Using LTPP Data to Develop Spring Load Restrictions: Pilot Study (05-1284) - MP-05
Patrick Leong, University of Waterloo, Canada
Susan Louise Tighe, University of Waterloo, Canada
Guy Doré, Universite Laval, Canada

In northern parts of North America, the road network is weakened and extensively damaged by the seasonal loading. The yearly cycle of above and below freezing temperatures causes cycles of freezing and thawing of the groundwater underneath the pavement. As the groundwater freezes, the pavement undergoes uplift, while as the temperature rises to above freezing, the frozen ground thaws. As the pavement thaws from the surface down, the soil eventually becomes saturated as the water becomes trapped between the pavement surface and the frozen soil. The pavement is in a weakened state during this saturated period, which can last up to several weeks every year. Most authorities have opted to impose load restrictions on vehicles during this thawing period. Yet, since the pavement temperature tends to lag behind the air temperature, it is difficult to determine the exact time duration that the pavement is in this weakened state. An accurate time for imposing the load restriction is required since delayed restrictions will cause pavement damage, whereas premature load restrictions will cause undue economic hardship on industries that require transportation of their goods. A promising and convenient method is the thawing index method developed by the Minnesota Road Research Section. This paper will investigate ways to improve the determination of the start of load restrictions based on weather information, and the possibility of adopting it for use in Ontario.