pavement final

8/4/2019 Pavement Final

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FINAL REPORT

HIGH WAY DESIGN PROJECT, TRANSPORTATION ENGINERING DEVISION, UNIVERSITY OF MORATUWA

CHAPTER 3 By: Udila S. Pilanavithana 060369P PAVEMENT DESIGN Rathnasekara K. S. K. 060400F

3.1 Introduction

Road pavement is the most significant feature in highway designing. Just looking at the road pavement

everyone gets good or bad impression regarding the road designing. Generally road pavements are classified

as;

Rigid Pavements

Flexible Pavements

In Sri Lanka, most of the time we are dealing with the Asphalt Pavements including this road section which

is categorized as the flexible pavement. As we going to design a flexible pavement we have to concern it

methodology. These types of pavement structures maintain intimate contact with and distribute loads to the

sub grade profile and able to withstand very small tensile stresses. So that the dynamic, static loads and

Friction forces are applying on the pavement, all the time it faces to wear and tear during its life time with in

which the road going to utilize the transportation purposes and indirectly supporting to the economy.

Therefore, with the broad understanding about above considerations and highway designing aspects we

carried out the two tests for the bearing strength of sub soil layers where one test performed on site and other

is in laboratory. Namely

1. Dynamic Cone Penetration Test (DCP) - Field

2. California Bearing Ratio Test (CBR) - Laboratory

This experiment performs to design structural pavement layers in two lane road according to the guide line in

TRL Road note 31. With the help of parameter – Sub grade Strength we obtained by the above experiments

we have to consider other important parameter call CNSA – Cumulative number of Standard axel loads for

the design period which we will going to obtained from the Traffic Survey Data.

As far as we concern the deformation in soil layers underneath the road pavement is mainly Shear

deformation. So that we have to give prior attention for the bearing capacity of the sub layers before

construct the pavement. There are different types of layers with in a road pavement section namely ;



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Surface course

Base course

Sub base

Sub grade

When we considering the asphalt layer it compromise with two main failure modes call Permanent

Deformation and Fatigue Cracking. So we must design the pavement considering all the above key factors

affecting to the road pavement.

3.2 Objectives

1. Find out the CBR value from the DCP test in field.

2. Find out the CBR value from the CBR test in laboratory and choose the most suitable value.

Figure 3.1- Pavement Cross Section



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3.3 Methodology

3.3.1 Experiment: Dynamic Cone Penetration Test (DCP)

General

The Dynamic Cone Penetrometer (DCP) is an instrument designed to provide a measure of the in-situ

strength of fine grained and granular sub grades, granular base and sub base materials, and weakly cemented

materials. A schematic of the DCP is shown in Figure 1. The 8-kg (17.6-pound) weight is raised to a height

of 575 mm (22.6 inches) and then dropped, driving the cone into the soil or other material being tested.

DCP testing is conducted according to Illinois Test Procedure 501, in which the number of blows to achieve

150 mm (6 inches) of penetration is counted. Alternatively, the depth of penetration may be measured after

each blow when extremely soft materials are encountered. In either case, the output of the DCP test is a

penetration rate (PR), expressed in mm (inches) per blow.

Steps…

1. In the first stage Penetrometer was assembled accurately with its all features. Then it was hold in vertical.

2. Then we had selected the place for testing and remove the top soil layer for 150 mm depth.

3. Then we installed the ruler in that place and placed the instrument.

4. After fixing all the apparatus we took the initial reading in ruler and recorded it.

5. Then we had performed the test by lifting the 8kg weight and let it freely fall. Then we had taken the

reading that gives penetration.

6. Likewise test was performed for 200 m interval along the road and penetrated reading was recorded

against number of blows.

7. Then No of blows vs. Penetration graph was plotted and took the gradient of first layer.



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Figure 3.2- DCP Test Apparatus

Apparatus:



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3.3.1.2 Results

Location at 50 m distance from the Thalawathugoda junction and 1 m Right Hand Side of the road

Blows Penetration

0 55

1 66

2 75

3 85

4 95

5 105

6 115

7 124

8 131

9 138

10 144

11 150

12 158

13 166

14 17515 185

16 197

17 208

18 216

19 226

20 240

21 252

22 265

23 281

24 299

25 315

26 333



FINAL REPORT


27 354

28 384

29 417

30 437

31 455

32 477

33 515

34 569

35 592

36 636

37 672

38 710

39 772

40 820

41 860

Location at 250 m distance from the Thalawathugoda junction and 1.5 m Right Hand Side of the road

