Improved Performance Evaluation of Road Pavements by Using …asphalt.csir.co.za/sim/sim web/2010-presentation tire... · 2011-05-19 · Improved Performance Evaluation of Road Pavements

Improved Performance Evaluation of Road Pavements by

Using Measured Tyre LoadingJames Maina and Morris De Beer

CSIR Built Environment, South Africa

© CSIR 2008 www.csir.co.za

•• Part 1:Part 1:•• General introduction;General introduction;•• Quality and importance of road infrastructure in SA;Quality and importance of road infrastructure in SA;•• Trucks on our road infrastructure;Trucks on our road infrastructure;•• Truck tyre loading and stresses;Truck tyre loading and stresses;•• StressStress--InIn--Motion (SIM) Technology;Motion (SIM) Technology;•• Typical StressTypical Stress--InIn--Motion (SIM) Data;Motion (SIM) Data;•• Part 2:Part 2:•• Equations for mechanistic road analysis;Equations for mechanistic road analysis;•• Analysis for multiple loading;Analysis for multiple loading;•• Strain Energy of Distortion (SED);Strain Energy of Distortion (SED);•• Worked Examples and Analytical Results;Worked Examples and Analytical Results;•• Summary of research findings;Summary of research findings;•• Recommendations.

Paper today: Paper today: ““Improved Performance Evaluation of Road Improved Performance Evaluation of Road Pavements by Using Measured Tyre LoadingPavements by Using Measured Tyre Loading””

Recommendations.


SOUTH AFRICAN SOUTH AFRICAN MAJOR PAVED MAJOR PAVED ROAD NETWORK ROAD NETWORK ~ 20 000 km~ 20 000 km

BackgroundBackground……

•• SA: 750 000 km of roads SA: 750 000 km of roads -- 20 % paved;20 % paved;•• Road Pavement Engineering critical for upgrade & Road Pavement Engineering critical for upgrade &

sustainability of road infrastructure;sustainability of road infrastructure;•• Locally developed StressLocally developed Stress--InIn--Motion (SIM) study part Motion (SIM) study part

of this process;of this process;•• Analytical: Strain Energies of Distortion (SEDs) at Analytical: Strain Energies of Distortion (SEDs) at

various sections within the road pavement various sections within the road pavement structure were determined structure were determined –– good promise !;good promise !;



7 700 km National Roads in SA of

Freeway/Expressway standard

7 700 km National Roads in SA of

Freeway/Expressway standard

•• The 4The 4thth annual State of Logistics Survey for SA annual State of Logistics Survey for SA indicated that total indicated that total land transportland transport accounted for accounted for 1,5 billion tonnes1,5 billion tonnes, with recent , with recent growth of highergrowth of higherthan 5 per centthan 5 per cent, mainly captured by the road , mainly captured by the road transport sector, as opposed to the transport sector, as opposed to the rail sectorrail sectorcarrying only 0.2 billion tonnes.carrying only 0.2 billion tonnes.


Freight Transport in SAFreight Transport in SA…….(CSIR .(CSIR -- 44thth SA SA Logistics Report, 2007).Logistics Report, 2007).


Freight Transport in SAFreight Transport in SA…….(CSIR .(CSIR -- 44thth SA SA Logistics Report, 2007).Logistics Report, 2007).

Figure 1. Historical freight transport data (CSIR, 2007).

Traffic Volumes and Road DamageTraffic Volumes and Road Damage……..

•• Traffic volumes on our national highways are at all Traffic volumes on our national highways are at all time highs, for example, N3 has already carried time highs, for example, N3 has already carried the the equivalence of 20 yearsequivalence of 20 years of traffic over the of traffic over the last two years.last two years. (..2007..)(..2007..)

••Daily, newspapers carry articles on potholes and Daily, newspapers carry articles on potholes and other road shortcomings which cost motorists in other road shortcomings which cost motorists in excess of R200 billionexcess of R200 billion a year (News24, 2008).a year (News24, 2008).

It is therefore not surprising that there have been numerous calIt is therefore not surprising that there have been numerous calls ls for extensive revision of important parts of the SA road pavemenfor extensive revision of important parts of the SA road pavement t design method in order to cope with the new traffic realities, design method in order to cope with the new traffic realities, amongst other factors.amongst other factors.



Heavy VehiclesHeavy Vehicles……..

