Abstract
Crack size affects the freeze-thaw(F-T) degradation process of rocks. This paper investigates the effects of through-crack size and F-T cycles on the deformation and failure characteristics of red sandstone. The F-T micro-strain evolution law, nonlinear pore compaction characteristics, and the strength deterioration law of red sandstone with different cracks under the influence of F-T are discussed. The results show that during the early stages of freezing and thawing, all sandstones develop significant frost heave strain. As the number of F-T cycles increases, the residual frost heave strain of intact red sandstones and samples with small-sized cracks(Type I) gradually decreases, the compaction strain decreases, and the proportion of the compaction stage increases. In contrast, the red sandstone with large cracks (Type II) has the opposite damage characteristics. The compaction stress and uniaxial compressive strength of all samples gradually decrease. As the crack length increases from 10mm to 15mm, the influence of prefabricated cracks on the mechanical properties of red sandstone exceeds the influence of F-T damage. After 20 F-T cycles, radial cracks appear on the long side of the Type II crack under axial loading, and the strength of the fractured section is severely reduced.