In the context of climate warming, damage to road pavements and embankments in permafrost regions caused by thawing of underlying permafrost severely reduces the serviceability of roads. In this study, 10 types of asphalt pavement damage were measured every kilometer along the Qinghai–Tibet Highway (QTH), from Kunlun Mountain to Tonggula Mountain (approximately 440 km in permafrost regions). Based on observed data and embankment geometry along the QTH, and information about the characteristics of the permafrost, aspects of pavement deterioration are analyzed and discussed. The three most common forms of pavement damage in the permafrost regions are transverse cracking (TC), potholes, and longitudinal cracking (LC), observed in 87, 64, and 57% of the study section, respectively. About half of the damaged pavement was also affected by block cracking (BC) and alligator cracking (AC), in addition to LC and TC. Results also showed that pavement damage in the degrading permafrost regions was closely related to the underlying permafrost characteristics and embankment geometry. Damage from settlement and patching were more severe in sections with high ice content than low ice content. All the above forms of damage increase exponentially with higher underlying permafrost temperatures. Because of the significant thermal effects of sunlit/shaded slopes, BC, LC, and TC cracking is closely related to roadway orientation, with the most severe cracking damage observed in roads oriented approximately east to west (E–W). Also, more LC was seen in sections of greater embankment thickness, which exacerbates the sunlit/shaded thermal effect.

The warm and ice-rich frozen soil (WIRFS) that underlies roadway embankments in permafrost regions exhibit large compression and thaw deformation, which can trigger a series of distresses. Cement and additives were used in this study to improve the compressibility and thaw-settlement properties of WIRFS. We, therefore, selected optimum additives and studied the improvement effect on the frozen soil with 30% water content based on our previous research. Given constant load and variable temperatures, compression coefficients, thaw strains, and water content changes were obtained at temperatures of −1.0 °C, −0.5 °C, and 2.0 °C to evaluate the effect of improvements. A scanning electron microscope (SEM) was then used to observe the microstructure of improved soils and analyze causal mechanisms. Data show that hydration reactions, physical absorptions, cement, and additives formed new structures and changed the phase of water in frozen soil after curing at −1.0 °C for 28 days. This new structure, cemented with soil particles, unfrozen water, and ice, filled in the voids of frozen soil and effectively decreased the WIRFS compression coefficient and thaw strain.