Damage evolution behavior and constitutive model of sandstone subjected to chemical corrosion

Chemical corrosion has significant impact on the properties of rock materials. To investigate the effect of chemical corrosion on the porosity and mechanical properties of sandstones, the nuclear magnetic resonance (NMR) technique was used for the measurement of porosity. Uniaxial compression tests were then conducted for rock specimens treated with chemical corrosions. The test results showed that, compared with the rock specimens in their natural state, after chemical corrosions, the porosity increased, the uniaxial compressive strength and elastic modulus of sandstone both decreased, but the corresponding peak strain increased. A chemical damage variable derived from the change of porosity and the effective bearing area of rock samples was proposed. Based on the chemical damage variable, the corrosion order of different chemical solutions on sandstone was obtained as H₂SO₄ > NaOH > distilled water. The mechanism of chemical corrosion was also explored based on water-rock reactions. Finally, by introducing the compaction coefficient, an improved statistical damage constitutive model was established to describe the damage evolution of the sandstones treated with different chemical corrosions.