Experimental study on freezing deformation characteristics of unsaturated expansive soils considering cyclic freeze-thaw and initial anisotropy

The swelling and shrinkage deformation of the expansive soils in seasonally frozen regions is significant, which seriously induces engineering hazards and disasters. To investigate the freezing-induced deformation characteristics of the unsaturated expansive soils under the influences of cyclic freeze-thaw and initial anisotropy, a series of cyclic freeze-thaw tests and volumetric variation measurement tests on the compacted expansive soils are carried out. The test results show that: (1) Compared with the melting state, the volumetric strain of the expansive soils in freezing state is more significantly affected by the dry density and water content. The higher the water content and dry density, the greater the difference of frozen and melted volumetric strains. (2) With the increase of the initial saturation, the frozen volumetric strain of the expansive soil samples first decreases and then increases, indicating freezing shrinkage at low saturation and freezing swelling at high saturation. (3) There is a good quadratic relationship between the frozen volumetric strain and the water content, and there exists a characteristic value of "critical water content", at which the maximum volumetric shrinkage occurs. (4) Under the cyclic freeze-thaw action, the frozen volumetric strain of the samples with low water content is more stable than that with the higher water content. The cumulative effects of the axial strain with freezing times are more significant than those of the radial strain. (5) The frozen deformation has compaction-induced anisotropy, which is more significant at higher water contents. The research results can provide reference for the deformation control and disaster prevention of the expansive soils in seasonally frozen regions.