The deterioration of rock mechanical properties under chemical-freezing-thawing-loading will seriously threaten the stability and safety of engineering rock mass, so the study of its constitutive model has very important theoretical and engineering application significance. In view of the deficiency that the existing statistical damage constitutive model cannot describe the nonlinear characteristics of the compaction stage and the post-peak shape, the compaction index is introduced to measure the stress-strain nonlinear characteristics caused by the iso-compression of the pores in the rock, and the post-peak correction coefficient is introduced to optimize the post-peak shape of rock loading. Assuming that the strength and failure of rock microunits obey the Weibull distribution, on the basis of using the Drucker-Prager strength criterion to measure the strength of rock microunits, a statistical damage model for rock considering the compaction stage and post-peak shape under chemical-freezing-thawing-loading is established. Finally, it is compared with the test curve. The results show that the calculation curve of the established chemical-freezing-thawing-loading rock statistical damage model has the same trend as the rock uniaxial compression test curve. Furthermore, it can better describe the rock stress-strain law with different chemical solutions and different freeze-thaw cycles, which fully reflects the rationality and accuracy of the constructed constitutive model. The research results can provide a theoretical basis for the calculation of deformation and failure of rocks under chemical-freezing-thawing-loading.

The shear behavior of rock structural planes contains various symmetry laws, and the shear failure can be considered as an asymmetric state of the rock and rock mass. The study of shear deformation and the failure of rock structural planes plays a vital role in ensuring the safety and stability of engineered rock masses. In view of the inability of traditional shear constitutive models to describe the non-linear characteristics of the dilatancy stage and the single applicable failure form, firstly, we discuss, in depth, the law and mechanism of shear deformation and failure of structural planes, and introduce the compaction index α to measure the non-linear characteristics of shear stress–shear displacement caused by compaction of microcracks and internal pores of structural planes, and the structural plane damage model, considering the void compaction and failure mode, was established. Then, the statistical damage theory was introduced, and the strength and failure of the microunits of the rock structural plane were assumed to obey the Weibull distribution. Based on the Mohr-Coulomb strength criterion to measure the strength of the microunits of the rock structure surface, a statistical damage model of structural planes, which can describe void compaction and failure modes, was established. Finally, a comparative analysis was carried out with the test curve, and the results showed that: the calculation curve of the structural plane statistical damage model established, considering the void compaction and failure modes, has the same trend as the structural plane shear test curve, which can better describe the shear stress– shear displacement at the dilatancy stage, as well as the shearing stage and sliding stage in different failure modes. The changing law of shear displacement reflects the rationality and accuracy of the constructed constitutive model. The research results can provide a theoretical basis for the shear deformation and failure of rock structural planes.