MODIFICATION OF TEMPERATURE CORRECTION FACTOR IN FWD … · Keywords: Falling weight deflectometer,...

\http://www.iaeme.com/IJCIET/index.asp 2397 [email protected]

International Journal of Civil Engineering and Technology (IJCIET)

Volume 10, Issue 03, March 2019, pp. 2397-2409, Article ID: IJCIET_10_03_240

Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=10&IType=03

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© IAEME Publication Scopus Indexed

MODIFICATION OF TEMPERATURE

CORRECTION FACTOR IN FWD BASED ON

FIELD EXPERIENCE IN INDIAN CONTEXT

Kevin Garasia

PG Student,Department of Civil Engineering, Parul Institute of Engineering and Technology,

Parul University, Vadodara, India

Jayesh Juremalani

Asst. Professor, Department of Civil Engineering,

Parul Institute of Engineering and Technology, Parul University, Vadodara, India

ABSTRACT

Recently flexible pavements are evaluated by Falling Weight Deflectometer

(FWD) instead of Benkelbeam method because of several advantages. Now pavement

temperature is one of the most important parameters that influence the Falling Weight

Deflectometer (FWD) measurements. Since there is a huge temperature variation in

Vadodara City, Gujarat, India, it is necessary to study the temperature effect on the

FWD measurements. In this paper, temperature correction factor is modified based

on the field results. Five different sites are selected. The readings are taken at

temperature 35° C and 45° C. Some other tests like road condition survey and test pit

methods are used to know the thickness of the pavement. The field results are

compared with the calculated values of the elastic moduli. Comparisons show that

surface and base layer are mostly affected by the temperature variation but the sub

grade layer is not much affected.

Keywords: Falling weight deflectometer, flexible pavement, temperature correction

factor

Cite this Article: Kevin Garasia and Jayesh Juremalani, Modification of Temperature

Correction Factor in Fwd Based on Field Experience in Indian Context. International

Journal of Civil Engineering and Technology, 10(3), 2019, pp. 2397-2409

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=03

1. INTRODUCTION

Country economic growth and development Transportation are playing a lead role. The road

transport is the oldest and most widely mode of transport. Country infrastructure pavements

are key elements, which is to promote transportation activities, economic activities and to

Kevin Garasia and Jayesh Juremalani

http://www.iaeme.com/IJCIET/index.asp 2398 [email protected]

improve the standard of living. By the maintenance and rehabilitation activities, life of the

structure is improved. So, the capacity of the vehicle pass at the pavement is improved, at the

low cost.

Benkelman Beam Deflection (BBD) is replaced with Falling Weight Deflectometer

(FWD) nowadays. In the FWD the weight is constant at all the point and blows are fix so it is

comparatively easy to operate and fewer persons are required. The falling weight

deflectometer (FWD) has been broadly used to evaluate the structural capacity of flexible

pavement for routine pavement design, rehabilitation strategy selection, and other pavement

management activities. By analyzing FWD data, resilient modulus of pavement subgrade,

layer coefficients, and some other parameters can be calculated. Generally, FWD

measurement is carried out in a wide range of temperature conditions. However, the

measured FWD deflection is significantly influenced by various factors such as temperature,

pavement thickness, drop load, etc. Therefore, it is necessary to correct the FWD deflection

data on the basis of a reference temperature. Then the corrected FWD deflection can be used

to estimate pavement layer properties.

A number of software such as ELMOD, EVERCALC, BISDEF, NUS-BACK, MICK-

BACK, MODULUS, PADAL, etc. are available for the backcalculation of pavement layer

moduli from deflections measured using FWD. KGPBACK, a specific version of BACKGA

program, which was developed for the research scheme R-81 (2003) of the Ministry of Road

Transport and Highways, is recommended in these guidelines for backcalculation.

KGPBACK is a Genetic Algorithm based model for backcalculation of layer moduli.

Because of this Genetic Algorithms (GA) have become popular to solve complex problems.

