To analyze the effects of freeze‐thaw cycles and confining pressure on the mechanical properties of red sandstone, through freeze‐thaw cycles and triaxial compression tests, full stress‐strain curves of different freeze‐thaw cycles and different confining pressures were obtained. The degradation degree of red sandstone was quantitatively considered from different mechanical parameters of ultimate stress, elastic modulus, and Poisson’s ratio. Based on summarizing the characteristics of rock under freeze‐thaw and load, the total damage variable of rock was determined by the reasonable measurement of freeze‐thaw damage variable and load damage variable, and a damage constitutive model under freeze‐thaw and load was established. The research showed that the freeze‐thaw cycles aggravate the degree of rock damage deterioration, the rock stiffness and strength were reduced, and the characteristics of plastic deformation and ductile failure were more obvious. The confining pressure inhibited red sandstone internal damage, and with the increase of confining pressure, the stiffness and strength and the plastic characteristics were increased. In the overall trend, the mechanical parameters had different sensitivity to the degradation effect of freeze‐thaw cycles and confining pressure. Regardless of the increase in the number of freeze‐thaw cycles or confining pressure, the strain softening modulus tended to decrease gradually, and red sandstone plastic damage became more obvious after the stress peak. The total damage evolution path of red sandstone reflected the nonlinear influence of freeze‐thaw and load on the total damage propagation. The research results provide theoretical support for the improvement of the technology of the effluent coal rock in Balasu Coal Mine.

This article, on the basis of experimental research, combines theoretical analysis and numerical calculation. In addition, the research, while taking into consideration different fracture lengths, confining pressure of rock mass mechanics properties, and behavior of evolution law, establishes and reflects the unique characteristics of the processes of fractured rock mass deformation and destruction of the damage constitutive model. In this instance, the discrete element method numerical has been discussed from the perspective of mesoscopic fracture mechanism of the fractured rock mass. The results show that the capacity of resistance of rock mass deformation and destruction along with the increase of fracture length, the peak stress of rock mass, the elastic modulus, and peak strain are positively correlated with the confining pressure. Furthermore, an increase in the confining pressure, transition of rock mass from brittle to ductile, an intact sample to shear failure pattern by stretching evolution, and different fracture lengths are characterized by shear failure form. Based on the statistical damage theory and Drucker Prager yield criterion, the damage constitutive model of fractured rock mass has been determined, and the physical meaning of the model parameters has been clarified through experimental analysis. The strength characteristics and damage evolution law of fractured rock mass revealed by the damage constitutive model are consistent with the test results, thereby verifying the rationality of the model. According to the numerical simulation of the evolution characteristics of the number of microcracks, the failure process of rock mass can be divided into four stages, namely crack initiation stage, crack steady growth stage, pre-peak crack accelerated growth stage, and post-peak crack accelerated growth stage. The simulation results of the deformation failure process and model are basically the same as those of the laboratory experiment. The theoretical results are expected to provide an important theoretical foundation for theoretical research of rock mass mechanics and engineering stability evaluation.