干湿循环作用下含盐类遗址土盐渍劣化试验研究
发布时间：2019-06-25 20:48
【摘要】：在西北干旱和半干旱地区独特气候条件下遗存了大量珍贵的土遗址,如长城、故城等。这些宝贵的文化遗产不仅是智慧的结晶,也是政治、军事、科学、文化、经济和社会发展进程的历史见证,具有极其重要的意义。土遗址长期处在极端恶劣的气候环境之中,导致土体发育各种病害,其根本原因是土体劣化致使抵抗外界破坏能力下降所致。集中降雨和强烈蒸发的气候改变不但加剧了区域内的干湿循环,还加剧土的盐渍化,盐渍劣化成为西北地区土遗址中典型的工程地质问题之一。因此,加强干湿循环作用下盐分对遗址土的影响研究为预防这些建筑文物发生更大的变形破坏具有科学的指导性,同时也可为文物保护工作提供有效的具有针对性的理论依据。 在对西北地区遗址土盐渍劣化定性认识的前提下,选择合理的盐分含量、类别开展干湿循环作用下的含盐遗址土盐渍劣化试验。通过对不同盐分类别、不同盐分含量的试块,在三次干湿循环后所进行的直接剪切试验、无侧限抗压试验以及抗拉试验,较为直观的认识不同盐分类别、盐分含量对含盐遗址土的盐渍劣化程度；通过声波试验,测试在干湿循环过程中含盐遗址土的结构变化,从宏观的角度表现遗址土盐渍劣化过程；通过微结构观测揭示含盐遗址土力学特性与其微结构各参数之间的内在联系,建立具有微结构变化特征背景的关系式,从微观层面研究干湿循环对遗址土盐渍劣化。 主要研究成果为：(1)盐渍劣化后的遗址土力学性能测试表明：随着含盐量的增多,试样的黏聚力、抗压以及抗拉强度逐渐减小,内摩擦角则呈现先增大后减小的变化规律；掺入Na2SO4盐分的试样劣化程度更为严重,其表现出的力学性能也相应的比掺入NaCl盐分的试样有所降低；掺入复合盐(Na2SO4+NaCl)的试样,因为NaCl盐分的存在,致使Na2SO4的溶解度明显降低而提前析出,不具有表聚性,对试样整体破坏性最大,表面强度则介于掺入单盐的试样之间。(2)声波测试结果表明：经过三次干湿循环后的纵波波速相比第一次干湿循环后的纵波波速减小了10%以上,且随着含盐量的增加,波速减小幅度逐渐增大,从侧面证实了干湿循环作用下的含盐遗址土确实存在盐渍劣化的过程；经过回归分析发现,试样纵波波速与抗压、抗拉强度之间存在良好的幂指数关系,与抗剪强度之间的关系则表现较强的离散性。(3)通过微观结构观测,孔隙中确实存在针状的Na2SO4晶体以及颗粒状的NaCl晶体；随着含盐量的增加,微观结构类型由骨架状向基质状过渡,土颗粒表面的亮点增多,颗粒粒径趋于均一化,整体结构较为松散；利用多元逐步回归分析方法,分析盐渍劣化后遗址土力学强度参数与微结构参数之间的相关性,得出具有一定参考价值的回归方程和模型。
[Abstract]:In the northwest arid and semi-arid areas of the unique climate conditions left a large number of precious soil sites, such as the Great Wall, so the city and so on. These precious cultural heritages are not only the crystallization of wisdom, but also the historical witness of the process of political, military, scientific, cultural, economic and social development, which is of great significance. The soil site has been in extremely bad climate environment for a long time, which leads to the development of various diseases of the soil, the root cause of which is the decline of the ability to resist external damage caused by the deterioration of the soil. The climate change of concentrated rainfall and strong evaporation not only aggravates the dry and wet cycle in the region, but also aggravates the salinization of soil, which has become one of the typical engineering geological problems in soil sites in Northwest China. Therefore, strengthening the research on the influence of salt on the site soil under the action of dry and wet cycle has scientific guidance for preventing the greater deformation and destruction of these architectural cultural relics, and at the same time, it can also provide an effective and targeted theoretical basis for the protection of cultural relics. Based on the qualitative understanding of soil salt deterioration in northwest China, a reasonable salt content and category were selected to carry out the experiment of soil salt deterioration in salt-bearing sites under the action of dry and wet cycle. Through the direct shear test, unconfined compression test and tensile test after three dry and wet cycles, the salt deterioration degree of different salt categories and salt content was recognized intuitively, and the structural change of saline site soil during dry and wet cycle was tested by acoustic wave test, and the process of saline deterioration of saline site soil was demonstrated from a macro point of view. Through microstructure observation, the internal relationship between the mechanical properties of salt-bearing site soil and its microstructure parameters is revealed, and the relationship with the background of microstructure change is established, and the deterioration of salt stains caused by dry and wet cycle to the site soil is studied from the microscopic level. The main results are as follows: (1) with the increase of salt content, the cohesion, compression and tensile strength of the sample decrease gradually, and the internal friction angle increases at first and then decreases, and the deterioration degree of the sample mixed with Na2SO4 salt is more serious, and the mechanical properties of the sample are also lower than those of the sample mixed with NaCl salt. Because of the existence of NaCl salt, the solubility of Na2SO4 is obviously decreased and precipitated in advance, which is the most destructive to the sample, and the surface strength is between the samples mixed with single salt. (2) the results of acoustic wave test show that the longitudinal wave velocity after three dry and wet cycles is more than 10% lower than that after the first dry and wet cycle. With the increase of salt content, the decrease of wave velocity increases gradually, which proves that the salinization process does exist in the saline-bearing site soil under the action of dry and wet cycle. Through regression analysis, it is found that there is a good power exponential relationship between longitudinal wave velocity and compressive and tensile strength, but a strong discreteness between longitudinal wave velocity and compressive and tensile strength. (3) through microstructure observation, needle-like Na2SO4 crystals and granular NaCl crystals do exist in pores; With the increase of salt content, the microstructure types transition from skeleton to matrix, the bright spots on the surface of soil particles increase, the particle size tends to be uniform, and the overall structure is looser. The correlation between mechanical strength parameters and microstructure parameters of site soil after salinization is analyzed by means of multiple stepwise regression analysis, and the regression equations and models with certain reference value are obtained.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：K878;P642.13
