Foundation-engg-lab-mannual.pdf

LABORATORY MANUAL

FOUNDATION ENGINEERING (BACHELOR OF TECHNOLOGY)

DEPARTMENT OF CIVIL ENGINEERING

JAYPEE UNIVERSITY OF ENGINEERING & TECHNOLOGY A.B. ROAD RAGHOGARH-GUNA (M.P.)-473226 (INDIA)

DEPARTMENT OF CIVIL ENGINEERING, JUET GUNA

FOUNDATION ENGINEERING LABORATORY (COURSE CODE: 14B17CE671)

CONTENTS EXP. NO

NAME OF EXPERIMENTS

PAGE NO

---

Report Writing Instructions

2–2

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Sampling Method

3–3

Part-A

To be performed upto P-1 exam

1.

California Bearing Ratio Test (Un-Soaked)

4–8

2.

California Bearing Ratio Test (Soaked)

9 – 14

3.

Consolidation Properties Test

15 – 20

4.

Direct Shear Test

21 – 27

5.

Unconfined Compressive Strength (UCS) Test

28 – 32

Part-B

To be performed after P-1 & upto P-2 exam

6.

Tri-Axial Test (Undrained Unconsolidated)

33 – 38

7.

Laboratory Vane Shear Test

39 – 41

8.

Swelling Pressure Test By Constant Volume Method

42 – 44

9.

Swelling Pressure Test By Consolidometer Method

45 – 47

10.

Free Swell Index

48 – 49

Demonstration Type Experiments 11.

Standard Penetration Test (SPT)

50 – 52

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Least Count of Proving Rings

53 – 53

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References

54 – 54

INSTRUCTIONS FOR LABORATORY REPORT WRITING A full report is an extensive account of experiment, such as may be required for external readers. It should be a standalone document and so is likely to include a description of the apparatus and a summary of the experimental procedure. A full report is not to exceed 1500 words (excluding Tables and Diagrams). It is to be organized under the following headings: OBJECTIVE/OBJECTIVES EXPERIMENTAL SETUP WITH DIAGRAM THEORY TO BE USED FOR EXPERIMENT EXPERIMENTAL METHOD OBSERVATIONS/DATA COLLECTED SAMPLE CALCULATIONS EXPERIMENTAL RESULTS DISCUSSION/CONCLUSIONS

(Including that of errors)

OBJECTIVES: It contains the aim of the experiment and how the author is going to achieve his aim. EXPERIMENTAL SETUP WITH DIAGRAM Write every experimental setup and instruments you used with their dimensions. Draw a neat sketch of experimental setup. EXPERIMENTAL METHOD / PROCEDURE It should contain a brief description of experimental method, a neat sketch of experimental setup. THEORY TO BE USED FOR EXPERIMENT Write theory behind your experiment briefly. OBSERVATIONS/DATA COLLECTED Write down all data collected by you and also attached the signed lab data sheet. SAMPLE CALCULATIONS Give the sample calculations. EXPERIMENTAL RESULTS Represent experimental results in tabulated form and diagrams. PRECAUTIONS Write the necessary precautions to be kept in your mind during performing the experiment. DISCUSSIONS/ CONCLUSIONS Compare your results with available reported results from standard literature. Give the reason of departure of your results from reported results. The conclusions contains a summary (what has been done and what are the main results) and in addition to that some future prospective. Note: Failure to submit the report and attend the viva voce will result in a zero mark.

SIZE & QUANTITY OF SOIL SAMPLE REQUIRED FOR CONDUCTING THE TESTS Ref: - IS: 2720 (Part-1)-1983 S. No

NAME OF TEST

TYPE, TEMP & DURATION OF DRYING

1

Water content

Oven, 24 hrs

Specific gravity

Oven, 105-1100C 24 hrs

2

3 4 5 6 7

8 9 10

Grained size analysis Liquid limit Plastic limit Shrinkage factors Compaction i) Light compaction ii) Heavy compaction iii) Constant mass Unconfined compressive strength Triaxial compression test (Unconsolidated) Triaxial compression test (Consolidated)

11

Direct shear

12

Vane Shear

13 14

16

Swelling Pressure Density index (relative density) Consolidation properties CBR

17

Permeability

18

Field moisture equivalent Centrifuge moisture content Linear shrinkage Chemical tests i). Total soluble solids ii). Organic matter

15

19 20 21

AMOUNT OF SOIL SAMPLE REQUIRED 25 50 200 50 g for fine grained soils 400 gm for fine medium and coarse grained

DEG OF PULVERIZATION PASSING IS SIEVE 425 micron 2 mm 4.75

REFERENCE TO PART OF IS:2720

2 mm

Part-3/Sec-1

-

Part-3/Sec-2

400 g 1500 g 270 g 60 g 100g

4.75 mm 9.5 mm 425 micron 425 micron 425 micron

Air drying

6 kg 6 kg 2 kg

19 mm 19 mm 4.75 mm

Part-7 Part-8 Part-9

Oven 1100 ±5 0C

1 kg

-

Part-10

Oven 1100 ±5 0C

1kg/5kg

-

Part-11

Oven 1100 ±5 0C

1kg/5kg

-

Part-12

Air drying/ Oven 1100 ±5 0C Air drying/ Oven 1100 ±5 0C Air/Oven drying

1 kg 120 g 250 g

4.75 mm Above 4.75 mm

Part-13 Part-39/Sec-1 Part-30

2 kg

2 mm

Part-41

Oven, 24 hrs 105-1100C Air drying/ Oven 1100 ±5 0C Air drying Oven, 105-1100C,24 hr

12 kg 12 kg

37.5 mm / 19 mm 9.5 mm / 4.75 mm

Part-14

500 g

-

Part-15

6 kg 2.5 kg,100 mm φ 5 kg, 200 mm φ

19 mm 9.5 mm Granular Soil

Part-16 Part-17 Part-36

Air drying

15 g

425 micron

Part-18

Air drying

10 g

425 micron

Part-19

Air drying Oven, 105-1100C 24 hr Air drying

450 g

425 micron

Part-20

10 g 100 g

2 mm 2 mm

Part-21 Part-22

Air drying Air drying Air drying Air drying

--

Part-2

Part-4 Part-5 Part-5 Part-6

Experiment No-1

CALIFORNIA BEARING RATIO (UNSOAKED METHOD) Reference: - IS: 2720 (Part-16) - 1987 OBJECTIVE To determine the California Bearing Ratio (CBR Value) of a given soil sample by un-soaked method. THEORY It is the ratio of force per unit area required to penetrate a soil mass with standard circular piston at the rate of 1.25 mm/min to that required for the corresponding penetration of a standard material.

C .B.R. 

Test ..Load P  100...Or C.B.R.  T  100 Std ...Load PS

The test may be performed on undisturbed specimens and on remoulded specimens who may be compacted either statically or dynamically. TERMINOLOGY For the purpose of this standard the definitions given in IS: 2809-1972 and the following shall apply. 1. Standard Load- load which has been obtained from the test on crushed stone which was defined as having California Bearing Ratio of 100 percent. 2. California Bearing Ratio (CBR) – The ratio expressed in percentage of force per unit area required to penetrate a soil mass with a circular plunger of 50 mm diameter at the rate of 1.25 mm/min to that required for corresponding penetration in a standard material. The ratio is usually determined for penetration of 2.5 and 5.0 mm. Where the ratio at 5 mm is consistently higher than that at 2.5 mm, the ratio at 5 mm is used. NEED AND SCOPE The California bearing ratio test is penetration test meant for the evaluation of sub grade strength of roads and pavements. The results obtained by these tests are used with the empirical curves to determine the thickness of pavement and its component layers. This is the most widely used method for the design of flexible pavement. This instruction sheet covers the laboratory method for the determination of C.B.R. of undisturbed and remolded /compacted soil specimens, both in soaked as well as un-soaked state. The test essentially measures the soil resistance to penetration prior to reaching its ultimate shearing value. It is not exactly a measure of the shearing modulus since the confining effects of the molds to exert some influence. APPARATUS

        

Moulds with base plate and collar Spacer disc with handle Metal Rammer- 2.6 Kg (for light compaction) & 4.89 Kg (for heavy compaction) Annular Weights – 2.5 Kg or 5 Kg Loading frame Cap - 50 kN Dial gauges –two dial gauges reading to 0.01 mm Sieves- 4.75 mm and 19 mm I.S. Sieve. Oven Miscellaneous Apparatus – Other general apparatus, such as a mixing bowl/tray, straight edge, scales, filter paper, dishes and calibrated measuring jar.

PREPARATION OF TEST SPECIMEN 1. Take about 5.0 kg soil passing from 4.75 mm (if clayey soil) and 19.0 mm (if granular soil) 2. Add the required water (at optimum moisture content) and mix thoroughly by mixing tools (trowels). 3. Fix the extension collar and the base plate to the mould. Insert the spacer disc over the base. Place the filter paper on the top of the spacer disc. 4. Compact the mix soil in the mould using either light compaction or heavy compaction. 5. For light compaction, compact the soil in 3 equal layers, each layer being given 56 blows by the 2.6 kg rammer. 6. For heavy compaction compact the soil in 5 layers, 56 blows to each layer by the 4.89 kg rammer. 7. After compaction remove the collar and trim off soil. 8. Turn the mould upside down and remove the base plate and the displacer disc. 9. Weigh the mould with compacted soil and determine the bulk density and dry density. PROCEDURE FOR TESTING; 1. Place the mould assembly with the surcharge weight on the penetration test machine. 2. Seat the penetration piston at the center of the specimen with the smallest possible load, but in no case in excess of 4 kg so that full contact of the piston on the sample is established. 3. Set the stress and strain dial gauge to read zero. Apply the load on the piston so that the penetration rate is about 1.25 mm/min. 4. Record the load readings at penetrations of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 10 and 12.5 mm. 5. Note the maximum load and corresponding penetration if it occurs for a penetration less than 12.5 mm. 6. Detach the mould from the loading equipment. Take about 20 to 50 g of soil from the top 3 cm layer and determine the moisture content.

RECORD OF OBSERVATIONS S. No.

Water Content after test

Sample taken from Top

Dry Density Determination Sample-1 Sample-2 Center Bottom Particulars

1.

Can No.

Wt of mould + Soil

2.

Wt of empty can (g)

Wt of mould

3.

Wt. of can + wet soil (g)

Wt of soil, gm

4.

Wt. of can + dry soil (g)

Vol of specimen,cc

5.

Wt of water (g)

Bulk density, g/cc

6.

Wt of dry soil (g)

Avg Water content

7.

