structural properties evaluation for flexible … · with the structural capacity of the pavement...

http://www.iaeme.com/IJCIET/index.asp 531 [email protected]

International Journal of Civil Engineering and Technology (IJCIET)

Volume 10, Issue 12, December 2019, pp. 531-544, Article ID: IJCIET_10_12_052

Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=10&IType=12

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

© IAEME Publication

STRUCTURAL PROPERTIES EVALUATION

FOR FLEXIBLE PAVEMENT USING NON

DESTRUCTIVE TESTING GPR AND LWD

Vishal Kumar Narnoli

Department of Civil Engineering,

National Institute of Technology Patna, Patna, Bihar, India

Sanjeev Kumar Suman

Department of Civil Engineering,

National Institute of Technology Patna, Patna, Bihar, India

ABSTRACT

The structural properties evaluation for in-service road is layer thickness, elastic

modulus and stiffness value. The structural capacity of pavement, measured by

deflection testing, is an important parameter for maintenance and rehabilitation of

existing pavement. The increase or decrease in deflection of pavement layer indicates

corresponding decrease or increase in structural capacity of pavement layers. In-situ

investigation of flexible pavement sections was carried out using two non-destructive

testing devices (NDT); the Light Weight Deflectometer (LWD) and Ground

Penetrating Radar (GPR). The main motivation behind the research is to use the LWD

and GPR over time-consuming, laborious, and unsafe destructive testing such as

coring and costly falling weight deflectometer testing, as a support tool for pavement

maintenance and rehabilitation decision. The analysis of GPR data showed lower

accuracy in layer thickness prediction for appreciably deteriorated pavements but

higher accuracy was found for newly constructed pavements. Elastic modulus value

obtained using LWD showed high variability on pavement section with and without

distresses. To look over the combined effect of thickness and elastic modulus value a

single parameter is introduced known as stiffness that reflect the structural capacity of

the pavement. Stiffness value shows a trend for good and poor road condition.

However, sufficient data is required to create a limiting vale for stiffness related to

pavement condition.

Keywords: GPR, LWD, Deflection, Composite modulus, Stiffness, Pavement

condition.

Cite this Article: Vishal Kumar Narnoli, Sanjeev Kumar Suman, Structural Properties

Evaluation for Flexible Pavement Using Non Destructive Testing GPR and LWD.

International Journal of Civil Engineering and Technology 10(12), 2019, 531-544.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=12

Structural Properties Evaluation for Flexible Pavement Using Non Destructive Testing GPR and LWD


1. INTRODUCTION

The pavement is a fundamental transportation infrastructure system to sustain both moving

vehicles and people. Under the action of traffic loading and prevailing environmental

conditions, the section of pavement deteriorates. To maintain the condition of the pavement

for efficient and comfortable movement of traffic, its evaluation is needed on a routine basis.

The primary objective of pavement condition evaluation is to asses as to whether and to what

extent the pavement fulfils the intended requirements so that the maintenance and

rehabilitation jobs could be planned in time. Generally, pavements performances are

evaluated based on both functional and structural performance. The structural performance of

the pavement is required to make effective decisions on the type of maintenance or

rehabilitation to be carried out on a pavement section. Structural performance is concerned

with the structural capacity of the pavement as measured by deflection testing, layer thickness

and material properties. Structural evaluation of pavement may be carried out using

destructive testing and/or non-destructive testing (NDT). The core sample data is widely used

destructive testing technique. The core cutting is simple and cost effective technique but have

some limitations. The core cutting technique is time consuming, laborious, interrupts the

traffic flow and lower data collection efficiency[1]. NDT is the collective form of evaluations

conducted on an existing pavement structure that does not require subsequent maintenance

work to retain the pavement to its pre-testing step. Ground Penetrating Radar (GPR) is a NDT

type of tool used for subsurface monitoring. GPR provides continuous data along the

pavements. The main application of GPR in pavement engineering is to estimate the layer

thickness, void and moisture content detection. Recently some researcher and highway

authorities used GPR along with other deflection testing (FWD, HWD) for evaluating the

structural performance of flexible pavement. The Light Weight Deflectometer (LWD) is a

portable device traditionally used for quality control of granular materials at subgrade and

subbase level. LWD directly computes the surface modulus ELWD from the pavement surface

deflection measured using central geophone and load applied. However, the measuring depth

(normally 1.1-1.5 times the plate diameter) is lower than the FWD because it uses lower

amplitude of load, so the surface modulus ELWD is actually the composite modulus of two

pavement layers. Uma Shankar et al. (2005) performed LWD testing on expressway and low

volume road. The surface and base layer were tested to measure the modulus of deformation

ELWD. A relationship was established between the deformation modulus and in-situ density

obtained using sand cone test.

