Experimental study on effects of freeze-thaw fatigue damage on the cracking behaviors of sandstone containing two unparallel fissures

This paper investigates the effects of freeze-thaw (FT) fatigue damage on the cracking behaviors of sandstone specimens containing two unparallel fissures under uniaxial compression. First, the effects of FT fatigue damage and fissure angle on the mechanical properties of sandstone specimens are analyzed. Second, the real-time cracking process of sandstone specimens is captured by a high-speed digital video camera system. Seven crack coalescence patterns are observed in this experiment. Local strong fatigue-damaged zones, which are visualized as white zones, are observed in the specimens subjected to FT cycles during loading. Finally, scanning electron microscopy (SEM) observations show that the local strong fatigue-damaged zones mainly consisted of microcracks and micropores induced by the FT fatigue damage. These experimental results are helpful for improving the understanding of the cracking process in cold-region engineering.