Water content (%)

Dry density, g/cc

2250

2250

Penetration Data – The readings for the determination of the load penetration data shall be recorded in the data sheet. Surcharge weight used = 5.0 Kg, L.C. of Dial Gauge = 0.01 mm/div OBSERVATIONS S. No

Least Count (L.C.) of Proving Ring = ……….… kg/Div Dia. of Plunger = 50 mm

Area of Plunger = 19.625 cm2

CALCULATIONS

Dial gauge readings

Proving ring reading

Penetration

A

B

C

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 1000 1250

STANDARD VALUE

(mm)

Load on plunger C X L.C. (Kg)

Corrected Load from graph (Kg)

Corrected Unit Load 2 (Kg/cm )

Standard Load (Kg)

Standard Unit Load 2 (Kg/cm )

D

E

F

G

H

I

1370

70

2055

105

2630 3180 3600

134 162 183

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 10.0 12.5

CALCULATION 1. Load Penetration Curve - The load penetration curve shall be plotted. This curve is usually convex upwards although the initial position of the curve may be convex downwards due to surface irregularities. A correction shall then be applied by applied by drawing a tangent to the point of greatest slope and then transposing the axis of the load so that zero penetration is taken as the point where the tangent cuts the axis of penetration. The corrected load penetration curve would then consist of the tangent from the new origin to the point of tangency on the re-sited curve and then the curve itself. 2. California Bearing Ratio – The CBR values are usually calculated for penetrations of 2.5 mm and 5 mm. corresponding to the penetration value at which the CBR values is desired, corrected load value shall be taken from the load penetration curve and the CBR calculated as follows: California Bearing Ratio =

PT  100 PS

Where, 

PT = corrected unit (or total) test load corresponding to the chosen penetration from the load penetration curve and



PS = unit (or total) standard load for the same depth of penetration as for PT taken from the table.

INTERPRETATION AND RECORDING The results of the CBR test are presented as the CBR value in percentage. 1. CBR of specimen at 2.5 mm penetration =..............................% 2. CBR of specimen at 5.0 mm penetration =..............................% CBR of Specimen = ................ % Generally, the CBR value at 2.5 mm penetration will be greater than that at 5 mm penetration and in such a case; the former shall be taken as the CBR value for design purposes. If the CBR value corresponding to a penetration of 5 mm exceeds that for 2.5 mm, the test shall be repeated. If identical results follow, the CBR corresponding to 5 mm penetration shall be taken for design. CBR VALUE OF SOIL CBR VALUE

SUBGRADE STRENGTH

COMMENTS

3% and less

Poor

Capping* is required

3% - 5%

Normal

5% - 15%

Good

Widely encountered CBR range capping considered according to road category "Capping" normally unnecessary except on very heavily trafficked roads.

*Capping is a process used to cover contaminated soils to prevent the migration (movement) of the pollutants. This migration can be caused by rainwater or surface water moving over or vertically through the site, or by the wind blowing over the site. Caps are generally made of a combination of such materials as synthetic fibers, heavy clays, and sometimes concrete. The caps are designed to meet several goals

PRECAUTIONS 1. The CBR test should be performed on remoulded soils in laboratory. In-situ tests are recommended for design purposes. 2. The specimen should be prepared by static compaction whenever possible otherwise by dynamic compaction. 3. For the design of new roads the sub-grade soil sample should be compacted at OMC to proctor density whenever suitable compaction equipment is available to achieve this density in the field, otherwise the soil is compacted to the dry density expected to be achieved in the field. 4. In new constructions the CBR test samples may be soaked in water for four days period before testing. However in areas with arid climate or when the annual rainfall is less than 50cm and the water table is to affect the sub grade adversely and when thick impermeable bituminous surfacing is provided, it is not necessary to soak the soil sample before carrying out the CBR test 5. At least three samples should be tested on each soil sample at same density and moisture content. 6. If the maximum variation in the CBR values of three samples exceeds the specified limits, the design CBR should be the average of at least six samples. 7. The top 50cm of sub-grade should be compacted at least up to 95 to100% of proctor density.

GRAPH: Plot load/unit load versus penetration curve and find corrected load/unit load;

Experiment No-2

CALIFORNIA BEARING RATIO (SOAKED METHOD) Reference: - IS: 2720 (Part-16)-1987 OBJECTIVE To determine the California Bearing Ratio (CBR Value) of a given soil sample by soaked method. THEORY It is the ratio of force per unit area required to penetrate a soil mass with standard circular piston at the rate of 1.25 mm/min. to that required for the corresponding penetration of a standard material.

C .B.R. 

Test ..Load P  100...Or C.B.R.  T  100 Std ...Load PS

The test may be performed on undisturbed specimens and on remoulded specimens who may be compacted either statically or dynamically. TERMINOLOGY For the purpose of this standard the definitions given in IS: 2809-1972 and the following shall apply. 1. Standard Load- load which has been obtained from the test on crushed stone which was defined as having California Bearing Ratio of 100 percent. 2. California Bearing Ratio (CBR) – The ratio expressed in percentage of force per unit area required to penetrate a soil mass with a circular plunger of 50 mm diameter at the rate of 1.25 mm/min to that required for corresponding penetration in a standard material. The ratio is usually determined for penetration of 2.5 and 5.0 mm. Where the ratio at 5 mm is consistently higher than that at 2.5 mm, the ratio at 5 mm is used. NEED AND SCOPE The California bearing ratio test is penetration test meant for the evaluation of sub grade strength of roads and pavements. The results obtained by these tests are used with the empirical curves to determine the thickness of pavement and its component layers. This is the most widely used method for the design of flexible pavement. This instruction sheet covers the laboratory method for the determination of C.B.R. of undisturbed and remolded /compacted soil specimens, both in soaked as well as unsoaked state. The test essentially measures the soil resistance to penetration prior to reaching its ultimate shearing value. It is not exactly a measure of the shearing modulus since the confining effects of the molds to exert some influence. APPARATUS

1. 2. 3. 4. 5. 6.

7. 8. 9. 10.

Moulds with base plate and collar Spacer disc Metal Rammer 2.6 kg Expansion Measuring Apparatus Annular Weights Loading Machine – with a capacity of at least 5000 kg and equipped with a movable head or base which enables the plunger to penetrate into the specimen at a deformation rate of 1.25 mm/min. The machine shall be equipped with a load machine device that can read to suitable accuracy. Penetration plunger Dial gauges –two dial gauges reading to 0.01 mm. Sieves- 4.75 mm IS Sieve and 19 mm IS Sieve.

11. Miscellaneous Apparatus – Other general apparatus, such as a mixing bowl, straight edge, scales, soaking tanks or pan, drying oven, filter paper, dishes and calibrated measuring jar. PREPARATRION OF TEST SPECIMEN 1. Take about 5.0 kg soil passing from 4.75 mm (if clayey soil) and 19.0 mm (if granular soil) 2. Add the required water (at optimum moisture content) and mix thoroughly by mixing tools (trowels). 3. Fix the extension collar and the base plate to the mould. Insert the spacer disc over the base. Place the filter paper on the top of the spacer disc. 4. Compact the mix soil in the mould using either light compaction or heavy compaction. 5. For light compaction, compact the soil in 3 equal layers, each layer being given 56 blows by the 2.6 kg rammer. 6. For heavy compaction compact the soil in 5 layers, 56 blows to each layer by the 4.89 kg rammer. 7. Remove the collar and trim off soil. 8. Turn the mould upside down and remove the base plate and the displacer disc. 9. Weigh the mould with compacted soil and determine the bulk density and dry density. 10. Put filter paper on the top of the compacted soil (collar side) and clamp the perforated base plate on to it. 11. Weights to produce a surcharge equal to the base material and pavement to the nearest 5.0 kg shall be placed on the compacted soil specimen. 12. The whole mould and weights shall be immersed in a tank of water allowing free access of water to the top and bottom of the specimen. 13. The tripod for the expansion measuring shall be mounted on the edge of the mould and the initial dial gauge reading recorded.

14. This setup shall be kept undisturbed for 96 hours (4-days) noting down the readings every day against the time of reading. A constant water level shall be maintained in the tank throughout the period. 15. At the end of the soaking period, the change in dial gauge shall be noted, the tripod removed and the mould taken out of the water tank. 16. The free water collected in the mould shall be removed and the specimen allowed draining downwards for 15 minus. Care shall be taken not to disturb the surface of the specimen during the removal of the water. 17. The weights, the perforated plate and the top filter paper shall be removed and the mould with the soaked soil sample shall be weighed and the mass recorded. PROCEDURE 1. Place the mould assembly with the surcharge weights on the penetration test machine. 2. Seat the penetration piston at the center of the specimen with the smallest possible load, but in no case in excess of 4 kg so that full contact of the piston on the sample is established. 3. Set the stress and strain dial gauge to read zero. Apply the load on the piston so that the penetration rate is about 1.25 mm/min. 4. Record the load readings at penetrations of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 7.5, 10 and 12.5 mm. 5. Note the maximum load and corresponding penetration if it occurs for a penetration less than 12.5 mm. 6. Detach the mould from the loading equipment. Take about 20 to 50 g of soil from the top 3 cm layer and determine the moisture content. RECORD OF OBSERVATIONS Dia. of Mould : 150 mm Area of Mould : 176.625 cm2 Period of soaking (days) = 4 days (96 hrs) WATER CONTENT DETERMINATION S. NO.

DESCRIPTION

1.

Can No.

2.

Wt. of can + wet soil (g)

3.

Wt. of can + dry soil (g)

4.

Wt of water (g)

5.

Wt of can (g)

6.

Wt of dry soil (g)

7.

Water content (%)

Height of Mould : 175 mm Volume of specimen : 2250 cc

BEFORE TEST Sample-1

Sample-2

AFTER TEST Sample-1

Sample-2

DETERMINATION OF DRY DENSITY S. No. 1. 2. 3. 4. 5. 6. 7.

DESCRIPTION

BEFORE TEST

AFTER TEST

SAMPLE - 1

SAMPLE - 2

SAMPLE - 1

SAMPLE - 2

2250

2250

2250

2250

Wt of mould +soil Wt of mould Wt of soil, gm Volume of the specimen, cc Bulk density (g/cc) Avg. water content Dry density (g/cc)

Penetration Data – The readings for the determination of expansion ratio and penetration data shall be recorded in the data sheet. Surcharge weight used = 5.0 Kg, Least count of Dial Gauge = 0.01 mm/div Area of Plunger = 19.62 cm2 OBSERVATIONS S. No A 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Dial Gauge Readings B 0 50 100 150 200 250 300 350 400 450 500 600 700 750 1000 1250

Proving Ring Reading C

the load

Least Count of Proving Ring = ………….kg/Div Dia of Plunger = 50 mm

CALCULATIONS Penetration Load on Corrected in Plunger Load from (mm) C X L.C. (Kg) graph (Kg) D E F 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 6.0 7.0 7.5 10.0 12.5

STANDARD VALUE Corrected Unit Load (Kg/cm2) G

Standard Standard Load Unit Load (Kg) (Kg/cm2)

H

I

1370

70

2055

105

2630 3180 3600

134 162 183

CALCULATION Expansion Ratio- The expansion ratio based on tests conducted as specified in 5.1 shall be calculated as follows: dt  ds Expansion ratio =  100 h  dt = final dial gauge reading in mm.  ds = initial dial gauge reading in mm, and  h = initial height of the specimen in mm The expansion ratio is used to qualitatively identify the potential expansiveness of the soil.

