Rational methodology for assessing spring load restrictions based on pavement structural capacity and damage

The objectives of this research have been to evaluate and analyze, from an engineering perspective, the current Manitoba spring load restriction (SLR) policy currently in place by Manitoba Transportation and Government Services as well as address the vulnerability of Manitoba's transportation infrastructure to climate change. There was also the intent to determine adaptation strategies and possible recommendations for the improvement of spring load restrictions with respect to current practices in addition to climate change.; This project and research objectives were completed in many stages. These included an extensive literature review to determine current industry practice and demonstrate pavement infrastructure dependence on climate; the creation of a GIS platform to visualize the extent of SLR testing, implementation and impact; calculation of freezing and thawing indices for two locations in Manitoba to compare and contrast theories and strategies and determine how they influence policy in Manitoba; backcalculation of seasonal strength values for typical pavement structures in Manitoba using Falling Weight Deflectometer testing to estimate the damage that occurs to pavements during spring thaw periods, and climate change events, as well as assist in the determination of adaptation strategies while reinforcing the idea of developing a mechanistic method of spring load restriction; mechanistic design models to determine the impact of spring load restrictions on a sample highway section in Manitoba; and a climate change model to determine the impacts seen in the future.; The GIS platform easily demonstrated the lack of sufficient testing of the network as well as the lack of sufficient testing of roads under SLR. With respect to the freezing and thawing indices, the analysis showed a difference of a few days can be very costly in terms of the potential damage to unrestricted roadways.; The determination of the structural capacity of the pavement structure demonstrated the granular base moduli values remain similar to one another regardless of thawing index (TI), and essentially, time of year. Conversely, the summer subgrade probability strength values are approximately double the early spring values, which was also demonstrated by the Long Term Pavement Performance site backcalculated data and the loss of effective bearing capacity. This analysis also demonstrated the difference in seasonal modulus fluctuation undergone by the granular base layer as compared to the subgrade layer. Based on the results, with respect to modulus values, the pavement structure remains frozen at SLR implementation. Further, both the granular and subgrade layers have not experienced strength recovery at the arbitrary end of SLR on May 31 for a given year and could take up to six further weeks of restrictions in order to recover. Cluster analysis also provided a framework for further network evaluations using FWD testing.; Damage analysis using mechanistic-empirical design models demonstrated the damage occurring the spring thaw and reinforced the need for an improved system with flexibility and climatic conditions to compensate and reduce the impact on the roadways.; Climate change impacts on SLR policy included an earlier SLR start date, leading to a decrease in the length of winter weight premiums for Manitoba. Also, due to the warmer air temperatures, a fundamental shift in the SLR start date will be seen by commencing in early March or late February. Ultimately, SLR policy should be condition or climate based, rather than fixed date, in order to provide the necessary flexibility to compensate for climate change impacts.