Growth in Heavy Vehicle (HV) TrafficGrowth in Heavy Vehicle (HV) Traffic……

•• In terms of growth in HVs on the toll portion of the In terms of growth in HVs on the toll portion of the road, the rate was approximately 8 per cent road, the rate was approximately 8 per cent since 2002since 2002--2007, 2007, 20 per cent 200620 per cent 2006--20072007, and , and almost 40 per centalmost 40 per cent between February and between February and October 2007. October 2007.

•• The N3 is therefore the national road with the The N3 is therefore the national road with the highest growth and HV composition in SA (Le highest growth and HV composition in SA (Le Roux, 2007).Roux, 2007).



More Specific issues in Paper todayMore Specific issues in Paper today……

•• South African Roads, Trucks @ Road Damage; South African Roads, Trucks @ Road Damage; •• Introduction into StressIntroduction into Stress--InIn--Motion (SIM) technology;Motion (SIM) technology;•• Tyre Studies with Heavy Vehicle Simulator (HVS);Tyre Studies with Heavy Vehicle Simulator (HVS);•• Full Scale SIM Testing @ N3Full Scale SIM Testing @ N3--Traffic Control Centre Traffic Control Centre

(TCC) (TCC) --Heidelberg, SA @ typical SIM Results;Heidelberg, SA @ typical SIM Results;•• Implications for Road Surface Design and Road Implications for Road Surface Design and Road

Preservation/Protection Preservation/Protection –– Analytical Evaluations..Analytical Evaluations..

•• Summary, Conclusions and RecommendationsSummary, Conclusions and Recommendations


Vehicle-Tyre-Pavement Interaction:

STRESS-IN-MOTION (SIM)Technology

Vehicle-Tyre-Pavement Interaction:

STRESS-IN-MOTION (SIM)Technology


Thin Asphalt Surfacings (30 mm to 50 mm) on crushed rock: Economical in dry regions.

Thin Asphalt Surfacings (30 mm to 50 mm) on crushed rock: Economical in dry regions.

North of Buccleuch facing South2008/11/13; 17:05:40

From: http://www.i-traffic.co.za/index.php?q=cameras

At Buccleuch2008/11/13; 17:05:40


Truck Tyre Inflation Pressure in South AfricaTruck Tyre Inflation Pressure in South Africa

FIGURE 1AVERAGE MEASURED TYRE INFLATION PRESSURE DISTRIBUTIONS

OF HEAVY VEHICLES (AXLE LOADS > 7 000 kg) ON ROADSIN THE PROVINCE OF GAUTENG, SOUTH AFRICA

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 15000

5

10

15

20

25

TYRE INFLATION PRESSURE (kPa)

% O

F TY

RE

PRES

SUR

E PE

R 5

0 kP

a IN

TER

VAL

Van Vuuren (1974) De Beer (1995)

Average: 620 kPa Average: 733 kPa

c:/capsaf1.wmf

~ 20 % Increase

in 20

Years


Road DamageRoad Damage……..


EXAMPLES OF ROAD SURFACE FAILURES..

Surface Disintegration…

SURFACE DISINTEGRATION

RUTTING Fatigue Cracking and aging

POTHOLES : Water & Loads …

Water & Safety…

D elam in ation ..

Longitudinal Flow of AsphaltLongitudinal Flow of AsphaltLongitudinal Flow of Asphalt

Tyres and Road Structures…..Tyres and Road StructuresTyres and Road Structures……....

……from SANRAL: from SANRAL: www.nra.co.zawww.nra.co.za


Modern Tyre science…Modern Tyre scienceModern Tyre science…””SectometerSectometer””

S. Eckens, 1928S. Eckens, 1928


Gautrans Heavy Vehicle Simulator (HVS) Mark IV+:Gautrans Heavy Vehicle Simulator (HVS) Mark IV+:Loading Device for Controlled loading tests on roads..Loading Device for Controlled loading tests on roads..


LOADS & STRESSES FROM TYRES:LOADS & STRESSES FROM TYRES:

+Z

+X

Tyre Rotation

+Y


425 /65 R22.5 HVS TYRE ON SIM SYSTEM425 /65 R22.5 HVS TYRE ON SIM SYSTEM


StressStress--InIn--Motion testing with HVSMotion testing with HVSDual Load Configuration Dual Load Configuration –– Twin SIM padsTwin SIM pads


STRESSSTRESS--ININ--MOTION TESTING USING THE HVSMOTION TESTING USING THE HVS

TYRE DEFLECTION & TYRE PRINTSTYRE DEFLECTION & TYRE PRINTS……



TYRE DEFLECTION & TYRE PRINTSTYRE DEFLECTION & TYRE PRINTS……

315/80 R22.5 HVS Tyre: 315/80 R22.5 HVS Tyre: OverloadedOverloaded


Overloading on Tyres….and contact with road..Overloading on TyresOverloading on Tyres…….and contact with road...and contact with road..

