Abstract: Environmental changes cause the surface evapotranspiration rate of naturally preserved sandstone to vary, resulting in capillary water migration within a specific range. This process not only induces repeated hydration expansion and drying shrinkage of minerals within the sandstone but also accelerates rock deterioration due to capillary migration, including salt crystallization, dissolution cycles, freeze-thaw effects, and biological weathering. To provide a reliable reference for the preservation of historical stone buildings, this study investigates the capillary water migration mechanism, focusing on the stone archway of “Jingnanxiongzhen” in Enshi, Hubei Province. Long-term microenvironment monitoring and laboratory experiments were conducted. Numerical simulations using Comsol Multiphysics software integrated microenvironment monitoring data with rock weathering patterns, establishing a research framework under partial continuous immersion conditions. The results show that: 1) From the perspective of liquid volume fraction distribution at different times, in the long time dimension, the hydraulic gradient near the wetting front is gentle, and the volume water content of sandstone changes most sharply, and the deterioration phenomenon of rock is most obvious in this height range. 2) Once capillary water reaches dynamic equilibrium, vertical water content varies, with higher values at the bottom and lower at the top. Horizontally, water content decreases from the center to the sides. The wetting front fluctuates with evapotranspiration rate changes, aligning with observed weathering patterns. 3) Reducing the pressure head at the base of historical stone structures significantly decreases water infiltration. Lowering groundwater levels around the stone archway achieves this reduction, mitigating capillary-induced deterioration.

Key words: damage of rock, capillary water migration, Penmane-Monteith equation, Richards equation, evaporation boundary condition