Shear Box Lab Report PDF

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UNIVERSITI TEKNOLOGI MARASHAH ALAM LABORATORY MANUALGEOTECHNICAL LABORATORYECGOPEN-ENDED LABSEMESTER 2TITLE OF EXPERIMENT : DETERMINATION OF THE DIRECT SHEAR STRENGTH BYUSING SHEAR BOX TESTDATE OF EXPERIMENT : 10 th JUNE 2020NAME :UiTM NO :CLASS GROUP :LECTURER :LEVEL OF OPENESS : 1MARKS COMMENTSINT...

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FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA SHAH ALAM LABORATORY MANUAL

GEOTECHNICAL LABORATORY ECG428 OPEN-ENDED LAB SEMESTER 2 TITLE OF EXPERIMENT DATE OF EXPERIMENT NAME UiTM NO CLASS GROUP : LECTURER LEVEL OF OPENESS

: DETERMINATION OF THE DIRECT SHEAR STRENGTH BY USING SHEAR BOX TEST : 10th JUNE 2020 : : : :

1

MARKS

COMMENTS

INTRODUCTION BASIC CONCEPTS METHODOLOGY RESULTS&ANALYSIS

1

2

3

4

5

DISCUSSION

1

2

3

4

5

CONCLUSION

1

2

3

4

5

ORGANIZATION

1

2

3

4

5

TOTAL MARKS

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FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA SHAH ALAM LABORATORY MANUAL

COURSE

GEOTECHNICAL LABORATORY

COURSE CODE

ECG428

LEVEL OF OPENNESS

1

CATEGORY

PARTIALLY OPEN

DEGREE OF OPEN-ENDED (%)

66

ENGINEERING PROPERTIES DETERMINATION OF THE DIRECT SHEAR STRENGTH BY USING SHEAR BOX TEST

PREAMBLE

Introduction Level 1 laboratory activity refers to condition where the problem and ways & means are guided and given to the students. However, the answers to the assignment are left to the students to solve using the group creativity and innovativeness. The activity is hope to slowly introduced and inculcate independent learning amongst students and prepare them for a much harder task of open ended laboratory activities. The shear strength of a soil is its maximum resistance to shearing stresses. It is usually considered to be equal to the shear stress at failure on the failure plane. The shear strength of soil mainly consists of the resistance due to interlocking of particle and friction between individual particles at their contact point i.e. internal friction and the resistance due to inter particle forces which tend to hold the particles together in a soil mass, what so called cohesion. The shear strength τ of soil can be represented by Coulomb’s equation of:

where

τf = c + σ tan φ σ = total normal stress on the failure plane. c = cohesion. φ = angle of internal friction.

Figure 1: Direct Shear Box Test apparatus

Objectives ©FKA, UiTM, SHAH ALAM

May 2020_mm

FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA SHAH ALAM LABORATORY MANUAL To determine the shear strength of soil using direct shear or shear box apparatus. A direct shear test is a laboratory or field test used by geotechnical engineers to measure the shear strength properties of soil or rock material, or of discontinuities in soil or rock masses.

Learning Outcomes At the end of the laboratory activities, students would be able to: 1. Acquire the understanding of engineering properties of soils in determination of the shear strength 2. Acquire the necessary skill in performing standard laboratory 3. Interpret and analyze data to report and present result to determine the value of internal friction angle, φ and the intercept on shear stress axis gives value of cohesion, c 4. Work in group to produce the relevant technical report

PROBLEM STATEMENT

WAYS & MEANS

The advantages of the direct shear test over other shear tests are the simplicity of setup and equipment used, and the ability to test under differing saturation, drainage, and consolidation conditions. These advantages have to be weighed against the difficulty of measuring pore-water pressure when testing in undrained conditions, and possible spuriously high results from forcing the failure plane to occur in a specific location.

Each group will be given representative samples of the soil to be used (sand, residual soil and undisturbed clay from the site). The load applied and the strain induced is recorded at frequent intervals to determine a stress-strain curve for each confining stress. Several specimens are tested at varying confining stresses to determine the shear strength parameters, the soil cohesion (c) and the angle of internal friction (commonly friction angle) ( ). 1. Check the inner dimension of the soil container. 2. Put the parts of the soil container together. 3. Calculate the volume of the container. Weigh the container. 4. Place the soil in smooth layers (approximately 10 mm thick). If a dense sample is desired tamp the soil. 5. Weigh the soil container, the difference of these two is the weight of the soil. Calculate the density of the soil. 6. Make the surface of the soil plane. 7. Put the upper grating on stone and loading block on top of soil. 8. Measure the thickness of soil specimen. 9. Apply the desired normal load. 10. 11. 12. 13.

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Remove the shear pin. Attach the dial gauge which measures the change of volume. Record the initial reading of the dial gauge and calibration values. Before proceeding to test check all adjustments to see that there is no connection between two parts except May 2020_mm

FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA SHAH ALAM LABORATORY MANUAL

14. 15. 16. 17.

sand/soil. Start the motor. Take the reading of the shear force and record the reading. Take volume change readings till failure. Add 5 kg normal stress 0.5 kg/cm2 and continue the experiment till failure Record carefully all the readings. Set the dial gauges zero, before starting the experiment.