Blows Penetration

0 50

1 62

2 70

3 75

4 81

5 87

6 93

7 99

8 102

9 108

10 114

11 120

12 125



FINAL REPORT


13 132

14 139

15 146

16 153

17 160

18 169

19 176

20 184

21 194

22 205

23 220

24 233

25 247

26 267

27 286

28 304

29 317

30 332

31 350

32 369

33 390

34 414

35 434

36 445

37 452

38 460

39 468

40 475

41 484

42 493

43 503

44 514



FINAL REPORT


45 525

46 535

47 546

48 556

49 567

50 580

51 595

52 606

53 615

54 624

55 633

56 644

57 652

58 662

59 674

60 685

61 698

62 710

63 726

64 745

65 760

Location at 550 m distance from the Thalawathugoda junction and 2 m Left Hand Side of the road

Blows Penetration

0 50

1 65

2 72

3 80

4 85

5 92

6 98



FINAL REPORT


7 106

8 114

9 120

10 127

11 134

12 139

13 142

14 146

15 150

16 155

17 159

18 163

19 166

20 171

21 174

22 181

23 189

24 193

25 204

26 211

27 218

28 226

29 232

30 244

31 256

32 269

33 285

34 304

35 319

36 332

37 341

38 350



FINAL REPORT


39 355

40 363

41 373

42 382

43 392

44 400

45 409

46 415

47 422

48 428

49 435

50 442

51 450

52 458

53 468

54 475

55 485

56 494

57 502

58 511

59 520

60 527

61 537

62 546

63 555

64 565

65 575

66 585

67 595

68 605

69 616

70 628



FINAL REPORT


71 638

72 650

73 660

74 669

75 676

76 690

77 700

78 707

79 715

80 722

81 733

82 745

83 757

84 772

85 792

86 810


Blows Penetration

0 56

1 67

2 73

3 79

4 84

5 88

6 95

7 99

8 104

9 110

10 112

11 116



FINAL REPORT


12 120

13 123

14 127

15 135

16 140

17 143

18 147

19 152

20 155

21 157

22 161

23 167

24 168

25 173

26 180

27 185

28 189

29 191

30 197

31 202

32 206

33 208

34 216

35 223

36 225

37 230

38 235

39 238

40 245

41 245

42 252

43 254



FINAL REPORT


44 257

45 264

46 269

47 273

48 279

49 281

50 285

51 287

52 291

53 293

54 300

55 302

56 308

57 308

58 313

59 318

60 323

61 328

62 330

63 337

64 342

65 353

66 355

67 368

68 370

69 390

70 400

71 415

72 428

73 433

74 445

75 452



FINAL REPORT


76 462

77 474

78 488

79 503

80 520

81 541

82 562

83 588

84 610

85 653

86 674

87 710

88 743

89 750

90 770

91 772

92 780

93 818

3.3.2 Experiment : California Bearing Ratio Test

General

The California bearing ratio (CBR) is a penetration test for evaluation of the mechanical strength of road

sub grades and base courses. It was developed by the California Department of Transportation.

The test is performed by measuring the pressure required to penetrate a soil sample with a plunger of

standard area. The measured pressure is then divided by the pressure required to achieve an equal penetration

on a standard crushed rock material. The CBR test is described in ASTM Standards D1883-05 (for

laboratory-prepared samples) and D4429 (for soils in place in field), and AASHTO T193.

http://en.wikipedia.org/wiki/Mechanical_strength

http://en.wikipedia.org/wiki/Road

http://en.wikipedia.org/wiki/Subgrade

http://en.wikipedia.org/wiki/California_Department_of_Transportation

http://en.wikipedia.org/wiki/Pressure

http://en.wikipedia.org/wiki/Soil

http://en.wikipedia.org/wiki/ASTM

http://en.wikipedia.org/wiki/AASHTO

http://en.wikipedia.org/wiki/AASHTO

http://en.wikipedia.org/wiki/ASTM

http://en.wikipedia.org/wiki/Soil

http://en.wikipedia.org/wiki/Pressure

http://en.wikipedia.org/wiki/California_Department_of_Transportation

http://en.wikipedia.org/wiki/Subgrade

http://en.wikipedia.org/wiki/Road

http://en.wikipedia.org/wiki/Mechanical_strength



FINAL REPORT


The CBR rating was developed for measuring the load-bearing capacity of soils used for building roads. The

CBR can also be used for measuring the load-bearing capacity of unimproved airstrips or for soils under

paved airstrips. The harder the surface, the higher the CBR rating. The standard material for this test is

crushed California limestone which has a value of 100.