Load Penetration Curve - The load penetration curve shall be plotted. This curve is usually convex upwards although the initial position of the curve may be convex downwards due to surface irregularities. A correction shall then be applied by applied by drawing a tangent to the point of greatest slope and then transposing the axis of the load so that zero penetration is taken as the point where the tangent cuts the axis of penetration. The corrected load penetration curve would then consist of the tangent from the new origin to the point of tangency on the re-sited curve and then the curve itself.

California Bearing Ratio – The CBR values are usually calculated for penetrations of 2.5 and 5 mm. corresponding to the penetration value at which the CBR values is desired, corrected load value shall be taken from the load penetration curve and the CBR calculated as follows:

PT  100 PS PT = corrected unit (or total) test load corresponding to the chosen penetration from the load penetration curve and California Bearing Ratio =





PS = unit (or total) standard load for the same depth of penetration as for PT taken from the table.

Generally, the CBR value at 2.5 mm penetration will be greater than that at 5 mm penetration and in such a case; the former shall be taken as the CBR value for design purposes. If the CBR value corresponding to a penetration of 5 mm exceeds that for 2.5 mm, the test shall be repeated. If identical results follow, the CBR corresponding to 5 mm penetration shall be taken for design INTERPRETATION AND RECORDING The results of the CBR test are presented as the CBR value in percentage. CBR of specimen at 2.5 mm penetration =..............................% CBR of specimen at 5.0 mm penetration =..............................% CBR of specimen = ................ %

RECOMMENDED VALUES S. No. 1 2 3 4

Soil type Silt Sand (poorly graded) Sand (well graded) Well graded sandy gravel

CBR Value (%) 1 10 15 20

CBR VALUE

SUBGRADE STRENGTH

COMMENTS

3% and less

Poor

" Capping* is required

3% - 5%

Normal

5% - 15%

Good

Widely encountered CBR range capping considered according to road category "Capping" normally unnecessary except on very heavily trafficked roads.

*Capping is a process used to cover contaminated soils to prevent the migration (movement) of the pollutants. This migration can be caused by rainwater or surface water moving over or vertically through the site, or by the wind blowing over the site. Caps are generally made of a combination of such materials as synthetic fibers, heavy clays, and sometimes concrete. The caps are designed to meet several goals

PRECAUTIONS 1. The CBR test should be performed on remoulded soils in laboratory. In-situ tests are recommended for design purposes. 2. The specimen should be prepared by static compaction whenever possible otherwise by dynamic compaction. 3. For the design of new roads the sub-grade soil sample should be compacted at OMC to proctor density whenever suitable compaction equipment is available to achieve this density in the field, otherwise the soil is compacted to the dry density expected to be achieved in the field. 4. In new constructions the CBR test samples may be soaked in water for four days period before testing. However in areas with arid climate or when the annual rainfall is less than 50cm and the water table is to affect the sub grade adversely and when thick impermeable bituminous surfacing is provided, it is not necessary to soak the soil sample before carrying out the CBR test 5. At least three samples should be tested on each soil sample at same density and moisture content. 6. If the maximum variation in the CBR values of three samples exceeds the specified limits, the design CBR should be the average of at least six samples. 7. The top 50cm of sub-grade should be compacted at least up to 95 to100% of proctor density.

GRAPH Plot load/unit load versus penetration curve and find corrected load/unit load;

Experiment No-3

CONSOLIDATION TEST Reference: - IS: 2720 (Part-15)-1986 OBJECTIVE To determine the consolidation properties of a given soil sample by conducting one dimensional test. THEORY When a compressive load is applied to soil mass, a decrease in its volume takes place, the decrease in volume of soil mass under stress is known as compression and the property of soil mass pertaining to its tendency to decrease in volume under pressure is known as compressibility. In a saturated soil mass having its void filled with incompressible water, decrease in volume or compression can take place when water is expelled out of the voids. Such a compression resulting from a long time static load and the consequent escape of pore water is termed as consolidation. Then the load is applied on the saturated soil mass, the entire load is carried by pore water in the beginning. As the water starts escaping from the voids, the hydrostatic pressure in water gets gradually dissipated and the load is shifted to the soil solids which increases effective on them, as a result the soil mass decrease in volume. The rate of escape of water depends on the permeability of the soil.

EQUIPMENTS/AAPARATUS 1. Consolidometer consisting essentially; a) b) c) d) e) f) g)

A ring of diameter 60 mm and height/thickness 20 mm Two porous plates or stones of silicon carbide, aluminum oxide or porous metal. Guide ring. Outer ring. Water jacket with base. Pressure pad. Rubber basket.

2. Loading device consisting of frame, lever system, loading yoke dial gauge fixing device 3. 4. 5. 6. 7.

and weights. Dial gauge to read to an accuracy of 0.002 mm. Thermostatically controlled oven. Stopwatch to read seconds. Sample extractor. Miscellaneous items like balance, soil trimming tools, spatula, filter papers, sample containers.

SAMPLE PREPARATION Specimens shall be prepared in a humid room to prevent evaporation of soil moisture. Extreme care shall be taken in preparing specimens of sensitive soils to prevent disturbance of their natural structure. Specimens of relatively soft soils may be prepared by progressive trimming in front of a calibrated, ring-shaped specimen cutter. REMOLDED SAMPLE:

1. Take the fine grained soil sample passing from 425 micron IS sieve.

2. Choose the density between 1.60 to 1.80 g/cc and water content Approx. 12% excluding natural moisture i.e. 2-4%, at which sample has to be compacted from the moisture density relationship (OMC-MDD). 3. Calculate the quantity/mass (required/assumed density x volume) of soil and water required to mix. Volume of ring = 56.52 cm3 4. Clean and dry the metal ring, measure its diameter and height. 5. Take the mass of the empty ring (W1) to calculate/find out the density/unit weight. 6. Compact the soil in mould/ring in layers using the standard rammer. 7. Trim the specimen flush with the top and bottom of the ring. 8. Remove any soil particles sticking to the outside of the ring. 9. Weigh the ring with specimen W2. 10. Take a small quantity of the soil (removed during trimming) for the water content determination. PROCEDURE 1. Saturate two porous stones either by boiling in distilled water about 15 minute or by keeping them submerged in the distilled water for 4 to 8 hrs. Wipe away excess water. Fittings of the consolidometer which is to be enclosed shall be moistened. 2. Assemble the consolidomter cell, with the soil specimen, filter paper and porous stones. Place the bottom porous stone, bottom filter paper, specimen, top filter paper and the top porous stone one by one. Position the loading block centrally on the top porous stone

3. Mount the mould assembly on the loading frame, and center it such that the load applied is axial.

4. Set the dial gauge in position to measure the vertical compression of the specimen. The dial gauge holder should be set so that the dial gauge is in the begging of its releases run, allowing sufficient margin for the swelling of the soil, if any.

6. Apply an initial load to the assembly. The magnitude of this load should be chosen by trial, such that there is no swelling. It should be not less than 50 g/cm2 for ordinary soils & 25 g/cm2 for very soft soils. The load should be allowed to stand until there is no change in dial gauge readings for two consecutive hours or for a maximum of 24 hours.

7. Note the final dial reading under the initial load. Apply first load of intensity 0.1 kg/cm2 start the stop watch simultaneously.

8. Record the dial gauge readings at various time intervals as mentioned in observation table. The dial gauge readings are taken until 90% consolidation is reached. Primary consolidation is gradually reached within 24 hrs.

9. At the end of the period, specified above take the dial reading and time reading. Double the load intensity and take the dial readings at various time intervals.

10. Repeat this procedure for successive load increments. The usual loading intensities are as 0.1, 0.2, 0.5, 1, 2, 4 and 8 kg/cm2. OBSERVATION TABLE

 

Diameter of Ring, D= 6 cm Initial Thickness of Ring, Hi = 2 cm



Area of Ring, A = 28.26 cm2



Volume of Ring, V = 56.52 cm3



Specific Gravity of soil, Gs = 2.67



Weight of dry soil, Wd = ………….gm (after test)

Wd W Ms or, d if ,  w  1 , or G. w . A G. A. Gs . A

Equivalent height of solids, Hs=

Pressure Increment Data; Pressure Intensity in Kg/cm2

Sl No.

Time, t in min

√t

1

2

3

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

0 0.25 (15 sec) 0.5 (30 sec) 1.0 (60 sec) 2.25 4.0 9.0 16.0 25.0 36.0 49.0 64.0 81.0 100.0 144.0 256.0 400.0 600.0 1444.0 (24 hrs)

Applied Final pressure dial gauge ' reading 2

(kgf/cm )

1

0.05

2

1.0

2.0

4.0

8.0

8

9

Dial Gauge Readings

4

5

6

7

0 0.5 .707 1.0 1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 12.0 16.0 20.0 24.5 38.0

Change in Specimen Void height of Height Ratio sample H  H i  H H e 1 H Hs (cm) (cm)

3

0.5

4

5

e



'

Coef. of Coef. of Volume Compresibility Change

av  2

e  '

Mv 

av 1 e

(cm /kg)

6

7

8

9

t50 Or t90

Coef. of Consoli dation

cv

(min) (cm2/min)

10

0 0.05 0.5 1.0 2.0 4.0 8.0

Determination of Bulk Density, Water Content and Dry Density of Soil

11

S. Particulars No.

Before Test

After Completion Of Test

Sample-1 Sample-2 Particulars

1.

Moisture Container No.

Wt of consolidation ring, W1

2.

Wt of empty can W1 gm

Wt of ring + specimen, W2

3.

Wt. of can + wet soil, W2 g

Dry Wt of ring + specimen, W3

4.

Wt. of can + dry soil, W3 gm

Dry Wt of specimen Wd = W3 - W1

5.

Wt of water , Ww  W2  W3

6.

Wt of dry soil Wd  W3  W1

7.

Water content w 

Sample-1 Sample-2

W2  W3  100 Wd W  W1 Bulk density,  b = 2 V  Dry density,  d  b 1 w Water Content, w 

Ww  100 Wd

CALCULATIONS Coefficient of Consolidation (Cv). The Coefficient of consolidation at each pressures increment is calculated by using the following equations:

i.

cv 

0.197d 2 (Log fitting method) (in double drainage, d will be half i.e. d/2) t 50

ii.

cv 

0.848d 2 (Square fitting method) t90

In the log fitting method, a plot is made between dial readings and logarithmic of time, the time corresponding to 50% consolidation is determined. In the square root fitting method, a plot is made between dial readings and square root of time and the time corresponding to 90% consolidation is determined. The values of Cv are recorded in table II. Compression Index (Cc). To determine the compression index, a plot of voids ratio (e) Vs log σ¯ is made. The initial compression curve would be a straight line and the slope of this line would give the compression index Cc.

