Mechanical properties and damage evolution of sandstone subjected to uniaxial compression considering freeze-thaw cycles

The effect of freeze-thaw (F-T) cycles on the mechanical behaviors and internal mechanism of rock mass is a critical research topic. In permafrost or seasonally frozen regions, F-T cycles have adverse effects on the mechanical properties of rock mass, leading to many serious disasters in mining and geotechnical operations. In this paper, uniaxial compression tests are carried out on cyan sandstone after different F-T cycles. The failure modes and damage evolution of cyan sandstone under F-T cycles are studied. In addition, from the perspective of fracture and pore volume, the calculation equations of rock strain under frost heaving pressure and F-T cycles are established and verified with the corresponding laboratory tests. Subsequently, based on the classical damage theory, the F-T damage variables of cyan sandstone under different F-T cycles are calculated, and the meso-damage calculation model of cyan sandstone under F-T-loading coupling conditions is derived. Furthermore, through the discrete element numerical simulation software (PFC3D), the microscopic damage evolution process of cyan sandstone under uniaxial compression after F-T cycles is studied, including the change of microcracks number, distribution of microcracks, and the acoustic emission (AE) count. The goal of this study is to investigate the damage evolution mechanism of rock from the mesoscopic and microscopic aspects, which has certain guiding value for accurately understanding the damage characteristics of rock in cold regions.