Damage evolution mechanism and constitutive model of freeze- thaw yellow sandstone in acidic environment

The study on the damage evolution mechanism of freeze-thaw of rock sample in acidic environment is of great theoretical and practical significance to the analysis and prevention of freeze-thaw disasters in cold area. Taking the yellow sandstone as the research object, the freeze-thaw cycle experiments, the NMR system experiments, the chemical composition analysis experiments and the uniaxial compression experiments under acidic environments with different pH are carried out to analyze the physical and chemical characteristics of the yellow sandstone. The damage evolution equation and constitutive model of rock are studied based on statistical strength theory, Lemaitre strain equivalent assumption and damage mechanics. In this paper, the damage evolution equation of chemical freeze-thaw sandstone under load is established. The damage correction coefficient is introduced to modify the total damage of chemical freeze-thaw sandstone under load. The constitutive model is deduced and the model parameters are deduced by the combination of theoretical derivation and experiment. The results show that the rock damage is the result of the coupling of freeze-thaw cycles and acid erosion, and the freeze-thaw cycle is the main reason and acidic erosion is the secondary reason. The experimental parameters are brought into the constitutive model, and the reliability of the model under uniaxial stress is verified by comparing with the experimental curve.