Coefficient of Permeability. It is calculated as follows;

k

Cv aa  w 1 e

Or, k  Cv  w mv

PRESENTATION OF RESULTS

Or, k  Cv  w gmv

The results of a consolidation test are presented in the form of a set of curves showing the relationship of e versus log ֿ ◌σ, av versus logσ and cv versus log ֿ ◌σ. The value of Cc is also reported separately. NEED AND SCOPE The test is conducted to determine the followings; 1. 2. 3. 4. 5.

Rate of consolidation under normal load. Degree of consolidation at any time. Pressure-void ratio relationship. Coefficient of consolidation (cv) at various pressures. Compression index (cc).

From the above information it will be possible for us to predict the time rate and extent of settlement of structures founded on fine-grained soils. It is also helpful in analyzing the stress history of soil. Since the settlement analysis of the foundation depends mainly on the values determined by the test, this test is very important for foundation design. SIGNIFICANCE/APPLICATION The consolidation properties determined from the consolidation test are used to estimate the magnitude and the rate of both primary and secondary consolidation settlement of a structure or earth fill. Estimate of this type are of key importance in the design of engineered structures and the valuation of their performance. GENERAL REMARKS 1. While preparing the specimen, attempts has to be made to have the soil strata orientated in the same direction in the consolidation apparatus. 2. During trimming care should be taken in handling the soil specimen with least pressure. 3. Smaller increments of sequential loading have to be adopted for soft soils. GRAPHS 1. Voids Ratio vs Log σ (average pressure for the increment). 2. Dial Reading VS Log of Time or 3. Dial Reading VS Square Root of Time.

Voids Ratio VS Log σ (average pressure for the increment Dial Reading VS Log of Time

Dial Reading VS Square Root of Time

Experiment No-4

DIRECT SHEAR TEST

Reference: - IS: 2720 (Part-13)-1986 OBJECTIVE To determine the shear parameters (C & ф) and shear strength of a sandy soil (with a maximum particle size of 4.75 mm) by direct shear test in un-drained condition. THEORY Shear strength of a soil has its maximum resistance to shearing stress at failure on the failure plane. Shear strength is composed of; 1. Internal friction (φ) which is the resistance due to friction between individual particles at their contact points and interlocking of particles. 2. Cohesion (c) which is resistance due to inter particles forces which tend to hold the particles together in a soil mass. Coulomb has represented the shear strength of soil by the equation:

t = c + n tan      

t = Shear strength of soil = shear stress at failure c = Cohesion n = Total normal stress on the failure plane = Angle of internal (shearing) friction

The parameters c and φ are not constant for type of soil but depend on it degree of saturation and the condition of laboratory testing. There are three types of laboratory test. 1. Undrained Test – water is not allowed to drain out during the entire test, hence there is no dissipation of pressure. 2. Consolidate under the initially applied normal stress only, hence drainage is permitted. But no drainage is allowed during shear. 3. Drained Test— Drainage is slowed throughout the test during the application of normal and shear stresses, No pore pressure is set-up at any stage of the test. Coulomb’s shear strength equation has been modified on the concept of pore pressure Development. Modified equation is; t = c’ + ’ tan Or,  c’ = effective cohesion  ’ = effective normal stress  u = pore pressure  = total normal stress  = effective angle of shearing resistance APPARATUS:

t = c’ + (u) tan 

The shear box grid plates, porous stones, base plates and loading pad and water jacket shall confirm to IS: 11229-1985.

Loading frame- it shall satisfy the following requirements: 1. The vertical stress on the sample shall remain vertical and constant during the test and there shall be arrangement to measure compression. 2. The shear stress or strain can be applied in the dividing plane of the two parts of the shear box. 3. It shall be possible to maintain a constant rate of increase in stress during the test (irrespective of the strain rate) with arrangement to get different rates of stress increase. 4. In case of a strain-controlled apparatus, the strain rate should remain constant irrespective of the stress. Suitable arrangement shall be provided to obtain different strain rates. 5. No vibrations should be transmitted to the sample during the test and there should not be any loss of shear force due to friction between the loading frame and the shear box container assembly. 6. Weights – for providing the required normal loads, if necessary. 7. Proving Ring – force measuring of suitable capacity. Fitted with a dial gauge accurate to 0.01 mm to measure the shear force. (Note: for normal testing, proving rings of 100 to 250 kg capacity, depending on the type of soil and the normal load on the sample during test, may be needed.) 8. Micrometer dial-gauges – accurate to 0.01 mm; one suitably mounted to measure horizontal movement and the other suitably mounted to measure the vertical compression of the specimen. 9. Sample trimmer or core cutter, Stop cock, Balance of 1 kg capacity sensitive to 0.1 g, Spatula and a straight edge.

Schematic showing direct shear equipment PREPARATION OF SPECIMEN 1. Cohesive soils may be compacted to the required density and moisture content, the sample extracted and then trimmed to the required size.

2. Alternatively the soil may be compacted to the required density and moisture content directly into the shear box after fixing the two halves of the shear box together by means of the fixing screws. 3. Cohesion less soils may be tamped in the shear box itself with the base plate and grid plate or porous stone as required in place at the bottom of the box. PROCEDURE Part-A (Sample Preparation) 1. Note the dimension/size of the mould and calculate the volume of the same. 2. Choose the density (1.60-1.80 g/cc) and calculate the mass/weight of fine grained soil or sand (W = d x V). 3. Add about 6 to 7 % water by weight of soil/sand as calculated above (excluding natural moisture present in soil/sand i.e. 1 to 2%) and mix it thoroughly. 4. Place the soil/sand in smooth layers (approximately 10 mm thick) into shear box and compact by wooden tamping flat. 5. Make the surface of the soil/sand plane. Part-B (Testing of Specimen) 6. Arrange the box by placing the base plate, porous/spacer stone and grooving plate in the order. The grooving plate should be placed perpendicular of the direction of force. 7. Now put the mould with soil/sand on the top of the shear box and transfer the specimen into box by a small wooden square plate. 8. Place the upper grooving, porous/spacer stone and loading pad in the order on soil specimen. 9. Place the box inside the container and mount it on loading frame. 10. Apply the desired normal load as 0.5, 1.0, 1.5, 2.0 kg/cm². 11. Attach the dial gauges which measure the change of volume. 12. Record the initial reading of the dial gauge and calibration values. 13. Remove the shear pin. 14. Before proceeding to test check all adjustments to see that there is no connection between two parts except sand/soil. 15. Set the strain rate as per requirement and depending on the type of material. 16. Set the dial gauges and proving ring zero, before starting the experiment 17. Start the motor and record readings of proving ring and vertical and shear movement dial gauges at every 50 divisions. 18. Record carefully all the readings until the specimen fails. 19. Repeat the test on identical specimen under increasing normal stress 0.5,1,2 and 4 kg/cm². 20. For sandy soils a rate of strain of 0.2 mm/min may be suitable. For clayey soils, a rate of strain of 0.01mm/min or slower may be used but actual rate of strain suitable for the soil under test may be ascertained. OBSERVATIONS & CALCULATIONS Soil Specimen Measurements 

Dimensions of mould: 6 x 6 x 2.5 cm

            

Initial Thickness Ho = 2.5 cm or 25 mm Area of Specimen, Ao= 36 cm2 Volume of Specimen, Vo= 90 cm3 Initial wt of wet specimen...........................gm Moisture content.............% Bulk density..................................g/cc Final wet wt. of the specimen.........................gm Moisture content at shear zone.....................% Rate of shearing ...............mm/min Least Count of Proving Ring = ………………… kg/div (Pls. see from Table) Least Count of horizontal dial = 0.01 mm/div. Least Count of vertical dial = 0.01mm/div. Normal stress = ……………….kg/cm2

OBSERVATIONS S. No.

A 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Horizontal Vertical dial dial readings reading (no of div) (no of div)

B 0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 475 500 GRAPH

C 0

CALCULATIONS Proving Horiz DisplVertical Shear ring acement Displacement force reading δh=B x 0.01 Δv = C x 0.01 D x 0.26 (Kg) (no of div) (mm) (mm)

D 0

E 0 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00

F 0

G 0

Corrected Area (cm²)    Ac  A0 1  h  3 

H 36.00

Shear stress q

S .F . Ac

I 0

Horizontal strain h Lo

J 0

Vertical Thickness of strain specimen v 25-Δv (mm) Ho

K 0

L 25.00

Shear Stress Vs Shear Displacement

SUMMARY OF RESULTS

Vertical Strain Vs Horizontal Strain

Test No.

Normal Stress (kg/cm2)

1

0.5

2

1.0

3

1.5

Shear Stress at failure (kg/cm2)

Shear displacement at failure (mm)

Thickness of specimen at failure (mm)

Angle of internal friction (φ) °

Cohesion ‘C’ (kg/cm2)

PRECAUTIONS:

1. Before starting the test upper half of the box should be brought in contact of the proving ring assembly 2. Before subjecting the specimen to shear, the fixing screws should be taken out. 3. Spacing screws should also be removed before shearing the specimen. 4. The vertical stress on the sample should remain uniform, vertical and constant during the test. 5. The rate of strain should be constant throughout the test. 6. The shearing strain and stress should be applied in the same plane as the dividing plans of the two part of the box 7. No vibrations should be transmitted to the specimen during the test. 8. For drained test, the porous stones should be de-aired and saturated boiling. 9. Do not forget to add the self weight of the loading yoke in the vertical loads 10. Do not mix with each other the least counts and readings of the three dial gauges. NEED AND SCOPE: In many engineering problems such as design of foundation, retaining walls, slab bridges, pipes, sheet piling, the value of the angle of internal friction and cohesion of the soil involved are required for the design. Direct shear test is used to predict these parameters quickly. The laboratory report covers the laboratory procedures for determining these values for cohesion less soils. This test is performed to determine the consolidated-drained shear strength of a sandy to silt soil. The shear strength is one of the most important engineering properties of a soil, because it is required whenever a structure is dependent on the soil’s shearing resistance. The shear strength is needed for engineering situations such as determining the stability of slopes or cuts, finding the bearing capacity for foundations, and calculating the pressure exerted by a soil on a retaining wall. SIGNIFICANCE: The direct shear test is one of the oldest strength tests for soils. In this laboratory, a direct shear device will be used to determine the shear strength of cohesion less soil (i.e. angle of internal friction (ф)). From the plot of the shear stress versus the horizontal displacement, the maximum shear stress is obtained for a specific vertical confining stress. After the experiment is run several times for various vertical-confining stresses, a plot of the maxi mum shear stresses versus the vertical (normal) confining stresses for each of the tests is produced. From the plot, a straight-line approximation of the Mohr-Coulomb failure envelope curve can be drawn, ф may be determined, and, for cohesion less soils (c = 0), the shear strength can be computed from the equation, S = C + σ tan ф APPLICATIONS

