兰州大学机构库 >土木工程与力学学院
干旱区土质文物劣化机理及材料耐久性研究
Alternative TitleStudy on Deterioration Mechanism and Materials Durability of Earthen Monument
严耿升
Thesis Advisor张虎元
2011-05-28
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name博士
Keyword土质文物 耐久性 干湿循环 冻融循环 盐类风化
Abstract本论文以干旱地区土遗址及石窟寺壁画地仗为原型,研究干旱气候条件下土质文物的干湿、冻融、盐类风化及风蚀耐久性问题。本研究以水分迁移为主线,围绕温度场的变化和可溶盐的发生发展,模拟土质文物的劣化过程,并提出土质文物耐久性的评定方法。具体研究中,首先在水分迁移过程中施加温度场,通过控制温度场的变化,研究水分迁移过程中土质文物产生的水力学效应;其次,从量的角度出发,研究土质文物的持水特性及非饱和情况下的水分渗透、迁移速率问题;再次,从水分作为载体辅助作用的角度,分析盐分迁移的方向、路径、聚集位置和形式,及盐分通过一系列病害形式表达其发生发展的过程。在可控环境条件(湿度、温度)及已知材料特性条件下,研究土质文物中水盐的迁移聚集和表现形式,可以采取有效手段延缓或者阻止其对土质文物本体的破坏,增强土质文物的耐久性。 我国西北地区,强烈干湿循环、冻融循环、风蚀等对性质脆弱的土遗址安全构成极大威胁。本文选择新疆交河故城原状生土试样(固结较好)和重塑土(欠固结)试样进行了干湿和冻融循环试验,之后进行了风蚀试验、强度试验和微观结构观测,来研究土遗址的干湿耐久性和冻融耐久性。干湿循环试验结果表明,在试样原始含水率比较低的情况下,试样首先经历了一个质量增大的过程,3个干湿循环后,试样的质量变化进入一个相对稳定的范围。随着增湿与脱湿过程中伴随的水分迁移,试样质量的总趋势是减小的。且随干湿循环次数增大,原状试样的强度减小,风蚀量增大,即耐久性持续变差。相反,随干湿循环次数增大,重塑样的强度反而有所增大,风蚀量减小,即耐久性有所提高。重塑样由于重塑过程中其微观结构受到破坏,强度弱化。干湿循环在某种意义上对重塑土起到“陈化作用”,具有愈合损伤微结构的能力。初期重塑土强度随干湿循环次数的增加逐渐增强,而后强度逐渐衰减抗风蚀能力减弱。 冻融试验结果表明,在试样初始含水率较低的情况下,前5个冻融循环,试样经历了一个质量增大的过程;在随后的冻融过程中伴随着冻干和吸湿,原状试样质量的总趋势是减小的,重塑样质量的变化趋势维持水平。随冻融循环次数增大,原状试样的微结构出现损伤,强度减小,风蚀量增大,即耐久性持续变差;相反,冻融循环初期,重塑样的强度有所增大,风蚀量减小,耐久性得到了提高。随着冻融循环的增加,重塑样的强度开始下降,这与干湿循环后土体耐久性的变化趋势一致。冻融循环同干湿循环一样可以引起重塑土的“陈化”,愈合了土体的结构,但随着冻融进行,矿物颗粒的微结构损伤不断增大,试样的耐久性降低。 使用Ku-pF非饱和导水率测定系统,测试了交河生土原状样与重塑样的土水特征曲线和非饱和导水率,从非饱和角度分析了土遗址的盐害机理。试验结果表明,遗址土的非饱和导水率随基质吸力的增大呈指数衰减,当生土的体积含水率小于渗透系数为6×10-8<上标!> cm/s所对应的含水率时,水分及孔隙盐溶液向土体表面的相对运移速率明显减慢,易溶盐可能发生结晶作用。根据已得到的非饱和导水率,利用一维渗流的盐分运移方程可以描述遗址土...
Other AbstractHypaethral earthen architecture and Cave temples wall paintings in arid area were treated as a research prototype. And this paper studies the deterioration mechanism and materials durability of earthen monument during cyclic wetting-drying, cyclic freeze-thaw, Salt crystallization and wind erosion. Firstly, moisture migration tests were imposed by temperature field to investigate the effect of moisture migration process on earthen architecture. Secondly, from the point of migration quantity, the infiltration rate has been presented. Once more, as the perspective of auxiliary function, moisture migration process decides the direction, path, location and forms of salt enrichment; simultaneously, the evolution of salt is expressed by a series of disasters. During controlled environments (humidity, temperature) and measured material properties condition, study of salt disasters in earthen monument can provide an effective means to prevent and retard the destruction on monument ontology. As a result, durability of earthen monument is lengthened. Earthen architecture is mostly found in the arid area, which suffers from strong freeze-thaw cycles, wetting-drying cycles and wind erosion process. This study reported the test results of wetting-drying cycles, freeze-thaw cycles and wind erosion on the durability of earthen architecture. Cyclic wetting-drying and freeze-thaw were conducted on the undisturbed and remolded specimens from Jiaohe cultural heritage, Xinjiang, China to understand the durability of earthen architecture to wind erosion and strength attenuation. Test results of wetting-drying cycles showed, under the circumstance of the low original water content, the specimens weight was increased during the beginning three wetting-drying cycles, and then proceeded to a relatively steady state. With the change of moisture content during the condensation-evaporation process, specimen’ weight expressed a decreasing tendency. With the increase in wetting-drying cycles, undisturbed specimens showed a decrease in compressive strength and an increase in wind erosion quantity, reflecting a weakening effect of durability. Comparatively, remolded specimens showed an increase in strength and a decrease in wind erosion quantity, or an inhencing effect of durability at the early wetting-drying cycles; but during the later cycles, a decrease in strength and an increase in wind erosion quantity, or weakening durability were found. It was considered the healing of dest...
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Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226463
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
严耿升. 干旱区土质文物劣化机理及材料耐久性研究[D]. 兰州. 兰州大学,2011.
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