= CBR [%]

= measured pressure for site soils [N/mm²]

= pressure to achieve equal penetration on standard soil [N/mm²]

This consists of causing a plunger of standard area to penetrate a soil sample, (this can be in the laboratory or

on site). The force (load) required to cause the penetration is plotted against measured penetration, the

readings noted at regular time intervals. This information is plotted on a standard graph, and the plot of the

test data will establish the CBR result Of the Soil tested.

It sounds complicated, but the basis behind it is quite simple. We are determining the resistance of the sub

grade, (i.e. the layer of naturally occurring material upon which the road is built), to deformation under the

Load from Vehicle Wheels.

Even more simply put, ''How strong is the ground upon which we are going to build the road''.

The BR test is a way of putting a figure on this inherent strength, the test is done in a standard manner so we

are able to compare the strengths of different sub grade materials, and we are able to use these figures as a

means of designing the road pavement required for a particular strength of sub grade. The stronger the sub

grade (the higher the CBR reading) the less thick it is necessary to design and construct the road pavement,

this gives a considerable cost saving. Conversely if CBR testing indicates the sub grade is weak (a low CBR

reading) we must construct a suitable thicker road pavement to spread the wheel load over a greater area of

the weak sub grade in order that the weak sub grade material is not deformed, causing the road pavement to

fail.

http://en.wikipedia.org/wiki/Load-bearing

http://en.wikipedia.org/wiki/Limestone

http://en.wikipedia.org/wiki/Limestone

http://en.wikipedia.org/wiki/Load-bearing



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Apparatus

Steps…

1. First soil samples weight 8 kg were taken from the each locations where DCP test was performed.

2. They were sealed using the polythene bags during the collecting to avoid the evaporation. Then they were

transported to the laboratory and ready for the testing.

3. Samples were mixed properly and sieved by 19 mm sieve. Also separate samples were kept in the oven

by recording the initial weight.

4. The mold with extension collar attached, was clamped to the based plate. Then the spacer disc was

inserted to the bottom of the mold.

5. The mold was filled with sample soil in layers and each layer was compacted by 2.5 kg Rammer for 56

blows. Blows were evenly distributed throughout the surface.

6. The extension collar was removed and sample was trimmed using a straight edge. Wholes that had

developed in the surface due to removal of the coarse material were patched with sample soil.

Figure 3.3- CBR Test Apparatus



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7. Then the spacer disc was removed and inverted the mould. Then it was placed in the CBR apparatus

placed the surcharge weight on the specimen. This is to produce sufficient intensity of loading equal to

the weight of base material pavement within 5 lb but not less than 10 lb.

8. Then the penetration piston was seated with the minimum possible load (but less than 44 N).

9. Both stress and strain gauges were set to zero.

10. The load was applied on the penetration piston so that rate of the penetration is approximately 0.5 inches

(1.27 mm) per minute.

11. While the load was being applied, stress gauge readings were taken against 0.64mm, 1.27mm, 1.91mm,

2.54mm, 3.18mm, 3.81mm, 4.45mm, 5.08mm, 7.62mm, 10.16mm & 12.7 mm penetrations.

3.3.2.2 Results

Location at 50 m distance from the Thalawathugoda junction and 1 m Right Hand Side of the road

Container 50m sample 250m sample 550m sample 800m sample

Initial weight 234.78 g 117.16 g 248.56 g 255.62 g

After oven dry 211.6 g 107.2 g 226.8 g 236.2 g

Penetration

(mm)

Dial reading

(Dev.)

0.64 53

1.27 90

1.91 121

2.54 145

3.18 164

3.81 184

4.45 200

5.08 215

7.62 268

10.16 310

12.7 350



FINAL REPORT



Penetration

(mm)

Dial Reading

(Dev.)

0.64 55

1.27 106

1.91 152

2.54 181

3.18 214

3.81 237

4.45 259

5.08 278

7.62 345

10.16 375

12.7 454

Location at 550 m distance from the Thalawathugoda junction and 2 m Left Hand Side of the road

Penetration

(mm)

Dial Reading

(Dev.)

0.64 42

1.27 76

1.91 110

2.54 148

3.18 152

3.81 164

4.45 174

5.08 185

7.62 229

10.16 261

12.7 296



FINAL REPORT



3.4 Calculations

All the graphs correspond to above tables are already attached as annexes. Calculations are shown for one

figure and all the values are taken according to that method.

Location at 50 m distance from the Thalawathugoda Junction

DCP test results

Gradient of the Graph = 9.857 mm/Blow

Equations

a) Log 10 (CBR) = 2.632- 1.280 log10 (mm/Blow)

b) Log 10 (CBR) = 2.555- 1.145 log10 (mm/Blow)

c) Log 10 (CBR) = 2.503- 1.150 log10 (mm/Blow)

d) Log 10 (CBR) = 2.480- 1.057 log10 (mm/Blow)

Penetration

(mm)

Dial Reading

(Dev.)

