Analysis of the main controlling factors of weathering rates in Yungang Grottoes sandstones

Analyzing the weathering rates and their main environmental controlling factors is fundamental in conserving rocky relics. In this study, using the sandstones of the Yungang Grottoes as a case study, the rock weathering rates were quantitatively expressed by the expansion rates of crack widths, changes in the column inclination angles and door settlements. Factor analysis was employed to explore the influences of environmental factors, including wall temperature, ambient temperature, ambient humidity, air pressure, wind speed, and accumulated rainfall, on the weathering rates of these sandstones. Multivariate linear regression techniques were subsequently used to identify the main controlling factors affecting these weathering rates. It was found that ambient humidity, wall temperature, and accumulated rainfall have the greatest influences on the expansion rates of crack widths during summer, while ambient temperature and wind speed are more influential in spring, with environmental humidity as the main controlling factor. For the changes in column inclination angles, wall temperature, ambient temperature, ambient humidity, air pressure, wind speed, and accumulated rainfall exert the greatest impacts in the summer, with smaller effects in other seasons, and wall temperature acting as the controlling factor. Regarding the change rates in door settlement, wall temperature, ambient temperature, ambient humidity, and accumulated rainfall have the most substantial effects in the summer, while air pressure and wind speed are more influential in spring, with environmental humidity again being the main controlling factor. These findings may provide useful references for both the analysis of weathering rates and the conservation of the grottoes.