Effect of Anion Concentration in the Acidic Environment on Rock’s Mechanical Properties

With the increasing complexity and broader scope of underground operations, groundwater is widely encountered during rock excavation. Groundwater has diverse pH levels and components, the hydro deterioration of rock is a significant factor that threatens sustainable mining. Environments with the presence of groundwater are prone to chemical corrosion. Generally, acidic groundwater contains various types of ions that affect the corrosion of rocks. Accurate assessment of the mechanical properties of corroded rock contributes to safe and sustainable mining. However, existing research on anionic and acidic coupled conditions is limited. This study shows that acid and anion concentrations decrease the mechanical properties and brittleness index of sandstone, while the damage variable has an opposite variation trend. In comparison, their effects on granite are less pronounced than those on sandstone. The reactions are explained based on chemical energy analysis and equations, where some minerals react and dissolve in the solutions. Microscopic images reveal that the generation of expensive hydrate compounds can further damage rock’s microstructure. In sandstone, the permeability of specimens increases with the ion concentration, and permeability is more sensitive to corrosive environments than porosity. While these effects in granite specimens consistently remain at a considerably low level. To summarise, the increment of anion concentration can intensify the weathering impact of acid on rock. The acid-induced expansion of pores and fissures also promotes the infiltration of the saline solution.