| 莫高窟壁画地仗持水特性研究 | |
| Alternative Title | Study on Moisture Retention Characteristics of Wall Paintings at Mogao Grottoes |
| 贾全全 | |
| Subtype | 硕士 |
| Thesis Advisor | 谌文武 |
| 2020-05-30 | |
| Degree Grantor | 兰州大学 |
| Place of Conferral | 兰州 |
| Degree Name | 工学硕士 |
| Degree Discipline | 地质工程 |
| Keyword | 莫高窟 壁画地仗 持水性能 非饱和土力学 |
| Abstract | ~莫高窟作为我国古丝绸之路上重要的文化遗产，以其中精美的壁画和彩塑闻名于世。历经千年，壁画正在受到各类病害的侵扰。莫高窟的壁画具有多层性的特点，而地仗层作为其中至关重要的一层，其持水性能关乎着壁画病害的形成与发育，分析研究地仗的持水特性是研究壁画盐害形成机理及脱盐方法的前提。 本文以莫高窟地仗作为研究对象，根据对莫高窟地仗层材料的分析制取了不同类型的地仗模拟试样，对其开展了土-水特征曲线试验，分析了全吸力范围内不同类型的模拟地仗的土水特征规律通过恒温吸湿-脱湿试验，探究了地仗对水汽的吸附-解吸特性运用设计的用于壁画地仗毛细迁移的装置，通过毛细上升试验，分析了氯化钠溶液在不同类型地仗内的迁移规律。并结合微观结构及热常数等分析，得出如下主要结论： （1）获得了可靠的全吸力范围内不同物质组成地仗的土-水特征曲线。澄板土加筋后其土水特性出现了一定的差异。但粗泥层与细泥层相比，土水特性差异不大。分别运用VG模型和F-X模型对所得SWCC进行拟合，F-X模型较为适宜描述地仗层的SWCC。根据地仗试样高吸力段SWCC的特点，推荐窟内相对湿度不宜高于58%。运用拟合所得SWCC加之非饱和渗透系数函数，可获得地仗试样非饱和导水率变化趋势。 （2）不同类型模拟地仗试样的孔隙特点各自不一，粗泥层中孔隙数目最多，其孔径分布也是最大的，且孔隙大多在麦秸杆之中及其周围。细泥层中有许多来自于麻纤维的小孔隙（<100nm），但这部分孔隙对于试样水分的吸附及迁移影响不大。各类型试样的导热性能差异不显著。 （3）壁画的地仗层在高湿度及低湿度环境下的吸湿脱湿规律是指数衰减形式的。其吸湿脱湿速率的特点是先快后慢。吸湿及脱湿速率在50h后出现明显的转折。地仗吸附的水分不能完全解吸。高湿度下对于水蒸气的吸附能力较强，而且这种吸附在相较于达到吸附平衡约1/6时已经完成吸附总量的约60%，所以日常维护中应注重洞窟内低湿度的保持。 （4）模拟地仗试样毛细上升速率都有先快后缓的趋势，其中复合地仗试样及粗泥层试样的毛细上升速率是最快的。随着试样高度的增加其含水率逐渐减小，粗泥层和复合地仗试样其含水率要远高于细泥层、加沙澄板土、天然澄板土以及脱盐澄板土试样试样。NaCl在毛细湿润锋部位产生大量的聚集，病害及盐结晶相应出现。 （5）对于复合地仗试样，其含水率分布规律及盐分分布规律都在粗泥层-细泥层交界面附近产生突变，即在界面处对于毛细水的运移有毛细屏障效应的存在，毛细屏障效应对于盐害的形成机理的讨论及脱盐的方法都提出了更高水平的要求。 |
| Other Abstract | ~As an important cultural heritage on the ancient Silk Road in China, Mogao Grottoes are famous for its exquisite wall paintings and colorful sculptures. After thousands of years, wall paintings are being invaded by various deteriorations. The wall paintings of Mogao Grottoes are multi-layered, and the plaster layer is the vital one of that. Its moisture retention performance is related to the formation and development of mural deteriorations. Analysis of the moisture retention characteristics of plaster is the premise of studying the formation mechanism of salt deterioration and the method of desalination in wall paintings. In this dissertation, the plaster of Mogao Grottoes is used as the research object. Different types of simulated plaster samples are prepared based on the analysis of the plaster layer of Mogao Grottoes. The soil-water characteristic test was carried out to analyze the soil-water characteristic law of different types of simulated plaster samples in the full suction range. Through constant temperature moisture absorption-desorption test, the adsorption-desorption characteristics of plaster to water vapor were investigated. Using the designed device for capillary migration of wall painting plaster, the migration law of sodium chloride solution in different types of plaster was analyzed by capillary rise test. Combined with the analysis of microstructure and thermal constant, the following main conclusions are drawn: (1) SWCC of simulated plaster with different material composition in full suction range were obtained. The SWCC of different samples have some differences. However, compared with the coarse plaster and the fine plaster, the soil water characteristics are not much different. Based on the experimental data in the full suction range, the fitted SWCC of the highly accurate can be obtained, and the F-X model is more suitable to describe the SWCC of the plaster. According to the characteristics of SWCC in the high suction range of the plaster samples, it is recommended that the relative humidity in the cave should not be higher than 58%. Using the fitted SWCC and unsaturated permeability coefficient function, the unsaturated hydraulic conductivity change trend of plaster samples can be obtained. (2) The pore characteristics of different types of simulated plaster samples are different. The number of pores in the coarse plaster is the largest, and the pore distribution is also the largest. Most of the pores are in and around the wheat straw. There are many small pores (<100nm) in the fine plaster that are not in the remaining samples. These pores come from hemp fibers, but they have little effect on the moisture absorption and migration of the samples. There is little difference in the thermal conductivity of each type of sample. (3) The moisture absorption-desorption law of the wall painting plaster under high and low humidity environment is in the form of exponential decay. The characteristic of its moisture absorption and desorption rate is "fast first and then slow". After 50h, the moisture absorption and desorption rate will obviously change. The moisture absorbed by the plaster cannot be completely desorbed. Under high humidity, it has a strong ability to adsorb moisture vapor, and this adsorption process has already completed about 60% of the total adsorption process only in 1/6 of the time. Extra attention should be paid to the increase in humidity in the cave. (4) The capillary rise rate of the simulated ground warfare samples has a tendency of fast first and then slower, and the coarse plaster sample is the fastest. the moisture content of the sample gradually decreases with the increase of height. The coarse plaster sample has a much higher moisture content than other types of plaster samples. The distribution of NaCl in the 0-7cm section of the sample is relatively uniform, and no accumulation will occur. A large amount of accumulation occurred in the 7-10 cm section, and deterioration and salt crystals appeared accordingly. (5) For the complex plaster sample, the moisture content distribution law and the salt distribution law are abruptly changed near the coarse-fine plaster layer interface, that is, there is a capillary barrier effect on the movement of capillary water at the interface. The capillary barrier effect puts forward a higher level of discussion on the formation mechanism of salt deterioration and the method of desalination. |
| Pages | 74 |
| URL | 查看原文 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | https://ir.lzu.edu.cn/handle/262010/463447 |
| Collection | 土木工程与力学学院 |
| Affiliation | 土木工程与力学学院 |
| First Author Affilication | School of Civil Engineering and Mechanics |
| Recommended Citation GB/T 7714 | 贾全全. 莫高窟壁画地仗持水特性研究[D]. 兰州. 兰州大学,2020. |
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