1. For most of the geotechnical designs concerning foundations, earthworks and slope stability issues the soils are required to withstand shearing stresses along with compressive stresses. 2. Shear stresses tend to displace a part of soil mass relative to rest of the soil mass. 3. Shear strength is the capacity of the soil to resist shearing stresses. 4. Relative sliding between soil particles is the major factor contributing to the shear resistance. 5. If the normal forces increase, the number of contact points also increase thus increasing the resistance. 6. The reverse may happen if the normal loads decrease (which is the case in excavations). 7. Hence the shear strength is a function of normal load, angle of friction (amount of interlocking among the soil particles) and cohesion (intrinsic property of clays due to which they stay close to each other even at zero normal load). GENERAL REMARKS 1. In the shear box test, the specimen is not failing along its weakest plane but along a predetermined or induced failure plane i.e. horizontal plane separating the two halves of the shear box. This is the main drawback of this test. Moreover, during loading, the state of stress cannot be evaluated. It can be evaluated only at failure condition i.e. Mohr circle can be drawn at the failure condition only. Also failure is progressive. 2. Direct shear test is simple and faster to operate. As thinner specimens are used in shear box, they facilitate drainage of pore water from a saturated sample in less time. This test is also useful to study friction between two materials one material in lower half of box and another material in the upper half of box. 3. The angle of shearing resistance of sands depends on state of compaction, coarseness of grains, particle shape and roughness of grain surface and grading. It varies between 28o (uniformly graded sands with round grains in very loose state) to 46 o (well graded sand with angular grains in dense state). 4. The volume change in sandy soil is a complex phenomenon depending on gradation, particle shape, state and type of packing, orientation of principal planes, principal stress ratio, stress history, magnitude of minor principal stress, type of apparatus, test procedure, method of preparing specimen etc. 5. In general loose sands expand and dense sands contract in volume on shearing. There is a void ratio at which either expansion contraction in volume takes place. This void ratio is called critical void ratio. Expansion or contraction can be inferred from the movement of vertical dial gauge during shearing. 6. The friction between sand particles is due to sliding and rolling friction and interlocking action. 7. The ultimate values of shear parameter for both loose sand and dense sand approximately attain the same value so, if angle of friction value is calculated at ultimate stage, slight disturbance in density during sampling and preparation of test specimens will not have much effect. Experiment No-5

UNCONFINED COMPRESSIVE STRENGTH (UCS) TEST

Reference: - IS: 2720 (Part-10)-1991 OBJECTIVE To determine the Unconfined Compressive Strength (UCS) of cohesive/clayey soil (undisturbed, remoulded or compacted) using controlled rate of strain. THEORY: It is the load per unit area at which an unconfined cylindrical specimen of soil will fail in the axial compression test. 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 (σu) 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: su = c =2 σu. 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 φ, 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 φ’ are drained shear strength parameters.

APPARATUS: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Compression Device Proving Ring Deformation Dial Gauge Timer (stop watch) Oven Weighing Balances Sampling tubes Sample extractor and split sampler Evaporating dish Miscellaneous equipments

PREPARATION OF TEST SPECIMEN: The type of soil specimen to be used for test shall depend on the purpose for which it is tested and may be compacted, remolded or undisturbed. Specimen Size: The specimen for the test shall have a minimum diameter of 38 mm and the Largest particle contained within the test specimen shall be smaller than 1/8 of the specimen diameter. If after completion of test on undisturbed sample it is found that larger particles then permitted for the particular specimen size tested are present it shall be noted in the report of test data under remarks. The height to diameter ratio shall be within 2 to 2.5 Measurements of height and diameter shall be made with vernier calipers or any other suitable measuring device to the nearest 0.1 mm. Undisturbed: 1. Push the sampling tube into in to the clay samples.

2. 3. 4. 5. 6. 7. 8. 9.

Remove the sampling tube along with the soil. Saturate the soil sample in sampling rube by a suitable method if possible. Coat the inside of the split mould with a thin layer of the soil. Extrude the specimen from the sampling tube to the split mould with the help of sample extractor and knife. Trim the two ends of the mould sample Weight the soil sample and the mould. Remove the sample from the mould by splitting it in two parts. Measure the length and diameter of the specimen.

Compacted Specimen: When compacting disturbed material it shall be done using a mould of circular cross section with dimensions corresponding to those given in compacted specimen may be prepared at any predetermined water content and density. After the Specimen is formed the ends shall be trimmed perpendicular to the long axis and removed from the mould representative sample cuttings shall be obtained or the entire specimen shall be used for the determination of water content after the test. PROCEDURE: 1. The initial length, diameter and weight of the specimen shall be measured and the specimen placed on the bottom plate of the loading device .The upper plate shall be adjusted to make contact with the specimen. 2. The deformation dial gauge shall be adjusted to a suitable reading preferably in multiples of 100 Force shall be applied so as to produce axial strain at a rate of 0.5 to 2 percent per minute causing failure with 5 to 10. The force reading shall be taken at suitable intervals of the deformations dial reading. 3. The specimen shall be compressed until failure surfaces have definitely developed or the stress strain of 20 percent is reached 4. The failure pattern shall be sketched carefully and shown on the date sheet or on the sheet presenting the stress strain plot. 5. The angle between the failure surface and the horizontal may be measured if possible and reported. 6. The water content of the specimen shall be determined in accordance with using samples taken from the failure zone of the specimen. OBSERVATIONS:       

Specific gravity of the solids, G= 2.67 Initial length Lo = 76 mm Initial volume Vo = 86.14 cm3 Initial mass of the specimen, M =…. .gm Initial density (M/V)…… gm/ cm3 Rate of Strain…………… Least Count of Proving ring = ………..kg/div OBSERVATIONS

Initial diameter Do = 38 mm Initial area Ao = 11.33 cm2 Maximum dry density -----------gm/ cm3 Initial water content, w =…….% Optimum water content ……….. % L.C. of Dial gauge = 0.01 mm/div CALCULATIONS

S. No.

Vertical dial gauge Readings

Proving Ring dial reading

Axial deformation ΔL=

Axial Force P

Axial Strain ε=

A 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

(div)

(div)

(mm)

(kgf)

B 0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 475 500

C 0

D 0.0 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00

E 0

L L0 F 0

Corrected Area Ac 

A0 1 

Compressive Stress 

C



P Ac

Final height of specimen L f  L0  E

(cm 2)

(kg/cm2)

(mm)

G 11.33

H 0

I 76.0

Note: 1. Plot a curve between the compressive stress as ordinate and axial strain as abscissa. Minimum three samples should be tested; correlation can be made between unconfined strength and field SPT value N. Up to 6% strain the readings may be taken at every ½ min (30 sec). 2. Three specimens obtained by trimming and carving from undisturbed soil samples shall be tested.

General Relationship of Consistency and Unconfined Compression Strength of Clays S. No.

Consistency

1. 2. 3. 4. 5. 6.

Very soft Soft Medium Stiff Very stiff Hard

Unconfined Compression Strength (qu) Sensitivity* kN/m2 Kg/cm2 Ton/ft2 0 - 25 < 0.25 0 – 0.25 1-4 25 – 50 0.25 to 0.5 0.25 – 0.50 4 -8 50 – 100 0.5 to 1.0 0.5 – 1.0 8-15 100 – 200 1.0 to 2.0 1.0 – 2.0 > 15 200 – 400 2.0 to 4.0 2.0 – 4.0 ---> 400 <4 >4 ----

* Sensitivity  PRECAUTIONS

qu (Undisturbed ) qu (Re moulded)

Designation Normal Sensitive Extra Sensitive Quick -------

1. The specimen should be handled carefully to prevent disturbance, change in density or loss of moisture. Loss of moisture during the testing may be checked by sealing the specimen with rubber membranes. 2. Two ends of the specimen should be perpendicular to the long axis of the specimen. 3. The seating of the sample should be proper on the upper and lower plates. 4. The loading of the sample should be at constant rate. 2. Remolded specimen should be prepared at the same moisture content and density as of undisturbed sample. 3. If degree pf saturation is less than 100% don’t forget to measure the failure angle. 4. The sample should always be pushed in the sampling tube or the mould along the same direction in which it enters the same direction in which it enters the tube in the field. 5. Do not interchange the least count and observations of deformation dial gauge with proving ring dial gauge. SIGNIFICANCE/APPLICATIONS 1. For soils, the undrained shear strength (su) is necessary for the determination of the bearing capacity of foundations, dams, etc. 2. A quick test to obtain the shear strength parameters of cohesive (fine grained) soils either in undisturbed or remolded state 3. The test is not applicable to cohesion less or coarse grained soils 4. The test is strain controlled and when the soil sample is loaded rapidly, the pore pressures (water within the soil) undergo changes that do not have enough time to dissipate 5. Hence the test is representative of soils in construction sites where the rate of construction is very fast and the pore waters do not have enough time to dissipate 6. The test results provide an estimate of the relative consistency of the soil 7. Almost used in all geotechnical engineering designs (eg. design and stability analysis of foundations, retaining walls, slopes and embankments) to obtain a rough estimate of the soil strength and viable construction techniques. 8. To determine Undrained Shear Strength or Undrained Cohesion (Su or Cu) = σu/2 NEED AND SCOPE It is not always possible to conduct the bearing capacity test in the field. Sometimes it is cheaper to take the undisturbed soil sample and test its strength in the laboratory. Also to choose the best material for the embankment, one has to conduct strength tests on the samples selected. Under these conditions it is easy to perform the unconfined compression test on undisturbed and remoulded soil sample. The primary purpose of this test is to determine the unconfined compressive strength, which is then used to calculate the unconsolidated undrained shear strength of the clay under unconfined conditions. 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. STRESS STRAIN CURVE:

Experiment No-6

TRIAXIAL COMPRESSION TEST (UNDRAINED UNCONSOLIDATED-UU)

Reference: - IS: 2720 (Part-11) -1993 OBJECTIVE To determine the shear strength parameters (C & ф) of undisturbed or remoulded soil specimen by unconsolidated un-drained tri-axial compression test without the measurement of pore pressure. THEORY The principle behind a triaxial shear test is that the stress applied in the vertical direction (along the axis of the cylinder) can be different than the stress applied in the horizontal directions (along the sides of the cylinder). This produces a non-hydrostatic stress state, which contains shear stress. From the triaxial test data, it is possible to extract fundamental material parameters about the sample, including its angle of internal friction, apparent cohesion, and dilatancy angle. These parameters are then used in computer models to predict how the material will behave in a larger-scale engineering application. An example would be to predict the stability of the soil on a slope, whether the slope will collapse or whether the soil will support the shear stresses of the slope and remain in place. Triaxial tests are used along with other tests to make such engineering predictions. Note: The diameter of the specimen is to be selected having regard to the character of the soil and the maximum size of the particles present in the sample. Generally, a diameter of 38 mm will be suitable for homogeneous fine grained soils. APPARATUS 1. Sampling tube: 38 mm diameter and 200 mm length to suit the test specimen. 2. Trimming knife – sharp-bladed for example a spatula or pallet knife. 3. Metal straight edge 4. Non-corrodible metal or plastic end-caps- of the same diameter as the test specimen. The upper end-cap is to have a central spherical seating to receive the loading ram. 5. Note: A plastic upper end cap, 20 mm thick, is normally satisfactory for use on soft or very soft soils. Metal end caps are considered preferable for use on stiff soils. Metal upper end cap 12 to 20 mm thick is normally satisfactory.

