Impact of Water Saturation on the Damage Evolution Characteristics of Sandstone Subjected to Freeze-Thaw Cycles

The degree of water saturation significantly affects the rate of rock deterioration caused by freeze-thaw weathering, which may trigger serious geological engineering hazards. This study aimed to explore the impacts of water saturation on freeze-thaw-induced deterioration of sandstone, and to improve our understanding of this damage mechanism. Sandstone specimens with varying degrees of moisture saturation were subjected to freeze-thaw tests, computed tomography scanning, and uniaxial compressive tests. The distribution of the areal porosity along the computed tomography slices, evolution of the pore volume, and changes in the pore network model parameters of the sandstone samples were visually and quantitatively characterised to assess the damage evolution. The results show that the parameters of the pore-fracture structure reflect the influence of saturation and cyclic freeze-thaw actions on rock deterioration. As the moisture saturation increased, the sandstone transformed from being dominated by pores with a radius ranging from 0 to 100 mu m to being dominated by pores of 200-300 mu m. The increase in the equivalent radii of pores caused the rock to be more susceptible to deformation and failure, whereas an increase in the number of throats represents a disruption of the cementation between the rock grains, making to rock more susceptible to freeze-thaw actions. Furthermore, the damage mechanisms of sandstone can be interpreted by volumetric expansion and hydrostatic pressure theory in a rapid freeze-thaw environment. The results of this study provide a comprehensive insight into the influence of water saturation on freeze-thaw-induced damage evolution of rocks in cold regions. With the increase of water saturation, the radius of the dominant pores in the rock gradually expands.With the increase of saturation, the number of throats between connected pores increases, which disrupts the cementation between the rock grains, thereby making the rock more susceptible to freeze-thaw cycles.The frost heave force accelerates the coalescence of pores and prolong the pore closure stage in the stress-strain curves of the tested rocks.Volumetric expansion and hydrostatic pressure are jointly responsible for the damage caused by freeze-thaw cycles.