| 黄土湿陷过程中微观结构的动态变化研究 |
| Alternative Title | Microsturcture Change of Loess Soil during Wet Collapsing
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| 邵显显 |
| Subtype | 硕士
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| Thesis Advisor | 周仲华
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| 2014-05-24
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| Degree Grantor | 兰州大学
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| Place of Conferral | 兰州
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| Degree Name | 硕士
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| Keyword | 黄土湿陷
增湿变形
微观结构
孔径分布
非饱和土力学
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| Abstract | 本文选取兰州地区的Q3马兰黄土，采用静力压实法制备含水率为9%，干密度分别为1.30g/cm3、1.40g/cm3、1.50g/cm3的黄土试样，进行分级浸水直至试样饱和的黄土增湿变形试验，并对增湿试验前后的试样进行扫描电镜试验和压汞试验。论文从非饱和角度研究了不同干密度黄土增湿变形特性随饱和度增大的动态变化规律，以及黄土湿陷过程中颗粒形态、孔隙结构的变化规律，进一步探讨了黄土湿陷的微观机理。主要结论如下：
（1）黄土在一定压力下分级浸水产生增湿变形时，试样的孔隙比随饱和度增大呈指数函数递减，湿陷后不同干密度黄土的孔隙比趋向于一致。
（2）对应于每一级压力大小，黄土试样存在一个临界干密度，当试样浸水前的干密度小于临界干密度时，浸水后才会产生湿陷。黄土湿陷的临界干密度随着竖向压力的增大呈指数函数形式递减，在已知黄土试样浸水前干密度的情况下，可通过该函数关系预测黄土的湿陷性。
（3）黄土湿陷过程中，其颗粒分布、颗粒扁圆度、颗粒排列的定向程度基本不发生变化。
（4）黄土在一定压力下的湿陷性与其内部大于颗粒尺寸的大孔隙数量有关，当黄土中大部分孔隙尺寸大于颗粒尺寸，呈架空结构时，具有强烈的湿陷性；反之，黄土中架空孔隙数量越少，其湿陷性越小。干密度越小，黄土中架空孔隙数量越多，湿陷前后孔隙结构变化越大，黄土的湿陷性越大；干密度越大，黄土中架空孔隙数量减少，湿陷后孔隙结构变化越小，黄土的湿陷性越低。
（5）不同干密度黄土湿陷后的单位孔隙体积相同。黄土干密度越小，湿陷后孔隙尺寸越小，数量越多；干密度越大，湿陷后孔隙尺寸更大，数量更少。 |
| Other Abstract | This article is based on moistening deformation test using the Malan(Q3) loess collected near Lanzhou city. Loess specimens were prepared by static compaction methods, which have a water content of 9% and dry density ranging from 1.30g/cm3, 1.40g/cm3 to 1.50g/cm3. The loess specimens were soaked gradually, step by step, until the saturation condition. The microstructure of the specimens at different soaking stage were explored with SEM and Mercury porosimetry analyzer. The dynamic change of the characteristics of collapse deformation with different dry densities is studied from the unsaturation viewpoint. Moreover, we give a quantitative description for the change of particle shape and pore size distribution before and after the collapse. The conclusions acquired are summarized as the followings.
(1) When the loess deformed by grading soaking under a certain pressure, the void ratio of loess decreases as an exponential function with increasing water saturation. Whatever the initial dry desity is, loess specimens with different dry desity tend to become a same void ratio after collspse.
(2) With respect to a certain vertical pressure, there exists a critical dry density: The loess specimen will collapse after soaking if the initial dry density before soaking is smaller than the critical one. The critical dry density of loess decreases as an exponential function with increasing vertical pressure, which is helpful for prediction of loess collapsibility with a given dry density.
(3) There is little evidence that loess particle is changed during the process of collapse, including particle size, ovality and orientation.
(4) Loess collapsibility is highly related to the number of pores whose sizes are greater than that of the particle sizes in a specimen. In case that a majoraty of the pores size is greater than the particles size within a specimen, the loess soil exhibit its collapsibility much stronger. The smaller the dry density, the more the over-hanged big pores, therefore the stronger the collapsibility.
(5) Even if the initial dry densities are different, the final volume of all pores tends to be the same after collapse. Loess specimen with a lower initial dry density, after wet collapse, exhibit a large number of pores with smaller sizes; while loess specimen with a higher initial dry density, after wet collapse, exhibit a smaller number of pores with biger sizes. |
| URL | 查看原文
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| Language | 中文
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| Document Type | 学位论文
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| Identifier | https://ir.lzu.edu.cn/handle/262010/226321
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| Collection | 土木工程与力学学院
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Recommended Citation
GB/T 7714 |
邵显显. 黄土湿陷过程中微观结构的动态变化研究[D]. 兰州. 兰州大学,2014.
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