22293861 california bearing ratio report

7/30/2019 22293861 California Bearing Ratio Report

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California Bearing Ratio Test ReportHighways & Traffic Engineering

Ivan ThomsonOlisanwendu Ogwuda

Group 5BN0903A

11NOV2004


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Table of Contents

Introduction iii

Objective of the Experiment 1

Testing Procedures & Apparatus 2

Tables of Data, Calculations & Graphs 3

Discussion of Results 8

Conclusions 9

Bibliography 11

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Introduction

This report is the result of the California Bearing Ratio laboratory testcarried out by Group 5 in the soils lab (Baxter building) at the University of

Abertay-Dundee on 28 OCT 2004.

This report is primarily concerned with the data gathered by Group 5.However, as required, data and graphs from Group 4 and Group 6 areincluded and discussed.

The members of Group 5 were:

Bruce ShearerIvan ThomsonRichard Todd

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Objective of the Experiment

The objective of the California Bearing Ratio test is to determine the CBRvalue for a soil under consideration as a pavement foundation. This value is

a percentage comparison with the standard crushed rock from California.Thus this test is a comparison test.

The CBR value is used to quantify the response of the pavement foundationand subgrade to loading1.

The standard crush rock from California values are as follows:

Standard Crushed Rock from California2

Load (kN) 13.24 19.96

Penetration(mm)

2.5 5.0

It should be noted that this test was created by the California Division ofHighways in the 1930s and as such is an empirical test and does not provideany data regarding properties of the soil except as to compare its resistanceto penetration to the base crushed rocks resistance to penetration.

The test remains in existence around the world due to its low equipmentrequirements, easy of performance and history of use.

It is important to realize that the CBR test is but one step in the roadpavement foundation design process; the test allows the roadEngineer to design the capping layer (if needed) and the sub-baseLayer by determining the strength of the underlying soil.

By knowing this the Engineer can determine if thisstrength is adequate to handle the desired road designor if additional procedures need to be done to increasethis strength.

1 University of Abertay Dundee, Sub grade and Unbound Pavement Foundation, pg 2.2 University of Abertay Dundee, Subgrade and Unbound Pavement Foundation, pg 3.

Map of the pavementfoundation design

process*.

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Testing Procedures & Apparatus

Apparatus:*

Loading machine (a loading press)Prepared soil sample in CBR mould with collarSurcharge weightsScalesCBR mould wrenchesSteel (or Brass) ramming rodMisc. lab equipment such as a tray or bucket to contain the soil*

Testing Procedure Carried Out:

Step:

1. Determined the mass of soil needed to fillthe mould bycalculation usingthe formula:

2. Poured the sample into the mould whilstramming with the steel rod.3. Placed filter paper and 50mm compaction plug on top of soil.4. Place mould into compression machine and applied load until top of

plug was flush with the top of the mould collar.5. Removed the sample from compression machine, compaction plug

and filter paper.6. At this point the sample was prepared and ready to be placed into

the CBR loading press.7. Mould was placed into CBR loading press and the surcharge weights

were placed on top.

8. Seated the CBR plunger on top of the soil sample and began theprocess of applying the load at a rate of 1mm per minuet.

9. Recorded the dial gauge readings for every .25mm of penetration upto a maximum of 7.5mm.

10.Removed the sample from the loading press, placed a top cap on thesample, flipped it over and removed the bottom cap. This effectivelyflipped the sample over without removing it from the mould.

11.Repeated the CBR test upon the same sample (except it was thebottom instead of the top of the sample being loaded).

*

CBR Equipment, Pavement Design Foundation Design*Google Images [online], Photographs of CBR equipment, http://images.google.com/images?

hl=en&lr=&q=CBR+test

Top -Typical CBR loadingPress.

Middle CBR moulds,wrenches, plungers, etc.Bottom Diagram of aCBR apparatus*.

d

)7.103(93865.

993.1)7.103(05.23

9.1)7.3100(05.23

.

