Rutting is a major distress mode in flexible pavements, results from the repetitive loading caused by traffic movement. Pavement deformation consists of both recoverable (elastic) and unrecoverable (plastic) components. The continuous movement of vehicles contributes to the overall deformation in the flexible pavement system, involving all pavement components. In regions with hot climates or in the hot summer season, rutting tends to be more prominent due to the substantial reduction in the viscosity of the asphalt binder. This decrease in viscosity, which is inversely linked to rutting, occurs as temperatures rise, leading to a heightened susceptibility of the Hot Mix Asphalt (HMA) blend to rut formation. However, according to studies, a significant amount of permanent deformation takes place in the unbound layers beneath the asphalt course, it is therefore essential to prioritize attention on these layers. Temperature exerts besides viscosity a substantial impact on asphalt stiffness, leading to the transfer of higher vertical deviatoric stresses to the unbound layers beneath the asphalt course (base, subbase, subgrade). This research presents a study integrating the High Cycle Accumulation (HCA) model into a laminar model to determine permanent deformations in the unbound granular layer of flexible pavements and taking into account the temperature dependent stiffness of asphalt. Rutting depths at the end of the design lifetime were computed, accounting for seasonal stiffness variations. It was shown that the softer asphalt behavior significantly increases the development of ruts in the underlaying soil layers. The findings were compared with results obtained from mean annual temperature and the typical equivalent asphalt stiffness utilized in fatigue tests. Additionally, an analysis was conducted to assess whether the timing of road implementation influences settlements throughout the design lifetime. The results suggest that the sequence of seasons is most relevant during the first year of service, showing a distinct effect at that time. However, with a higher number of axle passes, the initial differences fade away, and the curves start to merge.

Understanding permafrost soils' response to global warming is critical for understanding changing global ecosystems. In the present study, we developed a dynamic system for measuring gas emissions from permafrost soils at different soil temperatures and checked the validity of this methodology using 10 permafrost and active layer soil core samples collected under frozen conditions from northern Alaska in winter. We observed that more time (several hours to half a day) was required to control the temperature of permafrost soils than normal soils, particularly during freeze-thaw cycles. Gas emissions were quite variable between samples. However, CO2 emissions were positively related to temperature in all samples, as were CO emissions, particularly for the permafrost samples. CH4 emissions were not detected in any sample, possibly because of atmospheric air as the carrier gas, and H-2 was detected in only two samples. Conversely, NO emissions were detected in nearly all samples and were highly correlated with soil nitrogen content, while N2O emissions were detected in only one sample with very low NO emissions. Our findings demonstrate that this novel system could be a powerful tool for understanding gas emission dynamics in permafrost soils.