1.1. General Description of FWD

During FWD testing a load pulse is achieved by dropping a constant mass with rubber buffers

through a particular height into a loading platen. The load is usually transmitted to the

pavement via a 150mm diameter loading plate. The loading plate has a rubber mat attached to

the contact face and should preferably be segmented to ensure good contact with the road

surface. An example of a segmented loading plate is shown in figure 1. A load cell placed

between the platen and the loading plate measures the peak load. The resulting vertical

deflection of the pavement is recorded by a number of geophones, which are located on a

radial axis from the loading plate. One of the deflection sensors is located directly under the

load as shown in Figure. A typical FWD test set-up is shown diagrammatically in the Figure

1.

Figure: 1 Typical FWD test set-up

Modification of Temperature Correction Factor in Fwd Based on Field Experience in Indian

Context


1.2. Segmented FWD load plate

Figure 2 shows diagrammatic view of FWD

Figure: 2 Diagrammatic Representation of FWD

1.3. Load Pulse

As stated earlier the load pulse is achieved by dropping a constant mass into a loading platen

via rubber buffers. Differences in manufactures design have resulted in veering pulse shapes

for the same peak load. However, most FWD's have a load rise time from start of the pulse to

peak of between 5 and 30 milliseconds and have a load pulse width of between 20 and 60

milliseconds. The shape of the load pulse is intended to be similar to that produced by a

moving wheel load. Figure 3 shows a typical longitudinal strain profile for a wheel moving at

100 km/h on a rolled asphalt road base. Figure 4 shows a typical deflection profile for an

FWD load plate.

Figure 3 Typical longitudinal strain profile for a wheel moving (100 km/h)



Figure 4 Typical deflection profile for an FWD load plate

1.4. Choice of Test Lane, Test Load

The location of the FWD test will usually be governed by the information, which is required

from the FWD survey. In many cases, the tests will be carried out in the inner wheel track of

the slow lane (if applicable). The reason for this choice is that this is often the first location to

show distress signs on a road pavement. Tests can also be carried out between the wheel track

for Comparison purposes and to ascertain the residual life of the relatively untracked

pavement.

FWD survey on two-way single carriageway roads can be carried out in one direction or

alternatively in both directions using "staggered" locations as shown in the Figure 5.

It is generally recommended that at least three loading cycles, excluding a small drop for

settling the load plate, should be made at each location as shown in Figure 5.

It is generally recommended that at least three loading cycles, excluding a small drop for

settling the load plate, should be made at each location. The first drop is usually omitted from

calculations. A drop sequence of four drops ranging from 27kN to 50kN approximately

allows data analysis to be carried out at either the 40 or 50kN load level as required. Each

drop sequence takes approximately one minute or less.

Figure 5: two-way single carriageway roads

1.5. PAVEMENT TEMPERATURE

In general, FWD measurements can be carried out over a wide range of surface temperatures.

The range for testing flexible pavements should be 10 to 30°C and 45°C. Bituminous bound


Context


material behaves in a visco-elastic manner under load and therefore stiffness is temperature

dependent. The temperature of the bituminous material must, therefore, be measured at the

time of the test and corrected if necessary, to a reference temperature. Ideally, FWD testing

should be carried out at a temperature, which is as close as possible to the reference

temperature. It is not necessary to carry out temperature measurements on thin bituminous

pavements such as surfaced dressed granular roads as the thickness of bituminous material is

such that it would not have any significant effect on the overall pavement structure.

The temperature of the bituminous material is measured by first drilling a hole in the

bituminous layer and inserting a temperature probe into this hole. Holes for temperature

measured should be pre-drilled at least ten minutes before recording the temperature in order

that the heat generated by drilling has time to dissipate. A drop of glycerol or similar fluid

can be used to ensure good thermal contact between the temperature probe and the

bituminous material.

This procedure takes approximately 15 minutes and should be carried out at least every 4

hours during testing. The stiffness of the bituminous bound layers depends on both the test

temperature and the loading time. The loading time will be constant for a given FWD device.

However, in order to compare deflection/ layer module, they should be normalized to a

standard temperature. This will usually be the design temperature for the country or region.

