Thaw subsidence properties of soils under repeated freeze-thaw cycles

For the subgrade fillings of Naqu Logistics Center station along Qinghai-Tibet Railway, the influencing rules of compactness, load and freeze-thaw cycles on the thaw subsidence properties are deeply analyzed in laboratory tests. The results show that: compared with that of the 1^st freeze-thaw cycle, the frost heave and thaw subsidence deformation of the sample with higher compactness changes from small to large after several freeze-thaw cycles. The samples with higher compactness exhibit heave deformation, while those with lower compactness present compaction after repeated freeze-thaw cycles, namely, the samples with different compactnesses tend to a certain compactness. Meanwhile, there is a critical compactness, with which the height of the samples does not change after repeated freeze-thaw cycles. The compactness effect of load restrains the frost heave deformation and increases the thaw subsidence deformation, and the total deformation increases with the increasing increment of load. The moisture content of the samples is more greater than the initial moisture content after repeated freez-thaw cycles. The amount of water supply decreases with the increasing increment of freeze-thaw cycles and then becomes steady after 3 freeze-thaw cycles, and the amount of water supply in freezing process is larger than that in thawing process. The thaw subsidence ratio increases first and then decreases to be steady after 5 freeze-thaw cycles with the increasing increment of freeze-thaw cycles, and the thaw subsidence ratio of the 5^th freeze-thaw cycle is recommended for assessing the thaw subsidence of soils.