• The elastic modulus and damage threshold were significantly improved by the KCl solution, whereas only limited recovery was observed with the Na₂SO₄ solution. • A damage threshold correction method considering crystallization is proposed, aiding stability assessment of saline cavern reservoirs. • The distinct mechanisms through which KCl and Na₂SO₄ brines influence the mechanical properties of sandstone were further revealed via microscopic examination. During saline cavitation and injection operations, residual saturated saline undergoes prolonged physical‒chemical interactions with the surrounding rock, leading to changes in rock mechanical properties. To investigate the mechanical evolution characteristics of sandstone under different saline environments, conventional triaxial compression tests were conducted on saturated sandstone specimens immersed in various saline solutions. Combined with microstructural analysis, the mechanisms by which different saline solutions affect the mechanical properties of sandstone were revealed. The test results indicate that compared with those of dry specimens, the macroscopic mechanical parameters of saline-saturated sandstone specimens consistently decrease across all solutions. Notably, the elastic modulus, deformation modulus, and damage threshold of the specimens immersed in the KCl solution were significantly greater than those of the pure water-saturated specimens, whereas the Na₂SO₄ solution resulted in only limited recovery. Failure mode analysis revealed a marked increase in associated cracks during specimen failure following saline immersion. Microscopic examination further revealed that solution immersion caused surface dissolution in the specimens. The KCl crystals were distributed randomly and partially filled the pores, whereas the Na₂SO₄ crystals exhibited a piled-up covering pattern. These changes altered the pore structure and particle bonding of the sandstone to varying degrees. These findings provide a theoretical reference for assessing rock stability in saline cavern reservoirs.
Huang et al. (Sun,) studied this question.