To successfully perform its function, pavement as a whole should be capable enough to

transfer the axle load safely to the subgrade soil; this necessitates the reliable estimation of the

stiffness of pavement layers. The back-calculated elastic modulus obtained using deflection

testing such as Benkelman Beam (BB) test and falling Weight Deflectometer is generally used

worldwide as a reliable tool to estimate the stiffness of pavement layer and also to verify the

elastic modulus of pavement materials used for pavement design.

Among the various available in-situ deflections testing devices like the Benkelman beam

(BB) and Falling Weight Deflectometer (FWD) is mostly used by various transportation

departments. The BB and FWD test have salient demerits as they require a large magnitude of

load, time-consuming, costly and laborious. FWD has an advantage over conventional BB

test; the FWD simulates the actual traffic conditions whereas BB test applies static load. To

overcome these problems the lighter version of FWD it means the lightweight deflectometer

(LWD) is being developed and gained popularity mainly for compaction quality control of

bound and unbound materials.

The LWD device with a single geophone at the centre cannot back-calculate the modulus

of the multilayer pavement structure. To calculate the modulus Boussinesq, half-space theory

Vishal Kumar Narnoli, Sanjeev Kumar Suman


is used. When the testing is performed on the subgrade material the resulting modulus

represents resilient modulus. Whereas when LWD test is being performed on the bituminous

layer the calculated modulus represents the composite modulus for limited depth of pavement.

Since the depth of influence of LWD test extends to more than one layer of pavement, the

measured modulus represents the composite modulus [3], [4]. LWD test conducted on the

pavement layer having a thickness less than the depth of influence yields composite modulus

of pavement [5]. Use of back-calculated result for only one geophone can result in erroneous

result. Since several factors such as the stiffness of layers, stress magnitude and its stress

distribution and diameter of the testing plate affect the depth of influence of each test [6]. The

modulus of the top layer is independent on the positions of the additional geophones. The

lower layer modulus varies to some extent with changing the position of the second geophone

and 450 mm positioning of the second geophones could be considered to be reliable [7].

LWD achieves wide application such as quality control and quality assurance (QC/QA),

compactness of material, estimating the stiffness of bound/unbound granular material, for

measuring the stiffness of thin asphalt pavement layer [7]–[15]. Since low amplitude peak

load is generated from LWD so its use for thick asphalt pavement layer is very seldom.

Many researchers conducted a field test on modified and unmodified soils with different

test equipment. Elastic modulus obtained from the testing equipment was correlated with the

composite modulus obtained from LWD [16].The effect of layer thickness on the composite

modulus was studied on the aggregate layer placed on weak soil which was reinforced using

geosynthetic. The results showed that an increase in the thickness of the layer, the ELWD

modulus increased considerably. ELWD values for aggregate layer placed on geotextile were

having higher values than that placed directly on the weak subgrade [17].

FWD has been widely recognized as a tool for structural evaluation of flexible pavement.

The back-calculated elastic modulus has been used to develop the Structural Health Index

(SHI). The SHI was found to be an efficient tool for predicting the rate of deterioration of the

pavement section [18].

The subsurface anomalies, voids, location of dowel bar (applicable to concrete pavement),

the void below the pavement, depth of bedrock, groundwater level, pavement moisture

content and frost penetration depth, type of subgrade soil strata, etc. can be estimated by GPR

testing [20]. GPR has been reported as a versatile tool for pavement layer thickness evaluation

[21].

The scope of this study is LWD with single geophone and ground coupled antenna GPR,

testing performed on top surface of flexible pavement. The main objective of this paper is to

assess the structural properties of the pavement and look over the impact on pavement

condition.

2. STRUCTURAL PROPERTIES EVALUATION USING NDT

EQUIPMENT

2.1. Light Weight Deflectometer (LWD)

The LWD is light, compact, portable and quick testing equipment. The LWD is a miniature

version of conventional FWD developed to determine the E-modulus of pavement layers. The

LWD was developed in Germany as a substitute for in-situ plate load test and to overcome the

accessibility issues arising in the road under construction [22], [23]. The Dynatest LWD 3031

with its components is shown in Fig. 1, which conforms to the ASTM E 2583 specification. A

drop mass of 10 kg falls freely from a height of 850 mm. Total weight of equipment is

approximately 22 kg. The standard sizes of loading plates are 300 mm, 150 mm and 100 mm.



The peak force generated by 10 kg drop mass lies in the range about 6.9 kN to 7.1 kN with a

half-sine pulse of 15-millisecond duration.

Figure 1: Showing LWD and its components

The load cell having a capacity to measure the impact load ranging from 0-25 kN, with an

accuracy of 2 % ± 2 kPa and precision level of 0.0003 kN. The central deflection is measured

by a deflection sensor also called geophone, which is a velocity transducer having an accuracy

of 2% ± 2 µm and precision level of 0.1 µm. The dual plate system allows testing with the

two-plate diameter at the same spot without the movement of the instrument. The LWDmod

program based on the equivalent layer thickness developed using Boussinesq- Odemark

theory.

