【作者】 陈雨；

【导师】 王旭东；

【作者基本信息】 兰州大学 ， 地质工程（专业学位）， 2013， 硕士

【摘要】 土遗址是以土为主要建筑材料的具有历史、文化和科学价值的古遗址,是历史上遗留下来的人类生活和进行生产、文化、宗教等活动的场地或者场所。第六批全国重点文物保护单位,已公布的国家级重点文物保护单位的土遗址共计378个,仅西北地区的新疆维吾尔自治区、甘肃省、陕西省三省区就占全国土遗址的22%。西北地区大批土遗址是我国优秀、珍贵文化遗产的重要组成部分,不仅具有很高的学术研究价值,而且随着我国人民生活水平的提高,作为丰富的旅游资源成为提升我国文化软实力的重要标杆之一日温差大、集中式降雨和强烈的蒸发作用是干旱区的主要环境特征之一,正是这种极端气候环境导致这些遗址遭受着风蚀、雨蚀、反复干湿循环、冻融循环作用的破坏。通过大量的现场调查和文献报道发现,土遗址遭受掏蚀、酥碱、风蚀、表面风化、雨蚀、开裂坍塌等病害的威胁,而盐害在这些病害中扮演了重要的角色。因此,开展土遗址盐害研究,对于解释土遗址病害成因,制订相应的遗址保护对策具有重要意义。本论文基于西北干旱区土遗址现状调查和文献报道,对取自甘肃省敦煌市的土洗盐后,加入不同含量(1%、3%、5%)的NaCl.Na2SO4及二者不同比例的复合盐,制成5×5×5cm试块,进行了室内风化试验研究。在室内风化试验结果的基础上,对试验配比进行了改进,含盐量控制在3%以下,并开展了干湿循环试验、冻融循环试验,主要通过宏微观照片和力学性能的变化来表征,最后通过土遗址水盐运移试验、温度对含盐土体的影响研究对土遗址盐害机理进行了探讨。研究结果表明,土体盐害的发生与多种因素有关,含盐量、含盐种类、含水量、土体所处环境等。我们提出土遗址盐害阈值：在一定条件下,当土体含盐量超过某个值时,土体表面和结构发生比较明显的破坏、力学性能降低,该含盐量即为对应条件下的盐害阈值。基于此,本文认为,在本研究室内风化条件下,初步判断盐害阂值为：1%<NaCl<3%,Na2SO40.1%,复合盐FA(C：S=1：1)1%,0.2%<复合盐FB(C:S=1:2)<0.4%,1%<复合盐FC(C：S=2：1)<3%,(其中C代表NaCl, S代表Na2SO4)；在干湿循环、冻融循环条件下,土体外观发生显著变化,土体力学性能较未循环样基本都明显降低,反复干湿循环、冻融循环使得土体发生破坏,盐分在干湿冻融循环中扮演了催化作用。水盐运移试验表明：盐分随着土体水分蒸发由内向外运移,水分在盐分迁移过程中扮演了重要角色。红外热成像试验表明：含盐量越大,土体温度越高,试块吸收热量的能力越强,含盐量梯度越明显,温度变化曲线梯度差也越明显,这种温度差对水盐运移有重要推动作用,含盐土体温度的变化与含盐种类、含盐量、水分等因素有关。本研究探讨了不同条件下盐害发生的程度,提供了盐害研究的方法和思路,提出了盐害阈值并给出相应的值和范围,可为土遗址保护提供科学理论依据,对土遗址保护及对策的制定具有指导意义,同时对西北地区石窟寺壁画盐害机理和相关盐害研究及进一步完善亦可提供借鉴和参考。更多还原

【Abstract】 Earthen sites are ancient architecture with historical, cultural, and scientific value, which are based on soil as the main building materials, the place where ancient people are engaged in production, cultural exchange, religion and other activities.The number of national key cultural relics protection units has amounted to378in the sixth published national key cultural relics protection units,and the proportions of which accounted for22%in three places of Xinjiang Uygur Autonomous Region, Gansu province, Shanxi province in northwest area of China. A large number of earthen sites in northwest of China are important part of our excellent precious cultural heritage with high academic value, with the improvement of living standards of Chinese people, the rich tourism resources of the region will become an important symbol to enhance China’s cultural soft power.Large diurnal temperature, concentrated rainfall and intense evaporation are one of the environmental characteristics in the arid area, it is the extreme weather conditions that make ancient earthen sites suffer from damages of wind erosion, rain erosion, repeated wet and dry cycles, freeze-thaw cycles. According to on site survey and related references, we found that earthen sites suffered from damages of crisp base, wind erosion, weathering, rain erosion, cracking and collapse, and salt damage plays an important role in these damages.Therefore,exploring salt damage is of great significance for the interpretation of causes of earthen sites.then appropriate protection measures of earthen sites could be made.This thesis are based on references and field investigation of earthen sites. Firstly, the soil taken from Dunhuang City, Gansu Province, are mixed with different percentage (1%,3%,5%) of NaCl、Na2SO4and the combination of both to form5×5×5cm test block, and laboratory weathering tests are carried out. Then, on the basis of the laboratory weathering test results and related references, we improve experiment design, the percentage of salts added are controlled below3%, and wet and dry cycle test, freeze-thaw cycle test are carried out, mainly judged through macro and micro photos and mechanics changes in performance. Finally we explore the mechanism of salt damage to earthen sites by the test of water and salt transport in test block and the test of the effects of temperature on saline soil.The results showed that the occurrence of salt damage to earthen sites is related to many factors, such as salt content, salt types, moisture content and the environment. We propose threshold of salt damage to earthen sites:under certain conditions, when salt content of soil exceeds a certain value, the surface and the structure of the soil change obviously, the mechanical properties declined greatly, the salt content in this condition is called salt damage threshold. Based on this, the paper argues that in this study, under indoor weathering conditions, the thresholds of salt damage to soil are:1%<NaCl<3%, Na2S04,0.1%, complex salt FA (C:S=1:1)1%,0.2%<complex salt FB (C:S=1:2)<0.4%,1%<complex salt FC (C:S=2:1)<3%,(where C represents NaCl, S represents Na2SO4); in this study, after wet and dry cycle, freeze-thaw cycle tests, the appearance of test block change greatly, the physical properties declined greatly compared with controlled subjects. It is the repeated wet and dry cycles, freeze-thaw cycles that make the soil damaged, the salts in the cycles play a catalytic role. Water and salt transport experiments show that:the salts moved from inside of the soil to outside of it, water play an important role in the salt transport process. Infrared thermal imaging tests showed that the greater the salt content, the higher the temperature of the soil, the stronger the ability of the test block to absorb heat. This temperature difference of soil containing different salts play a important role in water-salt transport. The change of saline soil has connection with the types of salts, salt content, water and other factors.This study investigated the extent of salt damage to soil under different conditions, provided a method salt damage research, propose the threshold of salt damage to soil and the corresponding values and ranges. The results can provide scientific theoretical basis for earthen sites preservation, and guide the corresponding measures to be made to preserve earthen sites. At the same time, it can provide references to the Cave Temple murals mechanism of salt damage in northwest of China and related research on salts.更多还原