6. Seamless Rubber Membrane – In the form of a tube, open at both ends of internal diameter equal to the specimen diameter and length 50 mm greater than the height of the specimen. The membrane thickness should be selected having regard of the size, strength and nature of the soil to be tested. A thickness of 0.2 to 0.3 mm is normally satisfactory. 7. Rubber rings – of circular cross-section to suit the diameter of the end caps. 8. Moisture containers 9. Balance – readable and accurate to 0.5 g. Apparatus Required for Tri-Axial -Test

1. Tri-axial Test Cell- A tri-axial test cell of dimensions appropriate to the size of the specimen, capable of being opened for the insertion of the specimen, suitable for use with the fluid selected for use at internal pressure up to 1 MPa and provided with a means of applying additional axial compressive load to the specimen by means of a loading ram. A transparent chamber is recommended. The base of the cell shall be provided with a suitable central pedestal with drainage outlets with valves. 2. An Apparatus For Applying And Maintaining The Desired Pressure On The Fluid Within The Cell (Cell Pressure Constant) – To an accuracy of 10 KPa (preferably 5 KPa) with a gauge for measuring the pressure. The gauge shall be regularly calibrated.

1 kPa = 1 kN/m2

1 kPa = 0.01 kgf/cm2

1 kN = 100 kgf

3. Machine Capable of Applying Axial Compression to the Specimen – At convenient speeds to cover the range 0.05 to 5 mm per minute. The machine should have a capacity of 50 kN. A means of measuring the axial compression of the specimen to an accuracy of 0.01 mm shall be provided and the machine shall be capable of applying an axial compression of about one third the height of the specimen tested. 4. Provision shall be made for measuring the additional axial load on the specimen. Proving ring of 1 kN capacity with sensitivity of 2 N for low strength soils and one of 10 kN capacity with sensitivity of 10 N for high strength soils are found suitable. Note: - In case the travel of the dial gauges is not sufficient magnetic spacer of known thickness may be used

PREPARATION OF SPECIMENS

1. Undisturbed Specimen - The object of the specimen preparation is to produce cylindrical specimens of height twice the specimen diameter with plane ends normal to the axis and with the minimum change of the soil structure and moisture content. The method of preparation will depend on whether the sample is received in the laboratory in a tube or as a block sample. 2. Remoulded Samples – Remoulded samples prepared at the desired moisture and density by static and dynamic methods of compaction or by any other suitable method, where necessary. TESTING PROCEDURE 1. The specimen placed centrally on the pedestal of the tri-axial cell. The cell shall be assembled with the loading ram initially clear of the top cap of the specimen and the cell containing the specimen shall be placed in the loading machine. 2. The operating fluid shall be admitted to the cell and the pressure raised to the desired value. 3. The loading machine shall be adjusted to bring the loading ram a short distance away from the seat on the top cap of the specimen and the initial reading of the load measuring gauge shall be recorded. 4. The loading machine shall then be further adjusted to bring the loading ram just in contact with the seat on the top cap of the specimen and the initial reading of the gauge measuring the axial compression of the specimen shall be recorded. 5. A rate of axial compression shall be selected such that failure is produced within a period of approximately 5 to 15 minutes. 6. The test shall be commenced a sufficient number of simultaneous readings of the load and compression measuring gauges being taken to define the stress strain curve. 7. The test shall be continued until the maximum value of the stress has been reached. The specimen shall then be unloaded and the final reading of the load measuring gauge shall be recorded as a check on the initial reading. Note: It is often convenient to make a plot of load versus compression as the rest proceeds, to enable the point of failure to be determined.

8. The cell shall be determined of fluid and dismantled and the specimen taken out. The rubber membrane shall be removed from the specimen and the mode of failure shall be noted. The specimen shall be weighed and samples for the determination of the moisture content of the specimen shall be taken. If there is a moisture change in the specimen it should be recorded and discretion used with regard to acceptability of the test. Note: 1.

The most convenient method of recording the mode of failure is by means of sketch indicating the position of the failure planes. The angle of the failure plan (s) to the horizontal may be recorded if required. These records should be completed without undue delay to avoid loss of moisture from specimen.

2.

Comparison with the recorded mass of the specimen before testing provides a check on the impermeability of the rubber membrane if water has been used as the operating fluid in the cell.

OBSERVATIONS AND CALCULATIONS

Dia of sample: 38 mm,

Length, L 0 = 76 mm

Area: 11.33 cm2,

Volume: 86.14 cm3

Initial wt = ……….

Final wt ………………

Initial W.C. =…………..

Final W.C…………

Bulk density....................................

Load Gauge (Proving Ring) No…………….

Rate of strain.....................................

Description of sample.................................

Cell pressure (σ3) = ..................Kg/cm2

Final length ………..

Least Count of the Proving Ring = ………… kg/div. Least count of dial gauge = 0.01 mm/div. A correction to allow for the retraining effect of the rubber membrane shall be made as given below: Sl. No

OBSERVATIONS Vertical dial Gauge Reading (Div)

A 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

B 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800

CALCULATIONS

Proving Compression Load on ring of Sample sample Reading ΔL (P) B x 0.01 0.274 X C (Div) (mm) (Kg)

C 0

D 0

E 0

Strain vertical

 F 0

L L0

Corrected Area, A Ac  0 1 (cm2)

G 11.33

Deviator Stress P d  Ac (kgf/cm 2)

Major Principal Stress

Stress ratio

1   d   3

1 3

H 0

I 0

(kgf/cm2)

Final height of specimen L f  L0  D

J 0

1 D Where, M = the compression modulus of the rubber membrane in kg/cm of width ε = the axial strain at the maximum principal stress different D = initial diameter of the sample in cm. Correction = 4 M

The value of the correction calculated as above shall be deducted from the measured maximum principal stress difference to give the corrected value of the maximum principal stress different. REPORTING OF RESULTS 1. The dimensions of each test specimen the bulk density, the moisture content, the cell pressure, the value of the maximum principal stress difference (σ1-σ3) and the

(mm)

K 76.0

corresponding strain and time to failure and the rate of strain at which the test was conducted shall be recorded. 2. When required the stress strain curve of the test shall be plotted with the axial strain as abscissa and the principal stress difference as ordinate. 3. The type of the sampler and method of sampling in the field shall be reported. 4. The Shear parameters shall be obtained from a plot of Mohr circles for which purpose peak values of principal stress difference or principal stress ratio or the ultimate value as desired may be used. PRECAUTIONS 1. It is an essential to maintain the same initial density of sand in all the test using different lateral pressure. Small deference will rustle in appreciable errors the maximum failure stress. 2. During compaction sand in the mould, if rupture of membrane takes place, the test should be repeated with new membrane. 3. For test on saturated sand, there should be no bottom of the sample to the burette as the easy flow of water will be prevented 4. During compaction sand, the rate of testing is slow so that no excess pore pressure is generated 5. The mould should be removed carefully; it should not give any jar on the sample 6. Friction due to end cap should be minimum 7. There should no leakage through the cell 8. During entire period of the test, confining pressure should be kept constant. GENERAL REMARKS 1. 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 strain readings, from the proving ring, directly to the corresponding stress. 2. 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. 3. The stress results of the series of tri-axial 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. 4. 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  = C +  tan. 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 () is angle between the tangent and a line parallel to the shear stress. GRAPH:

Mohr Circle Experiment No-7

VANE SHEAR TEST Reference: - IS: 2720 (Part-XXX)-1980 OBJECTIVE To determine the un-drained shear strength of cohesive/clayey soils (having low shear strength) by conducting the lab vane shear test. THEORY The structural strength of soil is basically a problem of shear strength. Vane shear test is a useful method of measuring the shear strength of clay. It is a cheaper and quicker method. The test can also be conducted in the laboratory. The laboratory vane shear test for the measurement of shear strength of cohesive soils is useful for soils of low shear strength (less than 0.3 kg/cm2) for which tri-axial or unconfined tests cannot be performed. The test gives the undrained shear strength of the soil. The undisturbed and remoulded strength obtained are useful for evaluating the sensitivity of soil.

APPARATUS: VANE- The vane shall consist of four blades each fixed at 90° to the adjacent blades as illustrated. The vane should not deform under the maximum torque for which it is designed. The penetrating edge of the vane blades shall be sharpened having an included angle of 90°. The vane blades shall be welded together suitably to a central rod, the maximum diameter of which should preferably not exceed 2.5 mm in the portion of the rod which goes into the specimen during the test. The vane should be properly treated to prevent rusting and corrosion. The apparatus may be either of the hand operated type or motorized. Provisions should be made in the apparatus for the following. 1. Fixing of vane and shaft to the apparatus in such a way that the vane can be lowered gradually and vertically into the soil specimen. 2. Fixing the tube containing the soil specimen to the base of the equipment for which it should have suitable hole. 3. Arrangement for lowering the vane into the soil specimen (contained in the tube fixed to the base) gradually and vertically and for holding the vane properly and securely in the lowered position. 4. Arrangement for rotating the vane steadily at a rate of approximately 1/60 rev/min (0.1°/Sec) and for measuring the rotation of the vane. 5. A torque applicator to rotate the vane in the soil and a device for measuring the torque applied to an accuracy of 0.05 cm.kgf. 6. A set of springs capable of measuring shear strength of 0.5 kgf/cm2 PREPARATION OF TEST SPECIMEN

1. Take the clayey/cohesive soil sample about 200 gm passing 425 microns I.S. Sieve. 2. Add required water (Approx 30 to 35 %) and mix thoroughly to make homogeneous paste. 3. Fill the test mould with soil paste by compacting with compaction rod in 3 layers. 4. Place the mould on the apparatus and test the soil specimen as described in procedure. PROCEDURE: 1. The specimen in the tube should be at least 37.5 mm in diameter and 75 mm long. Mount the specimen container with the specimen on the base of the vane shear apparatus and fix it securely to the base. 2. If the specimen container is closed at one end it should be provided at the bottom with a hole of about 1 mm diameter. 3. Lower the shear vanes into the specimen to their full length gradually with minimum disturbance of the soil specimen so that the top of the vane is at least 10 mm below the top of the specimen. 4. Note the readings of the strain and torque indicators. Rotate the vane at a uniform rate approximately 0.1°/sec (6° per minute) by suitably operating the torque indicator. Torque readings and the corresponding strain readings may also be noted at desired intervals of time as the test proceeds. 5. Just after the determination of the maximum torque rotate the vane rapidly through a minimum of ten revolutions. The remoulded strength should then be determined within 1 minute after completion of the revolution. OBSEVATION AND CALCULATIONS S. No.

