The analysis of the effects of certain variables upon the deterioration of unpaved road strength

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University of New Brunswick
An experiment was conducted by the Pavement Test Facility, Transport Research Lab, Crowthorne, England for research by the University of New Brunswick regarding the effects of wheel load, tire inflation pressure and granular subbase thickness upon the strength of unpaved roads used for industry access roads. The experiment was designed to examine the effects of increasing tire inflation pressures or wheel loads, or decreasing the granular subbase thickness. The testing procedures involved using tire inflation pressures of 345 and 690 kPa, wheel loads of 44 and 80 kN, and granular subbase thicknesses of 200, 350 and 560 mm. This subbase material was placed upon a Gault clay subgrade layer of 2.5 to 2.8 metre thickness. The Falling Weight Deflectometer passed along each of the six traffic lines at a velocity of 15 km/hr to obtain deflection data. The testing of each of the traffic lines involved the use of a Falling Weight Deflectometer to perceive vertical displacement of the roadway for 10, 30, 100, 300, 1000, 3000 and 10000 passes of the wheel loading. This report illustrates the results obtained from these testing applications and compares the effects on unpaved road strength of each of the variables discussed. If the analysis is successful in determining the most significant variables, it will have several benefits for haul roads in the field of industry.