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

Laval University’s experience with the wide-base single tires. Guy Doré. Project background. Trucking industry pushing for unrestricted use of WBST Highway administrations concerned about possible damage to pavement networks

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

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  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 Strain gauges 100 mm 300 mm #4 7,60 m 800 mm #3 Travel direction #5 1100 mm #2 Strain gauges 0,30 m #6 #7 2500 mm #1 0,30 m Instrumentation layout

  9. Multi-depth deflectometer

  10. Fibre optic horizontal strain sensors

  11. L45 L44 L43 L42 L41 L40 TR36 TR35 TR34 TR33 TR32 TR31 TR30 V21 V20 V19 V18 V17 V16 V15 V14 V13 V12 V11 V10 V9 V8 V7 V6 V5 V4 V3 V2 V1 T3 • T2 T1 T4 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 highlights:Vertical 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 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 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 highlights:Strains 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

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