Constitutive model for damage of freeze-thaw rock under three-dimensional stress

Considering the random characteristics of defects of rock materials, the model for damage of freeze-thaw and loaded rock considering the influence of confining pressure is established based on the theory of continuum damage mechanics. According to the geometric condition of the deformation and failure curve of red sandstone, the expressions for model parameters containing only the basic characteristic parameters of rock are determined. The rationality of the model is verified by the experiments on mechanical characteristics of rock under freeze-thaw cycls. It is shown that the crack-dominated micro mechanical response of the red sandstone is consistent with the macroscopic deformation and failure characteristics. The damage degree of sandstone, which is shown as the deterioration of the mechanical properties of the materials in the macroscopic performance, increases with the increase of the number of freeze-thaw cycles. But the strain of rock increases and the plastic property increases with the same damage degree at the later stage of deformation. The confining pressure can improve the stress state of rock, so the damage degree decreases with the increase of the confining pressure, which is shown as the strength of the materials to resist damage and the increase of plastic deformation.