Monitoring Freeze-Thaw Performance of Pavement Foundations

In the cold, wet-freeze climate of Minnesota, the freeze-thaw cycles pose significant challenges to pavement integrity, often resulting in structural damages that shorten the lifespan of the state’s roadways. To address this issue, a pioneering study was conducted on the I-94 highway within the Minnesota Road Research Facility (MnROAD).  

For this project, ShapeArray were installed to monitor the freeze-thaw behaviour and subsurface displacement of a flexible pavement section. Collecting this valuable data was hoped to provide insights for transforming how transportation agencies manage and maintain road infrastructure in similar climatic zones. 

A primary objective was evaluating the effectiveness of ShapeArray in real-time monitoring of frost heave and thaw settlement in pavement foundations. By achieving this, the project aimed to: 

Provide continuous, accurate measurements of subsurface displacement. 

Determine the optimal timing for implementing and lifting spring load restrictions (SLR), potentially extending the pavement’s lifespan and reducing maintenance costs. 

For the implementation, ShapeArray were strategically placed along the cross-section of a reconstructed flexible pavement segment on the MnROAD mainline. Each ShapeArray was installed 12 cm below the top of the base layer, encased in Schedule 80 PVC pipes to ensure durability and minimal interference with the pavement structure.  

In total, this installation spanned a total length of five metres, covering both the shoulder and the passing lane to capture a comprehensive range of data across different traffic loads. Data collection was facilitated by a Campbell Scientific CR300 data logger, monitoring and recording consistent readings throughout the freeze-thaw season of 2022–23. 

Analysis of the collected data revealed that the maximum settlements of 3.5 mm and 10.3 mm occurred in the shoulder and passing lane, respectively. These measurements correlated closely with temperature data, indicating the ground began to settle when it dropped below freezing, suggesting ice lenses formation and contraction of the soil structure. Notably, after the spring thaw, a residual settlement remained but the ground stabilized, highlighting the dynamic response of the pavement to environmental conditions. 

Using ShapeArray provided a robust method for monitoring the structural health of pavement during critical freeze-thaw cycles. During this project, the real-time data not only confirmed the reliability of ShapeArray technology in such applications, but also demonstrated its potential to inform more timely and cost-effective decisions regarding the implementation of SLR. 

In future studies, deploying Falling Weight Deflectometer tests is the recommended next step. This testing could further validate the structural integrity at the ShapeArray locations and explore the integration of coupled Thermo-Hydro-Mechanical models for a deeper understanding of the interactions affecting pavement performance. 

Overall, this project marks a significant advancement in the field of pavement monitoring and maintenance. Utilizing ShapeArray offers a promising avenue for enhancing the resilience and longevity of roadways subjected to harsh environmental conditions, ultimately leading to safer, more reliable transportation networks. 

References 

2024. Fyaz Sadiq, M. Wasif Naqvi, J. Podolsky, and R. Velasquez. “Feasibility of SAA to Monitor Freeze–Thaw Performance of Pavement Foundations in Cold Regions.” 20th International Conference on Cold Regions Engineering [Online.] Anchorage, USA, 2024.