Impacts of Reduced Tire Pressure on Strain Response of Thaw-Weakened, Low-Volume Roads in Manitoba, Canada

The spring thaw period significantly reduces the bearing capacity of lowvolume asphalt roads. To compensate for the reduced bearing capacity, highway agencies apply spring load restrictions (SLR) to limit the damage caused by heavy loads during the period when the road is weakened by thaw. Although the imposition of SLR may reduce road damage, it has a major impact on truck productivity. An alternative to reducing truck loads during the spring is the reduction of truck tire pressure. The reduced tire pressure lowers the tire-pavement contact pressure and the associated damage during the spring period. In 2008, asphalt strain gauges were installed in a section of a low-volume haul road in Manitoba, Canada. Field testing was conducted in the spring and fall of 2009 with a double semitrailer or B-Train equipped with a semiautomated tire pressure control system. The tests were conducted at various loads and speeds and at normal and reduced tire pressures. The results of the field testing showed that when the tire pressure was reduced by 50%, the measured maximum tensile strain at the bottom of the asphalt layer decreased by an average of 15% to 20%. The effects of gauge orientation, truck speed, and tire offset from the strain gauge were analyzed and are presented.