=

+=

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Tables of Data, Calculations & Graphs

CBR Test (group 4) M=23.05(100+w)P d

Mass of Sample (M) 5.317 kg

Dry Density (P d) 2.166 Mg/m

Moisture Content (w) 6.50 %

Conversion Factor 18.48

Axial

Deflection

Readings

(test 1)

Readings (test

2)

Load (kN) (test

1)

Load (kN)

(test 2)

0.00 0 0 0.00 0.00

0.25 26 30 0.48 0.55

0.50 60 75 1.11 1.390.75 116 124 2.14 2.29

1.00 161 171 2.98 3.16

1.25 229 208 4.23 3.84

1.50 308 237 5.69 4.38

1.75 398 264 7.36 4.88

2.00 482 288 8.91 5.32

2.25 570 310 10.53 5.73

2.50 628 332 11.61 6.14

2.75 672 353 12.42 6.52

3.00 706 371 13.05 6.86

3.25 735 389 13.58 7.19

3.50 764 405 14.12 7.48

3.75 787 419 14.54 7.744.00 808 434 14.93 8.02

4.25 827 446 15.28 8.24

4.50 843 459 15.58 8.48

4.75 856 472 15.82 8.72

5.00 868 485 16.04 8.96

5.25 879 497 16.24 9.18

5.50 888 510 16.41 9.42

5.75 897 522 16.58 9.65

6.00 904 533 16.71 9.85

6.25 908 544 16.78 10.05

6.50 912 556 16.85 10.27

6.75 917 565 16.95 10.44

7.00 921 575 17.02 10.637.25 927 584 17.13 10.79

7.50 933 593 17.24 10.96

Test 1 Test 2

CBR1 98.19 46.34 @25pen

CBR2 82.22 44.90 @50pen

Max CBR 98.19 46.34 98.19

NOT Within 10%

Whichever CBR is greatest

96.19

100(%)

24.13

100(%) 22

11

LCBROR

LCBR

=

=

Corrected Values YES

Test 1 Test 2

Offset 0.625 0.000

New 2.5 Point 3.125 2.5

New 5.0 Point 5.625 5.0

For 2.5

Point Before 2.75 2.25

Point After 3.25 2.75

Average 3 2.5

Div Value 704 350

Load (kN) 13.00 6.14 L1

For 5.0



Average 5.50 5.00Div Value 888 485

Load (kN) 16.41 8.96 L2

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Dry Density (P d) 1.993 Mg/m



Axial

Deflection

Readings

(test 1)

Readings (test

2)

Load (kN) (test

1)

Load (kN)

(test 2)

0.00 0 0 0.00 0.00

0.25 14 53 0.26 0.98

0.50 55 124 1.02 2.29

0.75 120 174 2.22 3.22

1.00 183 203 3.38 3.75

1.25 226 225 4.18 4.16

1.50 255 242 4.71 4.47

1.75 277 256 5.12 4.73

2.00 295 270 5.45 4.99

2.25 314 282 5.80 5.21

2.50 330 295 6.10 5.45

2.75 347 306 6.41 5.65

3.00 362 318 6.69 5.88

3.25 377 329 6.97 6.08

3.50 391 339 7.23 6.26

3.75 406 349 7.50 6.45

4.00 420 359 7.76 6.63

4.25 433 370 8.00 6.84

4.50 447 380 8.26 7.02

4.75 460 389 8.50 7.19

5.00 473 398 8.74 7.36

5.25 486 406 8.98 7.50

5.50 497 415 9.18 7.67

5.75 510 423 9.42 7.82

6.00 521 432 9.63 7.98

6.25 531 441 9.81 8.15

6.50 542 449 10.02 8.30

6.75 552 455 10.20 8.41

7.00 561 466 10.37 8.61

7.25 570 474 10.53 8.76

7.50 579 482 10.70 8.91

Test 1 Test 2

CBR1 48.29 41.18 @25pen

CBR2 44.90 36.85 @50pen

Max CBR 48.29 41.18 48.29


96.19100(%)