Generally, a single person can be sufficient for handling LWD and it takes about 3 - 4

minutes for testing at each test point. The surface deflection is measured with central

geophone located at the centre of LWD. Using peak force applied and resulting deflection in

equation 1, the composite modulus or deformation modulus (Eo) is computed. According to

[24], the conventional LWD modulus (ELWD) is calculated from Equation 1 as follows

( )

(1)

where k = π/2 for rigid plate or 2 for flexible plates respectively, δc = centre deflection; σ

= applied stress in kPa; and R = radius of the plate in mm, Poisson‟s ratio taken as 0.3 for

granular layers and 0.4 for bituminous layers [25].

During operation, it requires a flat surface to function properly and three seating drops are

performed to ensure close contact. Then another three drops were performed, and the

deflection corresponding to each blow and the composite modulus of pavement were

calculated by the data acquisition system. The LWD is, however, not ideal for thicker

pavements because of low contact stress and a limited depth of influence to the pavement

layers. Also, it does not collect pavement temperature in both thin and thick asphalt

pavements; thus a further means of recording temperature is needed [26]. The correlations



shown in Table 1 are site, material and device-specific and cannot be generalized as they are

developed using regression analysis performed on a limited set of data[9].

From the past literature survey, it was observed that the depth of influence of LWD varies

from 270-280 mm [9]. The coefficient of variation (CoV) is a measure of relative variation

i.e. dispersion of data points around the mean value, is the ratio of the standard deviation to

mean. For fine-grained materials, the CoV value varies from 25-60 % when testing

performed using the LWD and FWD. Similarly, for granular materials CoV values lay from

10 – 40 % and for well-graded granular materials, CoV is less than 15 %. The composite

modulus reported after thawing were 645-504 MPa for bituminous layer having thickness of

127 -180 mm.[9]

Table 1: Correlation of LWD with other deflection testing equipment

Instrument Equation Type of Material Coefficient of

Correlation (R2)

Reference

TFT = (0.8-1.4)*FWD Granular Soils [9]

= (0.96)*LWD 0.92 [9]

LWD =0.97*FWD Granular layer on silty clay 0.6 [9]

LWD = 1.03* FWD [9]

LWD = 1.33 FWD Thin asphalt pavement 0.87 [9]

=0.75 FWD Thicker pavement layer 0.56 [9]

2.2. Ground Penetrating Radar (GPR)

GPR is a non-destructive, ground exploration technique which works on the principle of pulse

system using radio waves, mainly used in the pavement for layer thickness estimation, utility

detection, for inspection of subgrade soil, crack detection[21], [27]–[31]. The GPR system

consists of an antenna unit, a transmission/reception unit, a control unit and a storage/display

unit. GPR antenna transmits high-frequency radio signals through pavement structure, with

the change in layers properties the signals are reflected and are detected by the receiver

antenna. Since the change in material properties causes a change in energy of reflected

signals, these signals when intercepted by receivers are processed in processing unit to

visualize the sectional profile of pavement and then an interpretation is done for pavement

thickness [32], [33].

Figure 2: Units of Ground Coupled Radar



Ground-coupled penetrating radar of 400 MHz central frequency was deployed. The

ground-coupled GPR antennas find wide application in subsurface exploration. Higher

antenna frequency helps in the high-resolution image of pavement structure but also limits the

depth of exploration, since highways structure thicknesses varies from 0.5 m to 1.5 m in-

depth, and are of concern to highway engineers, thus making higher frequency antenna

mandatory in surveys. Since the antenna is ground-coupled no part of EM energy is lost due

to reflectance from the pavement surface hence extending the depth of penetration. For

measuring the layer thickness the Eqn. 2-4 is used, where t is the difference in time taken also

known as two-way travel time i.e. the time difference of transmitted and reflected EM wave

signal, is the dielectric constant of the material, c is the speed of light in free space. The

travel time of wave is divided by 2 as it is two-way travel time forming a trip.

Velocity (in. /ns) =

√ (2)

Thickness (in.) = velocity x

(3)

Thickness (in.) =

√ (4)

3. DATA COLLECTION

3.1. Study Area

The study carried out on four highways situated in the state of Bihar, India. The highways

under study are flexible pavement that caters daily commercial vehicles per day ranges from

1000 to 2500. The road sections of highways were located in four districts of Bihar namely

Patna, Nalanda, Jehanabad and Vaishali. Table 2 shows the details of the road section under

consideration and their pavement composition obtained from the detail project report (DPR)

of Department of road construction.