Tyre Contact Patches:Tyre Contact Patches:(square not circular)(square not circular)……


- Circular;- Variable Vertical load;- Variable pressure, but UNIFORM &No Shear Forcesincluded.

-- Circular;Circular;-- Variable Vertical load;Variable Vertical load;-- Variable pressure, Variable pressure, but UNIFORM &but UNIFORM &No Shear ForcesNo Shear Forcesincluded.included.

Tyre Loading, P (kN)Tyre Loading, P (kN)

Uniform Contact Stress, q (kPa)

Assumption of Tyre Loading Assumption of Tyre Loading -- Pavement Design Pavement Design Modeling:Modeling:



Dual Tyre: 3D-Contact Stresses (Pressure)…Dual Tyre: 3DDual Tyre: 3D--Contact Stresses (Pressure)Contact Stresses (Pressure)……

Stress Ratio: 10:3:1

Stress Stress Ratio: Ratio: 10:3:1 10:3:1


Typical SIM 3D Data Sets Typical SIM 3D Data Sets -- Variable loading:Variable loading:

3D 3D –– Z,X,Y Z,X,Y --Contact Stresses: Contact Stresses:

Variable loads: Variable loads: 315/80 R22.5 Tire315/80 R22.5 Tire


TYRE “FINGER PRINTING”: (11R22.5 TYRE)…

TYRE INFLATION PRESSURE

TYRE

LOAD


Truck Weighing Truck Weighing -- National Road 3 (N3), near Heidelberg National Road 3 (N3), near Heidelberg in Gautengin Gauteng……..


QUAD SIM PAD TESTING AT WEIGHQUAD SIM PAD TESTING AT WEIGH--BRIDGE SITE:BRIDGE SITE:N3 NORTH N3 NORTH –– HEIDELBERG TRAFFIC CONTROL CENTREHEIDELBERG TRAFFIC CONTROL CENTRE

4 x SIM Scales4 x SIM Scales


Quad (full) SIM pad configuration at a typical Quad (full) SIM pad configuration at a typical weighbridge site on National Road 3 (N3), near weighbridge site on National Road 3 (N3), near Heidelberg in GautengHeidelberg in Gauteng


Examples of StressExamples of Stress--InIn--Motion (SIM) Testing on theMotion (SIM) Testing on theN3 N3 –– Freeway near HeidelbergFreeway near Heidelberg……..


Quad (full) SIM pad configuration at a typical weighbridge site Quad (full) SIM pad configuration at a typical weighbridge site on on National Road 3 (N3), near Heidelberg in GautengNational Road 3 (N3), near Heidelberg in Gauteng


Quad (full) SIM Scale on National Road 3 (N3), near Quad (full) SIM Scale on National Road 3 (N3), near Heidelberg in GautengHeidelberg in Gauteng ……..


SIM Measurement: N3SIM Measurement: N3-- ““12321232”” TankerTanker……


SIM In operation SIM In operation –– N3N3--TCC TCC …………..


SIM Scales: Accuracy checking @ N3SIM Scales: Accuracy checking @ N3--TCCTCC……

SIM vs MULTI-DECK STATIC AND DAW 50 at N3-TCC (Heidelberg) (GVM/GCM)

05

10152025303540455055606570

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

SIM (Tonne)

STA

TIC

& D

AW

50

Sca

les

(Ton

ne)

STATIC (1861) DAW50 (1501) Line of Equality Linear (STATIC (1861)) Linear (DAW50 (1501))

STATIC = 1.0025 x SIM(n = 1 245), R2 = 0.99;

Std. Y-Error: 1.37 Tonne;Std. Error (Coef) :

0.0001.

DAW 50 = 0.9931 x SIM (n = 1 245), R2 = 0.99;

Std Y-Error: 1.42 Tonne;Std. Error (Coef):

0.00011.