The stiffness moduli of the various layers can be calculated from the measured deflection and

the bituminous bound layer stiffness then normalized. There are a number of normalization

methods available, some of which are contained within the backcalculation package. An

example of three such temperature stiffness relationships is shown as per IRC:115.

2. LITERATURE REVIEW

Dar-Hao Chen they conducted falling weight deflectometer (FWD) tests at three sites. The

tests were conducted at regular intervals for 2 to 3 consecutivedays per location and also done

during different seasons inorder that the widest possible range of temperatures could be

obtained.The influence of cracks on temperature correction was also investigated. It was

founded that only the W1 and W2 deflections are significantlyaffected by temperature. W3

through W7 deflections remainedalmost constant at various temperatures. The same trend

was observedfor all pavements used in this study.

Bin Zhang studied about the effect of temperature on the pavement. He conducted a

Falling Weight Deflectometer (FWD) measurement. They covered the different state of New

Mexico and for that, they are collecting the data of the different state of the New Mexico

Department of Transportation (NMDOT). Based on the data, two specific temperature

correction models for FWD deflection were developed. So, they have considered some data

as an independent variable like pavement temperature, FWD drop load, AC layer thickness

and the depth of layer temperature measurement. The developed model has done some of the

errors.

3. STUDY AREA DETAILS.

Survey is conducted on 5 roads near to Vadodara city. Road length is 3 to 6 km. so more data

is collected. The weather is hot during March to July, when the average maximum is 40° C,

and the average minimum is 23° C.

Five Sites are as below

(1) Sevasi – canal Road (2) Sevasi – Sindhrot Road (3) Ambada Road (4) Canal Road,

Channi (5) Vishwamitri road



4. DATA COLLECTION

4.1. Preliminary Studies:

To starting the deflection studies, it is essential to carry out preliminary studies consisting of

the following operations. Historical data of study area location like a map, annual rainfall,

temperature and traffic condition data, etc. Visual inspection of road stretches and

demarcation of the road into sub-stretches based on pavement surface condition. Marking of

deflection observation points along the selected wheel paths. Existing highway pavements

structural details by test pit.

4.2. Marking of the Deflection Observation Points

The deflection observations points are marked at a transverse distance of 500 m from the

starting point because road condition is good. Points are marked at both the outer wheel path

of the lane.

4.3. Road Condition Survey

Figure: 6 Road condition view

The visual inspection is taken at all the sites. Sevasi canal road data is shown in Table 1.

It is concluded from the inspection that road condition is good. To know the thickness of road

layer, test pit method is used. Table 2 shows the thickness of the road.

Table 1: Road condition survey data of Sevasi – canal road

Location Condition of Road Spacing(m) for test

points

0.250 RHS Good 500

0.750 LHS Good 500

1.250 RHS Good 500

1.750 LHS Good 500

2.250 RHS Good 500

2.750 LHS Good 500

3.250 RHS Good 500

3.750 LHS Good 500

4.250 RHS Good 500

4.750 LHS Good 500

5.250 RHS Good 500

5.750 LHS Good 500


Context


By the using test pit method, GSB (Granular sub base) and BT (Bituminous Thickness)

layers thickness were found.

Bituminous Layer

Granular Layer (Sub Base/ Base Layer)

Subgrade Layer

4.3. Crush Thickness

Table 2: Road crush thickness of Sevasi – canal road

Sr No

Existing Crust

Observed Chainage

km.

At Road Edge Bituminous Layer Granular Layer

Mm Mm

1 0.250 At Road Edge – RHS 130 290

2 0.750 At Road Edge – LHS 120 380

3 1.250 At Road Edge – RHS 120 360

4 1.750 At Road Edge – LHS 120 300

5 2.250 At Road Edge – RHS 120 390

6 2.750 At Road Edge – LHS 120 340

7 3.250 At Road Edge – RHS 120 380

8 3.750 At Road Edge – LHS 150 270

9 4.250 At Road Edge – RHS 140 350

10 4.750 At Road Edge – LHS 120 310

11 5.250 At Road Edge – RHS 130 310

12 5.750 At Road Edge – LHS 120 360

4.4. Falling Weight Deflect meters of data analysis

The FWD test data is collected from different load drops at each test point primarily consist

of peak load, peak deflections at different radial locations. Average value of load

anddeflections are calculated from the three drop test data collected at a given location.