Table 2: Details of the Road Sections for the Survey

Road

Selected

Road

Section

Latitude / Longitude

Length

(Km)

CBR of

Subgrade

(%)

Design thickness of layers

Start End

Bituminous

Layer

(mm)

Base

Course

Sub-

base

course

H1

Daniyawan

to Chandi

Road

25°25'38.8"N

85°18'24.9"E

25°23'49.1"N

85°20'41.8"E 5.5 8 100 250 200

H2

Patna - Gaya

– Dobhi

Road,

Shiunand to,

Jahanabad,

25°16'30.1"N

85°00'37.7"E

25°12'51.8"N

84°59'08.9"E 7.5 6 105 250 260

H3 Hajipur to

Muzzafarpur

25°47'44.6"N

85°16'48.2"E

25°51'21.7"N

85°17'34.5"E 7.25 8 120 250 240

H4

Patna

Bakhtiyarpur

4 lane

25.557810N

85.257732E

25°30'07.3"N

85°16'06.2"E 7 10 140 250 200

3.2. Testing Procedure

Non-destructive testing was performed along with pavement condition assessment in the

month of Oct-Nov in the year 2018. Ambient air temperature on the day of testing ranges

from 22 oC to 37

oC. Road sections scanned along the wheel path of the traffic by ground-

coupled GPR (400 MHz) to determine the pavement layer thickness. Before conducting the



test, GPR was calibrated with a known thickness of pavement layers. The bituminous layer

thickness of pavement was validated also with core samples. Testing by LWD performed on

the same path at an interval of 250 m as shown in Fig. 3 with both plate size namely 150 mm

and 300 mm. Before in-situ testing, it was ensured that the rubber pad makes proper contact

with the road surface. Where the surface was rough and undulated, a layer of fine sand was

placed to ensure uniform stress distribution. A total number of 12 drops at each point on each

plate were performed. The first three drops used to set the instrument and it is considered as

seating drops. The seating drops were not considered for the computation of composite

modulus. The rest of the nine drops were used for the analysis.

4. RESULT AND DISCUSSION

The collected GPR signal was post-processed in the RADAN-7 processing software. The time

zero correction was applied to remove the negative amplitude of the signal and initiate the

signal from the peak. Automatic peak detection algorithm built-in RADAN-7 was used for the

same.

Figure 3: Typical layout of LWD testing points on the selected road stretch

To remove the unwanted noise and horizontal band from the collected signal, background

removal technique was implemented using IIR filters. A vertical low pass and high pass filters

of 800 MHz and 100 MHz was used to filter the signals. The core data extracted from the

selected roads were applied as ground truth for vertical calibration of GPR signals. The layer

picking tool 2-D interactive was used to select the different layers. The 2-D interactive picks

different layers based on their similar amplitude or signal. A typical GPR output with 400

MHz antenna including oscilloscope trace and core sample is shown in the Fig. 4.

Figure 4: A typical GPR output with 400 MHz antenna



A summary of the layer thicknesses for various road sections is presented in Table-3. The

design thickness of pavement layers was obtained from road construction agencies that

compared with the measured average thickness of all the layers. The percentage error found

between them in the range of -3.5% to +3.5%, except road H2. Higher value of percentage

error (-11.2%) for the same may be due to bad condition of the road. On the other hand, four

core samples were extracted for each road sections on the random basis and measured the

height of the bituminous layer. Table-4 shows the difference between thickness measured by

GPR and core samples. The percentage error lies between -6.7% to +4.7% for bituminous

layers. Therefore, little difference exists among all the criteria taken into account. Using the

GPR technique thickness error for the surface layer and base course layer was around 3-5 %

and close to 8-10 % respectively as reported by the researcher [21].

Table 3: Summary of design and GPR thickness

Road

Design layer

thickness (mm)

Average layer thickness

from GPR (mm) Error (%)

Surface

Course

Base

Course

Sub base Surface

Course

Base

Course

Sub

base

Surface

Course

Base Sub

base

H1 100 250 200 112 243 205 -12 +2.8 -2.5

H2 105 250 260 117 268 256 -11.4 -7.2 +1.5

H3 120 250 240 123 254 248 -2.5 -1.6 -3.3

H4 140 250 200 135 246 207 +3.6 +1.6 -3.5

Table 4: Difference in thickness measured from core and GPR

Road

Section

Average of four core

sample thickness (mm)

Average layer thickness

from GPR (mm) Error (%)

H1 105 112 -6.7

H2 112 117 -4.5

H3 129 123 +4.7

H4 131 135 -3.1

4.1. LWD Test

In principle, the LWD device uses the concept of applying a dynamic force onto an elastic

medium to estimate the elastic modulus of the tested material. The Poisson ratio of 0.35 was

adopted for the bituminous layer. The layer thickness data obtained from GPR were used as

an input for calculation of composite modulus. The Indian Road Congress code [34] were

referred for taking the initial seed modulus of pavement material. The seed modulus value for

granular layer varies from 100 – 500 MPa. The seed modulus value for bituminous layers

without much cracking varies from 750 -3000 MPa and in distressed condition (fair to poor)

ranges from 400 - 1500 MPa.