D:\ICAP-2006\[MODIFIED-2SEPT-17OCT-ICAP-2006.xls]Total Load-GVM-GCM-

N3 TCC - SELECTED HEAVY VEHICLE (HV) TRUCK TYRE PRESSURE DATA (26 Feb 2003 - 06 March 2003)

0

0.2

0.4

0.6

0.8

1

1.2

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500

TYRE INFLATION PRESSURE (kPa)

Nor

mal

ised

Fre

quen

cy

LEFT-FRONT-(225 tyres) RIGHT-FRONT-(225 tyres) REST-LEFT-(845) REST-RIGHT-(845)

H:\CAPSA04\[Tyre Inflation Pressure Information-MORTON-MDB-

Tyre Inflation Pressure Distributions Tyre Inflation Pressure Distributions –– N3N3-- 20032003


GVM/GCM-SIM N3 TCC - 2003RESULT RATINGS 1 AND 2 (n = 2 297)

[2 Sept - 17 Oct 2003]

0

25

50

75

100

125

150

175

200

225

250

1.000

4.000

7.000

10.00

013

.000

16.00

019

.000

22.00

025

.000

28.00

031

.000

34.00

037

.000

40.00

043

.000

46.00

049

.000

52.00

055

.000

58.00

061

.000

64.00

067

.000

70.00

073

.000

76.00

079

.000

82.00

0

Bin: Vehicle Mass: GVM/GCM [Tonne]

Num

ber o

f Tru

cks

15 Tonne

29 Tonne

51 Tonne


Gross Vehicle Mass (GVMs)Gross Vehicle Mass (GVMs)…………..

ALL TYRES MEASURED: n = 45 227 (This Study) - N3 -TCC-2003

0

200

400

600

800

1000

1200

1400

1600

0.050

0.300

0.550

0.800

1.050

1.300

1.550

1.800

2.050

2.300

2.550

2.800

3.050

3.300

3.550

3.800

4.050

4.300

4.550

4.800

Bin: Tyre Mass Weight [Tonne]

Num

ber o

f Tyr

es

0

20

40

60

80

100

120

All Other Tyres Axle 1 Left Axle 1 Right

Steering Tyres:

2.95 Tonne

All other Tyers:

1.9 Tonne

H:\ICAP-2006 Summary N3 TCC-FINAL-4-B-ICAP-2006.xls TYRES-1-2 -Histogram-Paper (2)

Axle Mass Distributions Axle Mass Distributions –– N3N3-- 20032003


Vertical Stress Cumulative Frequency Vertical Stress Cumulative Frequency –– N3N3-- 20032003



Measured Tyre Foot PrintsMeasured Tyre Foot Prints :Two Axle Truck Two Axle Truck –– Vertical Vertical Contact Stress Contact Stress ––……....


4 Axle Truck4 Axle Truck……..








Eight (8) Axle Truck Eight (8) Axle Truck –– Vertical Contact Vertical Contact Stress Stress -- Foot PrintsFoot Prints……..



10 20 30 40 50 60 70 80

50

100

150

200

250

300

350

400

450

Across the SIM pads

Cou

nts

TEST 009: KTD 904 GP 13/10/2003: AXLE 1

266 mm; 3.739 Ton 185 mm; 1.938 Ton

STEERING AXLE STEERING AXLE –– UNEQUAL LOADINGUNEQUAL LOADING…………..


10 20 30 40 50 60 70 80

50

100

150

200

250

300

350

400

450

500

550

Across the SIM pads

Cou

ntsTEST 768-09/10/2003: DDT235N AXLE 2

189 mm;0.037 Ton

297 mm;4.312 Ton

202 mm;1.874 Ton

194 mm;1.223 Ton

TYRE BARELY IN CONTACT WITH SURFACETYRE BARELY IN CONTACT WITH SURFACE

UNEQUAL LOADING ON TRUCK TYRESUNEQUAL LOADING ON TRUCK TYRES……..


10 20 30 40 50 60 70 80

50

100

150

200

250

300

350

Across the SIM pads

Cou

nts

TEST 765: NKR 9519 - 09/10/2003 AXLE 2244 mm;1.782 Ton

196 mm;1.032 Ton

195 mm;0.661 Ton

AXLE 2: MISSING TYRE !! AXLE 2: MISSING TYRE !!

P/σ

Surfacing: h1, E1, v1

SelectedLayer:

h4, E4, v4

BaseLayer:

h2, E2, v2

Subgrade/Foundation:

h5, E5, v5

SubbaseLayer:

h3, E3, v3

APPLIED LOAD/STRESSESP/σ

Pavement Response:

Stresses &

Strains

StressRotation

Vertical,Longitudinal &

Lateral 3D ContactStresses

Side view of tyre

End viewof tyre

ANALYTICAL ROAD PAVEMENT MODELANALYTICAL ROAD PAVEMENT MODEL……..