The group will be required to plot the graph between shear stress and longitudinal displacement for each set of test. Note the maximum shear stress and corresponding longitudinal displacement. Finally plot a graph between normal stress and maximum shear stress. Horizontal displacement = Horizontal dial gauge reading x Least count of horizontal dial gauge Shear force = Proving ring reading x Proving ring constant Shear stress = (Proving ring reading x Proving ring constant)/A

1)

RESULTS

©FKA, UiTM, SHAH ALAM

Normal stress 0.5 kg/cm2, Horizontal Gauge

Proving Ring

Reading

Reading

Horizontal/shear Shear Force (kg) Shear Stress Deformation (mm) (kg/cm2)

0

0

0

0

0.000

50

16

0.5

6.8

0.241

100

21

1

8.925

0.316

150

26

1.5

11.05

0.391

200

29

2

12.325

0.436

250

33

2.5

14.025

0.496

300

35

3

14.875

0.526

350

37

3.5

15.725

0.556

400

38

4

16.15

0.571

450

39

4.5

16.575

0.586

500

40

5

17

0.601

550

40

5.5

17

0.601

600

41

6

17.425

0.616

650

41

6.5

17.425

0.616 May 2020_mm

FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA SHAH ALAM LABORATORY MANUAL

700

41

7

17.425

0.616

750

42

7.5

17.85

0.631

800

46

8

19.55

0.692

850

46

8.5

19.55

0.692

900

46

9

19.55

0.692

950

46

9.5

19.55

0.692

1000

45

10

19.125

0.677

2) Normal stress 1.0 kg/cm2, Horizontal Gauge

Proving Ring

Reading

Reading

Horizontal/shear Shear Force (kg) Shear Stress Deformation (mm) (kg/cm2)

50

13

0.5

5.525

0.195

100

17

1

7.225

0.256

150

20

1.5

8.5

0.301

200

23

2

9.775

0.346

250

24

2.5

10.2

0.361

300

26

3

11.05

0.391

350

27

3.5

11.475

0.406

400

27

4

11.475

0.406

450

28

4.5

11.9

0.421

500

28

5

11.9

0.421

550

29

5.5

12.325

0.436

600

29

6

12.325

0.436

650

29

6.5

12.325

0.436

700

29

7

12.325

0.436

3) Normal stress 1.5 kg/cm2, ©FKA, UiTM, SHAH ALAM

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FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA SHAH ALAM LABORATORY MANUAL

©FKA, UiTM, SHAH ALAM

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FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA SHAH ALAM LABORATORY MANUAL 150

52

1.5

22.1

0.782

200

61

2

25.925

0.917

250

69

2.5

29.325

1.037

300

74

3

31.45

1.112

350

79

3.5

33.575

1.188

400

83

4

35.275

1.248

450

87

4.5

36.975

1.308

500

89

5

37.825

1.338

550

90

5.5

38.25

1.353

600

90

6

38.25

1.353

650

89

6.5

37.825

1.338

700

87

7

36.975

1.308

750

86

7.5

36.55

1.293

800

84

8

35.7

1.263

850

83

8.5

35.275

1.248

900

82

9

34.85

1.233

950

81

9.5

34.425

1.218

Normal stress (kg/cm 2) 0.5 1.0 1.5 2.0

DATA ANALYSIS

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Shear stress (kg/cm2) 0.692 0.436 0.376 1.353

Graph 1: Shear Stress vs Horizontal Displacement

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FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA SHAH ALAM LABORATORY MANUAL

Graph 2: Shear Stress vs Normal Stress

From the Shear Stress vs Normal Stress graph, Cohesion, c = 0.23 kg/cm2 Internal friction angle, ɸ = 21˚ Using Coulomb’s equation;

τf = c + σ tan φ = 0.23 + 5 tan 21 τf = 2.149 kg/cm2

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FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA SHAH ALAM LABORATORY MANUAL

Based on the direct shear or shear box apparatus experiment, the value of shear strength of soil is 2.149 kg/cm2. Hence, the objective is achieved.

CONCLUSION

The purpose of a direct shear test is to determine the shear strength of the soil; this is done by forcing the soil to shear at a constant rate along the induced horizontal plane of weakness. Four subtests are carried out where the sample is consolidated using four different weights and then sheared at the same constant rate. Then, plot the graph between shear stress and horizontal displacement for each set of test. After that, plot the second graph between normal stress and maximum shear stress of each test. The cohesion and friction angle of the soil can be determined using the normal stress and shear stress graph. Where cohesion, c is 0.23 kg/cm2 and angle of internal friction, ɸ is 21˚.

DISCUSSION RECOMENDATION

Based on the data from the graph, the value shear strength of soil can be AND determined by Coulomb’s equation ; τf = c + σ tan φ Where the value of shear strength of soil,τ f is 2.149 kg/cm2. The advantages of using direct shear stress are direct measurement of shear strength, basic principles that are easily understood, simple and easy sample preparation and almost all soil types can be tested. While the disadvantages are shear strength is measured only on a predefined shear plane, distribution of stresses along the shear plane is not uniform and only total stresses are applied, except on the testing of dry granular material, as pore water pressures cannot be measured.

REFERENCES ; ©FKA, UiTM, SHAH ALAM

May 2020_mm

FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA SHAH ALAM LABORATORY MANUAL I.

K. H. Head and R. J. Epps. 2011. Manual of Soil Laboratory Testing, Vol. II: Permeability, Shear Strength and Compressibility Tests. Whittles Publishing, Caithness, Scotland, 3rd edition.

II.

Justin Humphrey, Lab 6 Direct Shear Stress, 2017 https://www.studocu.com/my/document/universityof-nebraska-lincoln/introduction-to-geotechnical-engineering/practical/lab-6-direct-sheartest/1779322/view

III. Peter Gawen, An introduction to Direct Shear Testing, 2018 https://www.vjtech.co.uk/blog/an-introduction-to-direct-shear-testing#:~:text=Advantages%20and %20Disadvantages%20of%20Direct%20Shear%20Tests&text=The%20continual%20decrease%20in %20the,This%20error%20is%20generally%20ignored. IV. Direct Shear Stess, http://meacorporation.com/direct-shear-tests/

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2019

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