4.2. Deflections and Composite Modulus Obtained using LWD

It has been observed that surface deflection corresponding to 150 mm diameter plate is higher

than the 300 mm diameter plate of the LWD. Deflection increases may be due to decreases in

plate size and increase in contact pressure under the contact area of the plate. The surface

deflection data of the four road section obtained from the LWD testing were presented in the

Fig 5-8. The surface deflection reported herewith is per km, which is average of the four

values carried out at an interval of 250 m. The surface deflection for road H3 measured using

150 mm plate range from 44–99 microns with COV 33 %, for 300 mm plate the deflection

ranges from 40-57 micron with COV 13%. The surface deflection for road H2 measured using

150 mm plate range from 74.4-90.22 micron with COV 6.9918%, for 300 mm plate the

deflection ranges from 63-82 micron with COV 9%. The surface deflection for road H1



measured using 150 mm plate range from 38.9-129 micron with COV 43.38%, for 300 mm

diameter plate the deflection ranges from 37-64 micron with the COV 21%. The surface

deflection for road H4 measured using 150 mm plate range from 38.9 – 129 microns with

COV 43.37%, with 300 mm diameter plate the deflection ranges from 32-104 micron with

COV 39.6%. It was observed that deflection values corresponding to 150 mm and 300 mm

plate size of LWD manifest little difference at distressed location whereas vital difference

exists at undistressed pavement condition. It may be stated that the difference in deflection

will decrease from excellent to fail condition of pavement. On an average, the composite

modulus values were found to be about 1.3 to 1.8 times greater when testing was performed

using 150 mm plate when compared with 300 mm diameter plate. According to the visual

inspection of the pavement condition, road H4 was in very poor condition whereas road H2

was in very good condition.

Road H4: Patna-Gaya-Dobhi Road

The distresses in the form of rutting, fatigue cracking and potholes were found to exist as

shown in Table 13. The pavement maintenance in the form of patchwork was also found at

some locations. The pavement layer constitutes a 105 mm thick bituminous layer on the top of

granular base layer 250 mm and a sub-base layer of 260 mm. The layer was supported on the

clayey subgrade of CBR 6 %. With reference to Eqn. (1), composite modulus increases with

decrease of deflection and vice-versa. The composite modulus values were found to decrease

with increase in the distressed area of pavement. The overall condition of this road was poor.

Road H2 : Hajipur to Muzaffarpur

The selected road section was found to be in good condition with smooth ride quality. Minor

cracking in the form of hairline cracks was found to exist on the pavement surface layers.

Only at single location, the distress in the form of rutting and low fatigue cracking was found.

The pavement layers were composed of a 120 mm thick bituminous layer on the top of wet

mix macadam of 250 mm thickness and a sub-base layer of 240 mm. The layers were

supported on the silty-clay subgrade having a design CBR of 8 %. The composite modulus

values were found to decrease with increase in the distressed area of pavement. This may be

due to the decrease in strength of bituminous material of the surface layer. By comparing the

data it was found that at the fatigued location the composite modulus significantly reduced.

The composite modulus lies between 300 MPa to 418 MPa for 300 mm diameter plate and

513 to 710 MPa for 150 mm diameter plate. The overall condition of the pavement was found

to be in fair.

Road H3: Patna to Bakhtiyarpur

The selected road section was found to be in fair condition with fair ride quality. Transverse

and longitudinal cracking was found to exist on the pavement surface layers. Distresses in

form of low to high fatigue cracking and rutting were found on many locations. Potholes and

ravelling were also encountered at some sections. The pavement layers were composed of a

140 mm thick bituminous layer made from crumbed rubber modified mix on the top of wet

mix macadam of 250 mm thickness and a sub-base layer of 200 mm. The layers were

supported on the clayey soil subgrade having a design CBR of 8 %. The composite modulus

values were found to decrease with increase in the distressed area of pavement. This may be

due to the decrease in strength of bituminous material of the surface layer. By comparing the

data it was found that at the fatigued location the composite modulus significantly reduced.

The composite modulus lies between 493 MPa to 690 MPa for 300 mm diameter plate and

629 to 1263 MPa for 150 mm diameter plate. The road condition was in the fair condition.



