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

The swelling and shrinkage deformation of expansive soils in seasonally frozen regions is significant, which seriously induces engineering hazards and disasters. To investigates the freezing-induced deformation characteristics of unsaturated expansive soil under the influence of cyclic freeze-thaw and initial anisotropy, a series of cyclic freeze-thaw tests and volumetric variation measurement tests of compacted expansive soils were carried out. The experimental results show that: (1) Compared with the melting state, the volumetric strain of expansive soil in freezing state is more significantly affected by 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 initial saturation, the frozen volumetric strain of expansive soil sample first decreases and then increases, it shows freezing shrinkage at low saturation and freezing swelling at high saturation. (3) There is a good quadratic relationship between frozen volumetric strain and water content, and there exists a characteristic value of "critical water content", at which the maximum volumetric shrinkage occurs. (4) Under cyclic freeze-thaw action, the frozen volumetric strain of the samples with low water content is more stable than the higher water content. The cumulative effect of axial strain with freezing times is more significant than that of 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 expansive soils in seasonally frozen regions.