Characterization and modeling of the dynamic mechanical behavior of acid-etched sandstone

Abstract

Understanding the energy dissipation and damage evolution of sandstone under acidic environments is critical for the safety and stability of deep rock engineering. In this paper, the dynamic mechanical behavior of sandstone subjected to acid erosion is systematically investigated through laboratory experiments and numerical modeling. Dynamic impact tests are conducted using a split Hopkinson pressure bar on sandstone specimens immersed for 30 days in acidic solutions with pH values of 2, 3, 4, 5, and 6. In addition, particle flow simulations implementing three-dimensional discrete elements are employed to analyze crack initiation and propagation characteristics under different acid conditions. The experimental results indicate that the dynamic compressive strength of sandstone increases with increasing pH value. Energy absorption, reflection, and fragmentation characteristics exhibit clear pH dependence, with stronger acid conditions leading to enhanced damage and comminution. Fragment size distributions of acid-etched sandstone exhibit distinct fractal characteristics, and the corresponding fractal dimension increases as pH decreases, indicating a higher degree of fragmentation and smaller average particle size. Numerical simulations further reveal pronounced differences in deformation and failure modes under varying acidity levels. Specimens exposed to pH 2 exhibit the most severe damage and the highest crack density, while both damage extent and crack number decrease progressively with increasing pH. These findings provide insight into the coupled effects of acidic erosion and dynamic loading on sandstone behavior and contribute to the assessment of rock stability in acidic underground environments.