Dependency of conservation conditions of Takase stone Buddha, Oita, Japan, on anisotropy of liquid water diffusivity

Takase Stone Buddhas is one of the important old stone buddha sculptures curved into the inner wall of a cave in Oita, Japan. It is located in the cave curved into the cliff of a hill of volcanic tuff. In general, because the cave is currently protected from rain and direct solar radiation by the roof shelter and waterproof treatment, the Buddhas is well conserved and no currently ongoing weathering can be clearly observed. However, because of a high ground water level, there is a concern in the influence of water evaporation at and near the surface of the stone buddhas and the wall of the cave on their deterioration. In the past, we conducted a long-term field survey of conservation environment to obtain yearly data set of the conservation environment that can be used as input of numerical simulations of heat and water transport in the material. In this paper, we report measurement data of the ground water level as well as the liquid water diffusivity of the tuff stone that significantly affects the conservation condition. We also performed numerical analyses on heat and moisture transport in the tuff stone layer and stone buddhas. The simulation results show that the conservation condition of Takase stone Buddha strongly depends on the anisotropy of liquid water diffusivity of the tuff stone.