Mechanical properties of Inuvik-Tuktoyaktuk highway built on permafrost over the years of operation from 2019 to 2024

Road infrastructure built over permafrost is increasingly vulnerable to climate change, with seasonal thawing causing significant degradation in mechanical performance. Variations in moisture content, active layer thickness, and freeze-thaw cycles can compromise structural integrity, especially in granular embankments without asphalt surfacing. Understanding how these environmental changes affect stress distribution and stiffness is critical for maintaining long-term road stability in northern regions. This study monitored the mechanical response of a granular road embankment along a permafrost-affected corridor during the thawing seasons of 2022 and 2024. Field instrumentation, including pressure cells and strain gauges installed in site, captured stress and deformation data under controlled truck loading at multiple speeds. Seasonal site visits were conducted in June, August, and September each year. Elastic modulus was calculated from stress–strain relationships and interpreted alongside temperature and moisture content profiles obtained during testing. The results revealed strong seasonal trends: in 2022, the modulus increased from 86.3 MPa in June to over 300 MPa in September, indicating progressive stiffening as the embankment dried. In 2024, modulus values were significantly lower across all months, suggesting deeper thaw penetration and a weaker subgrade layer. Higher stress magnitudes and pulse widths in August reflected dry, compacted conditions, while June responses showed energy dissipation in wetter, softer soils. These findings demonstrate the impact of permafrost degradation on embankment stiffness and stress transmission, emphasizing the need for improved monitoring and design adaptations in cold regions. • Seasonal stiffness shifts driven by thaw depth, moisture, and traffic loading. • Surface stiffness recovery masks persistent long-term weakening at depth. • Data from 2019 to 2024 show progressive stiffness loss due to permafrost thaw. • Findings highlight the need for adaptive design, monitoring, and moisture control.