General Features & AssumptionGeneral Features & AssumptionGeneral Features & Assumption

Pavement: Multilayer elastic system with a possibility of interface slip.

Surface load: Single/Multiple circular loads.

Analysis: Single/Multiple points of interest.

Response: Stresses, strains, and displacements


Uniformly distributed circular loadUniformly distributed circular load

vertical + horizontal loadsVertical

loadHorizontal load

surfaceBase

Subgrade


θr

x

y

z

Load

τrzτrz

σθσr

σz

τzθτzθ

τrθτrθ

Stresses within a Road Pavement Structure- rθz Axes -Stresses within a Road Pavement StructureStresses within a Road Pavement Structure-- rrθθzz Axes Axes --


Stresses within a Road Pavement Structure..Stresses within a Road Pavement Structure..Stresses within a Road Pavement Structure..


y

x

θ r

τrz=τzr

z

z

σz

τzθ=τθz

τrθ=τθrσθ

σrArrows give directions for positive sign

Local Cartesian and cylindrical coordinates

Global Cartesian coordinate system

θ

Stress acting on an element

Y

X

Z

αload

r


Multilayer Structural Model:Multilayer Structural Model:Multilayer Structural Model:

2a

measurement point

X

Y

(0, 0, 0)

(X0+r Cos(θ +α), Y0+r Sin(θ +α), 0)

y

xrθ

α

h1

h2

hi-1

hi

E1

E2

Ei-1

Ei

En

ν1

ν2

νi-1

νn

νi

Layer Modulus Poisson’s ratio



- Circular;- Variable Vertical load;- Variable pressure, but UNIFORM &No Shear Forcesincluded.

-- Circular;Circular;-- Variable Vertical load;Variable Vertical load;-- Variable pressure, Variable pressure, but UNIFORM &but UNIFORM &No Shear ForcesNo Shear Forcesincluded.included.

Tyre Loading, P (kN)Tyre Loading, P (kN)

Uniform Contact Stress, q (kPa)

Assumption of Tyre Loading Assumption of Tyre Loading -- Pavement Design Pavement Design Modeling:Modeling:



SIM systems..SIM systems..


RuttingRutting-- Controlled testing with Heavy Vehicle Controlled testing with Heavy Vehicle Simulator (HVS)Simulator (HVS)……

Controlled Field Tests with HVS…on R80 route.


Wide Base Single TyreWide Base Single Tyre-- Input Data: Vertical Input Data: Vertical Stress Patterns: Stress Patterns: ““nn”” and and ““mm”” –– ShapesShapes……

“n – Shape” “m – Shape”


Wide Base Single TyreWide Base Single Tyre-- Input Data: Vertical Input Data: Vertical Stress Patterns: Stress Patterns: ““nn”” and and ““mm”” –– ShapesShapes……

“n – Shape” “m – Shape”


RuttingRutting-- Controlled testing with Heavy Vehicle Controlled testing with Heavy Vehicle Simulator (HVS)Simulator (HVS)……


Vertical Tyre Stress: Vertical Tyre Stress: ““nn--ShapeShape”” tyre stress tyre stress results in results in ““nn--ShapeShape”” rutting in asphalt overlay..rutting in asphalt overlay..


Vertical Tyre Stress: Vertical Tyre Stress: ““mm--ShapeShape”” stress result in stress result in ““mm--ShapeShape”” rutting in asphalt overlay..rutting in asphalt overlay..


Vertical Tyre Stress: Vertical Tyre Stress: ““nn--ShapeShape”” tyre stress tyre stress distributiondistribution


Strain Energy of Distortion (SED) on road Strain Energy of Distortion (SED) on road surface: From surface: From ““nn”” –– Shape single tyre stressShape single tyre stress……


Vertical Tyre Stress: Vertical Tyre Stress: ““nn--ShapeShape”” tyre stress tyre stress distribution.distribution.


Road Surface: Strain Energy of Distortion (SED) Road Surface: Strain Energy of Distortion (SED) –– from from ““n n –– ShapeShape”” single tyre stresssingle tyre stress……


Road Surface: Strain Energy of Distortion (SED) Road Surface: Strain Energy of Distortion (SED) –– from from ““n n –– ShapeShape”” single tyre stresssingle tyre stress……


Strain Energy of Distortion (SED)Strain Energy of Distortion (SED)-- ““nn”” and and ””m m ––ShapeShape”” -- dual tyres..dual tyres..……..


