Deterioration effect of freeze-thaw on mechanical properties of roadbed clay under unfavorable conditions

Freeze-thaw seriously deteriorates the engineering properties of roadbed soil, and it will adversely affect the performance and service life of roads in seasonally frozen regions. Freeze-thaw and triaxial tests were conducted on a kind of roadbed clay to characterize the change rules of failure strength, cohesion, and friction angle under controlled thawing time, freezing temperature, moisture content, compaction degree, and numbers of freeze-thaw cycle. The thawed specimens had the weakest mechanical properties after thawing 2 h. Failure strength and cohesion of the freeze-thaw soil decreased considerably with the dropped freezing temperature, increasing moisture content, and improved compaction degree. The change in friction angle was less remarkable and exhibited an opposite trend with the freezing temperature and compaction degree. There was a great reduction in failure strength and cohesion after the first few cycles of freeze-thaw, and then a plateau was reached, whereas the friction angle decreased after one to two cycles and then recovered to a value higher than that of the unfrozen soil. The results demonstrated that the combined action of different factors should be considered to better understand the deterioration effect of freeze-thaw cycles under unfavorable conditions.