Guy Doré

Laval University’s experience with the wide-base single tires

Project background

• Trucking industry pushing for unrestricted use of WBST

• Highway administrations concerned about possible damage to pavement networks

• Decision to conduct experimental work to try to quantify impact of WBST on pavement performance

Project partners

• Quebec ministry of transportation (MTQ)

• Transport Robert

• Michelin Canada

• Laval University

Project outline

• State of the art

• Field testing– Spring time– Summer time

Test site

• Laval University Road Experimental Site (SERUL)

• Test section of vehicle-pavement interaction• « Typical » pavement structure:

– 100 mm HMAC– 200 mm DGAB– 450 mm GSB– Relatively stiff subgrade soil (silty till)

Pa villo nFo rê t M o ntm o re nc y

The heavy vehicle – pavement interaction section at the SERUL

Pavement instrumentation

• Pavement condition– Temperature sensors– Moisture sensors

• Pavement response– Vertical strain in pavement layers (MDD - ez)– Horizontal strains at base of bound layer (eh)– X-Y-Z strains at shallow depth in bound layer

(es)

Epoxy/aggregates plate

7,60 m

Strain gauges0,30 m

0,30 m

#7

#5

#6

Travel direction

Multi-level deflectometreStrain gauges

300 mm

800 mm

1100 mm

2500 mm

#1

#2

#3

#4

100 mm

Instrumentation layout

Multi-depth deflectometer

Fibre optic horizontal strain sensors

T1 T2

T3 T4

V21 V20 V19 V18 V17 V16 V15 V14 V13 V12 V11 V10 V9 V8 V7 V6 V5 V4 V3 V2 V1

L45 L44 L43 L42 L41 L40

TR36 TR35 TR34 TR33 TR32 TR31 TR30

Test plate including an array of 60 strain sensors at shallow depth in epoxy concrete

Testing protocol

• General:– Semi-trailer with tandem axle– Tests done under a moving load (50 km/h) for

r and z

• One test = average of 5 valid passes (within 50 mm of target)

– Test done under static loading for s

– All tests conducted relative to a standard load (BB truck)

Testing protocol

• Specific factors– Type of tyre

• Dual 11R22,5 & 12R22,5

• Single 385 & 455

– 5 levels of loading• 3000 – 7000 kg

– 3 levels of tyre pressure

• 560 – 730 – 900 kPa

Test vehicles

-0,1

-0,05

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0,4

0 0,5 1 1,5 2 2,5 3

Dé

fle

xio

n b

rute

(m

m)

Temps (seconde)

Deflecto 1

Deflecto 2

Deflecto 3

Deflecto 4

Characteristics of tire contact area

Vertical displacements of pavement interfaces – Vertical strains in pavement layers

Typical results

-350

-300

-250

-200

-150

-100

-50

0

50

100

0 100 200 300 400 500 600

Position on the instrumented plate (mm)

Str

ain

(10

-6 m

m/m

m) 0

50

100

150

200

250

300

350

-50

0

50

100

150

200

250

300

350

0 0,5 1 1,5 2 2,5

Time (s)

Str

ain

(1

0^

-6m

m/m

m)

Horizontal strains at the base of the HMAC layer

Vertical and shear strains at shallow depth in test plate

Typical results

Results highlights:Vertical strains on SS

(structural rutting)

• For same load level: no significant effect of tyre type or tire pressure (as expected)

Results highlightsHorizontal strains (spring) at the base of the HMAC layer (Fatigue cracking)

0

0,5

1

1,5

2

2,5

2500 3500 4500 5500 6500 7500

Charge (kg/demi-essieu)

Dˇfo

rmat

ion

(x 1

0-6

m

m/m

m)

12R22,511R22,5385455

WBST 25% - 65% more damaging during spring time

0

0,5

1

1,5

2

2,5

2500 3500 4500 5500 6500 7500

Charge (kg/demi-essieu)

Dˇfo

rmat

ion

(10

-6

mm

/mm

)

12R22,511R22,5385455

Longitudinal Transversal

Results highlights:Horizontal strains (summer) at the base

of the HMAC layer (Fatigue cracking)

WBST from 55% less to 50% more damaging during summer time

0

0,2

0,4

0,6

0,8

1

1,2

1,4

2500 3500 4500 5500 6500 7500

Charge (kg/demi-essieu)

Dˇfo

rmati

on (1

0-6

mm/

mm)

12R22,511R22,5385455

0

0,5

1

1,5

2

2,5

2500 3500 4500 5500 6500 7500

Charge (kg/demi-essieu)

Dˇfo

rmati

on (1

0-6

mm/

mm)

12R22,511R22,5385455

Longitudinal Transversal

• Horizontal strains at base of bound layer (Fatigue cracking)– WBST more damaging than dual tyres during

spring thaw– WBST slightly more damaging than dual tyres

during summer

Results highlightsHorizontal strains at the base of the

HMAC layer (Fatigue cracking)

Results highlights:Strains at shallow depth in bound

material (stability rutting – TD cracking)

0

50

100

150

200

250

300

350

400

450

0 1000 2000 3000 4000 5000 6000 7000 8000

Charge (kg/demi-essieu)

Défo

rmat

ion

(x 10̂

-6 m

m/mm

)

11R22,5

12R122,5

385

455

560 600 640 680 720 760 800 840 880T ire p ressure (kPa)

3 0

4 0

5 0

6 0

7 0

8 0

9 0

1 0 0

CS

(°)

Legend11R 22.5 - 3000 kg/ha lf ax le

455/55R 22.5 - 3000 kg /ha lf ax le

11R 22.5 - 5000 kg/ha lf ax le

455/55R 22.5 - 5000 kg /ha lf ax le

11R 22.5 - 7000 kg/ha lf ax le

455/55R 22.5 - 7000 kg /ha lf ax le

11R22,5

455

33% reduction in vertical strains 30% reduction in shear strains

Results highlights

• Strains at shallow depth in bound layer (stability rutting – TD cracking)– WBST less damaging than dual tyres

Conclusion

• Systematic investigation on the effect of WBST on pavements based on experimental results

• Tests valid for mid-class roads for results based on v and h

• Test valid for mid to high class roads for results based on s

Conclusion

• Experimental results suggest:– Based on structural rutting criteria: no

significant difference between WBST and dual tires

– Based on a fatigue cracking criteria: WBST appear to cause more damage than dual tires and more specifically during spring time

– Based on stability rutting criteria: WBST appear to cause less damage than dual tires

Future research activities

• CTI

• Effects of WBST on low volume roads– Thin HMAC– Surface treatment

• i3C industrial research chair