the most significant improvements of soils as a result of their compaction.

7. Mention the most usual construction works related with soil compaction and itls control.

References:

1. K. H. Head. Manual of Soil Laboratory Testing. Vol.1 Pp. 302-309.

2. B.S. 1377: Part 4. Pp. 2-11.

3. R. F. Craig. Soil Mechanics. Pp. 27-36.

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LABORATORY EXPERIMENT No. 10

CALIFORNIA BEARING RATIO (C B R)

OBJECT:

Determination of the California Bearing Ratio (CBR) of a soil, which is obtained by measuring the relationship

between force and penetration when a cylindrical plunger is made to penetrate the soil at a given rate.

APPARATUS:

General arrangement for CBR penetration test (fig.10.1,a) including mould (fig.10.2,a) and collar extension

(fig.10.2,b), loading device, proving ring, loading piston, dial gauge, surcharge weights; Equipment for soil

compaction; Steel rod, steel straight edge, spatula, balances, capable of weighting up to 25 kg, readable 5g,

apparatus for moisture content determination.

PROCEDURE:

1. Determine the mass of the mould with base plate attached.

2. Prepare soil sample. Mix the dry soil with water so that the mixture has a water content that is 1% below the

optimum moisture content. Prepare around 6 kg of mixture. Collect required data on soil properties and tabulate

into form 10.1.

3. Choose one of six methods for soil compaction (see flow chart in fig 10.3). For this test method No. 5 is

recommended for soil compaction. According to this method, compact the soil in the CBR mould with the

rammer (fig. 10.4, c). The soil should be poured into the mould in three layers. Each layer should be given 62

distributed blows over the surface.

4. Remove the detachable collar and trim the top of the mould.

5. Measure the mass of the mould with the base plate containing the specimen.

6. Place the mould with the specimen in the testing machine. Apply a surcharge over the specimen

corresponding to the mass of the pavement.

7. Seat the plunger on the surface of the specimen under a small load. Set the load and penetration measuring

dial gauges to zero.

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8. Apply load to the plunger at a uniform rate of 1 mm/min.

9. Record proving ring readings at intervals of penetration of 0.25 mm to a total not exceeding 7.5 mm. Fill data

into form 10.2.

10. Take a sample immediately below the penetrated surface for moisture content determination.

CALCULATIONS, PLOTTING AND QUESTIONS:

1. Draw a curve penetration of plunger - force on plunger (Use form 10.3).

2. Calculate the CBR value (See recommendations on fig. 10.1,b).

3. Determine the moisture content and dry unit weight of the sample and compare with the results of the

compaction test.

4. Is this test suitable for both natural subgrade and compacted subgrade?

5. Can this test be done in the field itself, and if so what are the possible discrepancies in results between

laboratory and the field test?

6. What are the uses of this test?

7. Can this result be used as an index of bearing capacity of the soil for foundations?

References:

1. K. H. Head. Manual of Soil Laboratory Testing. Vol. 2. Pp. 469-508.

2. B.S. 1377: Part 4. Pp. 20-26.

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LABORATORY EXPERIMENT No. 11

SOIL DIRECT SHEAR TEST

OBJECT:

To obtain soil shear strength parameters apparent cohesion c and angle of shear resistance φ.

APPARATUS:

Shear box apparatus (fig.11.1), consisting of shear box, vertical and horizontal loading systems, frame, proving

ring and dial gauges; Specimen cutter, 60 mm square , 20mm deep wood pusher; Cutting tools and straight

edge; Tamping rod, stop clock, balance, readable 0.01g, apparatus for determining moisture content.

PROCEDURE:

1. Measure shear box dimensions, set up shear box and record details into form 11.1.

2. Prepare specimen. Preparation procedures depends on type of soil. For dry, medium density soils place the

sand from the known quantity mass into the shear box in three layers and for each layer apply a controlled

amount of tamping with the square-ended tamper. Form 11.1 is suitable for recording specimen details and

measurements.

3. Assemble shear box into apparatus, set vertical dial gauge and apply normal stress.

4. Remove clamping screws, adjust proving ring and horizontal dial gauge, apply shearing force of constant rate.

Continue applying the shear force till the specimen fails, which is indicated by a kick back of the pointer in the

proving ring dial gauge. If such a failure does not occur, continue shearing till the specimen undergoes a

shearing displacement of 12 mm.

5. Conduct at least three tests on separate specimens having the same density and water content but applying

different normal loads.

6. Record results of each shear into form 11.2.

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CALCULATIONS, PLOTTING AND QUESTIONS:

1. Calculate initial soil index properties: moisture content, dry density, bulk density, void ratio, degree of

saturation (use form 11.1).

2. Draw graphs shear stress (in kPa) as ordinates against cumulative forward displacement (in mm) as abscise

for each shearing stage (use form 11.3, b).

3. From each graph calculate maximum shear stress. Record shear stress and corresponding displacement

values into form 11.4. Record also residual values of shear stress and corresponding displacement values.

4. Plot each value of maximum shear strength τf as ordinates against the corresponding normal stress σn (in

kPa) applied for that test as abscise both to the same linear scale (Use graph on fig.11.3, a).

