Severe rainfall events are becoming more frequent in Minnesota—which can be bad news for pavements. When the ground becomes saturated, excess water flows beneath the pavement surface. Too much moisture in the pavement foundation affects its strength, stiffness, and durability.
In a recent MnDOT-funded project, researchers investigated how heavy precipitation affects the resilience of pavement foundations. In the first step, the team analyzed historical weather data and moisture sensor data from the MnROAD test facility. The analysis confirmed that rainfall has been increasing during the months with heavy rain (June to August) in Minnesota in the 21st century.
The researchers then developed a model that simulates moisture fluxes in pavement foundations caused by heavy rain events and predicts changes in saturation levels and resulting reductions in pavement stiffness. The model supports the production of a GIS-based vulnerability framework that road engineers can use to prioritize maintenance in at-risk areas.
Although the model is currently calibrated to MnROAD test cells, the GIS mapping system framework could potentially be applied across the state, according to Raul Velasquez, MnDOT geomechanics research engineer and the project’s technical liaison.
The researchers, led by Halil Ceylan of Iowa State University, also offered several recommendations for managing assets. These include:
- Investing in advanced weather-monitoring and forecasting systems to provide real-time data on significant precipitation events.
- Further assessing climate change impacts on the state, including projections for increased heavy precipitation events and quantifying the potential effects to transportation infrastructure.
- Prioritizing vulnerable road networks for maintenance, especially in areas of heavy rainfall.
- Updating infrastructure design standards to ensure resiliency against heavy precipitation.
This study builds on a previous project led by Ceylan that explored whether warmer winters are increasing the number of freeze-thaw events that impact roads. Researchers found that at shallower pavement depths, freeze-thaw cycles are decreasing in early and late winter, and they observed no trend for the remainder of the winter or at deeper layers in the pavement and subsurface. However, the research team also found that precipitation has increased in early and late winter, which may increase pavement damage.
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