李凤洁, 王旭东, 郭青林. 2021. 湿度影响下莫高窟壁画地仗层吸附水及吸力变化特征研究[J]. 工程地质学报, 29(4): 1188-1198. doi: 10.13544/j.cnki.jeg.2019-455.
    引用本文: 李凤洁, 王旭东, 郭青林. 2021. 湿度影响下莫高窟壁画地仗层吸附水及吸力变化特征研究[J]. 工程地质学报, 29(4): 1188-1198. doi: 10.13544/j.cnki.jeg.2019-455.
    Li Fengjie, Wang Xudong, Guo Qinglin. 2021. Adsorbed moisture feature and suction variation characteristics of earthen plaster in Mogao Grottoes under influence of humidity[J]. Journal of Engineering Geology, 29(4): 1188-1198. doi: 10.13544/j.cnki.jeg.2019-455.
    Citation: Li Fengjie, Wang Xudong, Guo Qinglin. 2021. Adsorbed moisture feature and suction variation characteristics of earthen plaster in Mogao Grottoes under influence of humidity[J]. Journal of Engineering Geology, 29(4): 1188-1198. doi: 10.13544/j.cnki.jeg.2019-455.

    湿度影响下莫高窟壁画地仗层吸附水及吸力变化特征研究

    ADSORBED MOISTURE FEATURE AND SUCTION VARIATION CHARAC ̄TERISTICS OF EARTHEN PLASTER IN MOGAO GROTTOES UNDER INFLUENCE OF HUMIDITY

    • 摘要: 莫高窟气候干燥,窟内壁画地仗层常处于低含水率、高吸力的状态,受到洞窟环境湿度波动的影响较大。为了进一步了解湿度影响下地仗层土体中吸附水以及吸力变化特征,本文通过蒸汽吸附法测试莫高窟不同地仗层高吸力段内的土水特征曲线,并且根据测试结果分析土体中由于范德华力与毛细凝聚作用产生的不同吸力的变化特征;同时进一步利用蒸汽吸附法测试了含NaCl地仗层土水特征曲线并探讨水汽吸附过程中渗透吸力特征;此外利用热重分析方法测试地仗层土体中在范德华力与毛细凝聚作用下所吸附水分的特征。结果表明:地仗层水汽吸附过程中土体内大部分基质吸力来自于毛细凝聚作用,土颗粒分子间范德华力仅在含水率极低的情况下为土体提供比较明显的吸力,湿度影响下地仗层水汽吸附过程中土体内渗透吸力仅在外界环境湿度大于地仗层中盐分的潮解临界湿度时才比较明显;地仗层土体所吸附的水分大部分以弱结合水形式存在,并且地仗层中澄板土含量越高,弱结合水临界含水率越大。结论可以为湿度影响下的壁画病害机理以及地仗层中水汽运移等问题的研究提供理论基础。

       

      Abstract: The climate of the Mogao Grottoes is dry,so the earthen plaster of murals in the caves are in the state of low moisture content and high suction. This state of soil is greatly affected by the humidity in the cave environment. To further understand the characteristics of suction variation and the property of adsorbed moisture in earthen plaster under the influence of relative humidity in cave environment,we tested the soil-water characteristic curves at high suction range of different kinds of earthen plasters in Mogao Grottoes through vapor adsorption process,then calculated and analyzed the variation characteristics of different types of suction caused by Vander Waals force and capillary condensation respectively according to the test results. Meanwhile,we also tested the soil-water characteristic curves of plaster samples with different contents of NaCl and discuss the osmotic suction during moisture adsorption process. In addition,we utilized thermogravimetric to test and analyze the features of the moisture which adsorbed by earthen plaster under the action of Vander Waals force and capillary condensation. The results show the follows. Most matric suction in earthen plaster still comes from capillary condensation during the moisture adsorption process. The van der Waals forces between soil particles can provide obvious suction only in the case of very low moisture content. Significant osmotic suction can be present during the moisture adsorption process of earthen plaster only when environmental humidity is greater than the deliquescence relative humidity of the soluble salt in earthen plaster. Most moisture adsorbed by plaster is in the form of loose bound water. The critical moisture content of loose bound water increases with the Dengban soil content in earthen plaster. These findings can offer data and theoretical basis for the research of mechanism of mural damage with the participation of moisture and the water vapor transport in plaster.

       

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