Damage behavior of sandstone induced by dry-wet cycle combined with acid environment

Abstract Groundwater infiltration and ventilation drying have a significant influence on the stability of the surrounding rock mass during coal mine construction, especially when the groundwater quality is acidic. This paper presents an experimental study of the damage characteristics of sandstone that mimic the rock-fluid interactions affected by the combined action of acid environment and dry-wet cycle. Nuclear magnetic resonance(NMR) and uniaxial compression tests were conducted to characterize the physical and mechanical behavior, while X-ray diffraction(XRD) and scanning electron microscopy(SEM) were performed to analyze the compositional and microstructural changes respectively. The results reveal that as the number of cycles increases, the spectral area and porosity are always increasing, the peak strain increases, and the peak strength falls. And with higher acidity, the pore shifting trend is much more noticeable. With the rise of acidity, the minerals in the rock sample react violently with the acidic ion H+, resulting in a steady increase in the number of pores and fissures. The porosity is employed to define the rock damage. The functional relationship between the number of drying-wetting cycles and the damage degree was established by analysing the quantitative association of porosity with rock damage. Our study provides a better understanding of the damage mechanisms of sandstone, which could be used to predict the deformation and failure of rock.