• Triaxial tests reveal that increasing confining pressure enhances peak stress, dilatancy stress, peak strain, and elastic modulus while reducing Poisson's ratio and secondary crack formation.
• Pore pressure and confining pressure exert opposing effects on sandstone mechanical behavior.
• Permeability evolution exhibits three distinct stages (initial compaction, linear elasticity, plastic deformation), with peak permeability coinciding with maximum volumetric dilatancy.
• Salt solutions with pH 7 and 4 significantly degrade mechanical properties and increase permeability, highlighting the impact of hydrochemical corrosion.