Meso-macro damage deterioration of weakly cemented red sandstone under the coupling effect of high-humidity and uniaxial loading

The physical and mechanical damage of surrounding rock caused by water-rock interaction and excavation disturbance has an important influence on the stability of the chamber. Water absorption test was conducted for the weakly cemented red sandstone in the mine under highhumidity environment. Five rock samples with different water contents were obtained through different curing times. The microstructure variation characteristics and microfracture extension and penetration mechanism of rock samples with different water contents were analyzed by scanning electron microscopy (SEM). Combined with acoustic emission monitoring, comprehensive damage variables under two contiguous states of rock samples in high-humidity environment, i.e., initial damage induced by water absorption and hydraulic coupling damage, were constructed, and the stress-strain curve variation characteristics, damage evolution law, and macroscopic failure mode of red sandstone under uniaxial compression were analyzed. The results show that the water content of red sandstone in a high-humidity environment increased logarithmically with the water absorption time. The meso-fabric changes caused by water absorption can cause initial damage, resulting in subsequent significant variation characteristics, including mechanical loading stress-strain curve characteristics, energy evolution, and macroscopic failure modes. The comprehensive damage variable evolution law constructed by acoustic emission monitoring information reflected the coupling effect of initial damage and mechanical loading damage.