Determination of Water Vapor Transmission Properties of Sandstones in the Yungang Grottoes
Determination of Water Vapor Transmission Properties of Sandstones in the Yungang Grottoes
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DOI：
10.1080/15583058.2022.2147878
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发表时间：
2022-12
影响因子：
2.4
通讯作者：
Yue Zhang;Y. Zheng;Jizhong Huang
中科院分区：
文献类型：
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作者：
Yue Zhang;Y. Zheng;Jizhong Huang
摘要云冈石窟是中国最著名的文化遗产之一，位于砂岩地层中。在现场观察到的劣化的主要原因与水分作用有关，这极大地影响了材料的长期性能。特别是，对于常年暴露在自然气候波动中的不可移动的文化遗产，无法避免与水蒸气的相互作用。为了深入了解当地砂岩的水蒸气传输特性，采用湿杯法进行了一系列的室内试验。考察了水蒸气透过率与环境相对湿度和孔结构的相关性。结果表明，随着相对湿度的增加，毛细凝析液流对扩散系数的贡献显著增大。此外，扩散系数与开孔率呈正相关。水蒸气在砂岩中的扩散是暂态的，扩散系数由平均孔隙半径估算。计算值比试验实测值大两个数量级，反映了扩散路径和扩散面积的复杂微观结构特征。风化作用不断改变砂岩的扩散参数，对云冈石窟造成了不同程度的破坏。
ABSTRACT The Yungang Grottoes, one of China’s most notable cultural heritage sites, are located in sandstone strata. The main causes of deterioration observed in the field are associated with moisture action, which greatly affects the long-term performance of the material. In particular, for immovable cultural heritage that is exposed to natural climatic fluctuations throughout the year, interaction with water vapor cannot be avoided. To obtain an insight into the water vapor transmission properties of local sandstone, a series of laboratory tests were conducted using the wet-cup method. The correlation of water vapor transmission with environmental relative humidity and pore structure was examined. The results indicate that as the relative humidity increased, the diffusion coefficient increased considerably due to the contribution of capillary condensate flow. In addition, a positive relationship was found between the diffusion coefficient and open porosity. The water vapor diffusion in sandstone occurred in transitory mode and the diffusion coefficient was estimated from the average pore radius. The calculated values were two orders of magnitude larger than those measured in the tests, reflecting the complex microstructural features concerning diffusion paths and area. The weathering processes constantly alter the sandstone’s diffusion parameters, causing various damages in the Yungang Grottoes.