Strain Energy of Distortion (SED) Strain Energy of Distortion (SED) –– Dissipation Dissipation with road pavement depthwith road pavement depth……

50 mm AC layer50 mm AC layer

1 x Truck 1 x Truck -- 30 Tyres: 1 mm x 1 mm resolution 30 Tyres: 1 mm x 1 mm resolution –– 500k points 500k points ––SED under Steering Axle SED under Steering Axle …………


50 mm AC layer50 mm AC layer


……SED under Steering AxleSED under Steering Axle


Summary, Conclusions (1):Summary, Conclusions (1):Summary, Conclusions (1):

•• South African Roads, Trucks @ Road Damage South African Roads, Trucks @ Road Damage –– real real cause of concern; cause of concern;

•• Tyre Studies with Heavy Vehicle Simulator (HVS); Tyre Studies with Heavy Vehicle Simulator (HVS); •• Successful Demonstration Successful Demonstration -- StressStress--InIn--Motion (SIM) Motion (SIM)

technology;technology;•• Analytic approach Analytic approach -- SED shows good promise for SED shows good promise for

further implementation;further implementation;•• Implications for Road Surface Design and Road Implications for Road Surface Design and Road

Preservation/Protection Preservation/Protection –– Important to be Important to be implemented;implemented;

•• SIM future of existing WeighSIM future of existing Weigh--InIn--Motion (WIM) ??.Motion (WIM) ??.


Summary, Conclusions (2):Summary, Conclusions (2):Summary, Conclusions (2):

•• The concept of SED as a response parameter that The concept of SED as a response parameter that quantifies road pavementquantifies road pavement’’s s ““potential for failurepotential for failure””: : seems to resonate well with the applied tyre stresses seems to resonate well with the applied tyre stresses and its different shapes. and its different shapes.

•• Single wide base tyres induce more than double the Single wide base tyres induce more than double the potential for failure compared with the dual tyre potential for failure compared with the dual tyre configuration on the same road pavement. configuration on the same road pavement.

•• UnderUnder--inflatedinflated--heavilyheavily--loaded tyres may cause more loaded tyres may cause more damage on the surface of the road compared to damage on the surface of the road compared to correctly inflated tyres. correctly inflated tyres.

•• The combination of SIM technology and SED from The combination of SIM technology and SED from numerical modelling may be used to identify areas of numerical modelling may be used to identify areas of high potential for failure on the road pavement high potential for failure on the road pavement system.system.


Conclusions- based on SED Evaluation:…ConclusionsConclusions-- based on SED based on SED Evaluation:Evaluation:……

•• Depending on the shape of the vertical contact stress Depending on the shape of the vertical contact stress distribution, the damaging effect in terms of SED of distribution, the damaging effect in terms of SED of the single tyre appears to be 2.0 to 4.3 times higher the single tyre appears to be 2.0 to 4.3 times higher than dual tyres under the same total loading.than dual tyres under the same total loading.

•• For both tyres, the damaging effect appears to be For both tyres, the damaging effect appears to be between 1.7 and 3.5 higher for the mbetween 1.7 and 3.5 higher for the m--shape contact shape contact stress distribution.stress distribution.

•• The top 5 mm to 10 mm of road pavements is The top 5 mm to 10 mm of road pavements is potentially more prone to failure (toppotentially more prone to failure (top--down cracking down cracking or rutting) than was perhaps realised in the past.or rutting) than was perhaps realised in the past.


Recommendations:Recommendations:Recommendations:

•• Further research work is needed to establish Further research work is needed to establish if this trend of tyre type is similar for all road if this trend of tyre type is similar for all road pavement structures in South Africa before it pavement structures in South Africa before it is safe to argue against the use of is safe to argue against the use of single tyres single tyres vs dual tyresvs dual tyres or make recommendation on or make recommendation on tyre inflation pressure for HVs.tyre inflation pressure for HVs.

•• Implementing concept of SED in road design; Implementing concept of SED in road design;

Thank You for listening today……any Questions ?


Documents

Improved Performance Evaluation of Road Pavements by Using …asphalt.csir.co.za/sim/sim web/2010-presentation tire... · 2011-05-19 · Improved Performance Evaluation of Road Pavements