Guy Dor

1
Laval Universitys 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
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
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
• 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 highlightsVertical strains on
SS(structural rutting)

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

18
Results highlightsHorizontal strains (spring) at
the base of the HMAC layer (Fatigue cracking)
Transversal
Longitudinal
WBST 25 - 65 more damaging during spring time
19
Results highlightsHorizontal 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 highlightsHorizontal 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 highlightsStrains at shallow depth in
bound material (stability rutting TD cracking)
11R22,5
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

• CTI
• Effects of WBST on low volume roads
• Thin HMAC
• Surface treatment
• i3C industrial research chair