本文编号：2505992
[Abstract]:In the northwest arid and semi-arid areas of the unique climate conditions left a large number of precious soil sites, such as the Great Wall, so the city and so on. These precious cultural heritages are not only the crystallization of wisdom, but also the historical witness of the process of political, military, scientific, cultural, economic and social development, which is of great significance. The soil site has been in extremely bad climate environment for a long time, which leads to the development of various diseases of the soil, the root cause of which is the decline of the ability to resist external damage caused by the deterioration of the soil. The climate change of concentrated rainfall and strong evaporation not only aggravates the dry and wet cycle in the region, but also aggravates the salinization of soil, which has become one of the typical engineering geological problems in soil sites in Northwest China. Therefore, strengthening the research on the influence of salt on the site soil under the action of dry and wet cycle has scientific guidance for preventing the greater deformation and destruction of these architectural cultural relics, and at the same time, it can also provide an effective and targeted theoretical basis for the protection of cultural relics. Based on the qualitative understanding of soil salt deterioration in northwest China, a reasonable salt content and category were selected to carry out the experiment of soil salt deterioration in salt-bearing sites under the action of dry and wet cycle. Through the direct shear test, unconfined compression test and tensile test after three dry and wet cycles, the salt deterioration degree of different salt categories and salt content was recognized intuitively, and the structural change of saline site soil during dry and wet cycle was tested by acoustic wave test, and the process of saline deterioration of saline site soil was demonstrated from a macro point of view. Through microstructure observation, the internal relationship between the mechanical properties of salt-bearing site soil and its microstructure parameters is revealed, and the relationship with the background of microstructure change is established, and the deterioration of salt stains caused by dry and wet cycle to the site soil is studied from the microscopic level. The main results are as follows: (1) with the increase of salt content, the cohesion, compression and tensile strength of the sample decrease gradually, and the internal friction angle increases at first and then decreases, and the deterioration degree of the sample mixed with Na2SO4 salt is more serious, and the mechanical properties of the sample are also lower than those of the sample mixed with NaCl salt. Because of the existence of NaCl salt, the solubility of Na2SO4 is obviously decreased and precipitated in advance, which is the most destructive to the sample, and the surface strength is between the samples mixed with single salt. (2) the results of acoustic wave test show that the longitudinal wave velocity after three dry and wet cycles is more than 10% lower than that after the first dry and wet cycle. With the increase of salt content, the decrease of wave velocity increases gradually, which proves that the salinization process does exist in the saline-bearing site soil under the action of dry and wet cycle. Through regression analysis, it is found that there is a good power exponential relationship between longitudinal wave velocity and compressive and tensile strength, but a strong discreteness between longitudinal wave velocity and compressive and tensile strength. (3) through microstructure observation, needle-like Na2SO4 crystals and granular NaCl crystals do exist in pores; With the increase of salt content, the microstructure types transition from skeleton to matrix, the bright spots on the surface of soil particles increase, the particle size tends to be uniform, and the overall structure is looser. The correlation between mechanical strength parameters and microstructure parameters of site soil after salinization is analyzed by means of multiple stepwise regression analysis, and the regression equations and models with certain reference value are obtained.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：K878;P642.13
【引证文献】
相关硕士学位论文 前2条
1 江耀;非饱和黄土特征曲线的研究[D];兰州大学;2012年
2 陈雨;西北干旱区土遗址盐害室内试验研究[D];兰州大学;2013年
，本文编号：2505992
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