5. If it can be assumed that the relationships are linear, maximum strength envelope gives the angle of shearing

resistance, φ (in degrees) and the intercept gives the apparent cohesion, c (in kPa). The slope and intercept of

the residual strength envelope give the residual angle of shearing resistance, φR (in degrees) and the residual

cohesion value, cR.

Record the values into form 11,4.

References:

1. K. H. Head. Manual of Soil Laboratory Testing. Vol. 2. Pp. 542-571.

2. B.S. 1377: Part 7. Pp. 4-11.

3. R. F. Craig. Soil Mechanics. Pp. 105-106.

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LABORATORY EXPERIMENT No. 12

SOIL UNCONFINED COMPRESSIVE STRENGTH

OBJECT:

Determination of approximate value of the compressive strength of the soil either in the undisturbed or the

remoulded condition.

APPARATUS:

Unconfined compression apparatus (see fig 12.1), consisting of load frame, drive unit, force and axial load

deformation measuring devices, top and bottom platens; Timer readable 1s, balance readable 0.1g, calibrated

means of measuring the specimen dimensions, apparatus for determination of moisture content.

PROCEDURE:

1. Prepare the test specimen, determine mass, make at least three measurements of the length and of the

diameter to nearest 0.1 mm and record data into form 12.1.

2. Place the specimen on the pedestal of the compression machine, adjust the machine, adjust the axial

deformation and force measuring gauges, select rate of axial deformation such, that the rate of axial strain does

not exceed 2%/min.

3. Apply compression to the specimen and record simultaneously axial deformation and force at regular intervals

of compression, e.g. corresponding to each 0.5 % strain (Use form 12.1).

Continue test until the maximum value of the axial load has been passed or the axial strain reaches 20%.

4. Remove the load, make a sketch of the specimen, remove specimen from, determine dimensions, moisture

content and record data into form 12.1.

CALCULATIONS, PLOTTING AND QUESTIONS:

1. Calculate axial strain and axial compressive strength according to formulae’s given in the form 12.1.

2. Plot calculated values of compressive stress as ordinates against corresponding values of strain as abscise,

draw the stress-strain curve and determine unconfined compressive stress qu (use graph 12.2, a).

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3. Draw Mohr circle and determine apparent cohesion c (use graph 12.2, b).

4. Is it possible to conduct unconfined compression test on a sand?

5. Suppose you conduct unconfined compression tests on specimen which you get after compaction in a

laboratory compaction test. How does the compression strength vary with increase in moisture content.

References:

1. K. H. Head. Manual of Soil Laboratory Testing. Pp. 601-615.

2. B.S. Part 7. Pp. 19-22.

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LABORATORY EXPERIMENT No. 13

SOIL UNDRAINED TRIAXIAL COMPRESSION TEST

OBJECT:

Determination of the undrained strength of specimen of cohesive soil when it is subjected to a constant confining

pressure.

APPARATUS:

Triaxial apparatus (Fig. 13.1,a), consisting of triaxial cell, loading frame, base pedestal, loading piston,

pressurised water, membrane, proving ring and axial deformation dial gauge;

Apparatus for applying and maintaining the desired pressure on the water within the cell to accuracy of 5 kPa;

Apparatus for determination of moisture content.

PROCEDURE:

1. Remove soil from the sampling tube. Prepare test specimen of necessary diameter. Specimen diameter

ranges from 38 mm to 110 mm, height approximately equal to twice the diameter. Determine mass, measure

dimensions. Record data into form 13.1. When two or more similar specimens are tested as set the above data

for each specimen should be tabulated.

2. Place the specimen on base, place the membrane around the specimen, seal the membrane, assemble the

cell body and fill triaxial cell with water.

3. Pressurise the triaxial cell, raising the water pressure in the cell to the desired value.

4. Select the rate of axial deformation and start test by switching on the machine. Record readings of the force-

measuring device and the deformation gauge at regular intervals of the later. Suitable intervals for a soil of

medium compressibility are typically 0.25% strain up to 1% strain. Verify that the cell pressure remains constant.

5. Continue the test until the maximum value of the axial stress has been passed and peak is clearly defined, or

until an axial strain of 20% has been reached.

6. Remove the axial force, drain the water from the cell, remove specimen, tabulate specimen details into form

13.1.

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7. When two or more specimens are tested, repeat stages from 2 to 6.

CALCULATIONS, PLOTTING AND QUESTIONS:

1. From each set of readings calculate axial strain, corrected area of specimen, measured deviator stress.( Use

form 13.1).

2. Plot values of deviator stress as ordinates against corresponding values of strain as abscise, draw the stress-

strain curve and determine the maximum value of deviator stress for the each test. Correct the maximum value

of deviator stress by subtracting from it membrane correction derived from figure 13.1,b. See and use forms

13.2 for the one test graphical presentation and forms 13.3, a for the graphical presentation of set of tests.

3. When two or more similar specimens have been tested as a set, draw for the each test Mohr circle and derive

cohesion c and angle of shear resistance φ (Use graph 13.3, b).

4. Give definitions of "triaxial compression", "deviator stress", "Mohr circle".

References:

1. K. H. Head. Manual of Soil Laboratory Testing. Pp. 616-628.

2. B.S. 1377: Part 7. Pp. 22-25.

3. R. F. Craig. Soil Mechanics. Pp. 107-112.

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