1. Laval University’s experience with the wide-base single tires
Guy Doré

2. 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

3. Project partners Quebec ministry of transportation (MTQ)
Transport Robert
Michelin Canada
Laval University

4. Project outline
State of the art
Field testing
Spring time
Summer time

5. 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)

6. The heavy vehicle – pavement interaction section at the SERUL

7. 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)

8. Multi-level deflectometre
Epoxy/aggregates plate
7,60 m
Strain gauges
0,30 m #7 #5 #6
Travel direction
Multi-level deflectometre
Strain gauges
300 mm
800 mm
1100 mm
2500 mm
# 1
# 2
# 3
# 4
100 mm
Instrumentation layout

9. Multi-depth deflectometer

10. Fibre optic horizontal strain sensors

11. Test plate including an array of 60 strain sensors at shallow depth in epoxy concrete
V V20 V19 V V17 V16 V V14 V13 V12 V11 V10 V9 V8 V V V5 V V3 V2 V1
L L L L L L40
TR36 TR TR TR TR32 TR TR30

12. Testing protocol General: Semi-trailer with tandem axle
Tests done under a moving load (50 km/h) for er and ez
One test = average of 5 valid passes (within 50 mm of target)
Test done under static loading for es
All tests conducted relative to a standard load (BB truck)

13. Testing protocol Specific factors Type of tyre 5 levels of loading
Dual 11R22,5 & 12R22,5
Single 385 & 455
5 levels of loading
3000 – 7000 kg
3 levels of tyre pressure
560 – 730 – 900 kPa

14. Test vehicles

15. Typical results Characteristics of tire contact area
Vertical displacements of pavement interfaces – Vertical strains in pavement layers

16. Typical results Horizontal strains at the base of the HMAC layer
Vertical and shear strains at shallow depth in test plate

17. Results highlights: Vertical strains on SS (structural rutting)
For same load level: no significant effect of tyre type or tire pressure (as expected)

18. Results highlights Horizontal strains (spring) at the base of the HMAC layer (Fatigue cracking)
Transversal
Longitudinal
WBST 25% - 65% more damaging during spring time

19. Results highlights: Horizontal strains (summer) at the base of the HMAC layer (Fatigue cracking)
Longitudinal
Transversal
WBST from 55% less to 50% more damaging during summer time

20. Results highlights Horizontal strains at the base of the HMAC layer (Fatigue cracking)
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

21. Results highlights: Strains at shallow depth in bound material (stability rutting – TD cracking)
455
33% reduction in vertical strains
30% reduction in shear strains

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

23. Conclusion
Systematic investigation on the effect of WBST on pavements based on experimental results
Tests valid for mid-class roads for results based on ev and eh
Test valid for mid to high class roads for results based on es

24. 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

25. Future research activities
Effects of WBST on low volume roads
Thin HMAC
Surface treatment
i3C industrial research chair