In situ detection of spatial distribution information of temperature-pH-strain of sandstone cultural relics

To monitor in situ the temperature, pH, and micro-strain change information of sandstone artifacts in the process of oxalic acid corrosion, the temperature, pH, and micro-strain fiber Bragg grating (FBG) sensors are developed. A theoretical model of the sensors is established. The surface morphology, material composition, pore structure, temperature, pH, and micro-strain of sandstone corroded by oxalic acid solutions of different concentrations are investigated. The experimental results show that the higher the concentration of oxalic acid, the stronger the corrosiveness of the sandstone. Ferrous oxalate and calcium oxalate produced by corrosion continuously precipitate from the inside of the rock, and the dual reaction of crystallization and dissolution occurs, reducing the proportion of fine pores in the rock pore suction and gravity. The oxalic acid solution is transported to the middle of the sandstone (3 cm) and undergoes the strongest chemical reaction with ore particles and debris, resulting in the maximum wavelength drift of the temperature, pH, and micro-strain sensors. The results of this study provide important support for analyzing the acid dissolution mechanism of stone cultural relics and the preventive protection of cultural relics.