Study on the Effect of Dry-Wet Cycles on Dynamic Mechanical Properties of Sandstone Under Sulfuric Acid Solution

The influence of water-rock interaction in the process of coal mine construction cannot be ignored, especially when the groundwater quality is complex and contains acidic substances. In this paper, considering the influence of mining, blasting, and earthquake, the dynamic mechanical properties and fractal characteristics of sandstone under acid dry-wet cycle were studied. A comprehensive method combining X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometer mapping (EDS Mapping) technology for chemical damage analysis was established, and the damage mechanism of sandstone was summarized. The test results show that the acid dry-wet cycle has a great influence on the dynamic peak stress of sandstone (sigma(d)) and elastic modulus (E-d) is higher than neutral. And with the decrease of pH value of acidic solution, sigma(d) and E-d decrease and the peak strain increases, indicating that the acid solution has corrosion and softening effect on sandstone. With the increase of acid dry-wet cycles, the fractal dimension increases linearly. Sandstone fragments show more broken blocks and smaller particle sizes. Microscopic comprehensive analysis shows that acid solution (H2SO4) will preferentially react with metal oxides and salt cements to open rock pores, and gypsum (CaSO4) and other products will be formed in the process. In the process of the acid dry-wet cycle, the sandstone is corroded by acid solution, which leads to pore growth. Meanwhile, the dry-wet cycle causes repeated expansion and contraction of rock particles. Both of them accelerate rock failure.