Figure 5: Deflections at H1 Figure 6: Deflections at H2

Figure 7: Deflections at H3 Figure 8: Deflections at H4

Figure 9: Surface Deflection Modulus at H1 Figure 10: Surface Deflection Modulus at H2

Figure 11: Surface Deflection Modulus at H3 Figure 12: Surface Deflection Modulus at H4

Road H1: Daniyawan to Chandi Road

The selected road section was constructed very recently. The road section serves as all-

weather road built on an embankment. The blacktop of the flexible pavement was in good

condition free from any cracks. The ride quality on the selected road was good. For same

thickness of road the composite modulus was found to vary. This may be due to the quality of

road material. The composite modulus lies between 396.8 MPa to 695 MPa for 300 mm



diameter plate and 680 to 1092 MPa for 150 mm diameter plate. The overall condition of the

pavement was found to be in good.

These roads were selected for the current study because the traffic density for selected

roads varies from low to high, varying layer thickness, cracking and continuous failure of

pavements top layer is common to all selected locations. The failure of pavement sections

varies from low to severe failure with rutting failure, fatigue failure, block cracking,

transverse cracking, thermal cracking and potholes as most predominant types of distresses.

At some locations maintenance of pavement in the form of patching has also been done and

was investigated for their structural capacity. On the newly constructed roads, some

longitudinal and transverse cracking were also found this may be due to change in

temperature. The design thickness of bituminous layer for different road section varies from

100 mm to 140 mm.

Table 5: Structural Properties of pavements and their pavement condition rating

Road Layer

Thickness (mm)

Deflection (micrometer)

Composite Modulus

(MPa)

Composite

Modulus (MPa)

Overall Pavement

Condition Rating Surface

course

Base

course

150 mm

plate

300 mm

plate

150 mm

plate

300 mm

plate H1 1 112 243 75.0 64.8 679.5 396.8

Good

2 168 340 52.8 43.0 962.5 595.6 3 167 271 58.0 48.4 930.5 560.8

4 210 321 51.0 43.5 986.8 627.3

5 191 316 47.8 42.2 1091.6 617.4 6 213 310 47.0 37.1 1080.8 694.9

7 138 217 54.6 43.6 924.3 603.4 8 180 336 49.6 47.4 1038.2 541.6

H2 1 113 260 129.0 104.3 392.8 243.8

Fair

2 106 263 123.0 94.0 413.7 293.2

3 144 271 38.9 32.0 1334.6 804.6 4 101 238 98.2 102.4 490.9 269.6

5 187 256 46.9 46.6 1085.3 580.1 6 133 267 85.7 84.1 590.1 306.3

7 143 260 73.7 66.0 713.9 388.6

8 186 298 55.2 52.1 922.1 483.7 9 137 271 71.4 83.0 731.1 335.3

10 180 321 65.4 58.2 789.4 427.1 H3

1 128 274 90.22 82.7 590.67 323.3

Poor

2 152 279 74.44 63.2 709.56 422.7

3 127 257 82.63 71.5 648.75 377.2

4 93 213 82.33 77.6 651.89 369 5 118 271 87.11 73.1 638 345.7

6 133 243 89.68 78.1 694 360.8 7 84 286 103.89 73.1 513 298.2

H4

1 128 274 49.6 47.3 1154.3 650.5

Good

2 94 242 44.2 39.6 629.8 493.6

3 152 279 47.9 42.7 1262.7 689.8 4 127 257 75.7 52.4 1137.0 544.3

5 118 271 70.7 49.0 762.9 545.9 6 133 243 99.0 56.3 800.1 559.3

4.3. Stiffness Value for Pavements

Main structural properties of the pavements are thickness of the pavement layers and its

elastic modulus value. Based upon the non-destructive testing data of layer thickness and

elastic modulus value, it is difficult to judge a trend. Even low thickness of layers reveals high



elastic modulus value because of high quality material and vice-versa. Therefore, a structural

property is introducing known as Stiffness. Stiffness is the extent to which a pavement resists

deformation in the response to an applied traffic loads. It shows the response of the pavement

layers above subgrade layer. Since stiffness is the product of layer thickness and elastic

modulus, it reflects the composite effect. Fig. 13 shows the average value of stiffness for each

road that indicates the structural capacity of the pavement. High stiffness value was found for

road H1 whereas low value was found for H4.These roads pavement was also validated with

visual inspection condition survey. Road pavement H1 and H4 have high stiffness value and

rated as good whereas road pavement H3 has low stiffness value and rated as poor(See Table-

5).

Figure 13: Stiffness value

5. CONCLUSIONS

The deformation under a specific load depends upon subgrade soil type, its moisture content

and compaction, the thickness and quality of pavement course, drainage conditions, pavement

surface temperature etc. Though, this paper only presents the effect of layers thickness,

subgrade soil strength and pavement condition on composite modulus. The following

conclusions can be drawn from this study.