24.13100(%) 22

11

LCBRORLCBR ==

Corrected Values YES

Test 1 Test 2

Offset 0.254 0.000

New 2.5 Point 2.75 2.5

New 5.0 Point 5.25 5.0

For 2.5



Average 2.75 2.5

Div Value 346 294

Load (kN) 6.39 5.45 L1

For 5.0



Average 5.25 5.00

Div Value 485 398

Load (kN) 8.96 7.36 L2

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Dry Density (P d) 2.284 Mg/m 3



Axial

Deflection

Readings

(test 1)

Readings

(test 2)

Load (kN)

(test 1)

Load (kN)

(test 2)

0.00 0 0 0.00 0.00

0.25 3 3 0.06 0.06

0.50 5 5 0.08 0.09

0.75 6 7 0.11 0.13

1.00 7 10 0.13 0.18

1.25 8 12 0.15 0.21

1.50 10 15 0.18 0.28

1.75 11 18 0.20 0.33

2.00 12 21 0.22 0.39

2.25 14 25 0.25 0.46

2.50 15 30 0.28 0.55

2.75 17 35 0.30 0.65

3.00 19 38 0.34 0.70

3.25 20 45 0.37 0.83

3.50 22 51 0.41 0.94

3.75 24 56 0.44 1.03

4.00 27 62 0.49 1.15

4.25 29 69 0.53 1.28

4.50 31 75 0.57 1.39

4.75 34 81 0.62 1.505.00 36 87 0.66 1.61

5.25 39 94 0.71 1.74

5.50 41 101 0.76 1.87

5.75 43 107 0.79 1.98

6.00 46 113 0.84 2.09

6.25 48 119 0.89 2.20

6.50 51 126 0.94 2.33

6.75 53 131 0.98 2.42

7.00 55 137 1.02 2.53

7.25 58 143 1.07 2.64

7.50 60 149 1.11 2.75

Test 1 Test 2

CBR1 2.09 4.19 @25pen

CBR2 3.29 8.05 @50pen

Max CBR 3.29 8.05 8.05


96.19100(%)

24.13100(%) 2211

LCBROR

LCBR

=

=

Corrected Values No

Test 1 Test 2

Offset 0.000 0.000

New 2.5 Point 2.5 2.5

New 5.0 Point 5.0 5.0

For 2.5



Average 2.5 2.5

Div Value 15 30

Load (kN) 0.28 0.55 L1

For 5.0



Average 5.00 5.00

Div Value 36 88

Load (kN) 0.66 1.61 L2

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CBR Test Results (Group 4)

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

0.

00

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

5.

25

5.

50

5.

75

6.

00

6.

25

6.

50

6.

75

7.

00

7.

25

7.

50

Penetration (mm)

Load(

kN)

Load (kN) (test 1) Load (kN) (test 2)

0.6253.125

2.55

5.625

13.00

16.41

8.96

6.14


0.00

2.00

4.00

6.00

8.00

10.00

12.00

0.

00

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

5.

25

5.

50

5.

75

6.

00

6.

25

6.

50

6.

75

7.

00

7.

25

7.

50

Penetration (mm)

Load(

kN


0.2540.008 2.754

2.5

5.00

6.39

8.96

5.45

7.36


0.00

0.50

1.00

1.50

2.00

2.50

3.00

0.

00

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

5.

25

5.

50

5.

75

6.

00

6.

25

6.

50

6.

75

7.

00

7.

25

7.

50

Penetration (mm)

Load(

kN


0.28

0.660.55

1.61

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CBR Test Results (All Groups)

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

1 2 3 4 5 6 7 8 910

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

Penetration (mm)

Load(

kN

G4 (test 1) G4 (test 2) G5 (test 1) G5 (test 2) G6 (test 1) G6 (test 2)

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Max CBR 98.19 46.34 98.19

Max CBR 48.29 41.18 48.29

Max CBR 3.29 8.05 8.05

Discussion of Results

Group 5;

The graph for Group 5 shows fairly close lines with only one line needing aminor correction.

The CBR values were;

This value (48.29) indicates that the soil was at the top end of a WellGraded Sand and is a moderately strong soil.

