Spatial Distribution Information of Temperature-Humidity-Strain of Soil Cultural Relics During Salt Damage Process

Temperature, humidity, and microstrain fiber Bragg grating sensors (FBGs) were prepared to elucidate the mechanism of salt damage in soil relics. The theoretical models for sensing temperature, humidity, water migration rate, and microstrain were established. The changes in the spatial distribution of different parameters during the salt damage process in different salt solutions on the soil samples were investigated using five each of temperature FBGs, humidity FBGs, and microstrain FBGs. The changes in the material composition, morphology, and pore structure of the soil samples were also analyzed. After the soil samples were damaged by sodium sulfate, cotton-like crystals formed on the surface, and the internal porosity of the soil sample decreased. A gradient distribution of internal temperature, humidity, and strain was observed; the lowest temperature and strain and the highest humidity were observed at the bottom of the soil samples. However, after the soil samples were damaged by NaCl, the internal porosity increased and the surface became denser. Furthermore, compared with ultrapure water and sodium chloride solutions, the sodium sulfate solution had the lowest migration rate in soil samples and the strongest salt damage effect on soil samples.