Acid-induced geochemical and geomechanical deterioration of Siwalik sandstone: an experimental study

Abstract

This study presents an experimental investigation of the geomechanical, geochemical, and microstructural response of Shivalik sandstone under acidic environments. Controlled laboratory tests, including unconfined compressive strength (UCS), Brazilian tensile strength (BTS), and elastic modulus measurements, were conducted across pH levels ranging from 1 to 7. The results show that strong acidity (pH 1–2) leads to significant reductions in mechanical properties, with decreases of up to 30.2% in UCS, 60.8% in BTS, and 65.3% in elastic modulus, indicating pronounced material weakening. Ion chromatography results reveal increasing concentrations of dissolved cations (Ca²⁺, Mg²⁺, K⁺, Na⁺) with decreasing pH, suggesting enhanced mineral dissolution. X-ray diffraction (XRD) analysis and microstructural observations provide supporting qualitative evidence of mineralogical alteration associated with acidic exposure. These datasets are interpreted in a complementary manner to identify consistent trends in chemical alteration and mechanical degradation. The study focuses on establishing empirical relationships between acidity, ion release, and mechanical response. The interpretation of mineral dissolution and associated microstructural changes remains qualitative to semi-quantitative. Overall, the results provide a coherent experimental dataset highlighting acid-induced degradation trends in sandstone. The findings contribute to improved understanding of rock behaviour in chemically aggressive environments and may be useful for geotechnical and subsurface engineering applications.