The data is conducted at two different temperature one is at 35° C and second is at 45° C.

Sevasi – canal road data at

35° C shown in Table 3 and it is modified at 45° C with the formula

λ = temperature correction factor

T1 = temperature at survey conducted

T2 = temperature at required condition

data shown in Table 4. For same site test is conducted again at 45° C. The data are shown

in Table 5. For the other four sites the Elastic Moduli of three-layer surface, base and subbase

are presented in Table 6.



Table:3 - Sevasi – canal road data at 35°C

Locatio

n

Poi

nts

Te

mp

Fo

rce

Measured deflections (µm) Elastic Moduli

[Mpa]

D1

(0)

D2

(300)

D3

(450)

D4

(600)

D5

(900)

D6

(1200

)

D7

(1500

)

Surf

ace

Ba

se

Subg

rade

0.2

50

R

H

S

1 34.

4

41.

41 463 239 152 87 32 18 13 293

39

3 86.7

0.7

50

L

H

S

5 34.

4

40.

50 354 175 106 63 29 21 21

159

8

39

6 86.6

1.2

50

R

H

S

10 34.

4

39.

61 388 209 130 77 43 30 24

110

6

39

6 86.6

1.7

50

L

H

S

15 35.

2

40.

64 361 197 89 82 45 30 24

160

8

39

6 86.6

2.2

50

R

H

S

20 35.

2

40.

72 528 266 169 116 66 49 34 215

32

0 86.7

2.7

50

L

H

S

25 35.

2

40.

11 378 230 152 103 58 48 33

111

7

39

6 86.7

3.2

50

R

H

S

30 35.

2

41.

90 383 220 147 103 61 45 32

105

2

39

6 86.7

3.7

50

L

H

S

35 36.

9

39.

40 720 474 325 218 111 69 52 745 73 71.4

4.2

50

R

H

S

40 36.

9

41.

22 268 185 130 89 48 31 26

160

7

39

6 86.7

4.7

50

L

H

S

45 36.

9

39.

55 459 261 170 115 62 45 34 439

33

8 86.7

5.2

50

R

H

S

50 36.

9

40.

58 309 188 130 97 62 45 32

160

8

39

6 86.7

5.7

50

L

H

S

55 36.

4

41.

15 278 179 127 91 51 35 26

160

8

39

6 86.7


Context


Table:4 - Elastic Moduli Converted at 45° C (Calculated)

Elastic Moduli [Mpa] at 45

Surface Base Subgrade

479 643 142

2615 648 142

1810 648 142

2631 648 142

352 524 142

1828 648 142

1721 648 142

1219 119 117

2629 648 142

718 553 142

2631 648 142

2631 648 142

Table:5 - Sevasi – canal road data at 45°C (Actual)

Location Point

s

Tem

p

Forc

e

Measured deflections (µm) Elastic Moduli

[Mpa]

D1

(0)

D2

(300)

D3

(450)

D4

(600)

D5

(900)

D6

(1200)

D7

(1500)