Ground coupled penetrating radar bearing 400 MHz is enabled to measure the layers thickness

of flexible pavement. Almost 30 km roads were scanned lengthwise along the susceptible path

of pavement that reveals pavement layers thickness within tolerable extents.

LWD is a non destructive instrument and it is gaining popularity due to its portability, single

person handling, time saving and quick result displaying. For fully deteriorated pavement

sections, LWD testing with150 mm and 300 mm diameter showed no appreciable difference

in deflection.

Composite modulus obtained from LWD test was found to be dependent on pavement layer

thickness. The surface layer thickness showed considerable influence on composite modulus.

For the sections with no cracking and from low to medium cracking the deflection modulus

obtained at from 150 mm diameter plate was found to be 1.5 - 1.8 times higher than the

deflection modulus obtained using 300 mm diameter plates.

LWD data can be utilized for pavement condition assessment and maintenance at project level

in pavement management system. At network level there was no correlation found in

pavement layer thickness and its composite modulus.

The stiffness value of the pavement represents the overall structural requirement needed to

sustain the design‟s traffic loading.

0.00

100.00

200.00

300.00

400.00

500.00

H1 H2 H3 H4

Stif

fne

ss (

kN/m

m)

Road No.

Stiffness(150mm plate)

Stiffness(300mm plate)



Therefore, more study is needed before recommending GPR and LWD as a technique for

structural health monitoring and pavement maintenance management.

REFERENCES

[1] V. Marecos, M. Solla, S. Fontul, and V. Antunes, “Assessing the pavement subgrade by

combining different non-destructive methods,” Constr. Build. Mater., vol. 135, pp. 76–85,

2017.

[2] M. Nobakht, M. S. Sakhaeifar, and D. Newcomb, “Development of Rehabilitation

Strategies Based on Structural Capacity for Composite and Flexible Pavements,” J.

Transp. Eng. Part A Syst., vol. 143, no. 4, p. 04016016, 2017.

[3] Y.-C. Lin, A. Chen, C.-P. Chou, Y.-C. Lin, and A. Chen, “Temperature Adjustment for

Light Weight Deflectometer Application of Evaluating Asphalt Pavement Structural

Bearing Capacity Chia-Pei Chou, Corresponding Author,” Transp. Res. Rec. J. Transp.

Res. Board, vol. 2641, no. 1, pp. 1–16, 2017.

[4] C. Senseney and M. Mooney, “Characterization of Two-Layer Soil System Using a

Lightweight Deflectometer with Radial Sensors,” Transp. Res. Rec. J. Transp. Res. Board,

vol. 2186, no. 2186, pp. 21–28, 2010.

[5] A. K. Apeagyei and M. S. Hossain, “Stiffness-Based Evaluation of Base and Subgrade

Quality Using Three Portable Devices,” 88th Transp. Res. Board Annu. Meet., no.

February, pp. 10–1721, 2010.

[6] M. D. Nazzal, “Field evaluation of in-situ test technology for QC/QA during construction

of pavement layers and embankments,” 2003.

[7] A. Kavussi and S. Yasrobi, “Evaluation of Pfwd As Potential Quality Control Tool of

Pavement Layers,” J. Civ. Eng. Manag., vol. 16, no. 1, pp. 123–129, 2010.

[8] S. Commuri et al., “Pavement Evaluation Using a Portable Lightweight Deflectometer,”

Midwest City, 2012.

[9] P. R. Fleming, M. W. Frost, and J. P. Lambert, “Review of Lightweight Deflectometer for

Routine in Situ Assessment of Pavement Material Stiffness,” Transp. Res. Rec. J. Transp.

Res. Board, vol. 2004, no. 1, pp. 80–87, 2008.

[10] P. R. Fleming, M. W. Frost, and C. D. F. Rogers, “A comparison of devices for measuring

stiffness in situ,” Proc. Fifth Int. Symp. Unbound Aggregates Roads, UNBAR 5,

Nottingham, United Kingdom, pp. 193–200, 2000.

[11] K. A. Alshibli, M. Abu-farsakh, and E. Seyman, “Laboratory Evaluation of the Geogauge

and Light Falling Weight Deflectometer as Construction Control Tools,” vol. 17, no.

October, pp. 560–569, 2005.

[12] P. K. R. Vennapusa and D. J. White, “Comparison of light weight deflectometer

measurements for pavement foundation materials,” Geotech. Test. J., vol. 32, no. 3, pp.

239–251, 2009.

[13] S. S. Park, A. Bobet, and T. E. Nantung, Correlation between Resilient Modulus (MR) of

Soil, Light Weight Deflectometer (LWD), and Falling Weight Deflectometer (FWD).

2018.

[14] O. J.-M. Hoffmann, B. B. Guzina, and A. Drescher, “Stiffness Estimates Using Portable

Deflectometers,” Transp. Res. Rec. J. Transp. Res. Board, vol. 1869, no. 1, pp. 59–66,

2007.