Initial Reading Final Reading Difference

Torque, T S

(deg)

(deg)

(deg)

1 2 3 Where, D = 1.2 cm H = 2.4 cm S = shear strength in kgf/cm2 T = torque in cm.kgf. (Pls. see the table)

RESULT: Shear Strength, S = ………………… kgf/cm2

(from table)

T 2

3

D H D    6  2

  

Or ,

3 T 19

Experiment No-8

SWELLING PRESSURE TEST BY CONSTANT VOLUME METHOD Reference: - IS: 2720 (Part-41)-1977 OBJECTIVE To determine the swelling pressure of an expansive soil by constant volume method. THEORY: Swelling Pressure: - The pressure which the expansive soil exerts, if the soil is not allowed to swell or the volume change of the soil is arrested. Swelling of materials which are relevant in civil and underground engineering are counted among the most alarming phenomena in geotechnics. The volume increasing of clay by absorption of water is a physical effect (osmosis), whereas the volume increasing during the hydration of anhydrite into gypsum is a chemical effect. Nevertheless, the consequences for the constructions are always the same: destructive stresses, deformations and loss of strength, often occurring and recognized months or even years later. Common characteristics of both effects are the stress-dependent behavior, the distinct anisotropy and the long time lapse. A swelling test requires months, even years in hydration of anhydrite. Theoretical, the maximum volume increasing of clay is less than 20%, whereas it's 64% at the anhydrite-gypsum transformation. Due to different properties of soils, like black cotton soil which has swelling pressure from 1 .0 kg/cm2 to 3.5 kg/cm2, these soils lose their shear strength considerably when they are wet. To have projects of railways, highways, roads, building etc., on such kind of soils, determination of their swell pressure is essential. APPARATUS AND EQUIPMENT 1. Swell pressure test apparatus as shown in figure 2. Mould – 100 mm dia and 127 mm height 3. Rammer-2.6 kg 4. Dial Gauge 5. Soil Trimming Tools 6. Balance 7. Oven 8. Moisture content cans 9. Loading unit of 5000 kg capacity - Strain controlled type. 10. High sensitive proving ring of 200 kg capacity. SAMPLE PREPARATION

1. Take about 3 kg of black cotton soil passing from 2 mm IS sieve. 2. Take the water as per desired density & optimum moisture content (OMC) or shrinkage limit and mix it thoroughly with mixing tools. 3. Compact the soil in 3 layers with 2.6 kg rammer in 25 blows (310 mm free fall) to each layer. 4. After compacting third layer trimming the top surface. Note: - In the case of remolded soil samples the initial water content shall be at the shrinkage limit or field water content, so that the swelling pressure recorded shall be maximum PROCEDURE 1. Place the mould in the tank, set the dial gauge and proving ring reading and fill the water upto top of the tank. 2. The initial reading of the proving ring and dial gauge shall be noted. 3. The swelling of the specimen with increasing volume shall be obtained in the strain measuring dial gauge. 4. To keep the specimen at constant volume, the platen shall be so adjusted that the dial gauge always shows the original reading. This adjustment shall be done at every 0.1 mm of swell or earlier. 5. The dial gauge readings shall be taken till equilibrium is reached. This is ensured by making a plot of swelling dial reading versus time in hours, which plot becomes asymptotic with abscissa (time scale). The equilibrium swelling is normally reached over a period of 6 to 7 days in general for all expansive soil. 6. The assembly shall then be dismantled and the soil specimen extracted from the mould to determine final moisture content in accordance with IS: 2720 (Part-II)-1973 OBSERVATIONS NATURAL DENSITY S. No. 1. 2.

Description

3.

Wt of mould Wt. of mould + wet specimen Wt. of specimen

4. 5. 6. 7.

Volume of mould, cc Wet density in g/cc Moisture content Dry density in g/cc

MOISTURE CONTENT

Test-I

Test-II

S. No. 1. 2. 3.

1000

1000

4. 5. 6. 7.

Description Container number Wt. of container ring + wet soil Wt. of container +dry soil Wt. of container Weight of water Weight of dry soil Moisture content in percent

SWELL PRESSURE DATA

Before Test

After Test

1. Least Count of Proving Ring = 0.274 kg/div 2. Area of the specimen = 78.5 cm2 3. Volume of specimen, V = 1000 cc Sl. No.

Date

Time

A

B

C

Strain Dial Gauge Reading Before Adjustment

Proving Ring Reading (Initial)

D

E

Proving Ring Reading (Final)

F

Differ ence

Load P= 0.274 x G (Kg)

G

H

Area of Swell specimen Pressure A= P/A = (cm2) (Kg/cm2)

I

1

78.5

2

78.5

J

CALCULATION AND REPORT The difference between the final and initial dial readings of the proving ring gives total load in terms of division which when multiplied by the calibration factor gives the total load. This when divided by the cross-sectional area of the soil specimen gives the swell pressure expressed in kN/m2 (kgf/cm2) Swelling .. Pr essure 

Final ..Dial .. Re ading  Initial ..dial ..reading  Calibratio n.. factor ..of .. proving ..ring Area..of ..specimen

RESULT Swelling Pressure =............................. kgf/cm2. GRAPH:

Effect of treatment temperature on swelling pressure

Experiment No-9

SWELLING PRESSURE TEST BY CONSOLIDOMETER METHOD Reference: - IS: 2720 (Part-41)-1977

OBJECTIVE To determine the swelling pressure of an expansive soil by consolidometer method. THEORY: Swelling Pressure: - The pressure which the expansive soil exerts, if the soil is not allowed to swell or the volume change of the soil is arrested. Swelling of materials which are relevant in civil and underground engineering are counted among the most alarming phenomena in geotechnics. The volume increasing of clay by absorption of water is a physical effect (osmosis), whereas the volume increasing during the hydration of anhydrite into gypsum is a chemical effect. Nevertheless, the consequences for the constructions are always the same: destructive stresses, deformations and loss of strength, often occurring and recognized months or even years later. Common characteristics of both effects are the stress-dependent behavior, the distinct anisotropy and the long time lapse. A swelling test requires months, even years in hydration of anhydrite. Theoretical, the maximum volume increasing of clay is less than 20%, whereas it's 64% at the anhydrite-gypsum transformation. Due to different properties of soils, like black cotton soil which has swelling pressure from 1 .0 kg/cm2 to 3.5 kg/cm2, these soils lose their shear strength considerably when they are wet. To have projects of railways, highways, roads, building etc., on such kind of soils, determination of their swell pressure is essential. APPARATUS AND EQUIPMENT i) ii) iii) iv)

Consolidometer Specimen Diameter- The specimen shall be 60 mm in Specimen Thickness – The specimen shall be at least 20 mm thick in all cases. Ring – The ring shall be made of a material which is non-corrosive in relation to the soil tested. The inner surface shall be highly polished or coated with a thin coating of silicon grease or with a low friction material. v) Porous Stones – The stones shall be of silicon carbide or aluminum oxide and medium grade. it shall have a high permeability compared to that of the soil being tested. a) Dial Gauge – accurate to 0.01 mm with a traverse of at least 20 mm. b) Water Reservoir- to keep the soil sample submerged. c) Moisture Room- For storing samples and for preparing samples in climates where there is likelihood of excessive moisture loss during preparation (optional). d) Soil Trimming Tools - Fine wire saw, knife, spatula, etc. for trimming sample to fit into the inside diameter of the consolidometer ring with minimum disturbances. e) Oven - Thermostatically controlled oven with interior of non-corroding material to maintain the temperature between 105-1100C. f) Desiccators – With any desiccating agent other than sulphuric acid. g) Balance – Sensitive to 0.01 g. h) Containers – for water content determination. PREPARATION OF TEST SPECIMEN Preparation of Specimen from Disturbed Soil Samples – In case where it is necessary to use disturbed soil samples the soil sample shall be compacted to the desired (field) density and water content in a standard compaction proctor mould. Samples of suitable sizes are cut from

it. In the case of remoulded soil samples the initial water content shall be at the shrinkage limit or field water content, so that the swelling pressure recorded shall be maximum.

PROCEDURE 1. The porous stones shall be saturated. All surfaces of the consolidometer which are to be enclosed shall be moistened. 2. The consolidometer shall be assembled with the soil specimen (in the ring) and porous stones at top and bottom of the specimen, providing a filter paper rendered wet (Whatman No.1 or equivalent) between the soil specimen and porous stone. The loading block shall then be positioned centrally on the top porous stone. 3. This assembly shall then be mounted on the loading frame such that, the load when applied is transmitted to the soil specimen through the loading cap. The assembly shall be so centered that the load applied is axial. 4. An initial seating load of 0.05 kgf/cm2 (this includes the weight of the porous stone and the loading pad) shall be placed on the loading hanger and the initial reading of the dial gauge shall be noted. 5. The system shall be connected to a water reservoir with the level of water in the reservoir being at about the same level as the soil specimen and water allowed to flow in the sample. The soil shall then be allowed to swell. 6. The free swell readings shown by the dial gauge under the seating load of 5 kN/m2 (0.05 kgf/cm2) shall be recorded at different time intervals. 7. The dial gauge readings shall be taken till equilibrium is reached. This is ensured by making a plot of swelling dial reading versus time in minutes. The equilibrium swelling is normally reached over a period of 6 to 7 days in general for all expansive soil. 8. The swollen sample shall then be subjected to consolidation under different pressures. The compression dial readings shall be recorded till the dial readings attain a steady state for each load applied over the specimen. The consolidation loads shall be applied till the specimen attains its original volume.

OBSERVATIONS

S. No. 1. 2. 3. 4. 5. 6.

NATURAL DENSITY Description Test Test S. I II No. Wt. of container ring + 1. wet specimen Wt. of container 2. Diameter of container 3. Initial thickness of soil 4. sample Wet density in g/ml 5. Dry density in g/ml 6.

MOISTURE CONTENT Description Before After Test Test Wt. of container ring + wet soil Wt. of container +dry soil Wt. of container Weight of water Weight of dry soil Moisture content percent

in

TIME OF STARTING S. No. 1.

Elapsed Time In Hours 0

Swelling Dial Reading

2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.

0.5 1 2 4 8 12 16 20 24 36 48 60 72 96 120 144

DATA SHEET FOR SWELL-COMPRESSION TEST Sl. No. 1 2 3 4 5 6 7 8 9

Pressure Increment In kgf/cm2 In kN/m2 0.0-0.05 0-5 0.05-0.10 5-10 0.10-0.25 10-25 0.25-0.50 25-50 0.50-1.00 50-100 1.00-2.00 100-200 2.00-4.00 200-400 4.00-8.00 400-800 8.00-16.00 800-1600

Compression

Change in thickness of Expanded Specimen

CALCULATIONS AND REPORT The observed swelling dial reading recorded in table shall be plotted with elapsed time as abscissa and swelling dial reading as ordinates on natural scale. A smooth curve shall be drawn joining these points. If the curve so drawn becomes asymptotic with the abscissa, the swelling has reached its maximum and hence the swelling phase shall be stopped, and the consolidation phase shall be started. The compression readings shall be tabulated as in form 2 of observation and plot of change in thickness of expanded specimen as ordinates and consolidation pressure applied as abscissa in semi logarithmic scale shall be made. The swelling pressure exerted by the soil specimen under zero swelling condition shall be obtained by interpolation and expressed in kN/m2 (kgf/cm2).