Group 4;

The graph for Group 4 shows a very large difference in the results betweentest 1 and test 2 with one line needing a correction.


This value (98.19) indicates that this soil is a Well Graded Sand to a SandyGravel and is a fairly strong soil.

Group 6;

The graph for Group 6 shows a very large difference in the results and iskind of inverted compared to the graphs of Group 5 and Group 4. Thisinverted nature of the graph indicates there was higher moisture content inthe soil (13.7% - almost 4 times as high as Group 5) and shows that as theload increased the soil offered more resistance. However, overall this soiloffered little as far as a Max CBR value.


According to this value (8.05) this places the soil in the Sandy Clay rangeand is a weak soil.

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T e s t 2T e s t 1

B

B A

A

F O R C EF O R C E

Figure 2 Diagram showing thedirection of the force applied to thesample.

Conclusions

Group 4 and Group 5 had very similar results were the soil offered a decentamount of resistance to the initial loading but that this resistance decreased

with increased loading. The soils for these two groups were moderate instrength to fairly strong.

Group 6, however, had a soil that offeredlittle or no resistance to loading initially butthat resistance rapidly increased as the loadcontinued to increase. However, this soil wassignificantly weak when compared to the soilsof the other two groups.

The major difference between the soil for

Group 6 and the other groups appears to be dueto more of the voids in the soil being filled withwater rather than air. Air is much morecompressible than water and once the air waspushed out (or at maximum compression) thewater began to offer rapidly increasingresistance to loading.

The soil for Group 6 may have been much more representative of a soil inmoisture equilibrium.

The soils for Groups 4 and 5 would require less compaction than the soil forGroup 6 to achieve identical strengths.

Since the sample was compacted in the compacting machine only once andwas tested in the CBR machine twice (once on the A face {see figure 2} andonce on the B face) there will be different layers of compaction within thetest sample.

The samples appear to compress much more (have more penetration) on thefirst test and less after the sample has been flipped over and retested on

test 2. This would indicate that there are many more voids in test 1 thantest 2 since many of the voids were removed during test 1.

Additional. After test 1 (and before test 2) the soil will be at its highestcompaction along the horizontal plane at point A and the amount ofcompact will decrease until reaching its lowest compaction along thehorizontal plane at point B. In other words the compact will steadilydecrease from point A to point B.

After test 2 was performed the sample will have high compression along thehorizontal planes at both points A & B and lowest compaction in the center.

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Test one face of the sample then testing on the opposite face simulates theforces the sample will face since it will have a constant upward force uponit as will as a constant downward force.

Additionally, the downward force will include periodic increases anddecreases in the force as vehicles move over it. This will have duel effects

on the sample as the upward force will increase to deal with the increase inforce in the downward direction. In real-life situations the sample will besubjected to constant squeezing and release time and time again atrandom intervals as traffic moves over it.

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Bibliography

Craig, R.F. 2004. Craigs Soil Mechanics. 7th ed. London: Spon. ISBN 0-415-32703-2

Cover picture: CBR Testing Machine Picture: ELE International [online].Available from: http://www.ele.com/geot/images/24-9150.jpg [Accessedon 11 Nov 2004]

Google.com [online]. Available from: http://www.google.com [Accessed 28Nov 2004]

Google Images [online]. Available from http://images.google.com/ [Access28 Nov 2004]

Pavement Design [online]. Available from:http://www.dur.ac.uk/~des0www4/cal/roads/pavdes/pavfound.html[Accessed 11 Nov 2004]

The Idiots Guide to Highways Maintenance [online]. Available from:http://www.highwaysmaintenance.com/cbrtext.htm [Accessed on 11 Nov2004]

Napier University School of Built Environment Projects [online]. Availablefrom: http://sbe.napier.ac.uk/projects/compaction/chapter7a.htm

[Accessed on 11 Nov 2004]

University of Abertay Dundee. Unknown. Subgrade and Unbound PavementFoundation [Class information sheet provided by Mr. Ogwuda].

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22293861 california bearing ratio report

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