Surfac

e

Bas

e

Subgrad

e

0.25

0

RH

S 1 43.6

41.4

1 467 240 155 88 35 19 14 484 649 143

0.75

0

LH

S 5 43.6

40.5

0 360 177 108 65 30 22 22 2641 654 143

1.25

0

RH

S 10 43.6

39.6

1 390 213 134 79 42 31 24 1828 654 143

1.75

0

LH

S 15 44.2

40.6

4 360 204 91 85 48 31 24 2657 654 143

2.25

0

RH

S 20 44.2

40.7

2 530 270 172 119 67 52 35 355 529 143

2.75

0

LH

S 25 44.2

40.1

1 382 229 155 108 60 50 34 1846 654 143

3.25

0

RH

S 30 44.9

41.9

0 386 216 151 108 65 48 35 1738 654 143

3.75

0

LH

S 35 44.9

39.4

0 723 478 327 221 119 71 54 1231 121 118

4.25

0

RH

S 40 44.9

41.2

2 265 188 132 92 50 34 30 2656 654 143

4.75

0

LH

S 45 44.9

39.5

5 468 262 172 119 65 48 36 725 559 143

5.25

0

RH

S 50 45.2

40.5

8 312 190 135 102 63 48 34 2657 654 143

5.75

0

LH

S 55 45.2

41.1

5 281 181 130 101 54 39 27 2657 654 143



Table:6 - OTHER FOUR SITE ELASTIC MODULI [MPA]DATA

SURFACE ACTUAL BASE ACTUAL SUBGRADE ACTUAL

SITE

2

SITE

3

SITE

4

SITE

5

SITE

2

SITE

3

SITE

4

SITE

5

SITE

2

SITE

3

SITE

4

SITE

5

371 1608 631 219 205 396 323 396 86.7 86.7 86.7 86.7

215 264 403 729 300 396 227 396 86.7 86.7 86.7 86.7

232 1608 526 332 324 396 169 370 86.7 86.7 86.7 86.7

247 379 482 372 396 73 120 246 86.4 86.7 86.7 86.7

244 499 920 433 361 394 75 338 86.7 86.7 86.7 86.7

217 517 624 1276 346 395 165 396 86.7 86.7 86.7 86.7

214 1161 214 454 251 396 396 396 86.7 86.7 86.7 86.7

406 216 481

140 218 381

86.7 86.7 86.7

463 214

324 302

86.7 86.7

489 214

73 331

86.6 86.7

335 247

232 396

86.6 86.7

1608 261

396 189

86.7 86.6

1584 557

396 396

86.7 86.7

1522 253

396 166

86.7 86.7

319

388

86.7

5. ANALYSIS OF CALCULATED AND ACTUAL DATA TAKEN AT 45°

C

Chart 1: Comparison between Calculated and actual Elastic Moduli at Sevasi – Sindhrot Road

0 100 200 300 400 500 600 700

1

2

3

4

5

6

7

Elastic Moduli [ Mpa]

No

. of

read

ing

Sevasi – Sindhrot Road

Actual Elastic Moduli at 45°C Calculated Elastic Moduli at 45°C


Context


Chart 2: Comparison between Calculated and actual Elastic Moduli at Amboda Road

Chart 3: Comparison between Calculated and actual Elastic Moduli at Canal Road, Channi

Chart 4: Comparison between Calculated and actual Elastic Moduli at Vishwamitri Road

0 500 1000 1500 2000 2500 3000

1

3

5

7

9

11

13


No

. of

read

ing

Ambada Road


0 200 400 600 800 1000 1200 1400 1600 1800

1

3

5

7

9

11

13

15


No

. of

read

ing

Canal Road, Channi


0 500 1000 1500 2000 2500

1

2

3

4

5

6

7

8


No

. of

read

ing

Vishwamitri Road




Chart 1, 2, 3 & 4 show the comparison between Calculated Elastic Moduli at 45°C and

Actual Elastic Moduli at 45°C. X axis shows elastic moduli of actual and calculated data and

y axis shows number of readings taken. As per charts we shown that actual elastic moduli are

high compare to the calculated elastic moduli.

6. CONCLUSION

From the present study, it can be seen that elastic moduli vary with the temperature. The data

is collected are at two different temperature that is 35° C and 45° C respectively for which

elastic moduli is calculated and compared in the study. From the study it is found that elastic

moduli are more for surface and base layer; no significant change is seen on the subgrade

layer. Five different sites were evaluated at both the temperature and depending on its

temperature correction factor is modified. FWD can be used very easily and more reliable

values are obtained rather than using other methods. Based on the field study different sites of

Vadodara city was visited and formula is modified as below

The applicability of above formula is subject to verification.

REFERENCES

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“MONITORING STIFFNESS OF GRAVEL SURFACED ROADS DURINGSPRING

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