Effect of hydro-chemical corrosion on mechanical properties of red sandstone under uniaxial and triaxial compression

Abstract

The degradation of mechanical characteristics of sandstone, a common engineering material in acid environment, is directly related to the project service life forecast. In order to investigate the influence of water–rock interaction on the mechanical properties of red sandstone, a series of uniaxial and triaxial compression tests were conducted on sandstone immersed in solutions of different pH values and immersion times. Moreover, the effects of acid chemical corrosion on the microscopic structure of the sandstone were analyzed using scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) tests. A chemical damage strength model was then formulated within the theoretical framework of chemical reaction kinetics theory. The results indicate that the different hydro-chemical solutions have a significant deterioration effect on the sandstone. In immersion tests, the water–rock reaction of sandstone is essentially completed after 30 days of immersion. With increasing immersion time, the uniaxial compressive strength of sandstone immersed in neutral and weakly acidic saline solutions shows an initial rapid decrease followed by a slow increase, while sandstone immersed in distilled water and strongly acidic solutions shows varying degrees of decrease over time. High confining pressure weakens the corrosion effect of the solutions on the sandstone, particularly, the neutral solution. In the triaxial compression tests, strong acid has a great corrosion effect on sandstone. The average peak strength of sandstone immersed in pH2, pH4, pH7, and distilled water decreased by 30.2%, 28.7%, 25.1%, and 22.8%, respectively. The model considers calcium precipitation not only reflects the change in pH value of the immersion solution with time but also effectively predicts the strength of sandstone immersed in different solutions. The results deepen our understanding of the deterioration mechanism of silicon-based porous rock under different chemical solutions and would be of importance for the long-term stability analysis of rock engineering in complex groundwater environments.