Frost Boiling Mechanism
Another factor influencing the severity of the frost boils was when the thawing front penetrated down to the bottom of the pavement structure. The thawing front penetrated to the bottom of the pavement structure in late July or early August, which was almost three months after the thawing season began. Because the frozen soil in the west side of the roadway held a large amount of frozen water, it took a larger amount of solar energy to melt the frozen soil. The only drainage path for the melting snow and runoff water was to flow through the pavement structure. This would further reduce the soil stiffness and intensify the frost boil issue. Furthermore, the center of the pavement structure formed a hard, frozen core during the melting season. The frozen core altered the water flow direction and trapped a large amount of water in the west side of the pavement structure, which intensified the frost heave action during winter time.
It was also worth noting that a large amount of rainfall would cause another issue called pressurized water overflow, which might also have generated soft spots on the road surface in summer time. Rainfall duration served as a more deteriorating factor to the pavement performance than rainfall intensity. The soft areas would heal up if there were periods of no rain. The moisture contents in the pavement structure beneath 0.47 meter (1.5 feet) experienced short periods of time of overly saturated. By carefully examining the rainfall events summary in Table 2, it was seen that there were several days of rainfall before the sudden increases in moisture content. Since the road prism was built on a side hill, the water naturally flows from west to east. Also, the 11° downhill slope made the hydraulic gradient the highest at the test section. These factors were evidence that the sudden increases in moisture content were due to pressurized water overflow to the road surface. Although the two issues presented the same superficial phenomena, the mechanisms causing the phenomena were different. Wicking Fabric Performance during Rainfall EventsPapers and Manuscripts (PDF Format)
Quantifying Water Removal Rate of a Wicking Geotextile under Controlled Temperature and Relative Humidity - ASCE Meeting
Use of Wicking Fabric to Help Prevent Frost Boils in Alaskan Pavements - ASCE Material Manuscript
Long-Term Performance of Wicking Fabric in Alaskan Pavements - Journal of Performance of Constructed Facilities