Rock microstructure changes after hydrochemical reactions, which, in turn, leads to deterioration of mechanical properties. Thus, a quantification study on rock microstructural damage after chemical corrosion is necessary. Quantification of the microstructural damage of rocks after chemical corrosion was carried out in this study. We presented a proposal that included formulae for calculating the damage variable by analyzing the porosity changes of sandstone. The plastic deformation of sandstone specimens after soaking in chemical solution was observed. Plastic deformation can be divided into distinct stages over time. Results showed that the prepeak incremental deformation after chemical corrosion was partially due to the increase in plastic deformation before reaching the peak and to the deformation caused by pore compression. Plastic deformation is an indirect indicator of the degree of chemical corrosion of sandstone specimens. After chemical corrosion, the porosity of sandstone specimens changed consistently with the velocity of longitudinal wave. Therefore, the calculation formula of the damage variable can be used to calculate the porosity of sandstone specimens at different time periods. The chemical damage of sandstone specimens was highly consistent with the peak strain. Therefore, the damage variable based on porosity can be used to quantitatively describe the damage caused by chemical corrosion.

Long-term immersion was adopted to explore the damage deterioration and mechanical properties of granite under different chemical solutions. Here, granite was selected as the candidate of parent rocks for nuclear waste storage. The physical and mechanical properties of variation regularity immersed in various chemical solutions were analyzed. Meanwhile, the damage variable based on the variation in porosity was used in the quantitative analysis of chemical damage deterioration degree. Experimental results show that granite has a significant weakening tendency after chemical corrosion. The fracture toughnessKIC, splitting tensile strength, and compressive strength all demonstrate the same deteriorating trend with chemical corrosion time. However, a difference exists in the deterioration degree of the mechanical parameters; that is, the deterioration degree of fracture toughnessKICis the greatest followed by those of splitting tensile strength and compressive strength, which are relatively smaller. Strong acid solutions may aggravate chemical damage deterioration in granite. By contrast, strong alkaline solutions have a certain inhibiting effect on chemical damage deterioration. The chemical solutions that feature various compositions may have different effects on chemical damage degree; that is,SO42-ions have a greater effect on the chemical damage in granite thanHCO3-ions.