guy doré laval university’s experience with the wide-base single tires
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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
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