[15] S. Khosravifar, “Maryland department of tranportation state highway administration

research report standardizing lightweight deflectometer modulus measurements for

compaction quality assurance Dr . Charles W . Schwartz , Zahra Afsharikia , University of

Maryland,” no. September, 2017.



[16] K. A. Alshibli, M. A. Farsakh, and E. Seyman, “Laboratory Evaluation of the Geogauge

and Light Falling Weight Deflectometer as Construction Control Tools,” J. Mater. Civ.

Eng., vol. 17, no. October, pp. 560–569, 2005.

[17] M. J. Sulewska and G. Bartnik, “Application of the Light Falling Weight Deflectometer

(LFWD) to Test Aggregate Layers on Geosynthetic Base,” Procedia Eng., vol. 189, no.

May, pp. 221–226, 2017.

[18] O. Elbagalati, M. Elseifi, K. Gaspard, and Z. Zhang, “Development of the pavement

structural health index based on falling weight deflectometer testing,” Int. J. Pavement

Eng., pp. 1–8, 2016.

[19] G. Zang, L. Sun, Z. Chen, and L. Li, “A nondestructive evaluation method for semi-rigid

base cracking condition of asphalt pavement,” Constr. Build. Mater., vol. 162, pp. 892–

897, 2018.

[20] A. Goel and A. Das, “Nondestructive testing of asphalt pavements for structural condition

evaluation: A state of the art,” Nondestruct. Test. Eval., vol. 23, no. 2, pp. 121–140, 2008.

[21] T. Saarenketo and T. Scullion, “Road evaluation with ground penetrating radar,” J. Appl.

Geophys., vol. 43, no. 2–4, pp. 119–138, 2000.

[22] A. Benedetto, F. Tosti, and L. Di Domenico, “Elliptic model for prediction of deflections

induced by a light falling weight deflectometer,” J. Terramechanics, vol. 49, no. 1, pp. 1–

12, 2012.

[23] A. Kavussi, K. Rafiei, and S. Yasrobi, “Evaluation of PFWD as potential quality control

tool of pavement layers,” J. Civ. Eng. Manag., vol. 16, no. 1, pp. 123–129, 2010.

[24] C. T. Senseney and M. A. Mooney, “Characterization of Two-Layer Soil System Using a

Lightweight Deflectometer with Radial Sensors,” Transp. Res. Rec. J. Transp. Res. Board,

vol. 2186, no. 2186, pp. 21–28, 2010.

[25] J. P. Bilodeau and G. Doré, “Stress distribution experienced under a portable light-weight

deflectometer loading plate,” International Journal of Pavement Engineering, vol. 15, no.

6. Taylor & Francis, pp. 564–575, 2014.

[26] A. Patrick Icenogle and M. Sharear Kabir, “Evaluation of Non-Destructive Technologies

for Construction Quality Control of HMA and PCC Pavements in Louisiana LTRC

Project Number: 09-5C SIO Number: 30000153 13. Type of Report and Period Covered

Final Report,” 2013.

[27] D. H. Chen and T. Scullion, “Forensic Investigations of Roadway Pavement Failures,” J.

Perform. Constr. Facil., vol. 22, no. 1, pp. 35–44, 2008.

[28] A. Loulizi, I. Al-Qadi, and S. Lahouar, “Optimization of ground-penetrating radar data to

predict layer thicknesses in flexible pavements,” J. Transp. …, vol. 129, no. February, pp.

93–100, 2003.

[29] D. A. Willett and B. Rister, “Ground Penetrating Radar „pavement layer thickness

evaluation,‟” 2002.

[30] I. L. Al-Qadi and S. Lahouar, “Measuring layer thicknesses with GPR – Theory to

practice,” Constr. Build. Mater., vol. 19, pp. 763–772, 2005.

[31] D. A. Willett, K. C. Mahboub, and B. Rister, “Accuracy of Ground-Penetrating Radar for

Pavement-Layer Thickness Analysis,” J. Transp. Eng., vol. 132, no. 1, pp. 96–103, 2006.

[32] A. Loizos and C. Plati, “Accuracy of pavement thicknesses estimation using different

ground penetrating radar analysis approaches,” NDT E Int., vol. 40, no. 2, pp. 147–157,

2007.

[33] R. L. Lytton, “Backcalculation of Pavement Layer Properties,” Astm, no. September,

2012.IRC:115,

[34] “IRC:115 „Guidelines For Structural Evaluation and Strengthening of Flexible Road

Pavements using Falling Weight Deflectometer (FWD) Technique,‟” pp. 765–765, 2014.

structural properties evaluation for flexible … · with the structural capacity of the pavement...

Documents