RESULTS Swelling Pressure =....................... kgf/cm2. Experiment No-10

FREE SWELL INDEX Reference: - IS: 2720 (Part-40)-1977 OBJECTIVE

To determine the free swell index of an expansive soil. THEORY Free swell or differential free swell, also termed as free swell index, is the increase in volume of soil without any external constraint when subjected to submergence in water.

NED AND SCOPE Free swell index of soil helps to identify the potential of a soil to swell which might need further detailed investigation regarding swelling and swelling pressure under different field conditions. APPARATUS 1.

Sieve 425 micron IS Sieve

2.

Graduated measuring Cylinders (glass), Capacity - 100 ml-2 Nos

3.

Distilled water and kerosene.

4.

Oven

PROCEDURE 1. Take two 10 g soil specimens of oven dry soil passing through 425 micron IS Sieve. 2. Each soil specimen shall be poured in each of the two glass graduated cylinders of 100 ml capacity. 3. One cylinder shall then be filled with kerosene oil and the other with distilled water up to the 100 ml mark. 4. After removal of entrapped air (by gentle shaking or stirring with a glass rod) the soils in both the cylinders shall be allowed to settle. 5. Sufficient time (Not less than 24 h) shall be allowed for the soil sample to attain equilibrium state of volume without any further change in the volume of the soils. 6. The final volume of soils in each of the cylinders shall be read out. Note: In the case of highly swelling soils such as sodium bentonites, the sample size may be 5 g or alternatively a cylinder of 250 ml capacity may be used.

OBSERVATIONS

CALCULATION The level of the soil in the kerosene graduated cylinder shall be read as the original volume of the soil sample, kerosene being a non-polar liquid does not cause swelling of the soil. The level of the soil in the distilled water cylinder shall be read as the free swell level. The free swell index of the soil shall be calculated as follows, Free swell index, percent =

Vd  Vk 100 Vk

Where, 

Vd = The volume of the soil specimen read from the graduated cylinder containing distilled water



Vk = the volume of the soil specimen read from the graduated cylinder containing distilled kerosene.

RESULT Free swell index = …………………………………%

SOIL EXPANSIVITY S. No

Degree of expansion

Shrinkage limit (%)

Shrinkage index (%)

Free swell index (%)

1 2 3 4

Low Medium High Very high

>13 8-18 6-12 <10

<15 15-30 30-60 >60

<50 50-100 100-200 >200

Experiment No-11

STANDARD PENETRATION TEST (SPT) Reference: - IS: 2131-1981 OBJECTIVE To conduct the standard penetration test for soils to obtain the resistance of soil to penetration (N-value) INTRODUCTION This method describes the standard penetration test using the split-barrel sampler to obtain the resistance of soil to penetration (N-value), using a 63.5 kg hammer falling .76 cm; and to obtain representative samples for identification and laboratory tests. The method is applicable to all soil types. It is most often used in granular materials but also in other materials when simple in-place bearing strengths are required. It is also used when samples cannot easily be recovered by other means. EQUIPMENT:       

Drilling Equipment Split Spoon Sampler Drive Weight assembly Lifting Bail Tongs Rope Screw Jack

PROCEDURE: Driving the Casing 1. Where casing is used, it shall not be driven below the level at which the test is made or soil sample is taken. In the case of cohesion less soils which cannot stand without casing the advancement of the casing pipe should be such that it does not disturb the soil to be tested or sampled the casing shall preferably be advanced by slowly turning the casing rather than by driving as the vibration caused by driving may alter the density of such deposits immediately below the bottom of the borehole. Cleaning the Borehole: 1. In case wash boring is adopted for cleaning the borehole, side discharge bits are permissible, but in no case shall a bottom discharge bit be permitted. The process of jotting through an open tube sampler, and then testing and sampling when the desired depth is reached shall not be permitted. 2. While boring through soils, such as sands that may be disturbed by the flow of water into the drill hole no water shall be added to the borehole while boring above the water table. While boring below water table, the water in the borehole shall be maintained at Prepared By: M.L. Rathore (Lab Engineer) Civil Engg Dept, JUET Guna (M.P.): 50

least 1.5 m above the level of the water table. Betonies slurry of appropriate consistency may be required to help the water level to be maintained above the water table. The raised level of the water in the borehole should be maintained even if casing is used to stabilize the borehole. 3. While boring through sand using casing to stabilize the sides of the borehole, the outer diameter of the shell shall be at least 25 mm smaller then the inner diameter of the casing. The distance between the end of the casing and the bottom of the borehole should be as close as possible and in any case not exceed 150 mm, if only water is used to stabilize the borehole, in case betonies is used, this distance may be up to 300 mm. 4. The borehole shall be cleaned up to testing or sampling elevation, using suitable tools, such as augers, that will ensure that there is minimum mixing up of the soil from the bottom of the borehole. In cohesive soils, the borehole may be cleaned with bailer with a flap valve. This should not be used in sands. Obtaining the Samples: 1. Tests shall be made at every change in stratum or at intervals of not more than 1.5 m whichever is less. Tests may be made at lesser intervals if specified or considered necessary. The intervals are increased to 3 m if in between vane shear test is performed. 2. The sampler shall be lowered to the bottom of the borehole. The following information shall be noted and recorded:  Depth of bottom of borehole below ground level,  Penetration of the sampler and rods ( to noted from readings of the scale over the drill rod at the top)  Water level in the borehole or casing, and  Depth of bottom of casing below ground level. 3. The split spoon sampler resting on the bottom of borehole should be allowed to sink under its own weight; then the split spoon sampler shall be seated 15 cm with the blows of the hammer falling through 75 cm. Thereafter, the split spoon sampler shall be further driven by 30cm or 50 blows (except that driving shall cease before the split spoon sampler is full).The number of blows required to effect each 15 cm of penetration shall be recorded. The first 15 cm of drive may be considered to be seating drive. The total blows required for the second and third 15 cm of penetration shall be termed the penetration resistance N; if the split spoon sampler is driven less than 45cm (total), then the penetration resistance shall be for the last 30 cm of penetration (if less than 30cm is penetrated, the logs should state the number of blows and the depth penetrated) 4. The entire sampler may sometimes sink under its own weight when very soft sub soil stratum is encountered. Under such conditions, it may not be necessary to give any blow to the split spoon sampler and SPT value should be indicated as zero. 5. If on lowering the sampler by means of a String of rods it is found to rest at a level above the bottom of the casing, the penetration test and sampling should not be carried out at that stratum. Prepared By: M.L. Rathore (Lab Engineer) Civil Engg Dept, JUET Guna (M.P.): 51

Removal of Sampler and Labeling: 1. The sampler shall be raised to the surface and opened. A typical sample or samples of soil from the opened split spoon shall be put into jars without ramming. The jars shall have a self sealing top, or shall be sealed with wax to prevent evaporation of the soil moisture. Jars shall be of such a size that they can be filled without deforming the sample. Typical samples shall be cut to such a size as to fill the jars and thereby reduce the water loss to the air in the jars. If packing as specified is not available, liner may be used in the sampling spoon. In such a case the internal diameter of the sampling spoon should be so adjusted that the total internal diameter after incorporating the liner is 35mm. The sample in the liner shall be waxed properly at both the ends to keep up the natural moisture content during transit. 2. Labels shall be fixed to the jar or notations shall be written on the covers ( or both) with the following information; a) b) c) d) e) f) g) h)

Origin of sample, Job designation, Boring number Sample number Depth of sampling Penetration record Length of recovery Date of sampling

3. The jars containing samples shall be stored in suitable containers for shipment. Samples shall not be placed in the sun Field Observations: Information with regard to water table, elevations at which the drilling water was lost or elevations at which water under excess pressure was encountered shall be recorded on the field logs. Water levels before and after putting the casing where used shall be measured. In sands, the level shall be determined as the casing is pulled and then measured at least 30 min after the casing is pulled; in silts at least 24h after the casing is pulled in clays, no accurate water level determination is possible unless previous seams are present. However, the 24 h level shall be recorded for clays. When drilling mud is used and the water level is desired, casing perforated at the lower end shall be lowered into the borehole and the borehole bailed down. Ground water levels shall be determined after bailing at time intervals of 30 min and 24 h until all traces of drilling mud are removed from inside the casing. Corrections: 1. Due to Overburden--- The N value for cohesion less soil shall be corrected for overburden as per Fig 1 (N ‘) 2. Due to Dilatancy--- The value obtained in shall be corrected for dilatancy if the stratum consists of fine sand and silt below water table for values of N greater than 15 as under (N” ) N” = 15 + ½ (N’ – 15) Prepared By: M.L. Rathore (Lab Engineer) Civil Engg Dept, JUET Guna (M.P.): 52

FOUNDATION ENGINEERING LAB PROVING RING CALIBRATION CHART

Capacity

S. No.

Proving Ring Nos

Least Count

kN

Kg

1.

0353

50 kN

5000

5.8 Kg/div

2.

0637

25 kN

2500

2.987 Kg/div

3.

PR-0235

10 kN

1000

1.11 Kg/div

4.

PR-0236

10 kN

1000

1.148 Kg/div

5.

05542

2.5 kN

250

0.28 Kg/div

6.

PR-0118

2.5 kN

250

0.274 Kg/div

7.

PR-0119

2.5 kN

250

0.254 Kg/div

8.

PR-0121

2.5 kN

250

0.288 Kg/div

9.

PR-0154

2.0 kN

200

0.26 Kg/div

10.

PR-042

1.0 kN

100

0.106 Kg/div

11.

PR-043

1.0 kN

100

0.118 Kg/div

Prepared By: M.L. Rathore (Lab Engineer) Civil Engg Dept, JUET Guna (M.P.): 53

REFERENCES

1. Soil Mechanics and Foundation Engineering by B.C. Punmia 2. Geotechnical Engineering by K.R. Arora 3. I.S. Codes as below mentioned;  IS: 2720 (PART 16)-1987  IS: 2720 (PART 15) - 1986  IS: 2720 (PART 13) - 1986  IS: 2720 (PART-XLI)-1977  IS: 2720 (PART 10)-1991  IS: 2720 (PART 11) - 199  IS: 2720 (PART XII) - 1993  IS: 2720 (PART XXX) – 1980  IS: 2720 (Part-XL)-1977  IS: 2131-1981

Prepared By: M.L. Rathore (Lab Engineer) Civil Engg Dept, JUET Guna (M.P.): 54