Hygrothermal Evaluation of Waterline Rising of a Masonry Tower based on Measurements and Simulations

Abstract

Wet walls in ancient masonry buildings are common due to rainfall, groundwater and other environmental factors, and usually accompanied by the degradation phenomena such as powdering, shedding, salting out, which threatens the value and safety of ancient buildings. It is found that the bottom of Dayan Pagoda has been damp and gloomy for a long time. In recent 40 years, the waterline at the bottom has risen by about 0.5 ∼1m, and the wet area on the north wall is as high as 5m. This paper aims to clarify the cause of the rising waterline and the water source of Dayan Pagoda. The correlation between degradation of Dayan pagoda and environmental factors such as temperature, rainfall and solar radiation was established. Firstly, there was a field measurement on the waterline height in different orientations of Dayan Tower; Then, a coupled heat and moisture transfer model was developed to obtain the hygrothermal distribution in the brick wall, and the impact of rainfall and groundwater was evaluated, and the rising trend of waterline in the future was predicted. The field measured results show that during 2018-2020, the waterline of the west wall of Dayan Pagoda has the largest rise (about 20cm), while the south wall has the smallest rise (about 10cm). The simulation results show that the water source of rising waterline is mainly wind-driven rain rather than groundwater rising. The result contributes to propose environmental control measures to alleviate the degradation of masonry buildings caused by water.