0.64 56

1.27 110

1.91 171

2.54 232

3.18 296

3.81 355

4.45 415

5.08 466

7.62 660

10.16 784

12.7 905



FINAL REPORT


Corresponding Values

a) CBR = 22.91%

b) CBR = 26.89%

CBR test results

We obtained the Load values corresponding to the Dial reading from the table, consequently related Stress

Values were calculated after doing the necessary corrections.

Area of the Piston = (π*0.049532) / 4 = 0.0019268 m

2

Stress for 2.54 mm Pen. = 1.4332 MPa


CBR for 2.54 mm Pen. = (1.4332 / 6.90 ) * 100 % = 20.77%

CBR for 5.08 mm Pen. = (1.6534/ 10.3 ) * 100 % = 16.05%

Maximum Value = 20.77%

Comparing DCP test results and CBR test results the most suitable CBR value = 20.77%


DCP test results



a) CBR = 42.93%

b) CBR = 45.17%

CBR test results



CBR for 2.54 mm Pen. = (2.232/ 6.90 ) * 100 % = 32.34%



FINAL REPORT


CBR for 5.08 mm Pen. = (4.051/ 10.3 ) * 100 % = 39.33%




DCP test results



a) CBR = 37.71%

b) CBR = 40.58%

CBR test results



CBR for 2.54 mm Pen. = (1.594 / 6.90 ) * 100 % = 25.30%

CBR for 5.08 mm Pen. = (2.865/ 10.3 ) * 100 % = 27.81%




DCP test results





FINAL REPORT


a) CBR = 51.11%

b) CBR = 52.17%

CBR test results



CBR for 2.54 mm Pen. = (3.256/ 6.90 ) * 100 % = 47.19%

CBR for 5.08 mm Pen. = (5.993/ 10.3 ) * 100 % = 58.18%



According to the above California Bearing Ratio (CBR) values, the lowest CBR value at the road

section as the design CBR, which is 20.77%.

3.5 Traffic Survey

3.5.1 Estimation of Traffic Volume

Traffic count data for the both directions were added up for each vehicle type.

From those values the summation of different vehicles for both directions per 15 minutes were

calculated.

Hourly flows were calculated and took the maximum among them as peak our flow.

According to below table;



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Peak hour was occurred from 2.30 pm – 3.30 pm

Peak hour flow = 1831 vph

Traffic volume per day = 1831*10

= 18310 vpd

Modfication factor for design volume = 0.5

For two lane ( single carriage way)

Hence traffic volume per lane = 18310*0.5

= 9155 vpd

Determination of design life

Traffic volume = 9155 vpd

Since traffic volume > 3000,

Hence design life is 20 years.

Estimation of cumulative number of Standard Axles (CNSA)

Following formula is used to determine the CNSA

A = 365*∑ (()

n

-1) / r i

A = Cumulative number of standard axles for design life

Ai = ∑ (()

n

-1) / r i

Pi = Average number of Standard Axles per day for the first year of opening the road for

Traffic after construction for vehicle type i

r i = Rate of growth of traffic for vehicle type i

m = Number of the type of vehicle

n = Design period in years



FINAL REPORT


Used ESA values for vehicle types

Vehicle type Number of axles/wheels ESA

Heavy goods vehicles >2%/>6 1.88

Medium goods vehicles 2/6 1.17

Light goods vehicles 2/4 0.01

Long Buses 2/6 0.30

Medium Buses 2/4 0.09

Specimen calculation for Pi,

Pi = (Peak hour floor for vehicle type i ) * (Modification Factor) * 10 * ESA

For medium Buses;

P1 = 11 * 0.5 * 10 * 0.09 = 4.95

Other Pi values were calculated as above calculation.

For 20 year Design life;

A = 365*∑ (()

n -1) / ri

=365*∑ Ai

= 365 * [ 148 + 1162 + 74 + 18938 + 8299 + 1729 + 2421 ]= 365 * 32771

= 13,786,415 ESA / yr



FINAL REPORT

3.5.2 Results

Designed CBR value ( for 2.54 mm Penetration) = 20.77%

According to the TRL Road Note 31,

Sub Grade Strength Class S – 5

CNSA for 20 years Design life = 13.8 * 106 ESA / yr

Traffic Class T – 7

According to the Structural Catalogue given in TRL Road Note 31,

From Chart 5 Granular Road Base / Structural Surface

Designed Pavement Cross Section

Reference:

Highway Engineering by Paul H. Wright / Karen K. Dixon

Relevant Websites, Lecture Notes

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